How to lazy load images in ListView in Android

Question

I am using a ListView to display some images and captions associated with those images  I am getting the images from the Internet  Is there a way to lazy load images so while the text displays  the UI is not blocked and images are displayed as they are downloaded    The total number of images is not fixed

User · Answer

Update  Note that this answer is pretty ineffective now  The Garbage Collector acts aggressively on SoftReference and WeakReference  so this code is NOT suitable for new apps    Instead  try libraries like Universal Image Loader suggested in other answers    Thanks to James for the code  and Bao-Long for the suggestion of using SoftReference  I implemented the SoftReference changes on James  code  Unfortunately SoftReferences caused my images to be garbage collected too quickly  In my case it was fine without the SoftReference stuff  because my list size is limited and my images are small   There s a discussion from a year ago regarding the SoftReferences on google groups  link to thread  As a solution to the too-early garbage collection  they suggest the possibility of manually setting the VM heap size using dalvik system VMRuntime setMinimumHeapSize    which is not very attractive to me   public DrawableManager         drawableMap   new HashMap lt String  SoftReference lt Drawable gt  gt        public Drawable fetchDrawable String urlString        SoftReference lt Drawable gt  drawableRef   drawableMap get urlString       if  drawableRef    null            Drawable drawable   drawableRef get            if  drawable    null              return drawable             Reference has expired so remove the key from drawableMap         drawableMap remove urlString              if  Constants LOGGING  Log d this getClass   getSimpleName     image url     urlString       try           InputStream is   fetch urlString           Drawable drawable   Drawable createFromStream is   src            drawableRef   new SoftReference lt Drawable gt  drawable           drawableMap put urlString  drawableRef           if  Constants LOGGING  Log d this getClass   getSimpleName     got a thumbnail drawable      drawable getBounds                            drawable getIntrinsicHeight           drawable getIntrinsicWidth                            drawable getMinimumHeight           drawable getMinimumWidth             return drawableRef get          catch  MalformedURLException e            if  Constants LOGGING  Log e this getClass   getSimpleName     fetchDrawable failed   e           return null        catch  IOException e            if  Constants LOGGING  Log e this getClass   getSimpleName     fetchDrawable failed   e           return null           public void fetchDrawableOnThread final String urlString  final ImageView imageView        SoftReference lt Drawable gt  drawableRef   drawableMap get urlString       if  drawableRef    null            Drawable drawable   drawableRef get            if  drawable    null                imageView setImageDrawable drawableRef get                 return                       Reference has expired so remove the key from drawableMap         drawableMap remove urlString              final Handler handler   new Handler              Override         public void handleMessage Message message                imageView setImageDrawable  Drawable  message obj                         Thread thread   new Thread              Override         public void run                   TODO   set imageView to a  pending  image             Drawable drawable   fetchDrawable urlString               Message message   handler obtainMessage 1  drawable               handler sendMessage message                        thread start

User · Answer

Well  image loading time from the Internet has many solutions  You may also use the library Android-Query  It will give you all the required activity  Make sure what you want to do and read the library wiki page  And solve the image loading restriction   This is my code    Override public View getView int position  View convertView  ViewGroup parent        View v   convertView      if  v    null            LayoutInflater vi    LayoutInflater getSystemService Context LAYOUT INFLATER SERVICE           v   vi inflate R layout row  null              ImageView imageview    ImageView  v findViewById R id icon       AQuery aq   new AQuery convertView        String imageUrl    http   www vikispot com z images vikispot android-w png        aq id imageview  progress this  image imageUrl  true  true  0  0  new BitmapAjaxCallback              Override         public void callback String url  ImageView iv  Bitmap bm  AjaxStatus status                iv setImageBitmap bm                          return v      It should be solve your lazy loading problem

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High performance loader - after examining the methods suggested here  I used Ben s solution with some changes -    I realized that working with drawables is faster that with bitmaps so I uses drawables instead Using SoftReference is great  but it makes the cached image to be deleted too often  so I added a Linked list that holds images references  preventing from the image to be deleted  until it reached a predefined size To open the InputStream I used java net URLConnection which allows me to use web cache  you need to set a response cache first  but that s another story    My code   import java util Map   import java util HashMap   import java util LinkedList   import java util Collections   import java util WeakHashMap   import java lang ref SoftReference   import java util concurrent Executors   import java util concurrent ExecutorService   import android graphics drawable Drawable  import android widget ImageView  import android os Handler  import android os Message  import java io InputStream  import java net MalformedURLException   import java io IOException   import java net URL  import java net URLConnection   public class DrawableBackgroundDownloader        private final Map lt String  SoftReference lt Drawable gt  gt  mCache   new HashMap lt String  SoftReference lt Drawable gt  gt        private final LinkedList  lt Drawable gt  mChacheController   new LinkedList  lt Drawable gt      private ExecutorService mThreadPool    private final Map lt ImageView  String gt  mImageViews   Collections synchronizedMap new WeakHashMap lt ImageView  String gt         public static int MAX CACHE SIZE   80   public int THREAD POOL SIZE   3          Constructor     public DrawableBackgroundDownloader           mThreadPool   Executors newFixedThreadPool THREAD POOL SIZE                  Clears all instance data and stops running threads     public void Reset         ExecutorService oldThreadPool   mThreadPool      mThreadPool   Executors newFixedThreadPool THREAD POOL SIZE       oldThreadPool shutdownNow         mChacheController clear        mCache clear        mImageViews clear         public void loadDrawable final String url  final ImageView imageView Drawable placeholder          mImageViews put imageView  url         Drawable drawable   getDrawableFromCache url             check in UI thread  so no concurrency issues       if  drawable    null                Log d null   Item loaded from mCache      url             imageView setImageDrawable drawable           else             imageView setImageDrawable placeholder             queueJob url  imageView  placeholder                  private Drawable getDrawableFromCache String url          if  mCache containsKey url               return mCache get url  get                   return null       private synchronized void putDrawableInCache String url Drawable drawable          int chacheControllerSize   mChacheController size        if  chacheControllerSize  gt  MAX CACHE SIZE           mChacheController subList 0  MAX CACHE SIZE 2  clear         mChacheController addLast drawable       mCache put url  new SoftReference lt Drawable gt  drawable          private void queueJob final String url  final ImageView imageView final Drawable placeholder             Create handler in UI thread           final Handler handler   new Handler                Override           public void handleMessage Message msg                  String tag   mImageViews get imageView                 if  tag    null  amp  amp  tag equals url                     if  imageView isShown                        if  msg obj    null                            imageView setImageDrawable  Drawable  msg obj                           else                             imageView setImageDrawable placeholder                               Log d null   fail     url                                                                      mThreadPool submit new Runnable                Override           public void run                   final Drawable bmp   downloadDrawable url                  if the view is not visible anymore  the image will be ready for next time in cache             if  imageView isShown                                  Message message   Message obtain                      message obj   bmp                    Log d null   Item downloaded      url                      handler sendMessage message                                              private Drawable downloadDrawable String url          try             InputStream is   getInputStream url            Drawable drawable   Drawable createFromStream is  url           putDrawableInCache url drawable             return drawable           catch  MalformedURLException e              e printStackTrace            catch  IOException e              e printStackTrace                   return null          private InputStream getInputStream String urlString  throws MalformedURLException  IOException       URL url   new URL urlString       URLConnection connection      connection   url openConnection        connection setUseCaches true        connection connect        InputStream response   connection getInputStream         return response

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use below class to download and load images in listview It caches every images once download  Also loads images ad lazy loading   package com fudiyoxpress images   import java io File  import java io FileInputStream  import java io FileNotFoundException  import java io FileOutputStream  import java io IOException  import java io InputStream  import java io OutputStream  import java net HttpURLConnection  import java net URL  import java util Collections  import java util Map  import java util WeakHashMap  import java util concurrent ExecutorService  import java util concurrent Executors   import android content Context  import android graphics Bitmap  import android graphics BitmapFactory  import android os Handler  import android widget ImageView   import com fudiyoxpress R  import com fudiyoxpress config Config  import com fudiyoxpress twitter ScaleBitmap   public class ImageLoader           Initialize MemoryCache     MemoryCache memoryCache   new MemoryCache         FileCache fileCache       Context C          Create Map  collection  to store image and image url in key value pair     private Map lt ImageView  String gt  imageViews   Collections              synchronizedMap new WeakHashMap lt ImageView  String gt          ExecutorService executorService          handler to display images in UI thread     Handler handler   new Handler         public ImageLoader Context context             C   context          fileCache   new FileCache context               Creates a thread pool that reuses a fixed number of            threads operating off a shared unbounded queue          executorService   Executors newFixedThreadPool 5                  default image show in list  Before online image download      final int stub id   R drawable restlogoplaceholder       public void DisplayImage String url  ImageView imageView  Context context              boolean header flag             Bitmap largeIcon   BitmapFactory decodeResource context getResources                    R drawable restlogoplaceholder           header flag   false             Store image and url in Map         imageViews put imageView  url               Check image is stored in MemoryCache Map or not  see            MemoryCache java          Bitmap bitmap   memoryCache get url            if  bitmap    null                   if image is stored in MemoryCache Map then                Show image in listview row             Bitmap b   ScaleBitmap                      getScaledBitmap context  bitmap  header flag               imageView setImageBitmap b              else                  queue Photo to download from url             queuePhoto url  imageView  header flag                   Before downloading image show default image             imageView setImageBitmap ScaleBitmap getScaledBitmap context                      largeIcon  header flag                            private void queuePhoto String url  ImageView imageView  boolean header flag               Store image and url in PhotoToLoad object         PhotoToLoad p   new PhotoToLoad url  imageView  header flag               pass PhotoToLoad object to PhotosLoader runnable class            and submit PhotosLoader runnable to executers to run runnable            Submits a PhotosLoader runnable task for execution          executorService submit new PhotosLoader p                  Task for the queue     private class PhotoToLoad           public String url          public ImageView imageView          public boolean b           public PhotoToLoad String u  ImageView i  boolean header flag                url   u              imageView   i              b   header flag                       class PhotosLoader implements Runnable           PhotoToLoad photoToLoad           PhotosLoader PhotoToLoad photoToLoad                this photoToLoad   photoToLoad                      Override         public void run                 try                      Check if image already downloaded                 if  imageViewReused photoToLoad                       return                     download image from web url                 Bitmap bmp   getBitmap photoToLoad url                       set image data in Memory Cache                 memoryCache put photoToLoad url  bmp                    if  imageViewReused photoToLoad                       return                      Get bitmap to display                 BitmapDisplayer bd   new BitmapDisplayer bmp  photoToLoad                       Causes the Runnable bd  BitmapDisplayer  to be added to the                    message queue                     The runnable will be run on the thread to which this handler                    is attached                     BitmapDisplayer run method will call                 handler post bd                  catch  Throwable th                       th printStackTrace                                       private Bitmap getBitmap String url            File f   fileCache getFile url               from SD cache            CHECK   if trying to decode file which not exist in cache return null         Bitmap b   decodeFile f           if  b    null              return b              Download image file from web         try                      download the image             Bitmap bitmap   null               URL imageURL   null              try                    imageURL   new URL Config WEB URL     ServeBlob id     url                    HttpURLConnection connection    HttpURLConnection  imageURL                          openConnection                    connection setDoInput true                   connection connect                       if   new File imageURL toString     exists                                            imageURL new URL                                           InputStream inputStream   connection getInputStream                        Constructs a new FileOutputStream that writes to                    file                    if file not exist then it will create file                 OutputStream os   new FileOutputStream f                       See Utils class CopyStream method                    It will each pixel from input stream and                    write pixels to output stream  file                  Utils CopyStream inputStream  os                    os close                     BitmapFactory Options options   new BitmapFactory Options                    options inSampleSize   8                   bitmap   BitmapFactory decodeStream inputStream  null  options                  catch  IOException e                        e printStackTrace                                  Now file created and going to resize file with defined height                Decodes image and scales it to reduce memory consumption             bitmap   decodeFile f                return bitmap             catch  Throwable ex                ex printStackTrace                if  ex instanceof OutOfMemoryError                  memoryCache clear                return null                          Decodes image and scales it to reduce memory consumption     private Bitmap decodeFile File f             try                   Decode image size             BitmapFactory Options o   new BitmapFactory Options                o inJustDecodeBounds   true              FileInputStream stream1   new FileInputStream f               BitmapFactory decodeStream stream1  null  o               stream1 close                    Find the correct scale value  It should be the power of 2                  Set width height of recreated image             final int REQUIRED SIZE   85               int width tmp   o outWidth  height tmp   o outHeight              int scale   1              while  true                    if  width tmp   2  lt  REQUIRED SIZE                            height tmp   2  lt  REQUIRED SIZE                      break                  width tmp    2                  height tmp    2                  scale    2                                decode with current scale values             BitmapFactory Options o2   new BitmapFactory Options                o2 inSampleSize   scale              FileInputStream stream2   new FileInputStream f               Bitmap bitmap   BitmapFactory decodeStream stream2  null  o2               stream2 close                return bitmap             catch  FileNotFoundException e              catch  IOException e                e printStackTrace                      return null             boolean imageViewReused PhotoToLoad photoToLoad             String tag   imageViews get photoToLoad imageView              Check url is already exist in imageViews MAP         if  tag    null     tag equals photoToLoad url               return true          return false                Used to display bitmap in the UI thread     class BitmapDisplayer implements Runnable           Bitmap bitmap          PhotoToLoad photoToLoad           public BitmapDisplayer Bitmap b  PhotoToLoad p                bitmap   b              photoToLoad   p                     public void run                 if  imageViewReused photoToLoad                   return                  Show bitmap on UI             if  bitmap    null                    photoToLoad imageView setImageBitmap ScaleBitmap                          getScaledBitmap C  bitmap  photoToLoad b                  else                                 photoToLoad imageView setImageResource stub id                         public void clearCache                Clear cache directory downloaded images and stored data in maps         memoryCache clear            fileCache clear                 package com fudiyoxpress images   import java util Collections  import java util Iterator  import java util LinkedHashMap  import java util Map  import java util Map Entry  import android graphics Bitmap  import android util Log   public class MemoryCache        private static final String TAG    MemoryCache          Last argument true for LRU ordering     private Map lt String  Bitmap gt  cache   Collections synchronizedMap              new LinkedHashMap lt String  Bitmap gt  10 1 5f true          current allocated size     private long size 0          max memory cache folder used to download images in bytes     private long limit   1000000        public MemoryCache               use 25  of available heap size         setLimit Runtime getRuntime   maxMemory   4              public void setLimit long new limit            limit new limit          Log i TAG   MemoryCache will use up to   limit 1024  1024   MB               public Bitmap get String id           try              if  cache containsKey id                   return null                NullPointerException sometimes happen here http   code google com p osmdroid issues detail id 78              return cache get id            catch NullPointerException ex               ex printStackTrace                return null                       public void put String id  Bitmap bitmap           try              if cache containsKey id                   size- getSizeInBytes cache get id                cache put id  bitmap               size  getSizeInBytes bitmap               checkSize             catch Throwable th               th printStackTrace                         private void checkSize             Log i TAG   cache size   size   length   cache size             if size gt limit               Iterator lt Entry lt String  Bitmap gt  gt  iter cache entrySet   iterator     least recently accessed item will be the first one iterated               while iter hasNext                     Entry lt String  Bitmap gt  entry iter next                    size- getSizeInBytes entry getValue                     iter remove                    if size lt  limit                      break                            Log i TAG   Clean cache  New size   cache size                          public void clear             try                NullPointerException sometimes happen here http   code google com p osmdroid issues detail id 78              cache clear                size 0           catch NullPointerException ex               ex printStackTrace                         long getSizeInBytes Bitmap bitmap            if bitmap  null              return 0          return bitmap getRowBytes     bitmap getHeight                package com fudiyoxpress images   import java io InputStream  import java io OutputStream   public class Utils       public static void CopyStream InputStream is  OutputStream os                final int buffer size 1024          try                        byte   bytes new byte buffer size               for                                   Read byte from input stream                int count is read bytes  0  buffer size                 if count  -1                    break                   Write byte from output stream               os write bytes  0  count                                   catch Exception ex

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I had this issue and implemented lruCache  I believe you need API 12 and above or use the compatiblity v4 library  lurCache is fast memory  but it also has a budget  so if you re worried about that you can use a diskcache    It s all described in Caching Bitmaps   I ll now provide my implementation which is a singleton I call from anywhere like this     Where the first is a string and the other is a imageview to load   DownloadImageTask getInstance   loadBitmap avatarURL  iv avatar     Here s the ideal code to cache and then call the above in getView of an adapter when retrieving the web image   public class DownloadImageTask        private LruCache lt String  Bitmap gt  mMemoryCache          Create a singleton class to call this from multiple classes         private static DownloadImageTask instance   null       public static DownloadImageTask getInstance             if  instance    null                instance   new DownloadImageTask                      return instance               Lock the constructor from public instances     private DownloadImageTask                 Get max available VM memory  exceeding this amount will throw an            OutOfMemory exception  Stored in kilobytes as LruCache takes an            int in its constructor          final int maxMemory    int   Runtime getRuntime   maxMemory     1024               Use 1 8th of the available memory for this memory cache          final int cacheSize   maxMemory   8           mMemoryCache   new LruCache lt String  Bitmap gt  cacheSize                 Override             protected int sizeOf String key  Bitmap bitmap                       The cache size will be measured in kilobytes rather than                    number of items                  return bitmap getByteCount     1024                                      public void loadBitmap String avatarURL  ImageView imageView            final String imageKey   String valueOf avatarURL            final Bitmap bitmap   getBitmapFromMemCache imageKey           if  bitmap    null                imageView setImageBitmap bitmap             else               imageView setImageResource R drawable ic launcher                new DownloadImageTaskViaWeb imageView  execute avatarURL                        private void addBitmapToMemoryCache String key  Bitmap bitmap            if  getBitmapFromMemCache key     null                mMemoryCache put key  bitmap                        private Bitmap getBitmapFromMemCache String key            return mMemoryCache get key                 A background process that opens a http stream and decodes a web image          class DownloadImageTaskViaWeb extends AsyncTask lt String  Void  Bitmap gt            ImageView bmImage           public DownloadImageTaskViaWeb ImageView bmImage                this bmImage   bmImage                     protected Bitmap doInBackground String    urls                 String urldisplay   urls 0               Bitmap mIcon   null              try                   InputStream in   new java net URL urldisplay  openStream                    mIcon   BitmapFactory decodeStream in                               catch  Exception e                    Log e  Error   e getMessage                     e printStackTrace                               addBitmapToMemoryCache String valueOf urldisplay   mIcon                return mIcon                        After decoding we update the view on the main UI             protected void onPostExecute Bitmap result                bmImage setImageBitmap result

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I found the Glide as better option than Picasso  I was using picasso to load around 32 images of size around 200-500KB each and I was always getting OOM  But the Glide solved my all OOM issues

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1   Picasso allows for hassle-free image loading in your application   often in one line of code  Use Gradle  implementation  com squareup picasso picasso  insert latest version    Just one line of code  Picasso get   load  quot http   i imgur com DvpvklR png quot   into imageView    2  Glide An image loading and caching library for Android focused on smooth scrolling Use Gradle  repositories     mavenCentral      google      dependencies      implementation  com github bumptech glide glide 4 11 0     annotationProcessor  com github bumptech glide compiler 4 11 0        For a simple view    Glide with this  load  quot http   i imgur com DvpvklR png quot   into imageView    3  fresco  is a powerful system for displaying images in Android applications Fresco takes care of image loading and display  so you don t have to  Getting Started with Fresco

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Use the glide library  It worked for me and will work for your code too It works for both images as well as gifs too    ImageView imageView    ImageView  findViewById R id test image        GlideDrawableImageViewTarget imagePreview   new GlideDrawableImageViewTarget imageView       Glide              with this               load url               listener new RequestListener lt String  GlideDrawable gt                       Override                 public boolean onException Exception e  String model  Target lt GlideDrawable gt  target  boolean isFirstResource                                               return false                                      Override                 public boolean onResourceReady GlideDrawable resource  String model  Target lt GlideDrawable gt  target  boolean isFromMemoryCache  boolean isFirstResource                        return false                                                into imagePreview

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Here s what I created to hold the images that my app is currently displaying  Please note that the  Log  object in use here is my custom wrapper around the final Log class inside Android   package com wilson android library       Licensed to the Apache Software Foundation  ASF  under one or more contributor license agreements   See the NOTICE file distributed with this work for additional information regarding copyright ownership   The ASF licenses this file to you under the Apache License  Version 2 0  the  License    you may not use this file except in compliance with the License   You may obtain a copy of the License at  http   www apache org licenses LICENSE-2 0  Unless required by applicable law or agreed to in writing  software distributed under the License is distributed on an  AS IS  BASIS  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND  either express or implied   See the License for the specific language governing permissions and limitations under the License     import java io IOException   public class DrawableManager       private final Map lt String  Drawable gt  drawableMap       public DrawableManager             drawableMap   new HashMap lt String  Drawable gt                public Drawable fetchDrawable String urlString            if  drawableMap containsKey urlString                 return drawableMap get urlString                      Log d this getClass   getSimpleName     image url     urlString           try               InputStream is   fetch urlString               Drawable drawable   Drawable createFromStream is   src                  if  drawable    null                    drawableMap put urlString  drawable                   Log d this getClass   getSimpleName     got a thumbnail drawable      drawable getBounds                                    drawable getIntrinsicHeight           drawable getIntrinsicWidth                                    drawable getMinimumHeight           drawable getMinimumWidth                   else                 Log w this getClass   getSimpleName     could not get thumbnail                               return drawable            catch  MalformedURLException e                Log e this getClass   getSimpleName     fetchDrawable failed   e               return null            catch  IOException e                Log e this getClass   getSimpleName     fetchDrawable failed   e               return null                       public void fetchDrawableOnThread final String urlString  final ImageView imageView            if  drawableMap containsKey urlString                 imageView setImageDrawable drawableMap get urlString                       final Handler handler   new Handler                  Override             public void handleMessage Message message                    imageView setImageDrawable  Drawable  message obj                                     Thread thread   new Thread                  Override             public void run                       TODO   set imageView to a  pending  image                 Drawable drawable   fetchDrawable urlString                   Message message   handler obtainMessage 1  drawable                   handler sendMessage message                                    thread start               private InputStream fetch String urlString  throws MalformedURLException  IOException           DefaultHttpClient httpClient   new DefaultHttpClient            HttpGet request   new HttpGet urlString           HttpResponse response   httpClient execute request           return response getEntity   getContent

User · Answer

Some answers have already mentioned using various image libraries like Universal Image Loader and androidimageloader etc  This is an old quesion but for anyone still looking for something like this  there are several such libraries for image loading caching

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I think this issue is very popular among Android developers  and there are plenty of such libraries that claims to resolve this issue  but only a few of them seems to be on the mark  AQuery is one such library  but it is better than most of them in all aspects and is worth trying for

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You must try this Universal Loader is best  I am using this after done many RnD on lazy loading    Universal Image Loader  Features   Multithread image loading  async or sync  Wide customization of ImageLoader s configuration  thread executors  downloader  decoder  memory and disk cache  display image options  etc   Many customization options for every display image call  stub images  caching switch  decoding options  Bitmap processing and displaying  etc   Image caching in memory and or on disk  device s file system or SD card  Listening loading process  including downloading progress    Android 2 0  support

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All above code have their own worth but with my personal experience just give a try with Picasso   Picasso  is a library specifically for this purpose  in-fact it will manage cache and all other network operations automatically You will have to add library in your project and just write a single line of code to load image from remote URL   Please visit here   http   code tutsplus com tutorials android-sdk-working-with-picasso--cms-22149

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public class ImageDownloader    Map lt String  Bitmap gt  imageCache   public ImageDownloader         imageCache   new HashMap lt String  Bitmap gt            download function public void download String url  ImageView imageView        if  cancelPotentialDownload url  imageView                 Caching code right here         String filename   String valueOf url hashCode             File f   new File getCacheDirectory imageView getContext                     filename               Is the bitmap in our memory cache          Bitmap bitmap   null           bitmap    Bitmap  imageCache get f getPath              if  bitmap    null                 bitmap   BitmapFactory decodeFile f getPath                  if  bitmap    null                    imageCache put f getPath    bitmap                                       No  download it         if  bitmap    null                try                   BitmapDownloaderTask task   new BitmapDownloaderTask                          imageView                   DownloadedDrawable downloadedDrawable   new DownloadedDrawable                          task                   imageView setImageDrawable downloadedDrawable                   task execute url                 catch  Exception e                    Log e  Error   gt    e toString                              else                  Yes  set the image             imageView setImageBitmap bitmap                         cancel a download  internal only  private static boolean cancelPotentialDownload String url          ImageView imageView        BitmapDownloaderTask bitmapDownloaderTask   getBitmapDownloaderTask imageView        if  bitmapDownloaderTask    null            String bitmapUrl   bitmapDownloaderTask url          if   bitmapUrl    null       bitmapUrl equals url                  bitmapDownloaderTask cancel true             else                  The same URL is already being downloaded              return false                      return true        gets an existing download if one exists for the imageview private static BitmapDownloaderTask getBitmapDownloaderTask          ImageView imageView        if  imageView    null            Drawable drawable   imageView getDrawable            if  drawable instanceof DownloadedDrawable                DownloadedDrawable downloadedDrawable    DownloadedDrawable  drawable              return downloadedDrawable getBitmapDownloaderTask                        return null        our caching functions    Find the dir to save cached images private static File getCacheDirectory Context context        String sdState   android os Environment getExternalStorageState        File cacheDir       if  sdState equals android os Environment MEDIA MOUNTED             File sdDir   android os Environment getExternalStorageDirectory                TODO   Change your diretcory here         cacheDir   new File sdDir   data ToDo images          else         cacheDir   context getCacheDir         if   cacheDir exists            cacheDir mkdirs        return cacheDir     private void writeFile Bitmap bmp  File f        FileOutputStream out   null       try           out   new FileOutputStream f           bmp compress Bitmap CompressFormat PNG  80  out         catch  Exception e            e printStackTrace          finally           try               if  out    null                  out close              catch  Exception ex                          download asynctask public class BitmapDownloaderTask extends AsyncTask lt String  Void  Bitmap gt        private String url      private final WeakReference lt ImageView gt  imageViewReference       public BitmapDownloaderTask ImageView imageView            imageViewReference   new WeakReference lt ImageView gt  imageView               Override        Actual download method  run in the task thread     protected Bitmap doInBackground String    params               params comes from the execute   call  params 0  is the url          url    String  params 0           return downloadBitmap params 0                Override        Once the image is downloaded  associates it to the imageView     protected void onPostExecute Bitmap bitmap            if  isCancelled                  bitmap   null                     if  imageViewReference    null                ImageView imageView   imageViewReference get                BitmapDownloaderTask bitmapDownloaderTask   getBitmapDownloaderTask imageView                  Change bitmap only if this process is still associated with                it             if  this    bitmapDownloaderTask                    imageView setImageBitmap bitmap                       cache the image                  String filename   String valueOf url hashCode                     File f   new File                          getCacheDirectory imageView getContext     filename                    imageCache put f getPath    bitmap                    writeFile bitmap  f                                     static class DownloadedDrawable extends ColorDrawable       private final WeakReference lt BitmapDownloaderTask gt  bitmapDownloaderTaskReference       public DownloadedDrawable BitmapDownloaderTask bitmapDownloaderTask            super Color WHITE           bitmapDownloaderTaskReference   new WeakReference lt BitmapDownloaderTask gt                   bitmapDownloaderTask              public BitmapDownloaderTask getBitmapDownloaderTask             return bitmapDownloaderTaskReference get                the actual download code static Bitmap downloadBitmap String url        HttpParams params   new BasicHttpParams        params setParameter CoreProtocolPNames PROTOCOL VERSION              HttpVersion HTTP 1 1       HttpClient client   new DefaultHttpClient params       final HttpGet getRequest   new HttpGet url        try           HttpResponse response   client execute getRequest           final int statusCode   response getStatusLine   getStatusCode            if  statusCode    HttpStatus SC OK                Log w  ImageDownloader    Error     statusCode                         while retrieving bitmap from     url               return null                     final HttpEntity entity   response getEntity            if  entity    null                InputStream inputStream   null              try                   inputStream   entity getContent                    final Bitmap bitmap   BitmapFactory                          decodeStream inputStream                   return bitmap                finally                   if  inputStream    null                        inputStream close                                      entity consumeContent                                  catch  Exception e               Could provide a more explicit error message for IOException or            IllegalStateException         getRequest abort            Log w  ImageDownloader    Error while retrieving bitmap from                     url   e toString           finally           if  client    null                   client close                        return null

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Except load the data cache asynchronously  you may require the UI cache  like setViewCacheSize Except the the loading visible item data  you may require to load the approximity-visible item data AndroidX Paging Library is another option  for example  you can load and cache and  display 10 000 000 items to a RecyclerView from a SQLite database  refer to PagedList Example  Suppose the listview visible item is  6 7 8 9 10   you may require to load  6 7 8 9 10  AND pre-load the item  1  2  3  4  5   amp   11  12  13  14  15   because user probably scroll to the pre-page or post-page

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Check my fork of LazyList  Basically  I improve the LazyList by delaying the call of the ImageView and create two methods    When you need to put something like  Loading image     When you need to show the downloaded image    I also improved the ImageLoader by implementing a singleton in this object

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Just a quick tip for someone who is in indecision regarding what library to use for lazy-loading images   There are four basic ways    DIY    Not the best solution but for a few images and if you want to go without the hassle of using others libraries Volley s Lazy Loading library    From guys at android  It is nice and everything but is poorly documented and hence is a problem to use  Picasso  A simple solution that just works  you can even specify the exact image size you want to bring in  It is very simple to use but might not be very  performant  for apps that has to deal with humongous amounts of images  UIL  The best way to lazy load images  You can cache images you need permission of course   initialize the loader once  then have your work done  The most mature asynchronous image loading library I have ever seen so far

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Multithreading For Performance  a tutorial by Gilles Debunne   This is from the Android Developers Blog  The suggested code uses    AsyncTasks  A hard  limited size  FIFO cache  A soft  easily garbage collect-ed cache  A placeholder Drawable while you download

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I have been using NetworkImageView from the new Android Volley Library com android volley toolbox NetworkImageView  and it seems to be working pretty well  Apparently  this is the same view that is used in Google Play and other new Google applications  Definitely worth checking out    Google I O 2013 volley image cache tutorial Developers Google events

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I can recommend a different way that works like a charm  Android Query   You can download that JAR file from here  AQuery androidAQuery   new AQuery this     As an example   androidAQuery id YOUR IMAGEVIEW  image YOUR IMAGE TO LOAD  true  true  getDeviceWidth    ANY DEFAULT IMAGE YOU WANT TO SHOW     It s very fast and accurate  and using this you can find many more features like animation when loading  getting a bitmap  if needed   etc

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You can use some third party library such as Piccaso or Volley for effective lazy loading  You can also create your own by implementing the below   Implement code for downloading the image from the url Implement caching mechanism for storing and retrieving image Use LruCache of android for caching

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This is a common problem on Android that has been solved in many ways by many people   In my opinion the best solution I ve seen is the relatively new library called Picasso   Here are the highlights    Open source  but headed up by Jake Wharton of ActionBarSherlock fame  Asynchronously load images from network or app resources with one line of code Automatic ListView detection Automatic disk and memory caching Can do custom transformations Lots of configurable options Super simple API Frequently updated

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Another way to do it  is through your adapter in a thread in your getView   method    Thread pics thread   new Thread new Runnable          Override     public void run             Bitmap bitmap   getPicture url           if bitmap    null                runOnUiThread new Runnable                      Override                 public void run                         holder imageview setImageBitmap bitmap                                   adapter notifyDataSetChanged                                                                                                                             pics thread start      of course  you should always cache your images to avoid extra operations  you could put your images in a HashMap array  check if the image exists in the array  if not  proceed with the thread or else load the image from you HashMap array  Also always check that you are not leaking memory  bitmaps and drawables are often heavy on memory  It is up to you to optimize your code

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You can try the Aquery Android library for lazy loading image and listview    The below code may help you      download library from here   AQuery aq   new AQuery mContext   aq id R id image1  image  http   data whicdn com images 63995806 original jpg

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If you want to display Shimmer layout like Facebook there is a official facebook library for that  FaceBook Shimmer Android  It takes care of everything  You just need to put your desired design code in nested manner in shimmer frame  Here is a sample code    lt com facebook shimmer ShimmerFrameLayout      android id      id shimmer view container         android layout width    wrap content         android layout height  wrap content       shimmer duration  1000  gt     lt here will be your content to display   gt    lt  com facebook shimmer ShimmerFrameLayout gt    And here is the java code for it   ShimmerFrameLayout shimmerContainer    ShimmerFrameLayout  findViewById R id shimmer view container   shimmerContainer startShimmerAnimation      Add this dependency in your gradle file   implementation  com facebook shimmer shimmer 0 1 0 aar    Here is how it looks like

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I use droidQuery  There are two mechanisms for loading an image from a URL  The first  shorthand  is simply     with myView  image url     This can be added into an ArrayAdapter s getView      method very easily     The longhand method will give a lot more control  and has options not even discussed here  such as cacheing and callbacks   but a basic implementation that specifies the output size as 200px x 200px can be found here     ajax new AjaxOptions   url url       type  GET        dataType  image        imageWidth 200  imageHeight 200       success new Function              Override         public void invoke   droidQuery  Object    params                myImageView setImageBitmap  Bitmap  params 0                          error new Function              Override         public void invoke   droidQuery  Object    params                AjaxError e    AjaxError  params 0               Log e       Error     e status          e error

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URLImageViewHelper is an amazing library that helps you to do that

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I recommend open source instrument Universal Image Loader  It is originally based on Fedor Vlasov s project LazyList and has been vastly improved since then    Multithread image loading Possibility of wide tuning ImageLoader s configuration  thread executors  downlaoder  decoder  memory and disc cache  display image options  and others  Possibility of image caching in memory and or on device s file sysytem  or SD card  Possibility to  listen  loading process Possibility to customize every display image call with separated options Widget support Android 2 0  support

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I made a simple demo of a lazy list  located at GitHub  with images       Basic Usage   ImageLoader imageLoader new ImageLoader context       imageLoader DisplayImage url  imageView          Don t forget to add the   following permissions to your AndroidManifest xml     lt uses-permission android name  android permission INTERNET   gt    lt uses-permission android name  android permission WRITE EXTERNAL STORAGE   gt  Please       create only one instance of ImageLoader and reuse it all around your   application  This way image caching will be much more efficient    It may be helpful to somebody  It downloads images in the background thread  Images are being cached on an SD card and in memory  The cache implementation is very simple and is just enough for the demo  I decode images with inSampleSize to reduce memory consumption  I also try to handle recycled views correctly

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Picasso   Use Jake Wharton s  Picasso Library    A Perfect ImageLoading Library form the developer of ActionBarSherlock   A powerful image downloading and caching library for Android   Images add much-needed context and visual flair to Android applications  Picasso allows for hassle-free image loading in your application   often in one line of code   Picasso with context  load  http   i imgur com DvpvklR png   into imageView     Many common pitfalls of image loading on Android are handled automatically by Picasso   Handling ImageView recycling and download cancellation in an adapter  Complex image transformations with minimal memory use  Automatic memory and disk caching   Picasso Jake Wharton s Library  Glide  Glide is a fast and efficient open source media management framework for Android that wraps media decoding  memory and disk caching  and resource pooling into a simple and easy to use interface   Glide supports fetching  decoding  and displaying video stills  images  and animated GIFs  Glide includes a flexible api that allows developers to plug in to almost any network stack  By default Glide uses a custom HttpUrlConnection based stack  but also includes utility libraries plug in to Google s Volley project or Square s OkHttp library instead   Glide with this  load  http   goo gl h8qOq7   into imageView     Glide s primary focus is on making scrolling any kind of a list of images as smooth and fast as possible  but Glide is also effective for almost any case where you need to fetch  resize  and display a remote image   Glide Image Loading Library  Fresco by Facebook   Fresco is a powerful system for displaying images in Android applications   Fresco takes care of image loading and display  so you don t have to  It will load images from the network  local storage  or local resources  and display a placeholder until the image has arrived  It has two levels of cache  one in memory and another in internal storage   Fresco Github  In Android 4 x and lower  Fresco puts images in a special region of Android memory  This lets your application run faster - and suffer the dreaded OutOfMemoryError much less often   Fresco Documentation

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DroidParts has ImageFetcher that requires zero configuration to get started    Uses a disk  amp  in-memory Least Recently Used  LRU  cache  Efficiently decodes images  Supports modifying bitmaps in background thread  Has simple cross-fade  Has image loading progress callback    Clone DroidPartsGram for an example

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I just want to add one more good example  XML Adapters  As it s is used by Google and I am also using the same logic to avoid an OutOfMemory error    Basically this ImageDownloader is your answer  as it covers most of your requirements   Some you can also implement in that

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UPDATE  if you re searching for a solution in 2020 backed by Kotlin Coroutines  try Coil  Coil is an acronym for Coroutine Image Loader  Features  Fast  Coil performs a number of optimizations including memory and disk caching  downsampling the image in memory  re-using bitmaps  automatically pausing cancelling requests  and more  Lightweight  Coil adds  2000 methods to your APK  for apps that already use OkHttp and Coroutines   which is comparable to Picasso and significantly less than Glide and Fresco  Easy to use  Coil s API leverages Kotlin s language features for simplicity and minimal boilerplate  Modern  Coil is Kotlin-first and uses modern libraries including Coroutines  OkHttp  Okio  and AndroidX Lifecycles   Gradle Setup  Coil is available on mavenCentral    implementation  quot io coil-kt coil 1 0 0 quot    Quick Start To load an image into an ImageView  use the load extension function     URL imageView load  quot https   www example com image jpg quot       Resource imageView load R drawable image      File imageView load File  quot  path to image jpg quot     or on Background threads    Coil  suspends the current coroutine  non-blocking and thread safe  val request   ImageRequest Builder context       data url       size width  height       build   val drawable   context imageLoader execute request  drawable  You can also migrate from Picasso Glide Full documentation here

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Have a look at Shutterbug  Applidium s lightweight SDWebImage  a nice library on iOS  port to Android  It supports asynchronous caching  stores failed URLs  handles concurrency well  and helpful subclasses are included   Pull requests  and bug reports  are welcome  too

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I ve written a tutorial that explains how to do lazy-loading of images in a listview  I go into some detail about the issues of recycling and concurrency  I also use a fixed thread pool to prevent spawning a lot of threads   Lazy loading of images in Listview Tutorial

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The way I do it is by launching a thread to download the images in the background and hand it a callback for each list item   When an image is finished downloading it calls the callback which updates the view for the list item     This method doesn t work very well when you re recycling views however

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I have followed this Android Training and I think it does an excellent job at downloading images without blocking the main UI   It also handles caching and dealing with scrolling through many images  Loading Large Bitmaps Efficiently

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Novoda also has a great lazy image loading library and many apps like Songkick  Podio  SecretDJ and ImageSearch use their library   Their library is hosted here on Github and they have a pretty active issues tracker as well  Their project seems to be pretty active too  with over 300  commits at the time of writing this reply

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Give Aquery a try  It has amazingly simple methods to load and cache images asynchronously

[android] How to lazy load images in ListView in Android

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