What does LayoutInflater in Android do

Question

What is the use of LayoutInflater in Android

User · Answer

This class is used to instantiate layout XML file into its corresponding View objects. It is never be used directly -- use getLayoutInflater() or getSystemService(String) to retrieve a standard LayoutInflater instance that is already hooked up to the current context and correctly configured for the device you are running on. For example:

LayoutInflater inflater = (LayoutInflater)context.getSystemService
      (Context.LAYOUT_INFLATER_SERVICE);

Reference: http://developer.android.com/reference/android/view/LayoutInflater.html

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Inflating means reading the XML file that describes a layout  or GUI element  and to create the actual objects that correspond to it  and thus make the object visible within an Android app   final Dialog mDateTimeDialog   new Dialog MainActivity this       Inflate the root layout final RelativeLayout mDateTimeDialogView    RelativeLayout  getLayoutInflater   inflate R layout date time dialog  null       Grab widget instance final DateTimePicker mDateTimePicker    DateTimePicker  mDateTimeDialogView findViewById R id DateTimePicker     This file could saved as date time dialog xml    lt RelativeLayout xmlns android  http   schemas android com apk res android      android id    id DateTimeDialog  android layout width  100px      android layout height  wrap content  gt       lt com dt datetimepicker DateTimePicker             android id    id DateTimePicker  android layout width  fill parent              android layout height  wrap content    gt       lt LinearLayout android id    id ControlButtons              android layout width  fill parent  android layout height  wrap content              android layout below    id DateTimePicker              android padding  5dip  gt               lt Button android id    id SetDateTime  android layout width  0dip                      android text   android string ok  android layout weight  1                      android layout height  wrap content                       gt               lt Button android id    id ResetDateTime  android layout width  0dip                      android text  Reset  android layout weight  1                      android layout height  wrap content                        gt               lt Button android id    id CancelDialog  android layout width  0dip                      android text   android string cancel  android layout weight  1                      android layout height  wrap content                         gt       lt  LinearLayout gt      This file could saved as date time picker xml     lt RelativeLayout xmlns android  http   schemas android com apk res android      android layout width  match parent  android layout height  wrap content   enter code here      android padding  5dip  android id    id DateTimePicker  gt   lt LinearLayout android layout width  wrap content  android layout height  wrap content  android baselineAligned  true  android orientation  horizontal  gt        lt LinearLayout     android id    id month container      android layout width  wrap content      android layout height  wrap content      android layout marginLeft  1dp      android layout marginTop  5dp      android layout marginRight  5dp      android layout marginBottom  5dp      android gravity  center      android orientation  vertical  gt       lt Button         android id    id month plus          android layout width  45dp          android layout height  45dp            android background   drawable image button up final   gt       lt EditText         android id    id month display          android layout width  45dp          android layout height  35dp          android background   drawable picker middle          android focusable  false          android gravity  center          android singleLine  true          android textColor   000000  gt       lt  EditText gt       lt Button         android id    id month minus          android layout width  45dp          android layout height  45dp                 android background   drawable image button down final   gt   lt  LinearLayout gt   lt LinearLayout     android id    id date container      android layout width  wrap content      android layout height  wrap content      android layout marginLeft  0 5dp      android layout marginTop  5dp      android layout marginRight  5dp      android layout marginBottom  5dp      android gravity  center      android orientation  vertical  gt       lt Button         android id    id date plus          android layout width  45dp          android layout height  45dp                 android background   drawable image button up final   gt       lt EditText         android id    id date display          android layout width  45dp          android layout height  35dp          android background   drawable picker middle          android gravity  center          android focusable  false          android inputType  number          android textColor   000000          android singleLine  true   gt       lt Button         android id    id date minus          android layout width  45dp          android layout height  45dp                android background   drawable image button down final   gt   lt  LinearLayout gt   lt LinearLayout     android id    id year container      android layout width  wrap content      android layout height  wrap content      android layout marginLeft  0 5dp      android layout marginTop  5dp      android layout marginRight  5dp      android layout marginBottom  5dp      android gravity  center      android orientation  vertical  gt       lt Button         android id    id year plus          android layout width  45dp          android layout height  45dp                     android background   drawable image button up final   gt       lt EditText         android id    id year display          android layout width  45dp          android layout height  35dp          android background   drawable picker middle          android gravity  center          android focusable  false          android inputType  number          android textColor   000000          android singleLine  true   gt       lt Button         android id    id year minus          android layout width  45dp          android layout height  45dp                 android background   drawable image button down final   gt   lt  LinearLayout gt   lt LinearLayout         android id    id hour container          android layout width  wrap content          android layout height  wrap content          android layout marginLeft  5dp          android layout marginRight  5dp          android layout marginTop  5dp          android layout marginBottom  5dp          android gravity  center          android orientation  vertical  gt           lt Button             android id    id hour plus              android layout width  45dp              android layout height  45dp                        android background   drawable image button up final   gt           lt EditText             android id    id hour display              android layout width  45dp              android layout height  35dp              android background   drawable picker middle              android gravity  center              android focusable  false              android inputType  number              android textColor   000000              android singleLine  true  gt           lt  EditText gt           lt Button             android id    id hour minus              android layout width  45dp              android layout height  45dp                     android background   drawable image button down final   gt       lt  LinearLayout gt       lt LinearLayout         android id    id min container          android layout width  wrap content          android layout height  wrap content          android layout marginLeft  0 35dp          android layout marginTop  5dp          android layout marginRight  5dp          android layout marginBottom  5dp          android gravity  center          android orientation  vertical  gt           lt Button             android id    id min plus              android layout width  45dp              android layout height  45dp                     android background   drawable image button up final   gt           lt EditText             android id    id min display              android layout width  45dp              android layout height  35dp              android background   drawable picker middle              android gravity  center              android focusable  false              android inputType  number              android textColor   000000              android singleLine  true   gt           lt Button             android id    id min minus              android layout width  45dp              android layout height  45dp                     android background   drawable image button down final   gt       lt  LinearLayout gt        lt LinearLayout          android id    id meridiem container          android layout width  wrap content          android layout height  wrap content          android layout marginLeft  0 35dp          android layout marginTop  5dp          android layout marginRight  5dp          android layout marginBottom  5dp          android gravity  center          android orientation  vertical  gt           lt ToggleButton              android id    id toggle display              style   style SpecialToggleButton              android layout width  40dp              android layout height  32dp              android layout marginLeft  5dp              android layout marginTop  45dp              android layout marginRight  5dp              android layout marginBottom  5dp              android padding  5dp              android gravity  center              android textOn   string meridiem AM              android textOff   string meridiem PM              android checked  true   gt               lt  --  android checked  true  -- gt         lt  LinearLayout gt   lt  LinearLayout gt   lt  RelativeLayout gt    The MainActivity class saved as MainActivity java   public class MainActivity extends Activity       EditText editText      Button button click      public static Activity me   null      String meridiem       Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout activity main           editText    EditText findViewById R id edittext1           button click    Button findViewById R id button1           button click setOnClickListener new OnClickListener                  Override             public void onClick View view                   final Dialog mDateTimeDialog   new Dialog MainActivity this                   final RelativeLayout mDateTimeDialogView    RelativeLayout    getLayoutInflater   inflate R layout date time dialog  null                   final DateTimePicker mDateTimePicker    DateTimePicker  mDateTimeDialogView findViewById R id DateTimePicker                      mDateTimePicker setDateChangedListener                      Button  mDateTimeDialogView findViewById R id SetDateTime   setOnClickListener new OnClickListener                         public void onClick View v                            mDateTimePicker clearFocus                            int hour   mDateTimePicker getHour                            String result string   mDateTimePicker getMonth           String valueOf mDateTimePicker getDay             String valueOf mDateTimePicker getYear                                     mDateTimePicker getHour   lt  9  String valueOf  0  mDateTimePicker getHour      String valueOf mDateTimePicker getHour              mDateTimePicker getMinute   lt  9 String valueOf  0  mDateTimePicker getMinute    String valueOf mDateTimePicker getMinute         mDateTimePicker getMeridiem                            editText setText result string                           mDateTimeDialog dismiss                                                                 Cancel the dialog when the  Cancel  button is clicked                   Button  mDateTimeDialogView findViewById R id CancelDialog   setOnClickListener new OnClickListener                         public void onClick View v                               TODO Auto-generated method stub                         mDateTimeDialog cancel                                                                 Reset Date and Time pickers when the  Reset  button is clicked                   Button  mDateTimeDialogView findViewById R id ResetDateTime   setOnClickListener new OnClickListener                         public void onClick View v                               TODO Auto-generated method stub                         mDateTimePicker reset                                                                  Setup TimePicker                    No title on the dialog window                 mDateTimeDialog requestWindowFeature Window FEATURE NO TITLE                      Set the dialog content view                 mDateTimeDialog setContentView mDateTimeDialogView                      Display the dialog                 mDateTimeDialog show

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Layout inflater is a class that reads the xml appearance description and convert them into java based View objects

User · Answer

here is an example for geting a refrence for the root View of a layout    inflating it and using it with setContentView View view    protected void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       LayoutInflater li getLayoutInflater        View rootView li inflate R layout activity main null       setContentView rootView

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When you use a custom view in a ListView you must define the row layout  You create an xml where you place android widgets and then in the adapter s code you have to do something like this   public MyAdapter Context context  List lt MyObject gt  objects  extends ArrayAdapter     super context  1  objects        We get the inflator in the constructor      mInflater    LayoutInflater  context getSystemService Context LAYOUT INFLATER SERVICE       Override public View getView int position  View convertView  ViewGroup parent      View view       We inflate the xml which gives us a view      view   mInflater inflate R layout my list custom row  parent  false         Get the item in the adapter      MyObject myObject   getItem position         Get the widget with id name which is defined in the xml of the row      TextView name    TextView  view findViewById R id name         Populate the row s xml with info from the item      name setText myObject getName           Return the generated view      return view      Read more in the official documentation

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my customize list hope it illustrate concept  public class second extends ListActivity     Override protected void onCreate Bundle savedInstanceState           TODO Auto-generated method stub     super onCreate savedInstanceState       setContentView R layout second       TextView textview  TextView findViewById R id textView1       textview setText getIntent   getExtras   getString  value          setListAdapter new MyAdapter this R layout list item R id textView1  getResources   getStringArray R array counteries        private class MyAdapter extends ArrayAdapter lt String gt        public MyAdapter Context context  int resource  int textViewResourceId              String   objects            super context  resource  textViewResourceId  objects              TODO Auto-generated constructor stub             Override     public View getView int position  View convertView  ViewGroup parent             LayoutInflater inflater  LayoutInflater  getSystemService Context LAYOUT INFLATER SERVICE           View row inflater inflate R layout list item parent false           String  items getResources   getStringArray R array counteries            ImageView iv  ImageView  row findViewById R id imageView1           TextView tv  TextView  row findViewById R id textView1           tv setText items position             if items position  equals  unitedstates                 iv setImageResource R drawable usa            else   if items position  equals  Russia                 iv setImageResource R drawable russia            else   if items position  equals  Japan                 iv setImageResource R drawable japan                        TODO Auto-generated method stub         return row

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The LayoutInflater class is used to instantiate the contents of layout XML files into their corresponding View objects   In other words  it takes an XML file as input and builds the View objects from it

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LayoutInflater is a fundamental component in Android  You must use it all the time to turn xml files into view hierarchies

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LayoutInflater inflate   provides a means to convert a res layout   xml file defining a view into an actual View object usable in your application source code   basic two steps  get the inflater and then inflate the resource  How do you get the inflater    LayoutInflater inflater    LayoutInflater  context              getSystemService Context LAYOUT INFLATER SERVICE     How do you get the view assuming the xml file is  list item xml    View view   inflater inflate R layout list item  parent  false

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What inflater does  It takes a xml layout as input  say  and converts it to View object    Why needed  Let us think a scenario where we need to create a custom listview  Now each row should be custom  But how can we do it  Its not possible to assign a xml layout to a row of listview  So  we create a View object  Thus we can access the elements in it  textview imageview etc  and also assign the object as row of listview  So  whenever we need to assign view type object somewhere and we have our custom xml design we just convert it to object by inflater and use it

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Inflater actually some sort of convert to data   views  instances  to visible UI representation     thus it make use of data feed into from maybe adapters   etc  programmatically  then integrating it with an xml you defined  that tells it how the data should be represented in UI

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Here is another example similar to the previous one  but extended to further demonstrate inflate parameters and dynamic behavior it can provide   Suppose your ListView row layout can have variable number of TextViews  So first you inflate the base item View  just like the previous example   and then loop dynamically adding TextViews at run-time  Using android layout weight additionally aligns everything perfectly   Here are the Layouts resources    list layout xml   lt  xml version  1 0  encoding  utf-8   gt   lt LinearLayout xmlns android  http   schemas android com apk res android      android layout width  match parent       android layout height  wrap content       android orientation  horizontal   gt       lt TextView          android id    id field1          android layout width  0dp            android layout height  wrap content           android layout weight  2   gt       lt TextView          android id    id field2          android layout width  0dp            android layout height  wrap content           android layout weight  1    gt   lt  LinearLayout gt    schedule layout xml   lt  xml version  1 0  encoding  utf-8   gt      lt TextView xmlns android  http   schemas android com apk res android      android layout width  0dp        android layout height  wrap content       android layout weight  1   gt    Override getView method in extension of BaseAdapter class   Override public View getView int position  View convertView  ViewGroup parent        LayoutInflater inflater   activity getLayoutInflater        View lst item view   inflater inflate R layout list layout  null       TextView t1    TextView  lst item view findViewById R id field1       TextView t2    TextView  lst item view findViewById R id field2       t1 setText  some value        t2 setText  another value            dinamically add TextViews for each item in ArrayList list schedule     for int i   0  i  lt  list schedule size    i             View schedule view   inflater inflate R layout schedule layout   ViewGroup  lst item view  false             TextView schedule view  setText list schedule get i              ViewGroup  lst item view  addView schedule view             return lst item view      Note different inflate method calls   inflater inflate R layout list layout  null      no parent inflater inflate R layout schedule layout   ViewGroup  lst item view  false      with parent preserving LayoutParams

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LayoutInflater creates View objects based on layouts defined in XML  There are several different ways to use LayoutInflater  including creating custom Views  inflating Fragment views into Activity views  creating Dialogs  or simply inflating a layout file View into an Activity   There are a lot of misconceptions about how the inflation process works  I think this comes from poor of the documentation for the inflate   method  If you want to learn about the inflate   method in detail  I wrote a blog post about it here   https   www bignerdranch com blog understanding-androids-layoutinflater-inflate

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LayoutInflater is a class used to instantiate layout XML file into its corresponding view objects which can be used in Java programs  In simple terms  there are two ways to create UI in android  One is a static way and another is dynamic or programmatically  Suppose we have a simple layout main xml  having one textview and one edittext as follows    lt  xml version  1 0  encoding  utf-8   gt   lt LinearLayout xmlns android  http   schemas android com apk res android      android orientation  vertical      android layout width  fill parent      android layout height  fill parent      android id    id layout1       gt   lt TextView         android id    id namelabel          android layout width  wrap content          android layout height  wrap content          android text  Enter your name          android textAppearance   android attr textAppearanceLarge   gt       lt  TextView gt       lt EditText         android id    id name          android layout width  match parent          android layout height  wrap content          android layout alignParentLeft  true          android layout marginTop  14dp          android ems  10  gt       lt  EditText gt   lt  LinearLayout gt    We can display this layout in static way by  public void onCreate Bundle savedInstanceState      super onCreate savedInstanceState     setContentView R layout main     A dynamic way of creating a view means the view is not mentioned in our main xml but we want to show with this in run time  For example  we have another XML in layout folder as  footer xml   lt  xml version  1 0  encoding  utf-8   gt   lt TextView xmlns android  http   schemas android com apk res android      android id    id TextView1      android layout width  match parent      android layout height  wrap content      android gravity  center horizontal      android text  Add your record      android textSize  24sp   gt    lt  TextView gt    We want to show this textbox in run time within our main UI  So here we will inflate text xml  See how   public void onCreate Bundle savedInstanceState       super onCreate savedInstanceState     setContentView R layout main     final LayoutInflater  inflater    LayoutInflater getSystemService Context LAYOUT INFLATER SERVICE     TextView t    TextView inflater inflate R layout footer null      lLayout    LinearLayout findViewById R id layout1     lLayout addView t     Here I have used getSystemService  String  to retrieve a  LayoutInflater instance  I can use getLayoutInflator   too to inflate instead of using getSystemService  String  like below   LayoutInflator inflater   getLayoutInflater    TextView t    TextView  inflater inflate R layout footer  null   lLayout addView t

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What does LayoutInflator do   When I first started Android programming  I was really confused by LayoutInflater and findViewById  Sometimes we used one and sometimes the other    LayoutInflater is used to create a new View  or Layout  object from one of your xml layouts  findViewById just gives you a reference to a view than has already been created  You might think that you haven t created any views yet  but whenever you call setContentView in onCreate  the activity s layout along with its subviews gets inflated  created  behind the scenes    So if the view already exists  then use findViewById  If not  then create it with a LayoutInflater   Example  Here is a mini project I made that shows both LayoutInflater and findViewById in action  With no special code  the layout looks like this     The blue square is a custom layout inserted into the main layout with include  see here for more   It was inflated automatically because it is part of the content view  As you can see  there is nothing special about the code   public class MainActivity extends AppCompatActivity        Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout activity main             Now let s inflate  create  another copy of our custom layout and add it in     LayoutInflater inflater   getLayoutInflater    View myLayout   inflater inflate R layout my layout  mainLayout  false     To inflate the new view layout  all I did was tell the inflater the name of my xml file  my layout   the parent layout that I want to add it to  mainLayout   and that I don t actually want to add it yet  false    I could also set the parent to null  but then the layout parameters of my custom layout s root view would be ignored    Here it is again in context   public class MainActivity extends AppCompatActivity         Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState               inflate the main layout for the activity         setContentView R layout activity main               get a reference to the already created main layout         LinearLayout mainLayout    LinearLayout  findViewById R id activity main layout               inflate  create  another copy of our custom layout         LayoutInflater inflater   getLayoutInflater            View myLayout   inflater inflate R layout my layout  mainLayout  false               make changes to our custom layout and its subviews         myLayout setBackgroundColor ContextCompat getColor this  R color colorAccent            TextView textView    TextView  myLayout findViewById R id textView           textView setText  New Layout                add our custom layout to the main layout         mainLayout addView myLayout             Notice how findViewById is used only after a layout has already been inflated   Supplemental Code  Here is the xml for the example above   activity main xml   lt  xml version  1 0  encoding  utf-8   gt   lt LinearLayout     xmlns android  http   schemas android com apk res android      android id    id activity main layout      android orientation  horizontal      android layout width  match parent      android layout height  match parent      android padding  16dp  gt        lt  -- Here is the inserted layout -- gt       lt include layout   layout my layout   gt    lt  LinearLayout gt    my layout xml   lt  xml version  1 0  encoding  utf-8   gt   lt RelativeLayout     xmlns android  http   schemas android com apk res android      android layout width  100dp      android layout height  100dp      android background   color colorPrimary  gt        lt TextView         android id    id textView          android layout width  wrap content          android layout height  wrap content          android layout centerInParent  true          android padding  5dp          android textColor   android color white          android text  My Layout   gt    lt  RelativeLayout gt    When do you need LayoutInflater   The most common time most people use it is in a RecyclerView   See these RecyclerView examples for a list or a grid   You have to inflate a new layout for every single visible item in the list or grid  You also can use a layout inflater if you have a complex layout that you want to add programmatically  like we did in our example   You could do it all in code  but it is much easier to define it in xml first and then just inflate it

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