Android Only the original thread that created a view hierarchy can touch its views

Question

I ve built a simple music player in Android  The view for each song contains a SeekBar  implemented like this    public class Song extends Activity implements OnClickListener Runnable       private SeekBar progress      private MediaPlayer mp                   private ServiceConnection onService   new ServiceConnection               public void onServiceConnected ComponentName className              IBinder rawBinder                  appService     MPService LocalBinder rawBinder  getService       service that handles the MediaPlayer               progress setVisibility SeekBar VISIBLE                 progress setProgress 0                 mp   appService getMP                  appService playSong title                 progress setMax mp getDuration                   new Thread Song this  start                          public void onServiceDisconnected ComponentName classname                  appService   null                          public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout song                            progress    SeekBar  findViewById R id progress                              public void run         int pos   0      int total   mp getDuration        while  mp    null  amp  amp  pos lt total            try               Thread sleep 1000               pos   appService getSongPosition              catch  InterruptedException e                return            catch  Exception e                return                    progress setProgress pos             This works fine  Now I want a timer counting the seconds minutes of the progress of the song  So I put a TextView in the layout  get it with findViewById   in onCreate    and put this in run   after progress setProgress pos    String time   String format   d  d               TimeUnit MILLISECONDS toMinutes pos               TimeUnit MILLISECONDS toSeconds pos               TimeUnit MINUTES toSeconds TimeUnit MILLISECONDS toMinutes                      pos                  currentTime setText time       currentTime    TextView  findViewById R id current time     But that last line gives me the exception      android view ViewRoot CalledFromWrongThreadException  Only the original thread that created a view hierarchy can touch its views    Yet I m doing basically the same thing here as I m doing with the SeekBar - creating the view in onCreate  then touching it in run   - and it doesn t give me this complaint

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This happened to my when I called for an UI change from a doInBackground from Asynctask instead of using onPostExecute   Dealing with the UI in onPostExecute solved my problem

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Solved   Just put this method in doInBackround Class    and pass the message  public void setProgressText final String progressText           Handler handler   new Handler Looper getMainLooper                   Override             public void handleMessage Message msg                       Any UI task  example                 progressDialog setMessage progressText                                    handler sendEmptyMessage 1

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You can use Handler to Delete View without disturbing the main UI Thread  Here is example code new Handler Looper getMainLooper    post new Runnable          Override     public void run                 do stuff like remove view etc           adapter remove selecteditem

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Use this code  and no need to runOnUiThread function   private Handler handler  private Runnable handlerTask   void StartTimer        handler   new Handler           handlerTask   new Runnable                  Override          public void run                     do something               textView setText  some text                handler postDelayed handlerTask  1000                            handlerTask run

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I was working with a class that did not contain a reference to the context  So it was not possible for me to use runOnUIThread    I used view post    and it was solved   timer scheduleAtFixedRate new TimerTask           Override     public void run             final int currentPosition   mediaPlayer getCurrentPosition            audioMessage seekBar setProgress currentPosition   1000           audioMessage tvPlayDuration post new Runnable                  Override             public void run                     audioMessage tvPlayDuration setText ChatDateTimeFormatter getDuration currentPosition                                       0  1000

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For the people struggling in Kotlin  it works like this   lateinit var runnable  Runnable   global variable   runOnUiThread     Lambda             runnable   Runnable                      do something here                  runDelayedHandler 5000                                   runnable run       you need to keep the handler outside the runnable body to work in kotlin  fun runDelayedHandler timeToWait  Long               Keep it running         val handler   Handler           handler postDelayed runnable  timeToWait

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In my case  the caller calls too many times in short time will get this error  I simply put elapsed time checking to do nothing if too short  e g  ignore if function get called less than 0 5 second       private long mLastClickTime   0       public boolean foo             if    SystemClock elapsedRealtime   - mLastClickTime   lt  500                return false                    mLastClickTime   SystemClock elapsedRealtime                   do ui update

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If you are within a fragment  then you also need to get the activity object as runOnUIThread is a method on the activity  An example in Kotlin with some surrounding context to make it clearer - this example is navigating from a camera fragment to a gallery fragment     Setup image capture listener which is triggered after photo has been taken imageCapture takePicture         outputOptions  cameraExecutor  object   ImageCapture OnImageSavedCallback               override fun onError exc  ImageCaptureException               Log e TAG   quot Photo capture failed    exc message  quot   exc                     override fun onImageSaved output  ImageCapture OutputFileResults                            val savedUri   output savedUri    Uri fromFile photoFile                          Log d TAG   quot Photo capture succeeded   savedUri quot                                  Do whatever work you do when image is saved                                       Now ask navigator to move to new tab - as this                updates UI do on the UI thread                         activity  runOnUiThread                     Navigation findNavController                          requireActivity    R id fragment container                    navigate CameraFragmentDirections                          actionCameraToGallery outputDirectory absolutePath

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Kotlin coroutines can make your code more concise and readable like this   MainScope   launch       withContext Dispatchers Default              TODO  Background processing                TODO  Update UI here        Or vice versa   GlobalScope launch         TODO  Background processing          withContext Dispatchers Main               TODO  Update UI here              TODO  Continue background processing

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I ve been in this situation  but I found a solution with the Handler Object   In my case  I want to update a ProgressDialog with the observer pattern  My view implements observer and overrides the update method   So  my main thread create the view and another thread call the update method that update the ProgressDialop and          Only the original thread that created a view hierarchy can touch its   views    It s possible to solve the problem with the Handler Object   Below  different parts of my code   public class ViewExecution extends Activity implements Observer       static final int PROGRESS DIALOG   0      ProgressDialog progressDialog      int currentNumber       public void onCreate Bundle savedInstanceState             currentNumber   0          final Button launchPolicyButton      Button  this findViewById R id launchButton            launchPolicyButton setOnClickListener new OnClickListener                   Override             public void onClick View v                    showDialog PROGRESS DIALOG                                         Override     protected Dialog onCreateDialog int id            switch id            case PROGRESS DIALOG              progressDialog   new ProgressDialog this               progressDialog setProgressStyle ProgressDialog STYLE HORIZONTAL               progressDialog setMessage  Loading                progressDialog setCancelable true               return progressDialog          default              return null                        Override     protected void onPrepareDialog int id  Dialog dialog            switch id            case PROGRESS DIALOG              progressDialog setProgress 0                            Define the Handler that receives messages from the thread and update the progress     final Handler handler   new Handler             public void handleMessage Message msg                int current   msg arg1              progressDialog setProgress current               if  current  gt   100                   removeDialog  PROGRESS DIALOG                                          The method called by the observer  the second thread       Override     public void update Observable obs  Object arg1             Message msg   handler obtainMessage            msg arg1     currentPluginNumber          handler sendMessage msg             This explanation can be found on this page  and you must read the  Example ProgressDialog with a second thread

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If you do not want to use runOnUiThread API  you can in fact implement AsynTask for the operations that takes some seconds to complete  But in that case  also after processing your work in doinBackground    you need to return the finished view in onPostExecute    The Android implementation allows only main UI thread to interact with views

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If you couldn t find a UIThread you can use this way    yourcurrentcontext mean  you need to parse Current Context   new Thread new Runnable             public void run                 while  true                     Activity  yourcurrentcontext  runOnUiThread new Runnable                         public void run                              Log d  Thread Log   I am from UI Thread                                                              try                       Thread sleep 1000                     catch  Exception ex                                                      start

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In my case  I have EditText in Adaptor  and it s already in the UI thread  However  when this Activity loads  it s crashes with this error   My solution is I need to remove  lt requestFocus   gt  out from EditText in XML

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In Kotlin simply put your code in runOnUiThread activity method  runOnUiThread         write your code here  for example     val task   Runnable               Handler   postDelayed                   var smzHtcList   mDb  smzHtcReferralDao    getAll                   tv showSmzHtcList text   smzHtcList toString                  10                 mDbWorkerThread postTask task

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When using AsyncTask Update the UI in onPostExecute method       Override     protected void onPostExecute String s          Update UI here

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I was facing a similar problem and none of the methods mentioned above worked for me  In the end  this did the trick for me   Device BeginInvokeOnMainThread      gt                myMethod              I found this gem here

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I had a similar issue  and my solution is ugly  but it works   void showCode         hideRegisterMessage       Hides view      final Handler handler   new Handler        handler postDelayed new Runnable              Override         public void run                 showRegisterMessage       Shows view                  3000      After 3 seconds

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I solved this by putting runOnUiThread  new Runnable       inside run     thread   new Thread             Override         public void run                 try                   synchronized  this                        wait 5000                        runOnUiThread new Runnable                              Override                         public void run                                 dbloadingInfo setVisibility View VISIBLE                               bar setVisibility View INVISIBLE                               loadingText setVisibility View INVISIBLE                                                                                      catch  InterruptedException e                    e printStackTrace                              Intent mainActivity   new Intent getApplicationContext   MainActivity class               startActivity mainActivity                           thread start

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For me the issue was that I was calling onProgressUpdate   explicitly from my code  This shouldn t be done  I called publishProgress   instead and that resolved the error

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Well  You can do it like this  https   developer android com reference android view View post java lang Runnable  A simple approach currentTime post new Runnable                 Override             public void run                      currentTime setText time                                 it also provides delay https   developer android com reference android view View postDelayed java lang Runnable  20long

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Usually  any action involving the user interface must be done in the main or UI thread  that is the one in which onCreate   and event handling are executed  One way to be sure of that is using runOnUiThread    another is using Handlers   ProgressBar setProgress   has a mechanism for which it will always execute on the main thread  so that s why it worked   See Painless Threading

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This is explicitly throwing an error  It says whichever thread created a view  only that can touch its views  It is because the created view is inside that thread s space  The view creation  GUI  happens in the UI  main  thread  So  you always use the UI thread to access those methods      In the above picture  the progress variable is inside the space of the UI thread  So  only the UI thread can access this variable  Here  you re accessing progress via new Thread    and that s why you got an error

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You have to move the portion of the background task that updates the UI onto the main thread  There is a simple piece of code for this   runOnUiThread new Runnable           Override     public void run                 Stuff that updates the UI              Documentation for Activity runOnUiThread   Just nest this inside the method that is running in the background  and then copy paste the code that implements any updates in the middle of the block  Include only the smallest amount of code possible  otherwise you start to defeat the purpose of the background thread

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Kotlin Answer    We have to use UI Thread for the job with true way  We can use UI Thread in Kotlin   runOnUiThread Runnable        TODO  Your job is here          canerkaseler

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I use Handler with Looper getMainLooper    It worked fine for me       Handler handler   new Handler Looper getMainLooper               Override         public void handleMessage Message msg                     Any UI task  example               textView setText  your text                         handler sendEmptyMessage 1

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RunOnUIThread didn t seem to work for me but the following ended up solving my issues                  MainThread InvokeOnMainThreadAsync async      gt                              this LoadApplication Startup Init this ConfigureServices                    var authenticationService   App ServiceProvider GetService lt AuthenticationService gt                    if  authenticationService AuthenticationResult    null                                      await authenticationService AuthenticateAsync AuthenticationUserFlow SignUpSignIn  CrossCurrentActivity Current Activity  ConfigureAwait false                                    Within the Startup Init method there is ReactiveUI routing and this needs to be invoked on the main thread  This Invoke method also accepts async await better than RunOnUIThread  So anywhere I need to invoke methods on the mainthread I use this  Please comment on this if anyone knows something I don t and can help me improve my application

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My solution to this   private void setText final TextView text final String value       runOnUiThread new Runnable              Override         public void run                 text setText value                         Call this method on a background thread

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This is the stack trace of mentioned exception          at android view ViewRootImpl checkThread ViewRootImpl java 6149          at android view ViewRootImpl requestLayout ViewRootImpl java 843          at android view View requestLayout View java 16474          at android view View requestLayout View java 16474          at android view View requestLayout View java 16474          at android view View requestLayout View java 16474          at android widget RelativeLayout requestLayout RelativeLayout java 352          at android view View requestLayout View java 16474          at android widget RelativeLayout requestLayout RelativeLayout java 352          at android view View setFlags View java 8938          at android view View setVisibility View java 6066    So if you go and dig then you come to know  void checkThread         if  mThread    Thread currentThread              throw new CalledFromWrongThreadException                   Only the original thread that created a view hierarchy can touch its views               Where mThread is initialize in constructor like below  mThread   Thread currentThread      All I mean to say that when we created particular view we created it on UI Thread and later try to modifying in a Worker Thread   We can verify it via below code snippet  Thread currentThread   getName     when we inflate layout and later where you are getting exception

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I see that you have accepted  providence s answer  Just in case  you can also use the handler too  First  do the int fields       private static final int SHOW LOG   1      private static final int HIDE LOG   0    Next  make a handler instance as a field         TODO             Handler                  SuppressLint  HandlerLeak       protected Handler handler   new Handler                  Override         public void handleMessage Message msg                           Put code here                    Set a switch statement to toggle it on or off              switch msg what                            case SHOW LOG                                ads setVisibility View VISIBLE                   break                            case HIDE LOG                                ads setVisibility View GONE                   break                                                 Make a method     TODO             Callbacks              Override public void showHandler boolean show        handler sendEmptyMessage show   SHOW LOG   HIDE LOG       Finally  put this at onCreate   method   showHandler true

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If you simply want to invalidate  call repaint redraw function  from your non UI Thread  use postInvalidate    myView postInvalidate      This will post an invalidate request on the UI-thread   For more information   what-does-postinvalidate-do

[android] Android "Only the original thread that created a view hierarchy can touch its views."

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