Can t create handler inside thread which has not called Looper prepare

Question

I have an Activity  and in that I have a class   text new Dynamictext       text setText  txt      in my DynamicText java I have this code   public void setText String text        this text text      new asyncCreateText   execute          this createText text        private Handler handler   new Handler     private class asyncCreateText extends AsyncTask lt Void  Void  Void gt          Override     protected Void doInBackground Void    unused            return null              Override     protected void onPostExecute Void unused               I get       ERROR AndroidRuntime 5176   Caused by  java lang RuntimeException  Can t create handler inside thread that has not called Looper prepare     How can I handle this error   ERROR AndroidRuntime 5370   java lang ExceptionInInitializerError ERROR AndroidRuntime 5370       at com l start DynamicText setText DynamicText java 125  ERROR AndroidRuntime 5370       at com l start OpenGLRenderer initfonts OpenGLRenderer java 168  ERROR AndroidRuntime 5370       at com l start OpenGLRenderer init OpenGLRenderer java 119  ERROR AndroidRuntime 5370       at com l start OpenGLRenderer onSurfaceChanged OpenGLRenderer java 90  ERROR AndroidRuntime 5370       at android opengl GLSurfaceView GLThread guardedRun GLSurfaceView java 1120  ERROR AndroidRuntime 5370       at android opengl GLSurfaceView GLThread run GLSurfaceView java 975   ERROR AndroidRuntime 5370   Caused by  java lang RuntimeException       Can t create handler inside thread that has not called Looper prepare   ERROR AndroidRuntime 5370       at android os Handler  lt init gt  Handler java 121  ERROR AndroidRuntime 5370       at android os AsyncTask InternalHandler  lt init gt  AsyncTask java 421  ERROR AndroidRuntime 5370       at android os AsyncTask InternalHandler  lt init gt  AsyncTask java 421  ERROR AndroidRuntime 5370       at android os AsyncTask  lt clinit gt  AsyncTask java 152  ERROR AndroidRuntime 5370           6 more

User · Answer

Activity runOnUiThread   does not work for me  I worked around this issue by creating a regular thread this way   public class PullTasksThread extends Thread      public void run            Log d Prefs TAG   Thread run                and calling it from the GL update this way   new PullTasksThread   start

User · Answer

Try this      Handler mHandler   new Handler Looper getMainLooper                             mHandler post new Runnable                                  Override                             public void run        your code here that talks with the UI level widgets  try to access the UI    elements from this block because this piece of snippet will run in the UI MainThread

User · Answer

All the answers above are correct  but I think this is the easiest example possible   public class ExampleActivity extends Activity       private Handler handler      private ProgressBar progress        Override     public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout main           progress    ProgressBar  findViewById R id progressBar1           handler   new Handler               public void clickAButton View view               Do something that takes a while         Runnable runnable   new Runnable                  Override             public void run                     handler post new Runnable        This thread runs in the UI                      Override                     public void run                             progress setProgress  anything       Update the UI                                                                            new Thread runnable  start              What this does is update a progress bar in the UI thread from a completely different thread passed through the post   method of the handler declared in the activity   Hope it helps

User · Answer

You create handler in background thread this way  private void createHandler             Thread thread   new Thread               public void run                    Looper prepare                    final Handler handler   new Handler                   handler postDelayed new Runnable                          Override                     public void run                               Do Work                         handler removeCallbacks this                           Looper myLooper   quit                                            2000                    Looper loop                                     thread start

User · Answer

The error is self-explanatory    doInBackground   runs on a background thread which  since it is not intended to loop  is not connected to a Looper   You most likely don t want to directly instantiate a Handler at all    whatever data your doInBackground   implementation returns will be passed to onPostExecute   which runs on the UI thread      mActivity   ThisActivity this        mActivity runOnUiThread new Runnable          public void run          new asyncCreateText   execute                    ADDED FOLLOWING THE STACKTRACE APPEARING IN QUESTION   Looks like you re trying to start an AsyncTask from a GL rendering thread    don t do that cos they won t ever Looper loop   either  AsyncTasks are really designed to be run from the UI thread only   The least disruptive fix would probably be to call Activity runOnUiThread   with a Runnable that kicks off your AsyncTask

User · Answer

Try running you asyntask from the UI thread  I faced this issue when I wasn t doing the same

[android] Can't create handler inside thread which has not called Looper.prepare()

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