AsyncTask crashes in doInBackground()

Question

You see I'm trying to load some data on this adapter, but I can not make a AsyncTask to show a progress dialog so.

This is the complete code of the program it gives me error. I completely revised so do not edit any of the UI.

public class MatchNowGames extends Activity {
Games games = new Games();
Iterator iterador;
private ProgressDialog dialog;
GamesArrayAdapter adapter;
ListView lv;
public void onCreate(Bundle savedInstanceState) {       
    super.onCreate(savedInstanceState);        
    // INCIO PROGRAMA        
    setContentView(R.layout.games_list);
    lv = (ListView) this.findViewById(R.id.gamesLV);
    // Creamos el thread
    dialog = new ProgressDialog(this);
    dialog.setMessage("Cargando...");
    dialog.setTitle("Progreso");
    dialog.setCancelable(false);

    // INIT VARIABLES
    new CargandoJuegos().execute(); 
    adapter = new GamesArrayAdapter(App.context().getApplicationContext(), R.layout.games_list, games.getGames());      


}
private class CargandoJuegos extends AsyncTask<Void, Void, Void>{
    protected void onPreExecute() {
            dialog.show();
            }

     protected Void doInBackground(Void... urls) {
         // AÑADIMOS LOS JUEGOS
        try {
            games.addGames(MatchNow.serverGames);
            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {

                e.printStackTrace();
            }
        } catch (JSONException e) {}
        return null;
     }
     protected void onPostExecute(Void unused) {
         dialog.dismiss();
         lv.setAdapter(adapter);
     }


  }

}

And this is what we should do while displaying the progressdialog:

// Start progress dialog
    try {
            games.addGames(MatchNow.serverGames);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    // Finish progress dialog
    GamesArrayAdapter adapter = new GamesArrayAdapter(App.context().getApplicationContext(), R.layout.games_list, games.getGames());
    ListView lv = (ListView) this.findViewById(R.id.gamesLV);
    lv.setAdapter(adapter);

Thank you very much in advance =)

The logcat:

09-07 02:18:07.916: D/AndroidRuntime(890): Shutting down VM
09-07 02:18:07.916: W/dalvikvm(890): threadid=3: thread exiting with uncaught exception (group=0x4001b188)
09-07 02:18:07.926: E/AndroidRuntime(890): Uncaught handler: thread main exiting due to uncaught exception
09-07 02:18:07.936: E/AndroidRuntime(890): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{match.now.play/match.now.play.MatchNowGames}: java.lang.NullPointerException
09-07 02:18:07.936: E/AndroidRuntime(890):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2417)
09-07 02:18:07.936: E/AndroidRuntime(890):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
09-07 02:18:07.936: E/AndroidRuntime(890):  at android.app.ActivityThread.access$2200(ActivityThread.java:119)
09-07 02:18:07.936: E/AndroidRuntime(890):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
09-07 02:18:07.936: E/AndroidRuntime(890):  at android.os.Handler.dispatchMessage(Handler.java:99)
09-07 02:18:07.936: E/AndroidRuntime(890):  at android.os.Looper.loop(Looper.java:123)
09-07 02:18:07.936: E/AndroidRuntime(890):  at android.app.ActivityThread.main(ActivityThread.java:4363)
09-07 02:18:07.936: E/AndroidRuntime(890):  at java.lang.reflect.Method.invokeNative(Native Method)
09-07 02:18:07.936: E/AndroidRuntime(890):  at java.lang.reflect.Method.invoke(Method.java:521)
09-07 02:18:07.936: E/AndroidRuntime(890):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
09-07 02:18:07.936: E/AndroidRuntime(890):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
09-07 02:18:07.936: E/AndroidRuntime(890):  at dalvik.system.NativeStart.main(Native Method)
09-07 02:18:07.936: E/AndroidRuntime(890): Caused by: java.lang.NullPointerException
09-07 02:18:07.936: E/AndroidRuntime(890):  at android.app.Activity.findViewById(Activity.java:1612)
09-07 02:18:07.936: E/AndroidRuntime(890):  at match.now.play.MatchNowGames.<init>(MatchNowGames.java:40)

I solved the problem of the line 1612, was an oversight. Logcat really gives problems. Sorry for the inconvenience.

    09-07 02:18:07.936: E/AndroidRuntime(890):  at java.lang.Class.newInstanceImpl(Native Method)
    09-07 02:18:07.936: E/AndroidRuntime(890):  at java.lang.Class.newInstance(Class.java:1479)
    09-07 02:18:07.936: E/AndroidRuntime(890):  at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
    09-07 02:18:07.936: E/AndroidRuntime(890):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2409)
    09-07 02:18:07.936: E/AndroidRuntime(890):  ... 11 more


09-07 02:34:31.486: D/dalvikvm(930): GC freed 404 objects / 23688 bytes in 60ms
09-07 02:34:32.976: I/global(930): Default buffer size used in BufferedReader constructor. It would be better to be explicit if an 8k-char buffer is required.
09-07 02:34:32.986: I/System.out(930): {"games":[{"id":"1","image":"http:\/\/cibermaniacos.com\/images\/stories\/call_of_duty_modern_warfare_3_desvelado_dest01.jpg","name":"Call Of Duty MW3","descrip":"","modes":[{"id":"1","name":"1vs1","mode_icon":"none"},{"id":"2","name":"2vs2","mode_icon":"none"}],"console":"PS3,XBOX"},{"id":"2","image":"http:\/\/www.hry-na-mobil.eu\/data\/ikonky\/hry-na-mobil-eu\/46801\/call-of-duty-world-at-war-codww-1000x1000jpg-12.png","name":"Prueba","descrip":"afafs","modes":[{"id":"1","name":"1vs1","mode_icon":"none"},{"id":"2","name":"2vs2","mode_icon":"none"}],"console":"steam,PS3"},{"id":"4","image":"http:\/\/cibermaniacos.com\/images\/stories\/call_of_duty_modern_warfare_3_desvelado_dest01.jpg","name":"Call Of Duty MW2","descrip":"AWDAWD","modes":[{"id":"1","name":"1vs1","mode_icon":"none"},{"id":"2","name":"2vs2","mode_icon":"none"}],"console":"steam,PS3"}]}                  
09-07 02:34:33.036: I/System.out(930): Call Of Duty MW2
09-07 02:34:33.046: I/System.out(930): Call Of Duty MW3
09-07 02:34:33.068: W/dalvikvm(930): threadid=15: thread exiting with uncaught exception (group=0x4001b188)
09-07 02:34:33.068: E/AndroidRuntime(930): Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception
09-07 02:34:33.086: E/AndroidRuntime(930): java.lang.RuntimeException: An error occured while executing doInBackground()
09-07 02:34:33.086: E/AndroidRuntime(930):  at android.os.AsyncTask$3.done(AsyncTask.java:200)
09-07 02:34:33.086: E/AndroidRuntime(930):  at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
09-07 02:34:33.086: E/AndroidRuntime(930):  at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
09-07 02:34:33.086: E/AndroidRuntime(930):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
09-07 02:34:33.086: E/AndroidRuntime(930):  at java.util.concurrent.FutureTask.run(FutureTask.java:137)
09-07 02:34:33.086: E/AndroidRuntime(930):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
09-07 02:34:33.086: E/AndroidRuntime(930):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
09-07 02:34:33.086: E/AndroidRuntime(930):  at java.lang.Thread.run(Thread.java:1096)
09-07 02:34:33.086: E/AndroidRuntime(930): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
09-07 02:34:33.086: E/AndroidRuntime(930):  at android.os.Handler.<init>(Handler.java:121)
09-07 02:34:33.086: E/AndroidRuntime(930):  at android.app.Activity.<init>(Activity.java:673)
09-07 02:34:33.086: E/AndroidRuntime(930):  at match.now.play.functions.Game.<init>(Game.java:52)
09-07 02:34:33.086: E/AndroidRuntime(930):  at match.now.play.functions.Games.addGames(Games.java:58)
09-07 02:34:33.086: E/AndroidRuntime(930):  at match.now.play.MatchNowGames$CargandoJuegos.doInBackground(MatchNowGames.java:67)
09-07 02:34:33.086: E/AndroidRuntime(930):  at match.now.play.MatchNowGames$CargandoJuegos.doInBackground(MatchNowGames.java:1)
09-07 02:34:33.086: E/AndroidRuntime(930):  at android.os.AsyncTask$2.call(AsyncTask.java:185)
09-07 02:34:33.086: E/AndroidRuntime(930):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
09-07 02:34:33.086: E/AndroidRuntime(930):  ... 4 more

Answer 1

It looks like the only real code in your doInBackground() method is this:

  games.addGames(MatchNow.serverGames);

But, you don't show us what happens in the addGames() method. Are you attempting to do something with the UI in that method? If so, that's going to be a problem.

doInBackground() is not for making any UI calls directly. If the UI needs to be updated during background processing, you would often call publishProgress() from within doInBackground() to trigger onProgressUpdate(). You are allowed to make UI calls from within onProgressUpdate().

Answer 2

You can reference this: Can't create handler inside thread that has not called Looper.prepare() inside AsyncTask for ProgressDialog