Pare handler.postDelayed ()

Eu chamo vários Handlers por new Handler (). PostDelayed (new Runnable () ..... Como posso interromper quando clico em voltar?

public class MyActivity extends AppCompatActivity implements OnClickListener {

    private Button btn;
    private Handler handler;
    private Runnable myRunnable;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState); 
        btn = (Button) findViewById(R.id.trainingsstart);
        btn.setOnClickListener(this);   
    }

    @Override
    public void onClick(View v) {
        Handler handler =  new Handler();
        Runnable myRunnable = new Runnable() {
            public void run() {
                // Things to be done
            }
        };

        handler.postDelayed(myRunnable, 3000);
    }

    @Override 
    public void onBackPressed() { 
        super.onBackPressed();
        handler.removeCallbacks(myRunnable);
    }   
}

Tenho o problema de meus Handlers não terem um nome como "myHandler". Como posso lidar com isso?

Obrigado pela ajuda!

Agora recebo este erro:

03-28 17:47:03.662: E/AndroidRuntime(1961): FATAL EXCEPTION: main
03-28 17:47:03.662: E/AndroidRuntime(1961): java.lang.NullPointerException
03-28 17:47:03.662: E/AndroidRuntime(1961):     at de.basti12354.tage.uebungen.Tag1.onBackPressed(Tag1.java:120)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.app.Activity.onKeyUp(Activity.java:2159)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.KeyEvent.dispatch(KeyEvent.java:2647)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.app.Activity.dispatchKeyEvent(Activity.java:2389)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1860)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent(ViewRootImpl.java:3791)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3774)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3429)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3398)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3483)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3406)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3540)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3429)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3398)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3406)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3429)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3398)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3516)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.ViewRootImpl$ImeInputStage.onFinishedInputEvent(ViewRootImpl.java:3666)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.inputmethod.InputMethodManager$PendingEvent.run(InputMethodManager.java:1982)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.inputmethod.InputMethodManager.invokeFinishedInputEventCallback(InputMethodManager.java:1698)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.inputmethod.InputMethodManager.finishedInputEvent(InputMethodManager.java:1689)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.inputmethod.InputMethodManager$ImeInputEventSender.onInputEventFinished(InputMethodManager.java:1959)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.view.InputEventSender.dispatchInputEventFinished(InputEventSender.java:141)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.os.MessageQueue.nativePollOnce(Native Method)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.os.MessageQueue.next(MessageQueue.java:132)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.os.Looper.loop(Looper.java:124)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at android.app.ActivityThread.main(ActivityThread.java:5103)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at java.lang.reflect.Method.invokeNative(Native Method)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at java.lang.reflect.Method.invoke(Method.java:525)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
03-28 17:47:03.662: E/AndroidRuntime(1961):     at dalvik.system.NativeStart.main(Native Method)

Você pode usar:

 Handler handler = new Handler()
 handler.postDelayed(new Runnable())

Ou você pode usar:

 handler.removeCallbacksAndMessages(null);

Docs

public final void removeCallbacksAndMessages (token de objeto)

Adicionado no nível 1 da API. Remova quaisquer postagens pendentes de retornos de chamada e mensagens enviadas cujo obj seja um token. Se o token for nulo, todos os retornos de chamada e mensagens serão removidos.

Ou você também pode fazer o seguinte:

Handler handler =  new Handler()
Runnable myRunnable = new Runnable() {
public void run() {
    // do something
}
};
handler.postDelayed(myRunnable,zeit_dauer2);

Então:

handler.removeCallbacks(myRunnable);

Docs

public final void removeCallbacks (Runnable r)

Adicionado no nível 1 da API. Remova todas as postagens pendentes do Runnable r que estão na fila de mensagens.

public final void removeCallbacks (Runnable r, token de objeto)

Editar:

Mude isso:

@Override
public void onClick(View v) {
    Handler handler =  new Handler();
    Runnable myRunnable = new Runnable() {

Para:

@Override
public void onClick(View v) {
    handler = new Handler();
    myRunnable = new Runnable() { /* ... */}

Porque você tem o abaixo. Declarado antes, onCreatemas você o declarou novamente e, em seguida, o inicializou onClicklevando a um NPE.

Handler handler; // declared before onCreate
Runnable myRunnable;

Você pode definir um booleano e alterá-lo para falso quando quiser parar o manipulador. Como isso..

boolean stop = false;

handler.postDelayed(new Runnable() {
    @Override
    public void run() {

        //do your work here..

        if (!stop) {
            handler.postDelayed(this, delay);
        }
    }
}, delay);

isto pode ser antigo, mas para quem procura uma resposta pode usar isto ...

public void stopHandler() {
   handler.removeMessages(0);
}

Felicidades

  Boolean condition=false;  //Instance variable declaration.

 //-----------------Inside oncreate--------------------------------------------------- 
  start =(Button)findViewById(R.id.id_start);
        start.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                starthandler();

                if(condition=true)
                {
                    condition=false;
                }


            }
        });

        stop=(Button) findViewById(R.id.id_stoplocatingsmartplug);

        stop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                stophandler();

            }
        });


    }

//-----------------Inside oncreate---------------------------------------------------

 public void starthandler()
    {

        handler = new Handler();
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {


                if(!condition)
                {
                    //Do something after 100ms 


                }

            }
        }, 5000);

    }


    public void stophandler()
    {
        condition=true;
    }