Stop handler.postDelayed()

Question

I call multiple Handlers by new Handler().postDelayed(new Runnable()..... How can I stop it when I click on back?

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);
    }   
}

I have the problem that my Handlers haven't a name like "myHandler". How can I handle it?

Thanks for help!

Now I got these error:

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)

Answer 1

You can use:

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

Or you can use:

 handler.removeCallbacksAndMessages(null);

Docs

public final void removeCallbacksAndMessages (Object token)

Added in API level 1 Remove any pending posts of callbacks and sent messages whose obj is token. If token is null, all callbacks and messages will be removed.

Or you could also do like the following:

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

Then:

handler.removeCallbacks(myRunnable);

Docs

public final void removeCallbacks (Runnable r)

Added in API level 1 Remove any pending posts of Runnable r that are in the message queue.

public final void removeCallbacks (Runnable r, Object token)

Edit:

Change this:

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

To:

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

Because you have the below. Declared before onCreate but you re-declared and then initialized it in onClick leading to a NPE.

Handler handler; // declared before onCreate
Runnable myRunnable;