title: Stop handler.postDelayed()
body: <p>I call multiple Handlers by new Handler().postDelayed(new Runnable().....
  How can I stop it when I click on back? </p>
  
  <pre><code>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);
      }   
  }
  </code></pre>
  
  <p>I have the problem that my Handlers haven't a name like "myHandler". How can I handle it?</p>
  
  <p>Thanks for help!</p>
  
  <p>Now I got these error:</p>
  
  <pre><code>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)
  </code></pre>