title: Android debugging: java.lang.ArrayIndexOutOfBoundsException
body: <p>I received this stack trace today and am having a problem finding the problem.</p>
  
  <pre><code>java.lang.ArrayIndexOutOfBoundsException
  at android.view.MotionEvent.getY(MotionEvent.java:792)
  at android.widget.ScrollView.onTouchEvent(ScrollView.java:509)
  at android.view.View.dispatchTouchEvent(View.java:3766)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:897)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:936)
  at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1720)
  at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1117)
  at android.app.Activity.dispatchTouchEvent(Activity.java:2086)
  at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1704)
  at android.view.ViewRoot.handleMessage(ViewRoot.java:1794)
  at android.os.Handler.dispatchMessage(Handler.java:99)
  at android.os.Looper.loop(Looper.java:143)
  at android.app.ActivityThread.main(ActivityThread.java:4701)
  at java.lang.reflect.Method.invokeNative(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:521)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
  at dalvik.system.NativeStart.main(Native Method)
  </code></pre>
  
  <p>It looks to me that the problem is in this piece of code. But it's so small and simple, I'm just not seeing it. Any ideas?</p>
  
  <pre><code>@Override 
       public boolean dispatchTouchEvent(MotionEvent me){ 
         this.detector.onTouchEvent(me);
         return super.dispatchTouchEvent(me); 
       }
  
       public void onSwipe(int direction) {
        String str = "";
  
        switch (direction) {
  
        case SimpleGestureFilter.SWIPE_RIGHT : wv.loadUrl("javascript:slideRight()");
                                                       break;
        case SimpleGestureFilter.SWIPE_LEFT :  wv.loadUrl("javascript:slideLeft()");
                                                       break;
        case SimpleGestureFilter.SWIPE_DOWN :  wv.loadUrl("javascript:slideDown()");
                                                       break;
        case SimpleGestureFilter.SWIPE_UP :    wv.loadUrl("javascript:slideUp()");
                                                       break;
  
        } 
  
       }
  </code></pre>
  
  <p>Could it just be a bug that is native to android?</p>
  
  <p>Edit:
  I'm using this for this.detector.onTouchEvent(me); to listen for swipe events. </p>
  
  <pre><code>public class SimpleGestureFilter extends SimpleOnGestureListener{
  
       public final static int SWIPE_UP    = 1;
       public final static int SWIPE_DOWN  = 2;
       public final static int SWIPE_LEFT  = 3;
       public final static int SWIPE_RIGHT = 4;
  
       public final static int MODE_TRANSPARENT = 0;
       public final static int MODE_SOLID       = 1;
       public final static int MODE_DYNAMIC     = 2;
  
       private final static int ACTION_FAKE = -13; //just an unlikely number
       private int swipe_Min_Distance = 200;
       private int swipe_Max_Distance = 800;
       private int swipe_Min_Velocity = 100;
  
       private int mode = MODE_DYNAMIC;
       private boolean running = true;
       private boolean tapIndicator = false;
  
       private Activity context;
       private GestureDetector detector;
       private SimpleGestureListener listener;
  
  
       public SimpleGestureFilter(Activity context,SimpleGestureListener sgl) {
  
        this.context = context;
        this.detector = new GestureDetector(context, this);
        this.listener = sgl; 
       }
  
       public void onTouchEvent(MotionEvent event){
  
         if(!this.running)
        return;  
  
         boolean result = this.detector.onTouchEvent(event); 
  
         if(this.mode == MODE_SOLID)
          event.setAction(MotionEvent.ACTION_CANCEL);
         else if (this.mode == MODE_DYNAMIC) {
  
           if(event.getAction() == ACTION_FAKE) 
             event.setAction(MotionEvent.ACTION_UP);
           else if (result)
             event.setAction(MotionEvent.ACTION_CANCEL); 
           else if(this.tapIndicator){
            event.setAction(MotionEvent.ACTION_DOWN);
            this.tapIndicator = false;
           }
  
         }
         //else just do nothing, it's Transparent
       }
  
       public void setMode(int m){
        this.mode = m;
       }
  
       public int getMode(){
        return this.mode;
       }
  
       public void setEnabled(boolean status){
        this.running = status;
       }
  
       public void setSwipeMaxDistance(int distance){
        this.swipe_Max_Distance = distance;
       }
  
       public void setSwipeMinDistance(int distance){
        this.swipe_Min_Distance = distance;
       }
  
       public void setSwipeMinVelocity(int distance){
        this.swipe_Min_Velocity = distance;
       }
  
       public int getSwipeMaxDistance(){
        return this.swipe_Max_Distance;
       }
  
       public int getSwipeMinDistance(){
        return this.swipe_Min_Distance;
       }
  
       public int getSwipeMinVelocity(){
        return this.swipe_Min_Velocity;
       }
  
  
       @Override
       public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
         float velocityY) {
  
        final float xDistance = Math.abs(e1.getX() - e2.getX());
        final float yDistance = Math.abs(e1.getY() - e2.getY());
  
        if(xDistance &gt; this.swipe_Max_Distance || yDistance &gt; this.swipe_Max_Distance)
         return false;
  
        velocityX = Math.abs(velocityX);
        velocityY = Math.abs(velocityY);
              boolean result = false;
  
        if(velocityX &gt; this.swipe_Min_Velocity &amp;&amp; xDistance &gt; this.swipe_Min_Distance){
         if(e1.getX() &gt; e2.getX()) // right to left
          this.listener.onSwipe(SWIPE_LEFT);
         else
          this.listener.onSwipe(SWIPE_RIGHT);
  
         result = true;
        }
        else if(velocityY &gt; this.swipe_Min_Velocity &amp;&amp; yDistance &gt; this.swipe_Min_Distance){
         if(e1.getY() &gt; e2.getY()) // bottom to up 
          this.listener.onSwipe(SWIPE_UP);
         else
          this.listener.onSwipe(SWIPE_DOWN);
  
         result = true;
        }
  
         return result;
       }
  
       @Override
       public boolean onSingleTapUp(MotionEvent e) {
        this.tapIndicator = true;
        return false;
       }
  
       @Override
       public boolean onDoubleTap(MotionEvent arg0) {
        this.listener.onDoubleTap();;
        return true;
       }
  
       @Override
       public boolean onDoubleTapEvent(MotionEvent arg0) {
        return true;
       }
  
       @Override
       public boolean onSingleTapConfirmed(MotionEvent arg0) {
  
        if(this.mode == MODE_DYNAMIC){        // we owe an ACTION_UP, so we fake an       
           arg0.setAction(ACTION_FAKE);      //action which will be converted to an ACTION_UP later.                                    
           this.context.dispatchTouchEvent(arg0);  
        }   
  
        return false;
       }
  
  
          static interface SimpleGestureListener{
           void onSwipe(int direction);
           void onDoubleTap();
       }
  
      }
  </code></pre>