Android onClick blocking onFling

问题:

I have an Activity that implements a Gesture Detector to catch the user fling input for navigation to other screens. That was working fine - but - I recently updated a class that derives from BaseActivity to add an onClick function and now that click event seems to block the onFling from being hit. The onClick is tied to a TextView area (in a LinearLayout) I have on my screen. The resultsClick method is wired to the TextView using its onClick property in the XML layout.

I've tried changing the return values in onSingleTapUp and onDown without luck. I've also tried adding log statements to all the functions below as well. None of them fire when I fling in the TextView area but they do on other areas of the screen.

Maybe I am using the wrong search terms, but I couldn't seem to find an example that addressed this - yet I'm sure this problem has been solved before.

public class DerivedActivity extends BaseActivity
{
   ...
   /**
    * resultsClick - The user clicked on the Results area
    * @param v
    */
   public void resultsClick(View v)
   {
      try
      {
         Log.i(this.toString(), "resultsClick");
         startActivity(new Intent(this, Results_TabHost.class ));
      }
      catch (Exception e)
      {
         Log.e(this.toString(), "Exception" + e.toString());
      }

   }// end resultsClick
   ...
}

Here is the base class that implements the GestureListener code

public class BaseActivity extends    ActivityGroup 
                          implements OnGestureListener
{
   ...
   private static final int SWIPE_MIN_DISTANCE = 120;
   private static final int SWIPE_MAX_OFF_PATH = 250;
   private static final int SWIPE_THRESHOLD_VELOCITY = 200;

   public boolean onFling(MotionEvent e1, 
                          MotionEvent e2, 
                          float velocityX, 
                          float velocityY)
   {
      try
      {
         Log.i(this.toString(), "onFling");

         // jump right out if not a swipe/fling
         if (Math.abs( e1.getY() - e2.getY() ) > SWIPE_MAX_OFF_PATH)
         {
            return false;
         }

         // right to left swipe
         if (e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && 
             Math.abs(velocityX)   > SWIPE_THRESHOLD_VELOCITY )
         {
            Log.i(this.toString(), "fling left");
            rightArrowClick(null);

         }
         else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && 
                  Math.abs(velocityX)   > SWIPE_THRESHOLD_VELOCITY )
         {
            Log.i(this.toString(), "fling right");
            leftArrowClick(null);
         }
      }
      catch (Exception e)
      {
         Log.e(this.toString(), "Exception" + e.toString());
      }

      return true;

   }// end onFling

   // These next methods we are required to have - even if unused - 
   // in order for the Gesture Handling to work

   @Override
   public boolean onTouchEvent(MotionEvent motionEvent)
   {
      return this.gestureDetector.onTouchEvent(motionEvent);
   }

   @Override
   public void onLongPress(MotionEvent e)
   {
      // Intentionally not handling - must be overridden by listener class
   }

   @Override
   public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY)
   {
      // Intentionally not handling - must be overridden by listener class
      // Intentionally returning true - per code examples
      return true;
   }

   @Override
   public void onShowPress(MotionEvent e)
   {
      // Intentionally not handling - must be overridden by listener class
   }

   @Override
   public boolean onSingleTapUp(MotionEvent e)
   {
      // Intentionally not handling - must be overridden by listener class
      // Intentionally returning true - per code examples
      return true;
   }

   @Override
   public boolean onDown(MotionEvent e)
   {
      // Intentionally not handling - must be overridden by listener class
      // Intentionally returning true - per code examples
      return true;
   }
...
}

回答1:

Your implementation of onTouchEvent is incorrect. You simply return the value of the gestureDector's result.

If your gesture detector doesn't detect any gestures however, you tell the caller "I didn't have anything to do here" and the touch event will never be sent down to the Activity's children.

You need to call super.onTouchEvent() if your gesture detector didn't handle the event.

@Override
public boolean onTouchEvent(MotionEvent motionEvent)
{
  if(this.gestureDetector.onTouchEvent(motionEvent))
  {
      return true;
  }
  //no gesture detected, let Activity handle touch event
  return super.onTouchEvent(motionEvent);
}

回答2:

Please give attention to this function:

@Override
   public boolean onDown(MotionEvent e)
   {
      // Intentionally not handling - must be overridden by listener class
      // Intentionally returning true - per code examples
      return true;
   }

Please change the return value to false.

回答3:

You can just return false, when nothing is done by your code...It will let the motion event system manage everything on it's own. Return true, when you wanna stop the event to be dispatched to other childs view..

回答4:

imageView.setOnTouchListener(new View.OnTouchListener() {
                                        @Override
                                        public boolean onTouch(View v, MotionEvent event) {
                                            if (mDetector.onTouchEvent(event)) {
                                                return true;
                                            }

                                            return HomeScreen.super.onTouchEvent(event);
                                        }
                                    });

public class JGestureDetector extends GestureDetector.SimpleOnGestureListener {
        private static final int SWIPE_MIN_DISTANCE = 120;
        private static final int SWIPE_MAX_OFF_PATH = 250;
        private static final int SWIPE_THRESHOLD_VELOCITY = 200;

        private SwipeHandler handler;

        public SwipeHandler getHandler() {
            return handler;
        }

        public void setHandler(SwipeHandler handler) {
            this.handler = handler;
        }

        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {

            if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH)
                return false;

            // left
            if (e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE
                    && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {

                if (handler != null) {
                    handler.onLeft();

                    return true;
                }

                // right
            } else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE
                    && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {

                if (handler != null) {
                    handler.onRight();

                    return true;
                }
            }

            return super.onFling(e1, e2, velocityX, velocityY);
        }

        public static abstract class SwipeHandler {
            public void onLeft() {
            }

            public void onRight() {
            }
        }
    }