Differentiate between zooming and moving a Google Map?

Question

My goal is for an ImageView to appear if the camera is moving, but only when the user is moving the map, not when zooming in or out. How can i differentiate between the two?

I tried using the OnCameraMove and OnCameraIdle Listeners but the zoom is registered as a move, and the OnCameraMoveStartedListener only can register if the move was user related or not.

Also when zooming i need the zoom to be centered. Hope this makes sense.

Answer i was looking for can be found [here](https://stackoverflow.com/questions/47961908/centered-zooming-a-google-map-through-a-wrapper). — Marko Grbic, Dec 26 '17 at 22:08

mhdtouban · Answer 1 · 2017-12-25T15:21:07.003

Unforuntilly there is no way to be able to distinguish between zooming and moving the map straight away. However, there is a hacky way to be able to accomplish what you are looking for. You can create a wrapper class which extends a FrameLayout. Inside the wrapper override the dispatchTouchEvent method and implemented the logic for handling zoom/drag or whatever needed to distinguish between user interaction. For example, to detect zoom we simply want to make sure that there are 2 fingers, they have moved beyond a certain threshold and that they are moving in opposite directions. To do so we have to override dispatchTouchEvent

switch (ev.getAction()) {
case MotionEvent.ACTION_MOVE:
boolean isPrimMoving = isScrollGesture(event, 0, mPrimStartTouchEventX,
mPrimStartTouchEventY);
boolean isSecMoving = (mPtrCount > 1 && isScrollGesture(event, 1,
mSecStartTouchEventX, mSecStartTouchEventY));
if (mPtrCount > 1 && isPinchGesture(event)) {
Log.d("TAG", "PINCH! OUCH!");
} else if (isPrimMoving || isSecMoving) {
    // A 1 finger or 2 finger scroll.
    if (isPrimMoving && isSecMoving) {
      Log.d("TAG", "Two finger scroll");
    } else {
      Log.d("TAG", "One finger scroll");
    }}
break;

This class will declare an interface which will update the activity based on the user interaction.Then, Initiate this class inside your fragment

mTouchView = new myWrapperClass(getActivity());
mTouchView.addView(mOriginalContentView);
return mTouchView;

You need to override onTouch

private float mPrimStartTouchEventX = -1;
private float mPrimStartTouchEventY = -1;
private float mSecStartTouchEventX = -1;
private float mSecStartTouchEventY = -1;
private float mPrimSecStartTouchDistance = 0;
...
@Override
public boolean onTouch(View v, MotionEvent event) {
  int action = (event.getAction() & MotionEvent.ACTION_MASK);

  switch (action) {
    case MotionEvent.ACTION_POINTER_DOWN:
    case MotionEvent.ACTION_DOWN:
      mPtrCount++;
      if (mPtrCount == 1) {
        mPrimStartTouchEventX = event.getX(0);
        mPrimStartTouchEventY = event.getY(0);
        Log.d("TAG", String.format("POINTER ONE X = %.5f, Y = %.5f", mPrimStartTouchEventX, mPrimStartTouchEventY));
      }
      if (mPtrCount == 2) {
        // Starting distance between fingers
        mSecStartTouchEventX = event.getX(1);
        mSecStartTouchEventY = event.getY(1);
        mPrimSecStartTouchDistance = distance(event, 0, 1);
        Log.d("TAG", String.format("POINTER TWO X = %.5f, Y = %.5f", mSecStartTouchEventX, mSecStartTouchEventY));
      }

      break;
    case MotionEvent.ACTION_POINTER_UP:
    case MotionEvent.ACTION_UP:
      mPtrCount--;
      if (mPtrCount < 2) {
        mSecStartTouchEventX = -1;
        mSecStartTouchEventY = -1;
      }
      if (mPtrCount < 1) {
        mPrimStartTouchEventX = -1;
        mPrimStartTouchEventY = -1;
      }
      break;

    case MotionEvent.ACTION_MOVE:
      Log.d("TAG", "Move " + mPtrCount);
      break;

  }

  return true;
}

EDIT: below the implementation of the isPinchGesture & isScrollGesture

private boolean isPinchGesture(MotionEvent event) {
  if (event.getPointerCount() == 2) {
    final float distanceCurrent = distance(event, 0, 1);
    final float diffPrimX = mPrimStartTouchEventX - event.getX(0);
    final float diffPrimY = mPrimStartTouchEventY - event.getY(0);
    final float diffSecX = mSecStartTouchEventX - event.getX(1);
    final float diffSecY = mSecStartTouchEventY - event.getY(1);

    if (Math.abs(distanceCurrent - mPrimSecStartTouchDistance) > mViewScaledTouchSlop
            // and the fingers are moving in opposing directions
            && (diffPrimY * diffSecY) <= 0
            && (diffPrimX * diffSecX) <= 0) {
      return true;
    }
  }

  return false;
}
private boolean isScrollGesture(MotionEvent event, int ptrIndex, float originalX, float originalY){
  float moveX = Math.abs(event.getX(ptrIndex) - originalX);
  float moveY = Math.abs(event.getY(ptrIndex) - originalY);

  if (moveX > mViewScaledTouchSlop || moveY > mViewScaledTouchSlop) {
   return true;
  }
  return false;
}

EDIT 2: you can detect a pinch gesture in Android using an OnTouchListener using ScaleGestureDetector. for more info: https://developer.android.com/training/gestures/scale.html

static class MyPinchListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
  @Override
  public boolean onScale(ScaleGestureDetector detector) {
    Log.d("TAG", "PINCH! OUCH!");
    return true;
  }
}
/* Using it */
ScaleGestureDetector mScaleDetector = 
             new ScaleGestureDetector(this, new MyPinchListener());
mGestureView.setOnTouchListener(new View.OnTouchListener() {
  @Override
  public boolean onTouch(View v, MotionEvent event) {
    mScaleDetector.onTouchEvent(event);
    return true;
  }
});

Can you give me a more detailed explanation, like how are isPinchGesture() and isScrollGesture() implemented? And what exactly mPtrCount, mPrim and mSec vars are? — Marko Grbic, Dec 24 '17 at 15:49
ok, @mente86 I'll edit my post and add the implementation of those two methods. Please accept my answer. — mhdtouban, Dec 25 '17 at 15:09
Well i got zooming working on the map, but now moving the map does not work since the onTouch event of the mGestureView eats it up. How can i prevent this, and move the map if only one finger is touching it, and let the mScaleDetector work if it's two fingers? — Marko Grbic, Dec 25 '17 at 20:20
inside onTouch method detect the type of the event if it's just scrolling return false. — mhdtouban, Dec 25 '17 at 22:34
That did not work because detecting what type of event it is requires the onTouch method to be called multiple times (like ACTION_DOWN + ACTION_MOVE for drag), but the first time i return true on that event, the maps drag event gets eaten. If only i could run that switch statement in a while loop to detect what type of event it is, and then return false or true depending if it's a drag or not. — Marko Grbic, Dec 25 '17 at 23:28
I managed to do it, will be posting a full answer [here](https://stackoverflow.com/questions/47961908/centered-zooming-a-google-map-through-a-wrapper). Thanks for the help. — Marko Grbic, Dec 26 '17 at 17:56
Good to hear this, if my answer helped you figure it out, feel free to accept it. — mhdtouban, Dec 26 '17 at 17:58
Yes it did partly, the ScaleGestureDetector was used for centered pinch zooming, but it's not the full answer i needed to implement and i don't want to confuse future people looking for an answer to this. Nevertheless, thank you very much. — Marko Grbic, Dec 26 '17 at 20:01

Differentiate between zooming and moving a Google Map?

1 Answers1