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我在徘徊，是否可以在捏合时调用服务以在android中放大/缩小，请不要介意这对您来说是一个愚蠢的疑问，请帮助我理解。

startService(MyService);

如何在捏合时调用此服务以放大任何活动。

为了检测pinch to zoom我在我的MainActivity

private static final int INVALID_POINTER_ID = -1;

private int mActivePointerId = INVALID_POINTER_ID;

@Override
public boolean onTouchEvent(MotionEvent ev) {
final int action = ev.getAction();
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN: {
    final float x = ev.getX();
    final float y = ev.getY();

    mLastTouchX = x;
    mLastTouchY = y;

    // Save the ID of this pointer
    mActivePointerId = ev.getPointerId(0);
    break;
}

case MotionEvent.ACTION_MOVE: {
    // Find the index of the active pointer and fetch its position
    final int pointerIndex = ev.findPointerIndex(mActivePointerId);
    final float x = ev.getX(pointerIndex);
    final float y = ev.getY(pointerIndex);

    final float dx = x - mLastTouchX;
    final float dy = y - mLastTouchY;

    mPosX += dx;
    mPosY += dy;

    mLastTouchX = x;
    mLastTouchY = y;

    invalidate();
    break;
}

case MotionEvent.ACTION_UP: {
    mActivePointerId = INVALID_POINTER_ID;
    break;
}

case MotionEvent.ACTION_CANCEL: {
    mActivePointerId = INVALID_POINTER_ID;
    break;
}

case MotionEvent.ACTION_POINTER_UP: {
    // Extract the index of the pointer that left the touch sensor
    final int pointerIndex = (action & MotionEvent.ACTION_POINTER_INDEX_MASK) 
            >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
    final int pointerId = ev.getPointerId(pointerIndex);
    if (pointerId == mActivePointerId) {
        // This was our active pointer going up. Choose a new
        // active pointer and adjust accordingly.
        final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
        mLastTouchX = ev.getX(newPointerIndex);
        mLastTouchY = ev.getY(newPointerIndex);
        mActivePointerId = ev.getPointerId(newPointerIndex);
    }
    break;
}
}

return true;
}

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