I added a drawable to my app that I can move with touch and based on the finger move speed, I'd like to do different actions.
I checked the events and I can only use MotionEvent.ACTION_MOVE to detect if there is movement. So I save the timestamp of the last movement and get the actual and I calculate the delta distance of the moving and use the formula of
speed=distance/time
However, the speed value show various numbers, from 0 to aprox. 6 but it doesn't matter if I use my finger slowly or fast. What should I modify to get the speed of the touch move?
I use the following code:
@Override
public boolean onTouch(View view, MotionEvent motionEvent)
{
final int X = (int) motionEvent.getRawX();
final int Y = (int) motionEvent.getRawY();
switch (motionEvent.getAction() & MotionEvent.ACTION_MASK)
{
case MotionEvent.ACTION_DOWN:
RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
_xDelta = X - lParams.leftMargin;
_yDelta = Y - lParams.topMargin;
oldTimeStamp=System.currentTimeMillis();
break;
case MotionEvent.ACTION_UP:
speed=0;
textView.setText("speed: " + speed);
break;
case MotionEvent.ACTION_POINTER_DOWN:
break;
case MotionEvent.ACTION_POINTER_UP:
break;
case MotionEvent.ACTION_MOVE:
timeStamp= System.currentTimeMillis();
long diff=timeStamp-oldTimeStamp;
double dist=Math.sqrt(Math.pow(_xDelta,2)+Math.pow(_yDelta,2));
double speed=dist/diff;
textView.setText("speed: " + speed);
oldTimeStamp=timeStamp;
RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
layoutParams.leftMargin = X - _xDelta;
layoutParams.topMargin = Y - _yDelta;
layoutParams.rightMargin = -250;
layoutParams.bottomMargin = -250;
view.setLayoutParams(layoutParams);
break;
}
layoutRoot.invalidate();
return true;
}
Android supports detecting certain common gestures including single tap, double tap, long press, scroll and fling with GestureDetector . Implement an OnGestureListener , attach it to a GestureDetector and use it inside the View's OnTouchListener by passing it each touch event the View receives.
dispatchTouchEvent(MotionEvent) - This allows your Activity to intercept all touch events before they are dispatched to the window. • ViewGroup. onInterceptTouchEvent(MotionEvent) - This allows a ViewGroup to watch events as they are dispatched to child Views.
Use btn. setEnabled(false) to temporarily disable it and then btn. setEnabled(true) to enable it again.
@Override
public boolean onTouchEvent(MotionEvent event) {
int index = event.getActionIndex();
int action = event.getActionMasked();
int pointerId = event.getPointerId(index);
switch(action) {
case MotionEvent.ACTION_DOWN:
if(mVelocityTracker == null) {
// Retrieve a new VelocityTracker object to watch the velocity of a motion.
mVelocityTracker = VelocityTracker.obtain();
}
else {
// Reset the velocity tracker back to its initial state.
mVelocityTracker.clear();
}
// Add a user's movement to the tracker.
mVelocityTracker.addMovement(event);
break;
case MotionEvent.ACTION_MOVE:
mVelocityTracker.addMovement(event);
// When you want to determine the velocity, call
// computeCurrentVelocity(). Then call getXVelocity()
// and getYVelocity() to retrieve the velocity for each pointer ID.
mVelocityTracker.computeCurrentVelocity(1000);
// Log velocity of pixels per second
// Best practice to use VelocityTrackerCompat where possible.
Log.d("", "X velocity: " +
VelocityTrackerCompat.getXVelocity(mVelocityTracker,
pointerId));
Log.d("", "Y velocity: " +
VelocityTrackerCompat.getYVelocity(mVelocityTracker,
pointerId));
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
// Return a VelocityTracker object back to be re-used by others.
mVelocityTracker.recycle();
break;
}
return true;
}
Tracking Movement
Call mVelocityTracker.recycle() on view onDetachedFromWindow
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