speed or acceleration of motion event android

问题

Is it possible to get the speed or velocity or acceleration of touch event in android with the existing api? I have gone through MotionEvent class and none of the fields in that class seem to retrieve information that i need. Any help would be greatly appreciated

回答1:

MotionEvent does not help you in this case. You can use VelocityTracker class. It gets MotionEvent instances and calculates velocity of recent touch events. You can take a look at its documentation here: http://developer.android.com/reference/android/view/VelocityTracker.html

First you have to get an instance by obtain() method:

VelocityTracker velocity = VelocityTracker.obtain();

then you can add ACTION_MOVE events to its queue:

    if(event.getAction() == MotionEvent.ACTION_MOVE)
    {
        velocity.addMovement(event);
    }

then you can compute velocity and extract x_velocity and y_velocity

velocity.computeCurrentVelocity(1000);
float x_velocity = velocity.getXVelocity();
float y_velocity = velocity.getYVelocity();

I hope it works for you.

回答2:

You need to calculate velocity manually between each two events using System.nanoTime. Same way for acceleration (but using velocity instead of coordinates this time).

来源：https://stackoverflow.com/questions/10155907/speed-or-acceleration-of-motion-event-android