How to animate an icon for expand/collapse view?

User following code to click event of image:

ObjectAnimator anim = ObjectAnimator.ofFloat(v, "rotation",rotationAngle, rotationAngle + 180);
            anim.setDuration(500);
            anim.start();
            rotationAngle += 180;
            rotationAngle = rotationAngle%360;

and make rotationAngle a global variable:

int rotationAngle = 0;

For another solution, if you want it to rotate 180° every time the view is pressed then try this instead,

rotationAngle = rotationAngle == 0 ? 180 : 0;  //toggle
mExpandArrow.animate().rotation(rotationAngle).setDuration(500).start();

Just define rotationAngle initially as,

int rotationAngle = 0;