Rotate an Imagewith Animation

Question

What I Have

I have an arrow image (like the left one). Whe

Answer 1

If you want to rotate an image by 180 degrees clockwise.

private var isExpanded = true

private fun rotateImage(view: View) {
    val startAngle = if (isExpanded) 0f else 180f
    ObjectAnimator.ofFloat(view, View.ROTATION, startAngle, startAngle + 180f).apply {
        duration = 300
        interpolator = LinearInterpolator()
        start()
    }
    isExpanded = !isExpanded
}

Or more simply (as wrote @Alex.F):

view.animate().setDuration(300).rotationBy(180f).start()

Note that if you rotate the image many times too frequently, it doesn't stop in 0 - 180 - 360 positions. Because if you start a new animation before a previous finished, it will shift an angle.

So, a better way is written in the accepted answer. It doesn't depend on current animation state.

private var angle = 0f

angle += 180f
view.animate().setDuration(300).rotation(angle).start()