/**
* Handles a {@link MotionEvent#ACTION_DOWN} event.
*
* @param x the x-coordinate of the down action
* @param y the y-coordinate of the down action
*/
private void onActionDown(float x, float y) {
final float left = Edge.LEFT.getCoordinate();
final float top = Edge.TOP.getCoordinate();
final float right = Edge.RIGHT.getCoordinate();
final float bottom = Edge.BOTTOM.getCoordinate();
mPressedHandle = HandleUtil.getPressedHandle(x, y, left, top, right, bottom, mHandleRadius);
if (mPressedHandle == null) return;
// Calculate the offset of the touch point from the precise location
// of the handle. Save these values in a member variable since we want
// to maintain this offset as we drag the handle.
mTouchOffset = HandleUtil.getOffset(mPressedHandle, x, y, left, top, right, bottom);
invalidate();
}
