Android: How To Rotate A View With One Finger

I need to rotate a view which have some buttons. With the finger movement, view should also rotate along with it's child views accordingly. Till now I have implemented this: priva

Solution 1:

First, do not use animation, as you want to directly change the view as the finger moves.

Then, for the computations, it is a lot easier to attach the OnTouchListener to a parent view of the view you want to rotate, so that the coordinate of your touch event is not modified by the rotation itself.

Here is the code if you have a parent view with id "@+id/root":

private RelativeLayout mRoot;
private RelativeLayout mCircle;
inti=0;
float viewRotation;
double fingerRotation;
double newFingerRotation;

@OverrideprotectedvoidonCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mRoot = (RelativeLayout)findViewById(R.id.root);
     mCircle = (RelativeLayout) findViewById(R.id.circle);
     mRoot.setOnTouchListener(this);
}

@OverridepublicbooleanonTouch(View v, MotionEvent event) {

    finalfloatx= event.getX();
    finalfloaty= event.getY();

    finalfloatxc= mRoot.getWidth()/2;
    finalfloatyc= mRoot.getHeight()/2;

    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            viewRotation = mCircle.getRotation();
            fingerRotation = Math.toDegrees(Math.atan2(x - xc, yc - y));
            break;
        case MotionEvent.ACTION_MOVE:
            newFingerRotation = Math.toDegrees(Math.atan2(x - xc, yc - y));
            mCircle.setRotation((float)(viewRotation + newFingerRotation - fingerRotation));
            break;
        case MotionEvent.ACTION_UP:
            fingerRotation = newFingerRotation = 0.0f;
            break;
    }

    returntrue;
}

Solution 2:

        @Override
        public boolean onTouch(View view, MotionEvent event) {  

             switch (action) {
                    case MotionEvent.ACTION_UP:
                        break;
                    case MotionEvent.ACTION_DOWN:

                        rotateX = event.getRawX();
                        rotateY = event.getRawY();

                        centerX = view.getX() + ((View) getParent()).getX() + (float) view.getWidth() / 2;

                        centerY = view.getY() + statusBarHeight + (float) view.getHeight() / 2;

                        break;

                    case MotionEvent.ACTION_MOVE:

                        newRotateX = event.getRawX();
                        newRotateY = event.getRawY();

                        double angle = Math.atan2(event.getRawY() - centerY, event.getRawX() - centerX) * 180 / Math.PI;

                        view.setRotation((float) angle - 45);

                        rotateX = newRotateX;
                        rotateY = newRotateY;
                }
            }

            returntrue;
        }
    };