How to change view's size from 4 side in Android?

Question

Is it possible to resize by pulling the matrix on the 4 side of the view? I can resize from a single point to a ratio like this.

The example above works as follows:

protected boolean onTouchDown(@NonNull MotionEvent event) {
  oldDistance = (float) Math.sqrt((midPoint.x-event.getX()) * (midPoint.x-event.getX()) + (midPoint.y-event.getY()) * (midPoint.y-event.getY()));
...
}

float newDistance = (float) Math.sqrt((midPoint.x-event.getX()) * (midPoint.x-event.getX()) + (midPoint.y-event.getY()) * (midPoint.y-event.getY()));
moveMatrix.set(downMatrix);
moveMatrix.postScale(newDistance / oldDistance, newDistance / oldDistance, midPoint.x,
        midPoint.y);
handlingSticker.setMatrix(moveMatrix);

But, for example, how can I make the process of expanding on the right side like below pictures with matrix?

Answer 1

You can try following. The idea is, if you have only horizontal or only vertical scale, then you must provide actual scale for desired axis and 1 for the other axis. Checking if the scale is horizontal or vertical is a bit tricky, you can check either:

1 The first touch was near the "vertical" border of your view. Than scroll is horizontal (x axis). Otherwise its vertical (y axis).

2 If you have buttons to drag from as in the screenshot, this makes things even easier: you just need to remember which buttons the scale was initiated with.

protected boolean onTouchDown(@NonNull MotionEvent event) {
  oldDistance = (float) Math.sqrt((midPoint.x-event.getX()) * (midPoint.x-event.getX()) + (midPoint.y-event.getY()) * (midPoint.y-event.getY()));
...
}

boolean isHorizonalScale = ... // Check if the drag has been started on the "vertical" side. If no, the scale is vertical.

moveMatrix.set(downMatrix);

if (isHorizonalScale) {
    float newDistance = (float) Math.abs(midPoint.x-event.getX());
    moveMatrix.postScale(newDistance / oldDistance, 1, midPoint.x, midPoint.y);
} else if (isHorizonalScale) {
    float newDistance = (float) Math.abs(midPoint.y-event.getY());
    moveMatrix.postScale(1, newDistance / oldDistance, midPoint.x, midPoint.y);
}
handlingSticker.setMatrix(moveMatrix);