How to zoom ViewGroup?

Question

I need to create view which user can scale. List of this components I will show in view pager. So I cant do scaling in activity. Thats why I created custom view which extends RelativeLayout.

public class JsonRelativeLayout extends RelativeLayout {

private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;

public JsonRelativeLayout(Context context) {
    super(context);
    mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());

}

public JsonRelativeLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
    mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
}

public JsonRelativeLayout(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    mScaleDetector.onTouchEvent(event);
    return true;
}

@Override
public void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    canvas.save();
    canvas.scale(mScaleFactor, mScaleFactor);
    //...
    //Your onDraw() code
    //...
    canvas.restore();
}

private class ScaleListener extends SimpleOnScaleGestureListener {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        mScaleFactor *= detector.getScaleFactor();

        // Don't let the object get too small or too large.
        mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 5.0f));

        invalidate();
        return true;
    }

}

But method onScale not work. And I don`t know why.

Answer 1

To zoom view group you need to extend ScrollView and override dispatchTouchEvent and dispatchDraw.