Pinch zoom for custom view
Solution 1:
This article on the Android Developers Blog covers this topic very well (scroll down to the section on GestureDetectors):
Making Sense of Multitouch
If you just want to implement pinch-to-zoom, there's only a few lines of code you'll need:
private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;
public MyCustomView(Context mContext){
//...
//Your view code
//...
mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
// Let the ScaleGestureDetector inspect all events.
mScaleDetector.onTouchEvent(ev);
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 ScaleGestureDetector.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;
}
}
The rest of the article deals with handling other gestures but rather than using their implementation, you can use GestureDetector just like ScaleGestureDetector is used in the code above.
Solution 2:
Put your view inside ZoomView
.
Custom view available here https://github.com/Polidea/android-zoom-view it's easy, free and so much fun!