ZoomGestureHelper

ZoomGestureHelper is a utility class in Android that helps to detect zoom gestures on a view. It provides methods to calculate the distance between two fingers when they touch the screen and move away from each other, which can be used to determine the zoom level of the view.

The ZoomGestureHelper class can be instantiated with a View object and a listener interface that will be notified when zoom gestures are detected. The listener interface provides callbacks for when zooming starts, updates, and ends.

To use the ZoomGestureHelper class, you need to implement the OnZoomGestureListener interface and override the onZoomStarted, onZoomUpdated, and onZoomEnded methods. Then, create an instance of the ZoomGestureHelper class and pass in the View object and the listener interface.

Here is an example of how to use the ZoomGestureHelper class:

public class MyActivity extends Activity implements ZoomGestureHelper.OnZoomGestureListener {

    private ZoomGestureHelper mZoomGestureHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        View view = findViewById(R.id.my_view);

        mZoomGestureHelper = new ZoomGestureHelper(view, this);
    }

    @Override
    public void onZoomStarted(float zoom, float zoomx, float zoomy) {
        // Called when zooming starts
    }

    @Override
    public void onZoomUpdated(float zoom, float zoomx, float zoomy) {
        // Called when zooming is updated
    }

    @Override
    public void onZoomEnded(float zoom, float zoomx, float zoomy) {
        // Called when zooming ends
    }
}

In this example, the ZoomGestureHelper is created with a View object and an instance of the MyActivity class, which implements the OnZoomGestureListener interface. The onZoomStarted, onZoomUpdated, and onZoomEnded methods are overridden to handle the zoom events.