Pinch Zoom and 2 finger Rotation the ImageView in Android

Question

I've a problem from last 2 days and unable to tackle it as I'm newbie. Actually I'm working on an Android App that needs pinch-zoom and 2-finger rotation on Android ImageView. I got the multiple tutorials and solutions that work fine for Pinch Zoom and but does not work for 2 finger rotation. I'm sharing the simplest tutorial that's easy to understand and I want to extend it for 2 finger rotation. Here is the code snippet:

    public class MainActivity extends Activity {
    private ImageView mImageView;
    private Matrix mMatrix = new Matrix();
    private float mScale = 1f;
    private ScaleGestureDetector mScaleGestureDetector;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mImageView = (ImageView) findViewById(R.id.imageView);
        mScaleGestureDetector = new ScaleGestureDetector(this, new ScaleListener());
    }

    public boolean onTouchEvent(MotionEvent ev) {
        mScaleGestureDetector.onTouchEvent(ev);
        return true;
    }

    private class ScaleListener extends ScaleGestureDetector.
            SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            mScale *= detector.getScaleFactor();
            mScale = Math.max(0.1f, Math.min(mScale, 5.0f));
            mMatrix.setScale(mScale, mScale);
            mImageView.setImageMatrix(mMatrix);
            return true;
        }
    }
}

Also I want to use them for GPUImage, I mean despite of Android ImageView I want to use GPUImage. How to transform the GPUImage to ImageView? This is the 2nd thing. First I want to implement the 2 finger rotation (or MultiTouch in some sense). Thanks

Answer 1

Here is the solution that worked good for me. https://stackoverflow.com/a/18276033 Only one line I should add here and that should be

5. add imageView.setRotation(imageView.getRotation() + (-angle)); in OnRotation(RotationGestureDetector rotationDetector) method inside the activity to set the new rotation value to the ImageView

This is for basic help. Remaining of the implementation is just fine

Answer 2

This is the library I created, which creates a imageview class can drag, rotate and zoom

Requirement: (Add on build.gradle)

allprojects {
        repositories {
            ...
            maven { url 'https://jitpack.io' }
        }
    }

Add Dependency

dependencies {
            implementation 'com.github.lau1944:Zoom-Drag-Rotate-ImageView:1.0.0'
    }

first , add image on xml:

<com.easystudio.rotateimageview.RotateZoomImageView
        android:id="@+id/rotate"
        android:layout_width="150dp"
        android:layout_height="150dp"
        android:src="@drawable/money"/>

or add programmatically:

       RotateZoomImageView iv;
       RelativeLayout playground = findViewById(R.id.playground);
       iv = new RotateZoomImageView(getApplicationContext());
       iv.setImageDrawable(getDrawable(R.drawable.money));
       RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(250, 250);
       lp.addRule(RelativeLayout.BELOW);
       iv.setLayoutParams(lp);
       playground.addView(iv);

Step 2 : set up ontouchmethod

iv.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                return iv.onTouch(v,event);
            }
        });

And that is it .