ScaleGestureDetector doesnot work over recyclerview

Question

I have a project where I need to zoom a RecyclerView using ScaleGestureDetector. It works while pinch zooming outside of the RecyclerView but doesn't work on pinching over RecyclerView. I have been struggling to fix this for a while but not able to do solve it. Any help is highly appreciated. Thanks in advance!!

Here is my java code

recyclerView.addOnItemTouchListener(new GalleryAdapter.RecyclerTouchListener(getApplicationContext(), recyclerView, new GalleryAdapter.ClickListener() {
            @Override
            public void onClick(View view, int position) {
                Bundle bundle = new Bundle();
                bundle.putSerializable("images", images);
                bundle.putInt("position", position);

                FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
                SlideshowDialogFragment newFragment = SlideshowDialogFragment.newInstance();
                newFragment.setArguments(bundle);
                newFragment.show(ft, "slideshow");
            }

            @Override
            public void onLongClick(View view, int position) {

            }
        }));

scaleGestureDetector = new ScaleGestureDetector(
                this, new MySimpleOnScaleGestureListener(textMsg, recyclerView, factor));

private class MySimpleOnScaleGestureListener
            extends ScaleGestureDetector.SimpleOnScaleGestureListener{

        TextView viewMessage;
        RecyclerView viewMyImage;

        float factor;

        public MySimpleOnScaleGestureListener(TextView v, RecyclerView iv ,float f) {
            super();
            viewMessage = v;
            viewMyImage = iv;
            factor = f;
        }

        @Override
        public boolean onScaleBegin(ScaleGestureDetector detector) {
            //factor = 10.0f;
            return true;
            //return super.onScaleBegin(detector);
        }

        @Override
        public boolean onScale(ScaleGestureDetector detector) {

            float scaleFactor = detector.getScaleFactor() - 1;
            factor += scaleFactor;
            viewMessage.setText(String.valueOf(scaleFactor)
                    + "\n" + String.valueOf(factor));
            viewMyImage.setScaleX(factor);
            viewMyImage.setScaleY(factor);
            return true;
            //return super.onScale(detector);
        }
    }

Answer 1

Recycleview Zoomed in & zoomed out by use this class.

import android.content.Context;
import android.graphics.Canvas;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;


public class PinchRecyclerView extends RecyclerView {
    private static final int INVALID_POINTER_ID = -1;
    private int mActivePointerId = INVALID_POINTER_ID;
    private ScaleGestureDetector mScaleDetector;
    private float mScaleFactor = 1.f;
    private float maxWidth = 0.0f;
    private float maxHeight = 0.0f;
    private float mLastTouchX;
    private float mLastTouchY;
    private float mPosX;
    private float mPosY;
    private float width;
    private float height;


    public PinchRecyclerView(Context context) {
        super(context);
        if (!isInEditMode())
            mScaleDetector = new ScaleGestureDetector(getContext(), new ScaleListener());
    }

    public PinchRecyclerView(Context context, AttributeSet attrs) {
        super(context, attrs);
        if (!isInEditMode())
            mScaleDetector = new ScaleGestureDetector(getContext(), new ScaleListener());
    }

    public PinchRecyclerView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        if (!isInEditMode())
            mScaleDetector = new ScaleGestureDetector(getContext(), new ScaleListener());
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        width = MeasureSpec.getSize(widthMeasureSpec);
        height = MeasureSpec.getSize(heightMeasureSpec);
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        try {
            return super.onInterceptTouchEvent(ev);
        } catch (IllegalArgumentException ex) {
            ex.printStackTrace();
        }
        return false;
    }

    @Override
    public boolean onTouchEvent(@NonNull MotionEvent ev) {
        super.onTouchEvent(ev);
        final int action = ev.getAction();
        mScaleDetector.onTouchEvent(ev);
        switch (action & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN: {
                final float x = ev.getX();
                final float y = ev.getY();
                mLastTouchX = x;
                mLastTouchY = y;
                mActivePointerId = ev.getPointerId(0);
                break;
            }

            case MotionEvent.ACTION_MOVE: {

                final int pointerIndex = (action & MotionEvent.ACTION_POINTER_INDEX_MASK)
                        >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
                final float x = ev.getX(pointerIndex);
                final float y = ev.getY(pointerIndex);
                final float dx = x - mLastTouchX;
                final float dy = y - mLastTouchY;

                mPosX += dx;
                mPosY += dy;

                if (mPosX > 0.0f)
                    mPosX = 0.0f;
                else if (mPosX < maxWidth)
                    mPosX = maxWidth;

                if (mPosY > 0.0f)
                    mPosY = 0.0f;
                else if (mPosY < maxHeight)
                    mPosY = maxHeight;

                mLastTouchX = x;
                mLastTouchY = y;

                invalidate();
                break;
            }

            case MotionEvent.ACTION_UP: {
                mActivePointerId = INVALID_POINTER_ID;
                break;
            }

            case MotionEvent.ACTION_CANCEL: {
                mActivePointerId = INVALID_POINTER_ID;
                break;
            }

            case MotionEvent.ACTION_POINTER_UP: {
                final int pointerIndex = (action & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
                final int pointerId = ev.getPointerId(pointerIndex);
                if (pointerId == mActivePointerId) {
                    final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
                    mLastTouchX = ev.getX(newPointerIndex);
                    mLastTouchY = ev.getY(newPointerIndex);
                    mActivePointerId = ev.getPointerId(newPointerIndex);
                }
                break;
            }
        }

        return true;
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.save(Canvas.MATRIX_SAVE_FLAG);
        canvas.translate(mPosX, mPosY);
        canvas.scale(mScaleFactor, mScaleFactor);
        canvas.restore();
    }

    @Override
    protected void dispatchDraw(@NonNull Canvas canvas) {
        canvas.save(Canvas.MATRIX_SAVE_FLAG);
        if (mScaleFactor == 1.0f) {
            mPosX = 0.0f;
            mPosY = 0.0f;
        }
        canvas.translate(mPosX, mPosY);
        canvas.scale(mScaleFactor, mScaleFactor);
        super.dispatchDraw(canvas);
        canvas.restore();
        invalidate();
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            mScaleFactor *= detector.getScaleFactor();
            mScaleFactor = Math.max(1.0f, Math.min(mScaleFactor, 3.0f));
            maxWidth = width - (width * mScaleFactor);
            maxHeight = height - (height * mScaleFactor);
            invalidate();
            return true;
        }
    }
}

Hope it will help you!!