Scale limits on pinch zoom of android

Question

How to set Max and Min zoom levels for Pinch-Zoom?

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Here is my code: //

public class TouchImageView extends ImageView {

     private static final String TAG = "Touch";

        // These matrices will be used to move and zoom image
        Matrix matrix = new Matrix();
        Matrix savedMatrix = new Matrix();
        static PinchZoomExample sPinchZoomExample = null;
        // We can be in one of these 3 states
        static final int NONE = 0;
        static final int DRAG = 1;
        static final int ZOOM = 2;
        int mode = NONE;
        static Bitmap sCurrentImage;

        // Remember some things for zooming
        PointF start = new PointF();
        PointF mid = new PointF();
        float oldDist = 1f;

        Context context;


        public TouchImageView(Context context) {
            super(context);
            super.setClickable(true);
            this.context = context;

            matrix.setTranslate(1f, 1f);
            setImageMatrix(matrix);
            setScaleType(ScaleType.MATRIX);

            setOnTouchListener(new OnTouchListener() {

                @Override
                public boolean onTouch(View v, MotionEvent rawEvent) {
                    WrapMotionEvent event = WrapMotionEvent.wrap(rawEvent);

                    // Dump touch event to log
                   /* if (Viewer.isDebug == true){
                        dumpEvent(event);
                    }*/

                    // Handle touch events here...
                    switch (event.getAction() & MotionEvent.ACTION_MASK) {
                    case MotionEvent.ACTION_DOWN:
                        savedMatrix.set(matrix);
                        start.set(event.getX(), event.getY());
                        Log.d(TAG, "mode=DRAG");
                        mode = DRAG;
                        break;
                    case MotionEvent.ACTION_POINTER_DOWN:
                        oldDist = spacing(event);
                        Log.d(TAG, "oldDist=" + oldDist);
                        if (oldDist > 10f) {
                            savedMatrix.set(matrix);
                            midPoint(mid, event);
                            mode = ZOOM;
                            Log.d(TAG, "mode=ZOOM");
                        }
                        break;
                    case MotionEvent.ACTION_UP:
                        int xDiff = (int) Math.abs(event.getX() - start.x);
                        int yDiff = (int) Math.abs(event.getY() - start.y);
                        if (xDiff < 8 && yDiff < 8){
                            performClick();
                            sPinchZoomExample.displayGallery();
                        }
                    case MotionEvent.ACTION_POINTER_UP:
                        mode = NONE;
                        Log.d(TAG, "mode=NONE");
                        break;
                    case MotionEvent.ACTION_MOVE:
                        if (mode == DRAG) {
                            // ...
                            matrix.set(savedMatrix);
                            matrix.postTranslate(event.getX() - start.x, event.getY() - start.y);
                        } else if (mode == ZOOM) {
                            float newDist = spacing(event);
                            Log.d(TAG, "newDist=" + newDist);
                            if (newDist > 10f) {
                                matrix.set(savedMatrix);
                                float scale = newDist / oldDist;

                                matrix.postScale(scale, scale, mid.x, mid.y);

                                //Canvas canvas = new Canvas();

//                              Bitmap bm = Bitmap.createBitmap(sCurrentImage,0, 0, sCurrentImage.getWidth()
//                                      , sCurrentImage.getHeight(), matrix, true);
                                Log.d("SCALE", "scale=" + scale + "  " + getWidth() + "  " + getHeight());
                                //bm.recycle();
                            }
                        }
                        break;
                    }

                    setImageMatrix(matrix);
                    return true; // indicate event was handled
                }

            });
        }


        public void setImage(Bitmap bm, int displayWidth, int displayHeight , PinchZoomExample pze) { 
            super.setImageBitmap(bm);
            sCurrentImage = bm;
            sPinchZoomExample = pze;
            //Fit to screen.
            float scale;
            if ((displayHeight / bm.getHeight()) >= (displayWidth / bm.getWidth())){
                scale =  (float)displayWidth / (float)bm.getWidth();
            } else {
                scale = (float)displayHeight / (float)bm.getHeight();
            }

            savedMatrix.set(matrix);
            matrix.set(savedMatrix);
            matrix.postScale(scale, scale, mid.x, mid.y);
            setImageMatrix(matrix);


            // Center the image
            float redundantYSpace = (float)displayHeight - (scale * (float)bm.getHeight()) ;
            float redundantXSpace = (float)displayWidth - (scale * (float)bm.getWidth());

            redundantYSpace /= (float)2;
            redundantXSpace /= (float)2;


            savedMatrix.set(matrix);
            matrix.set(savedMatrix);
            matrix.postTranslate(redundantXSpace, redundantYSpace);   //matrix.postTranslate(50, 50);
            setImageMatrix(matrix);


        }




        /** Determine the space between the first two fingers */
        private float spacing(WrapMotionEvent event) {
            // ...
            float x = event.getX(0) - event.getX(1);
            float y = event.getY(0) - event.getY(1);
            return FloatMath.sqrt(x * x + y * y);
        }

        /** Calculate the mid point of the first two fingers */
        private void midPoint(PointF point, WrapMotionEvent event) {
            // ...
            float x = event.getX(0) + event.getX(1);
            float y = event.getY(0) + event.getY(1);
            point.set(x / 2, y / 2);
        }

}

Answer 1

private static final float MIN_ZOOM = 1.0f;
private static final float MAX_ZOOM = 5.0f;

scale = Math.max(MIN_ZOOM, Math.min(scale, MAX_ZOOM));

Answer 2

Check my answer here. It worked with very little extra coding effort.

https://stackoverflow.com/a/18395969/2709830