Android ImageView to include pinch zooming, panning, fling and double tap zoom.

TouchImageView.java

import android.annotation.TargetApi;
import android.content.Context;
import android.content.res.Configuration;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.RectF;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.os.Build;
import android.os.Build.VERSION;
import android.os.Build.VERSION_CODES;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.widget.ImageView;
import android.widget.OverScroller;
import android.widget.Scroller;

/**
 * Created by MyInnos on 28-11-2016.
 */

public class TouchImageView extends ImageView {

    private static final String DEBUG = "DEBUG";

    //
    // SuperMin and SuperMax multipliers. Determine how much the image can be
    // zoomed below or above the zoom boundaries, before animating back to the
    // min/max zoom boundary.
    //
    private static final float SUPER_MIN_MULTIPLIER = .75f;
    private static final float SUPER_MAX_MULTIPLIER = 1.25f;

    //
    // Scale of image ranges from minScale to maxScale, where minScale == 1
    // when the image is stretched to fit view.
    //
    private float normalizedScale;

    //
    // Matrix applied to image. MSCALE_X and MSCALE_Y should always be equal.
    // MTRANS_X and MTRANS_Y are the other values used. prevMatrix is the matrix
    // saved prior to the screen rotating.
    //
    private Matrix matrix, prevMatrix;

    private static enum State { NONE, DRAG, ZOOM, FLING, ANIMATE_ZOOM };
    private State state;

    private float minScale;
    private float maxScale;
    private float superMinScale;
    private float superMaxScale;
    private float[] m;

    private Context context;
    private Fling fling;

    private ScaleType mScaleType;

    private boolean imageRenderedAtLeastOnce;
    private boolean onDrawReady;

    private ZoomVariables delayedZoomVariables;

    //
    // Size of view and previous view size (ie before rotation)
    //
    private int viewWidth, viewHeight, prevViewWidth, prevViewHeight;

    //
    // Size of image when it is stretched to fit view. Before and After rotation.
    //
    private float matchViewWidth, matchViewHeight, prevMatchViewWidth, prevMatchViewHeight;

    private ScaleGestureDetector mScaleDetector;
    private GestureDetector mGestureDetector;
    private GestureDetector.OnDoubleTapListener doubleTapListener = null;
    private OnTouchListener userTouchListener = null;
    private OnTouchImageViewListener touchImageViewListener = null;

    public TouchImageView(Context context) {
        super(context);
        sharedConstructing(context);
    }

    public TouchImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        sharedConstructing(context);
    }

    public TouchImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        sharedConstructing(context);
    }

    private void sharedConstructing(Context context) {
        super.setClickable(true);
        this.context = context;
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
        mGestureDetector = new GestureDetector(context, new GestureListener());
        matrix = new Matrix();
        prevMatrix = new Matrix();
        m = new float[9];
        normalizedScale = 1;
        if (mScaleType == null) {
            mScaleType = ScaleType.FIT_CENTER;
        }
        minScale = 1;
        maxScale = 3;
        superMinScale = SUPER_MIN_MULTIPLIER * minScale;
        superMaxScale = SUPER_MAX_MULTIPLIER * maxScale;
        setImageMatrix(matrix);
        setScaleType(ScaleType.MATRIX);
        setState(State.NONE);
        onDrawReady = false;
        super.setOnTouchListener(new PrivateOnTouchListener());
    }

    @Override
    public void setOnTouchListener(OnTouchListener l) {
        userTouchListener = l;
    }

    public void setOnTouchImageViewListener(OnTouchImageViewListener l) {
        touchImageViewListener = l;
    }

    public void setOnDoubleTapListener(GestureDetector.OnDoubleTapListener l) {
        doubleTapListener = l;
    }

    @Override
    public void setImageResource(int resId) {
        super.setImageResource(resId);
        savePreviousImageValues();
        fitImageToView();
    }

    @Override
    public void setImageBitmap(Bitmap bm) {
        super.setImageBitmap(bm);
        savePreviousImageValues();
        fitImageToView();
    }

    @Override
    public void setImageDrawable(Drawable drawable) {
        super.setImageDrawable(drawable);
        savePreviousImageValues();
        fitImageToView();
    }

    @Override
    public void setImageURI(Uri uri) {
        super.setImageURI(uri);
        savePreviousImageValues();
        fitImageToView();
    }

    @Override
    public void setScaleType(ScaleType type) {
        if (type == ScaleType.FIT_START || type == ScaleType.FIT_END) {
            throw new UnsupportedOperationException("TouchImageView does not support FIT_START or FIT_END");
        }
        if (type == ScaleType.MATRIX) {
            super.setScaleType(ScaleType.MATRIX);

        } else {
            mScaleType = type;
            if (onDrawReady) {
                //
                // If the image is already rendered, scaleType has been called programmatically
                // and the TouchImageView should be updated with the new scaleType.
                //
                setZoom(this);
            }
        }
    }

    @Override
    public ScaleType getScaleType() {
        return mScaleType;
    }

    /**
     * Returns false if image is in initial, unzoomed state. False, otherwise.
     * @return true if image is zoomed
     */
    public boolean isZoomed() {
        return normalizedScale != 1;
    }

    /**
     * Return a Rect representing the zoomed image.
     * @return rect representing zoomed image
     */
    public RectF getZoomedRect() {
        if (mScaleType == ScaleType.FIT_XY) {
            throw new UnsupportedOperationException("getZoomedRect() not supported with FIT_XY");
        }
        PointF topLeft = transformCoordTouchToBitmap(0, 0, true);
        PointF bottomRight = transformCoordTouchToBitmap(viewWidth, viewHeight, true);

        float w = getDrawable().getIntrinsicWidth();
        float h = getDrawable().getIntrinsicHeight();
        return new RectF(topLeft.x / w, topLeft.y / h, bottomRight.x / w, bottomRight.y / h);
    }

    /**
     * Save the current matrix and view dimensions
     * in the prevMatrix and prevView variables.
     */
    private void savePreviousImageValues() {
        if (matrix != null && viewHeight != 0 && viewWidth != 0) {
            matrix.getValues(m);
            prevMatrix.setValues(m);
            prevMatchViewHeight = matchViewHeight;
            prevMatchViewWidth = matchViewWidth;
            prevViewHeight = viewHeight;
            prevViewWidth = viewWidth;
        }
    }

    @Override
    public Parcelable onSaveInstanceState() {
        Bundle bundle = new Bundle();
        bundle.putParcelable("instanceState", super.onSaveInstanceState());
        bundle.putFloat("saveScale", normalizedScale);
        bundle.putFloat("matchViewHeight", matchViewHeight);
        bundle.putFloat("matchViewWidth", matchViewWidth);
        bundle.putInt("viewWidth", viewWidth);
        bundle.putInt("viewHeight", viewHeight);
        matrix.getValues(m);
        bundle.putFloatArray("matrix", m);
        bundle.putBoolean("imageRendered", imageRenderedAtLeastOnce);
        return bundle;
    }

    @Override
    public void onRestoreInstanceState(Parcelable state) {
        if (state instanceof Bundle) {
            Bundle bundle = (Bundle) state;
            normalizedScale = bundle.getFloat("saveScale");
            m = bundle.getFloatArray("matrix");
            prevMatrix.setValues(m);
            prevMatchViewHeight = bundle.getFloat("matchViewHeight");
            prevMatchViewWidth = bundle.getFloat("matchViewWidth");
            prevViewHeight = bundle.getInt("viewHeight");
            prevViewWidth = bundle.getInt("viewWidth");
            imageRenderedAtLeastOnce = bundle.getBoolean("imageRendered");
            super.onRestoreInstanceState(bundle.getParcelable("instanceState"));
            return;
        }

        super.onRestoreInstanceState(state);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        onDrawReady = true;
        imageRenderedAtLeastOnce = true;
        if (delayedZoomVariables != null) {
            setZoom(delayedZoomVariables.scale, delayedZoomVariables.focusX, delayedZoomVariables.focusY, delayedZoomVariables.scaleType);
            delayedZoomVariables = null;
        }
        super.onDraw(canvas);
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        savePreviousImageValues();
    }

    /**
     * Get the max zoom multiplier.
     * @return max zoom multiplier.
     */
    public float getMaxZoom() {
        return maxScale;
    }

    /**
     * Set the max zoom multiplier. Default value: 3.
     * @param max max zoom multiplier.
     */
    public void setMaxZoom(float max) {
        maxScale = max;
        superMaxScale = SUPER_MAX_MULTIPLIER * maxScale;
    }

    /**
     * Get the min zoom multiplier.
     * @return min zoom multiplier.
     */
    public float getMinZoom() {
        return minScale;
    }

    /**
     * Get the current zoom. This is the zoom relative to the initial
     * scale, not the original resource.
     * @return current zoom multiplier.
     */
    public float getCurrentZoom() {
        return normalizedScale;
    }

    /**
     * Set the min zoom multiplier. Default value: 1.
     * @param min min zoom multiplier.
     */
    public void setMinZoom(float min) {
        minScale = min;
        superMinScale = SUPER_MIN_MULTIPLIER * minScale;
    }

    /**
     * Reset zoom and translation to initial state.
     */
    public void resetZoom() {
        normalizedScale = 1;
        fitImageToView();
    }

    /**
     * Set zoom to the specified scale. Image will be centered by default.
     * @param scale
     */
    public void setZoom(float scale) {
        setZoom(scale, 0.5f, 0.5f);
    }

    /**
     * Set zoom to the specified scale. Image will be centered around the point
     * (focusX, focusY). These floats range from 0 to 1 and denote the focus point
     * as a fraction from the left and top of the view. For example, the top left
     * corner of the image would be (0, 0). And the bottom right corner would be (1, 1).
     * @param scale
     * @param focusX
     * @param focusY
     */
    public void setZoom(float scale, float focusX, float focusY) {
        setZoom(scale, focusX, focusY, mScaleType);
    }

    /**
     * Set zoom to the specified scale. Image will be centered around the point
     * (focusX, focusY). These floats range from 0 to 1 and denote the focus point
     * as a fraction from the left and top of the view. For example, the top left
     * corner of the image would be (0, 0). And the bottom right corner would be (1, 1).
     * @param scale
     * @param focusX
     * @param focusY
     * @param scaleType
     */
    public void setZoom(float scale, float focusX, float focusY, ScaleType scaleType) {
        //
        // setZoom can be called before the image is on the screen, but at this point,
        // image and view sizes have not yet been calculated in onMeasure. Thus, we should
        // delay calling setZoom until the view has been measured.
        //
        if (!onDrawReady) {
            delayedZoomVariables = new ZoomVariables(scale, focusX, focusY, scaleType);
            return;
        }

        if (scaleType != mScaleType) {
            setScaleType(scaleType);
        }
        resetZoom();
        scaleImage(scale, viewWidth / 2, viewHeight / 2, true);
        matrix.getValues(m);
        m[Matrix.MTRANS_X] = -((focusX * getImageWidth()) - (viewWidth * 0.5f));
        m[Matrix.MTRANS_Y] = -((focusY * getImageHeight()) - (viewHeight * 0.5f));
        matrix.setValues(m);
        fixTrans();
        setImageMatrix(matrix);
    }

    /**
     * Set zoom parameters equal to another TouchImageView. Including scale, position,
     * and ScaleType.
     * @param
     */
    public void setZoom(TouchImageView img) {
        PointF center = img.getScrollPosition();
        setZoom(img.getCurrentZoom(), center.x, center.y, img.getScaleType());
    }

    /**
     * Return the point at the center of the zoomed image. The PointF coordinates range
     * in value between 0 and 1 and the focus point is denoted as a fraction from the left
     * and top of the view. For example, the top left corner of the image would be (0, 0).
     * And the bottom right corner would be (1, 1).
     * @return PointF representing the scroll position of the zoomed image.
     */
    public PointF getScrollPosition() {
        Drawable drawable = getDrawable();
        if (drawable == null) {
            return null;
        }
        int drawableWidth = drawable.getIntrinsicWidth();
        int drawableHeight = drawable.getIntrinsicHeight();

        PointF point = transformCoordTouchToBitmap(viewWidth / 2, viewHeight / 2, true);
        point.x /= drawableWidth;
        point.y /= drawableHeight;
        return point;
    }

    /**
     * Set the focus point of the zoomed image. The focus points are denoted as a fraction from the
     * left and top of the view. The focus points can range in value between 0 and 1.
     * @param focusX
     * @param focusY
     */
    public void setScrollPosition(float focusX, float focusY) {
        setZoom(normalizedScale, focusX, focusY);
    }

    /**
     * Performs boundary checking and fixes the image matrix if it
     * is out of bounds.
     */
    private void fixTrans() {
        matrix.getValues(m);
        float transX = m[Matrix.MTRANS_X];
        float transY = m[Matrix.MTRANS_Y];

        float fixTransX = getFixTrans(transX, viewWidth, getImageWidth());
        float fixTransY = getFixTrans(transY, viewHeight, getImageHeight());

        if (fixTransX != 0 || fixTransY != 0) {
            matrix.postTranslate(fixTransX, fixTransY);
        }
    }

    /**
     * When transitioning from zooming from focus to zoom from center (or vice versa)
     * the image can become unaligned within the view. This is apparent when zooming
     * quickly. When the content size is less than the view size, the content will often
     * be centered incorrectly within the view. fixScaleTrans first calls fixTrans() and
     * then makes sure the image is centered correctly within the view.
     */
    private void fixScaleTrans() {
        fixTrans();
        matrix.getValues(m);
        if (getImageWidth() < viewWidth) {
            m[Matrix.MTRANS_X] = (viewWidth - getImageWidth()) / 2;
        }

        if (getImageHeight() < viewHeight) {
            m[Matrix.MTRANS_Y] = (viewHeight - getImageHeight()) / 2;
        }
        matrix.setValues(m);
    }

    private float getFixTrans(float trans, float viewSize, float contentSize) {
        float minTrans, maxTrans;

        if (contentSize <= viewSize) {
            minTrans = 0;
            maxTrans = viewSize - contentSize;

        } else {
            minTrans = viewSize - contentSize;
            maxTrans = 0;
        }

        if (trans < minTrans)
            return -trans + minTrans;
        if (trans > maxTrans)
            return -trans + maxTrans;
        return 0;
    }

    private float getFixDragTrans(float delta, float viewSize, float contentSize) {
        if (contentSize <= viewSize) {
            return 0;
        }
        return delta;
    }

    private float getImageWidth() {
        return matchViewWidth * normalizedScale;
    }

    private float getImageHeight() {
        return matchViewHeight * normalizedScale;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        Drawable drawable = getDrawable();
        if (drawable == null || drawable.getIntrinsicWidth() == 0 || drawable.getIntrinsicHeight() == 0) {
            setMeasuredDimension(0, 0);
            return;
        }

        int drawableWidth = drawable.getIntrinsicWidth();
        int drawableHeight = drawable.getIntrinsicHeight();
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        viewWidth = setViewSize(widthMode, widthSize, drawableWidth);
        viewHeight = setViewSize(heightMode, heightSize, drawableHeight);

        //
        // Set view dimensions
        //
        setMeasuredDimension(viewWidth, viewHeight);

        //
        // Fit content within view
        //
        fitImageToView();
    }

    /**
     * If the normalizedScale is equal to 1, then the image is made to fit the screen. Otherwise,
     * it is made to fit the screen according to the dimensions of the previous image matrix. This
     * allows the image to maintain its zoom after rotation.
     */
    private void fitImageToView() {
        Drawable drawable = getDrawable();
        if (drawable == null || drawable.getIntrinsicWidth() == 0 || drawable.getIntrinsicHeight() == 0) {
            return;
        }
        if (matrix == null || prevMatrix == null) {
            return;
        }

        int drawableWidth = drawable.getIntrinsicWidth();
        int drawableHeight = drawable.getIntrinsicHeight();

        //
        // Scale image for view
        //
        float scaleX = (float) viewWidth / drawableWidth;
        float scaleY = (float) viewHeight / drawableHeight;

        switch (mScaleType) {
            case CENTER:
                scaleX = scaleY = 1;
                break;

            case CENTER_CROP:
                scaleX = scaleY = Math.max(scaleX, scaleY);
                break;

            case CENTER_INSIDE:
                scaleX = scaleY = Math.min(1, Math.min(scaleX, scaleY));

            case FIT_CENTER:
                scaleX = scaleY = Math.min(scaleX, scaleY);
                break;

            case FIT_XY:
                break;

            default:
                //
                // FIT_START and FIT_END not supported
                //
                throw new UnsupportedOperationException("TouchImageView does not support FIT_START or FIT_END");

        }

        //
        // Center the image
        //
        float redundantXSpace = viewWidth - (scaleX * drawableWidth);
        float redundantYSpace = viewHeight - (scaleY * drawableHeight);
        matchViewWidth = viewWidth - redundantXSpace;
        matchViewHeight = viewHeight - redundantYSpace;
        if (!isZoomed() && !imageRenderedAtLeastOnce) {
            //
            // Stretch and center image to fit view
            //
            matrix.setScale(scaleX, scaleY);
            matrix.postTranslate(redundantXSpace / 2, redundantYSpace / 2);
            normalizedScale = 1;

        } else {
            //
            // These values should never be 0 or we will set viewWidth and viewHeight
            // to NaN in translateMatrixAfterRotate. To avoid this, call savePreviousImageValues
            // to set them equal to the current values.
            //
            if (prevMatchViewWidth == 0 || prevMatchViewHeight == 0) {
                savePreviousImageValues();
            }

            prevMatrix.getValues(m);

            //
            // Rescale Matrix after rotation
            //
            m[Matrix.MSCALE_X] = matchViewWidth / drawableWidth * normalizedScale;
            m[Matrix.MSCALE_Y] = matchViewHeight / drawableHeight * normalizedScale;

            //
            // TransX and TransY from previous matrix
            //
            float transX = m[Matrix.MTRANS_X];
            float transY = m[Matrix.MTRANS_Y];

            //
            // Width
            //
            float prevActualWidth = prevMatchViewWidth * normalizedScale;
            float actualWidth = getImageWidth();
            translateMatrixAfterRotate(Matrix.MTRANS_X, transX, prevActualWidth, actualWidth, prevViewWidth, viewWidth, drawableWidth);

            //
            // Height
            //
            float prevActualHeight = prevMatchViewHeight * normalizedScale;
            float actualHeight = getImageHeight();
            translateMatrixAfterRotate(Matrix.MTRANS_Y, transY, prevActualHeight, actualHeight, prevViewHeight, viewHeight, drawableHeight);

            //
            // Set the matrix to the adjusted scale and translate values.
            //
            matrix.setValues(m);
        }
        fixTrans();
        setImageMatrix(matrix);
    }

    /**
     * Set view dimensions based on layout params
     *
     * @param mode
     * @param size
     * @param drawableWidth
     * @return
     */
    private int setViewSize(int mode, int size, int drawableWidth) {
        int viewSize;
        switch (mode) {
            case MeasureSpec.EXACTLY:
                viewSize = size;
                break;

            case MeasureSpec.AT_MOST:
                viewSize = Math.min(drawableWidth, size);
                break;

            case MeasureSpec.UNSPECIFIED:
                viewSize = drawableWidth;
                break;

            default:
                viewSize = size;
                break;
        }
        return viewSize;
    }

    /**
     * After rotating, the matrix needs to be translated. This function finds the area of image
     * which was previously centered and adjusts translations so that is again the center, post-rotation.
     *
     * @param axis Matrix.MTRANS_X or Matrix.MTRANS_Y
     * @param trans the value of trans in that axis before the rotation
     * @param prevImageSize the width/height of the image before the rotation
     * @param imageSize width/height of the image after rotation
     * @param prevViewSize width/height of view before rotation
     * @param viewSize width/height of view after rotation
     * @param drawableSize width/height of drawable
     */
    private void translateMatrixAfterRotate(int axis, float trans, float prevImageSize, float imageSize, int prevViewSize, int viewSize, int drawableSize) {
        if (imageSize < viewSize) {
            //
            // The width/height of image is less than the view's width/height. Center it.
            //
            m[axis] = (viewSize - (drawableSize * m[Matrix.MSCALE_X])) * 0.5f;

        } else if (trans > 0) {
            //
            // The image is larger than the view, but was not before rotation. Center it.
            //
            m[axis] = -((imageSize - viewSize) * 0.5f);

        } else {
            //
            // Find the area of the image which was previously centered in the view. Determine its distance
            // from the left/top side of the view as a fraction of the entire image's width/height. Use that percentage
            // to calculate the trans in the new view width/height.
            //
            float percentage = (Math.abs(trans) + (0.5f * prevViewSize)) / prevImageSize;
            m[axis] = -((percentage * imageSize) - (viewSize * 0.5f));
        }
    }

    private void setState(State state) {
        this.state = state;
    }

    public boolean canScrollHorizontallyFroyo(int direction) {
        return canScrollHorizontally(direction);
    }

    @Override
    public boolean canScrollHorizontally(int direction) {
        matrix.getValues(m);
        float x = m[Matrix.MTRANS_X];

        if (getImageWidth() < viewWidth) {
            return false;

        } else if (x >= -1 && direction < 0) {
            return false;

        } else if (Math.abs(x) + viewWidth + 1 >= getImageWidth() && direction > 0) {
            return false;
        }

        return true;
    }

    /**
     * Gesture Listener detects a single click or long click and passes that on
     * to the view's listener.
     * @author Ortiz
     *
     */
    private class GestureListener extends GestureDetector.SimpleOnGestureListener {

        @Override
        public boolean onSingleTapConfirmed(MotionEvent e)
        {
            if(doubleTapListener != null) {
                return doubleTapListener.onSingleTapConfirmed(e);
            }
            return performClick();
        }

        @Override
        public void onLongPress(MotionEvent e)
        {
            performLongClick();
        }

        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
        {
            if (fling != null) {
                //
                // If a previous fling is still active, it should be cancelled so that two flings
                // are not run simultaenously.
                //
                fling.cancelFling();
            }
            fling = new Fling((int) velocityX, (int) velocityY);
            compatPostOnAnimation(fling);
            return super.onFling(e1, e2, velocityX, velocityY);
        }

        @Override
        public boolean onDoubleTap(MotionEvent e) {
            boolean consumed = false;
            if(doubleTapListener != null) {
                consumed = doubleTapListener.onDoubleTap(e);
            }
            if (state == State.NONE) {
                float targetZoom = (normalizedScale == minScale) ? maxScale : minScale;
                DoubleTapZoom doubleTap = new DoubleTapZoom(targetZoom, e.getX(), e.getY(), false);
                compatPostOnAnimation(doubleTap);
                consumed = true;
            }
            return consumed;
        }

        @Override
        public boolean onDoubleTapEvent(MotionEvent e) {
            if(doubleTapListener != null) {
                return doubleTapListener.onDoubleTapEvent(e);
            }
            return false;
        }
    }

    public interface OnTouchImageViewListener {
        public void onMove();
    }

    /**
     * Responsible for all touch events. Handles the heavy lifting of drag and also sends
     * touch events to Scale Detector and Gesture Detector.
     * @author Ortiz
     *
     */
    private class PrivateOnTouchListener implements OnTouchListener {

        //
        // Remember last point position for dragging
        //
        private PointF last = new PointF();

        @Override
        public boolean onTouch(View v, MotionEvent event) {
            mScaleDetector.onTouchEvent(event);
            mGestureDetector.onTouchEvent(event);
            PointF curr = new PointF(event.getX(), event.getY());

            if (state == State.NONE || state == State.DRAG || state == State.FLING) {
                switch (event.getAction()) {
                    case MotionEvent.ACTION_DOWN:
                        last.set(curr);
                        if (fling != null)
                            fling.cancelFling();
                        setState(State.DRAG);
                        break;

                    case MotionEvent.ACTION_MOVE:
                        if (state == State.DRAG) {
                            float deltaX = curr.x - last.x;
                            float deltaY = curr.y - last.y;
                            float fixTransX = getFixDragTrans(deltaX, viewWidth, getImageWidth());
                            float fixTransY = getFixDragTrans(deltaY, viewHeight, getImageHeight());
                            matrix.postTranslate(fixTransX, fixTransY);
                            fixTrans();
                            last.set(curr.x, curr.y);
                        }
                        break;

                    case MotionEvent.ACTION_UP:
                    case MotionEvent.ACTION_POINTER_UP:
                        setState(State.NONE);
                        break;
                }
            }

            setImageMatrix(matrix);

            //
            // User-defined OnTouchListener
            //
            if(userTouchListener != null) {
                userTouchListener.onTouch(v, event);
            }

            //
            // OnTouchImageViewListener is set: TouchImageView dragged by user.
            //
            if (touchImageViewListener != null) {
                touchImageViewListener.onMove();
            }

            //
            // indicate event was handled
            //
            return true;
        }
    }

    /**
     * ScaleListener detects user two finger scaling and scales image.
     * @author Ortiz
     *
     */
    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScaleBegin(ScaleGestureDetector detector) {
            setState(State.ZOOM);
            return true;
        }

        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            scaleImage(detector.getScaleFactor(), detector.getFocusX(), detector.getFocusY(), true);

            //
            // OnTouchImageViewListener is set: TouchImageView pinch zoomed by user.
            //
            if (touchImageViewListener != null) {
                touchImageViewListener.onMove();
            }
            return true;
        }

        @Override
        public void onScaleEnd(ScaleGestureDetector detector) {
            super.onScaleEnd(detector);
            setState(State.NONE);
            boolean animateToZoomBoundary = false;
            float targetZoom = normalizedScale;
            if (normalizedScale > maxScale) {
                targetZoom = maxScale;
                animateToZoomBoundary = true;

            } else if (normalizedScale < minScale) {
                targetZoom = minScale;
                animateToZoomBoundary = true;
            }

            if (animateToZoomBoundary) {
                DoubleTapZoom doubleTap = new DoubleTapZoom(targetZoom, viewWidth / 2, viewHeight / 2, true);
                compatPostOnAnimation(doubleTap);
            }
        }
    }

    private void scaleImage(double deltaScale, float focusX, float focusY, boolean stretchImageToSuper) {

        float lowerScale, upperScale;
        if (stretchImageToSuper) {
            lowerScale = superMinScale;
            upperScale = superMaxScale;

        } else {
            lowerScale = minScale;
            upperScale = maxScale;
        }

        float origScale = normalizedScale;
        normalizedScale *= deltaScale;
        if (normalizedScale > upperScale) {
            normalizedScale = upperScale;
            deltaScale = upperScale / origScale;
        } else if (normalizedScale < lowerScale) {
            normalizedScale = lowerScale;
            deltaScale = lowerScale / origScale;
        }

        matrix.postScale((float) deltaScale, (float) deltaScale, focusX, focusY);
        fixScaleTrans();
    }

    /**
     * DoubleTapZoom calls a series of runnables which apply
     * an animated zoom in/out graphic to the image.
     * @author Ortiz
     *
     */
    private class DoubleTapZoom implements Runnable {

        private long startTime;
        private static final float ZOOM_TIME = 500;
        private float startZoom, targetZoom;
        private float bitmapX, bitmapY;
        private boolean stretchImageToSuper;
        private AccelerateDecelerateInterpolator interpolator = new AccelerateDecelerateInterpolator();
        private PointF startTouch;
        private PointF endTouch;

        DoubleTapZoom(float targetZoom, float focusX, float focusY, boolean stretchImageToSuper) {
            setState(State.ANIMATE_ZOOM);
            startTime = System.currentTimeMillis();
            this.startZoom = normalizedScale;
            this.targetZoom = targetZoom;
            this.stretchImageToSuper = stretchImageToSuper;
            PointF bitmapPoint = transformCoordTouchToBitmap(focusX, focusY, false);
            this.bitmapX = bitmapPoint.x;
            this.bitmapY = bitmapPoint.y;

            //
            // Used for translating image during scaling
            //
            startTouch = transformCoordBitmapToTouch(bitmapX, bitmapY);
            endTouch = new PointF(viewWidth / 2, viewHeight / 2);
        }

        @Override
        public void run() {
            float t = interpolate();
            double deltaScale = calculateDeltaScale(t);
            scaleImage(deltaScale, bitmapX, bitmapY, stretchImageToSuper);
            translateImageToCenterTouchPosition(t);
            fixScaleTrans();
            setImageMatrix(matrix);

            //
            // OnTouchImageViewListener is set: double tap runnable updates listener
            // with every frame.
            //
            if (touchImageViewListener != null) {
                touchImageViewListener.onMove();
            }

            if (t < 1f) {
                //
                // We haven't finished zooming
                //
                compatPostOnAnimation(this);

            } else {
                //
                // Finished zooming
                //
                setState(State.NONE);
            }
        }

        /**
         * Interpolate between where the image should start and end in order to translate
         * the image so that the point that is touched is what ends up centered at the end
         * of the zoom.
         * @param t
         */
        private void translateImageToCenterTouchPosition(float t) {
            float targetX = startTouch.x + t * (endTouch.x - startTouch.x);
            float targetY = startTouch.y + t * (endTouch.y - startTouch.y);
            PointF curr = transformCoordBitmapToTouch(bitmapX, bitmapY);
            matrix.postTranslate(targetX - curr.x, targetY - curr.y);
        }

        /**
         * Use interpolator to get t
         * @return
         */
        private float interpolate() {
            long currTime = System.currentTimeMillis();
            float elapsed = (currTime - startTime) / ZOOM_TIME;
            elapsed = Math.min(1f, elapsed);
            return interpolator.getInterpolation(elapsed);
        }

        /**
         * Interpolate the current targeted zoom and get the delta
         * from the current zoom.
         * @param t
         * @return
         */
        private double calculateDeltaScale(float t) {
            double zoom = startZoom + t * (targetZoom - startZoom);
            return zoom / normalizedScale;
        }
    }

    /**
     * This function will transform the coordinates in the touch event to the coordinate
     * system of the drawable that the imageview contain
     * @param x x-coordinate of touch event
     * @param y y-coordinate of touch event
     * @param clipToBitmap Touch event may occur within view, but outside image content. True, to clip return value
     * 			to the bounds of the bitmap size.
     * @return Coordinates of the point touched, in the coordinate system of the original drawable.
     */
    private PointF transformCoordTouchToBitmap(float x, float y, boolean clipToBitmap) {
        matrix.getValues(m);
        float origW = getDrawable().getIntrinsicWidth();
        float origH = getDrawable().getIntrinsicHeight();
        float transX = m[Matrix.MTRANS_X];
        float transY = m[Matrix.MTRANS_Y];
        float finalX = ((x - transX) * origW) / getImageWidth();
        float finalY = ((y - transY) * origH) / getImageHeight();

        if (clipToBitmap) {
            finalX = Math.min(Math.max(finalX, 0), origW);
            finalY = Math.min(Math.max(finalY, 0), origH);
        }

        return new PointF(finalX , finalY);
    }

    /**
     * Inverse of transformCoordTouchToBitmap. This function will transform the coordinates in the
     * drawable's coordinate system to the view's coordinate system.
     * @param bx x-coordinate in original bitmap coordinate system
     * @param by y-coordinate in original bitmap coordinate system
     * @return Coordinates of the point in the view's coordinate system.
     */
    private PointF transformCoordBitmapToTouch(float bx, float by) {
        matrix.getValues(m);
        float origW = getDrawable().getIntrinsicWidth();
        float origH = getDrawable().getIntrinsicHeight();
        float px = bx / origW;
        float py = by / origH;
        float finalX = m[Matrix.MTRANS_X] + getImageWidth() * px;
        float finalY = m[Matrix.MTRANS_Y] + getImageHeight() * py;
        return new PointF(finalX , finalY);
    }

    /**
     * Fling launches sequential runnables which apply
     * the fling graphic to the image. The values for the translation
     * are interpolated by the Scroller.
     * @author Ortiz
     *
     */
    private class Fling implements Runnable {

        CompatScroller scroller;
        int currX, currY;

        Fling(int velocityX, int velocityY) {
            setState(State.FLING);
            scroller = new CompatScroller(context);
            matrix.getValues(m);

            int startX = (int) m[Matrix.MTRANS_X];
            int startY = (int) m[Matrix.MTRANS_Y];
            int minX, maxX, minY, maxY;

            if (getImageWidth() > viewWidth) {
                minX = viewWidth - (int) getImageWidth();
                maxX = 0;

            } else {
                minX = maxX = startX;
            }

            if (getImageHeight() > viewHeight) {
                minY = viewHeight - (int) getImageHeight();
                maxY = 0;

            } else {
                minY = maxY = startY;
            }

            scroller.fling(startX, startY, (int) velocityX, (int) velocityY, minX,
                    maxX, minY, maxY);
            currX = startX;
            currY = startY;
        }

        public void cancelFling() {
            if (scroller != null) {
                setState(State.NONE);
                scroller.forceFinished(true);
            }
        }

        @Override
        public void run() {

            //
            // OnTouchImageViewListener is set: TouchImageView listener has been flung by user.
            // Listener runnable updated with each frame of fling animation.
            //
            if (touchImageViewListener != null) {
                touchImageViewListener.onMove();
            }

            if (scroller.isFinished()) {
                scroller = null;
                return;
            }

            if (scroller.computeScrollOffset()) {
                int newX = scroller.getCurrX();
                int newY = scroller.getCurrY();
                int transX = newX - currX;
                int transY = newY - currY;
                currX = newX;
                currY = newY;
                matrix.postTranslate(transX, transY);
                fixTrans();
                setImageMatrix(matrix);
                compatPostOnAnimation(this);
            }
        }
    }

    @TargetApi(VERSION_CODES.GINGERBREAD)
    private class CompatScroller {
        Scroller scroller;
        OverScroller overScroller;
        boolean isPreGingerbread;

        public CompatScroller(Context context) {
            if (VERSION.SDK_INT < VERSION_CODES.GINGERBREAD) {
                isPreGingerbread = true;
                scroller = new Scroller(context);

            } else {
                isPreGingerbread = false;
                overScroller = new OverScroller(context);
            }
        }

        public void fling(int startX, int startY, int velocityX, int velocityY, int minX, int maxX, int minY, int maxY) {
            if (isPreGingerbread) {
                scroller.fling(startX, startY, velocityX, velocityY, minX, maxX, minY, maxY);
            } else {
                overScroller.fling(startX, startY, velocityX, velocityY, minX, maxX, minY, maxY);
            }
        }

        public void forceFinished(boolean finished) {
            if (isPreGingerbread) {
                scroller.forceFinished(finished);
            } else {
                overScroller.forceFinished(finished);
            }
        }

        public boolean isFinished() {
            if (isPreGingerbread) {
                return scroller.isFinished();
            } else {
                return overScroller.isFinished();
            }
        }

        public boolean computeScrollOffset() {
            if (isPreGingerbread) {
                return scroller.computeScrollOffset();
            } else {
                overScroller.computeScrollOffset();
                return overScroller.computeScrollOffset();
            }
        }

        public int getCurrX() {
            if (isPreGingerbread) {
                return scroller.getCurrX();
            } else {
                return overScroller.getCurrX();
            }
        }

        public int getCurrY() {
            if (isPreGingerbread) {
                return scroller.getCurrY();
            } else {
                return overScroller.getCurrY();
            }
        }
    }

    @TargetApi(VERSION_CODES.JELLY_BEAN)
    private void compatPostOnAnimation(Runnable runnable) {
        if (VERSION.SDK_INT >= VERSION_CODES.JELLY_BEAN) {
            postOnAnimation(runnable);

        } else {
            postDelayed(runnable, 1000/60);
        }
    }

    private class ZoomVariables {
        public float scale;
        public float focusX;
        public float focusY;
        public ScaleType scaleType;

        public ZoomVariables(float scale, float focusX, float focusY, ScaleType scaleType) {
            this.scale = scale;
            this.focusX = focusX;
            this.focusY = focusY;
            this.scaleType = scaleType;
        }
    }

    private void printMatrixInfo() {
        float[] n = new float[9];
        matrix.getValues(n);
        Log.d(DEBUG, "Scale: " + n[Matrix.MSCALE_X] + " TransX: " + n[Matrix.MTRANS_X] + " TransY: " + n[Matrix.MTRANS_Y]);
    }
}

Hi, please help to modify this code so that the image can be zoomed according to the width and height of the screen and not only imageview.

It has issues. If we add some loader, this image doesn't load until you pinch for zoom out.