Android 手势放大图片

效果图：

放大前：

放大后：

ZoomImageView.java

@SuppressLint("AppCompatCustomView")
public class ZoomImageView extends ImageView implements ScaleGestureDetector.OnScaleGestureListener, View.OnTouchListener, ViewTreeObserver.OnGlobalLayoutListener {

    private static final String TAG = ZoomImageView.class.getSimpleName();
    public static final float SCALE_MAX = 3.0f;
    private static final float SCALE_MID = 1.5f;

    /**
     * 初始化时的缩放比例，如果图片宽或高大于屏幕，此值将小于0
     */
    private float initScale = 1.0f;
    private boolean once = true;

    /**
     * 用于存放矩阵的9个值
     */
    private final float[] matrixValues = new float[9];

    /**
     * 缩放的手势检测
     */
    private ScaleGestureDetector mScaleGestureDetector = null;
    private final Matrix mScaleMatrix = new Matrix();

    /**
     * 用于双击检测
     */
    private GestureDetector mGestureDetector;
    private boolean isAutoScale;

    private int mTouchSlop;

    private float mLastX;
    private float mLastY;

    private boolean isCanDrag;
    private int lastPointerCount;

    private boolean isCheckTopAndBottom = true;
    private boolean isCheckLeftAndRight = true;

    public ZoomImageView(Context context) {
        this(context, null);
    }

    public ZoomImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        super.setScaleType(ScaleType.MATRIX);
        mGestureDetector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener() {
            @Override
            public boolean onDoubleTap(MotionEvent e) {
                if (isAutoScale == true)
                    return true;

                float x = e.getX();
                float y = e.getY();
                Log.e("DoubleTap", getScale() + " , " + initScale);
                if (getScale() < SCALE_MID) {
                    //postDelayed(); 16 ：多久实现一次的定时器操作
                    ZoomImageView.this.postDelayed(new AutoScaleRunnable(SCALE_MID, x, y), 16);
                    isAutoScale = true;
                } /*else if (getScale() >= SCALE_MID  //连续双击放大 可放开
                        && getScale() < SCALE_MAX) {
                    ZoomImageView.this.postDelayed(new AutoScaleRunnable(SCALE_MAX, x, y), 16);
                    isAutoScale = true;
                }*/ else {
                    ZoomImageView.this.postDelayed(new AutoScaleRunnable(initScale, x, y), 16);
                    isAutoScale = true;
                }

                return true;
            }
        });
        mScaleGestureDetector = new ScaleGestureDetector(context, this);
        this.setOnTouchListener(this);
    }



    /**
     * 自动缩放的任务
     * @author zhy
     */
    private class AutoScaleRunnable implements Runnable {
        static final float BIGGER = 1.07f;
        static final float SMALLER = 0.93f;
        private float mTargetScale;
        private float tmpScale;

        /**
         * 缩放的中心
         */
        private float x;
        private float y;

        /**
         * 传入目标缩放值，根据目标值与当前值，判断应该放大还是缩小
         * @param targetScale
         */
        public AutoScaleRunnable(float targetScale, float x, float y) {
            this.mTargetScale = targetScale;
            this.x = x;
            this.y = y;
            if (getScale() < mTargetScale) {
                tmpScale = BIGGER;
            } else {
                tmpScale = SMALLER;
            }
        }

        @Override
        public void run() {
            // 进行缩放
            mScaleMatrix.postScale(tmpScale, tmpScale, x, y);
            checkBorderAndCenterWhenScale();
            setImageMatrix(mScaleMatrix);

            final float currentScale = getScale();
            // 如果值在合法范围内，继续缩放
            if (((tmpScale > 1f) && (currentScale < mTargetScale)) || ((tmpScale < 1f) && (mTargetScale < currentScale))) {

                ZoomImageView.this.postDelayed(this, 16);
            } else {
                // 设置为目标的缩放比例
                final float deltaScale = mTargetScale / currentScale;
                mScaleMatrix.postScale(deltaScale, deltaScale, x, y);
                checkBorderAndCenterWhenScale();
                setImageMatrix(mScaleMatrix);
                isAutoScale = false;
            }
        }
    }

    /**
     * 对图片进行缩放的控制，首先进行缩放范围的判断，然后设置mScaleMatrix的scale值
     * @param detector
     * @return
     */
    @SuppressLint("NewApi")
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        float scale = getScale();
        float scaleFactor = detector.getScaleFactor();

        if (getDrawable() == null)
            return true;

        /**
         * 缩放的范围控制
         */
        if ((scale < SCALE_MAX && scaleFactor > 1.0f) || (scale > initScale && scaleFactor < 1.0f)) {
            /**
             * 最大值最小值判断
             */
            if (scaleFactor * scale < initScale) {
                scaleFactor = initScale / scale;
            }
            if (scaleFactor * scale > SCALE_MAX) {
                scaleFactor = SCALE_MAX / scale;
            }
            /**
             * 设置缩放比例
             */
            mScaleMatrix.postScale(scaleFactor, scaleFactor, detector.getFocusX(), detector.getFocusY());

            checkBorderAndCenterWhenScale();
            setImageMatrix(mScaleMatrix);
        }
        return true;
    }

    /**
     * 在缩放时，进行图片显示范围的控制
     */
    private void checkBorderAndCenterWhenScale() {

        RectF rect = getMatrixRectF();
        float deltaX = 0;
        float deltaY = 0;

        int width = getWidth();
        int height = getHeight();

        // 如果宽或高大于屏幕，则控制范围
        if (rect.width() >= width) {
            if (rect.left > 0) {
                deltaX = -rect.left;
            }
            if (rect.right < width) {
                deltaX = width - rect.right;
            }
        }
        if (rect.height() >= height) {
            if (rect.top > 0) {
                deltaY = -rect.top;
            }
            if (rect.bottom < height) {
                deltaY = height - rect.bottom;
            }
        }
        // 如果宽或高小于屏幕，则让其居中
        if (rect.width() < width) {
            deltaX = width * 0.5f - rect.right + 0.5f * rect.width();
        }
        if (rect.height() < height) {
            deltaY = height * 0.5f - rect.bottom + 0.5f * rect.height();
        }
        Log.e(TAG, "deltaX = " + deltaX + " , deltaY = " + deltaY);

        mScaleMatrix.postTranslate(deltaX, deltaY);

    }

    /**
     * 根据当前图片的Matrix获得图片的范围
     * @return
     */
    private RectF getMatrixRectF() {
        Matrix matrix = mScaleMatrix;
        RectF rect = new RectF();
        Drawable d = getDrawable();
        if (null != d) {
            rect.set(0, 0, d.getIntrinsicWidth(), d.getIntrinsicHeight());
            matrix.mapRect(rect);
        }
        return rect;
    }

    @Override
    public boolean onScaleBegin(ScaleGestureDetector detector) {
        return true;
    }

    @Override
    public void onScaleEnd(ScaleGestureDetector detector) {
    }

    /**
     * 我们让OnTouchListener的MotionEvent交给ScaleGestureDetector进行处理
     * public boolean onTouch(View v, MotionEvent event){
     * return mScaleGestureDetector.onTouchEvent(event);
     * }
     */
    @Override
    public boolean onTouch(View v, MotionEvent event) {

        if (mGestureDetector.onTouchEvent(event))
            return true;
        mScaleGestureDetector.onTouchEvent(event);

        float x = 0, y = 0;
        // 拿到触摸点的个数
        final int pointerCount = event.getPointerCount();
        // 得到多个触摸点的x与y均值
        for (int i = 0; i < pointerCount; i++) {
            x += event.getX(i);
            y += event.getY(i);
        }
        x = x / pointerCount;
        y = y / pointerCount;

        /**
         * 每当触摸点发生变化时，重置mLasX , mLastY
         */
        if (pointerCount != lastPointerCount) {
            isCanDrag = false;
            mLastX = x;
            mLastY = y;
        }

        lastPointerCount = pointerCount;
        RectF rectF = getMatrixRectF();

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                if (rectF.width() > getWidth() || rectF.height() > getHeight()) {
                    getParent().requestDisallowInterceptTouchEvent(true);
                }
                break;
            case MotionEvent.ACTION_MOVE:
                if (rectF.width() > getWidth() || rectF.height() > getHeight()) {
                    getParent().requestDisallowInterceptTouchEvent(true);
                }
                Log.e(TAG, "ACTION_MOVE");
                float dx = x - mLastX;
                float dy = y - mLastY;

                if (!isCanDrag) {
                    isCanDrag = isCanDrag(dx, dy);
                }
                if (isCanDrag) {

                    if (getDrawable() != null) {
                        // if (getMatrixRectF().left == 0 && dx > 0)
                        // {
                        // getParent().requestDisallowInterceptTouchEvent(false);
                        // }
                        //
                        // if (getMatrixRectF().right == getWidth() && dx < 0)
                        // {
                        // getParent().requestDisallowInterceptTouchEvent(false);
                        // }
                        isCheckLeftAndRight = isCheckTopAndBottom = true;
                        // 如果宽度小于屏幕宽度，则禁止左右移动
                        if (rectF.width() < getWidth()) {
                            dx = 0;
                            isCheckLeftAndRight = false;
                        }
                        // 如果高度小雨屏幕高度，则禁止上下移动
                        if (rectF.height() < getHeight()) {
                            dy = 0;
                            isCheckTopAndBottom = false;
                        }

                        //设置偏移量
                        mScaleMatrix.postTranslate(dx, dy);
                        //再次校验
                        checkMatrixBounds();
                        setImageMatrix(mScaleMatrix);
                    }
                }
                mLastX = x;
                mLastY = y;
                break;

            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                Log.e(TAG, "ACTION_UP");
                lastPointerCount = 0;
                break;
        }
        return true;
    }

    /**
     * 获得当前的缩放比例
     * @return
     */
    public final float getScale() {
        mScaleMatrix.getValues(matrixValues);
        return matrixValues[Matrix.MSCALE_X];
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        getViewTreeObserver().addOnGlobalLayoutListener(this);
    }

    @SuppressWarnings("deprecation")
    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        getViewTreeObserver().removeGlobalOnLayoutListener(this);
    }

    /**
     * 根据图片的宽和高以及屏幕的宽和高，对图片进行缩放以及移动至屏幕的中心。
     * 如果图片很小，那就正常显示，不放大了~
     */
    @Override
    public void onGlobalLayout() {
        if (once) {
            Drawable d = getDrawable();
            if (d == null)
                return;
            Log.e(TAG, d.getIntrinsicWidth() + " , " + d.getIntrinsicHeight());
            int width = getWidth();
            int height = getHeight();
            // 拿到图片的宽和高
            int dw = d.getIntrinsicWidth();
            int dh = d.getIntrinsicHeight();
            float scale = 1.0f;
            // 如果图片的宽或者高大于屏幕，则缩放至屏幕的宽或者高
            if (dw > width && dh <= height) {
                scale = width * 1.0f / dw;
            }
            if (dh > height && dw <= width) {
                scale = height * 1.0f / dh;
            }
            // 如果宽和高都大于屏幕，则让其按按比例适应屏幕大小
            if (dw > width && dh > height) {
                scale = Math.min(width * 1.0f / dw, height * 1.0f / dh);
            }
            initScale = scale;

            Log.e(TAG, "initScale = " + initScale);
            mScaleMatrix.postTranslate((width - dw) / 2, (height - dh) / 2);
            mScaleMatrix.postScale(scale, scale, getWidth() / 2, getHeight() / 2);
            // 图片移动至屏幕中心
            setImageMatrix(mScaleMatrix);
            once = false;
        }
    }

    /**
     * 移动时，进行边界判断，主要判断宽或高大于屏幕的
     */
    private void checkMatrixBounds() {
        RectF rect = getMatrixRectF();

        float deltaX = 0, deltaY = 0;
        final float viewWidth = getWidth();
        final float viewHeight = getHeight();
        // 判断移动或缩放后，图片显示是否超出屏幕边界
        if (rect.top > 0 && isCheckTopAndBottom) {
            deltaY = -rect.top;
        }
        if (rect.bottom < viewHeight && isCheckTopAndBottom) {
            deltaY = viewHeight - rect.bottom;
        }
        if (rect.left > 0 && isCheckLeftAndRight) {
            deltaX = -rect.left;
        }
        if (rect.right < viewWidth && isCheckLeftAndRight) {
            deltaX = viewWidth - rect.right;
        }
        mScaleMatrix.postTranslate(deltaX, deltaY);
    }

    /**
     * 是否是推动行为
     *
     * @param dx
     * @param dy
     * @return
     */
    private boolean isCanDrag(float dx, float dy) {
        return Math.sqrt((dx * dx) + (dy * dy)) >= mTouchSlop;
    }

}

MainActivity.java

public class MainActivity extends AppCompatActivity {

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

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.turbosnail.android_app02.ZoomImageView
        android:layout_width="300dp"
        android:layout_height="300dp"
        android:layout_centerInParent="true"
        android:src="@drawable/img_activity04_1"
        tools:ignore="MissingConstraints" />

</RelativeLayout>