import android.content.Context;
        import android.graphics.Bitmap;
        import android.graphics.Canvas;
        import android.graphics.Matrix;
        import android.util.AttributeSet;
        import android.view.MotionEvent;
        import android.view.View;

public class ZoomImageView extends View {
    public static final int STATUS_INIT = 1;//常量初始化
    public static final int STATUS_ZOOM_OUT = 2;//圖片放大狀態(tài)常量
    public static final int STATUS_ZOOM_IN = 3;//圖片縮小狀態(tài)常量
    public static final int STATUS_MOVE = 4;//圖片拖動(dòng)狀態(tài)常量
    private Matrix matrix = new Matrix();//對(duì)圖片進(jìn)行移動(dòng)和縮放變換的矩陣
    private Bitmap sourceBitmap;//待展示的Bitmap對(duì)象
    private int currentStatus;//記錄當(dāng)前操作的狀態(tài)枫虏，可選值為STATUS_INIT是尖、STATUS_ZOOM_OUT、STATUS_ZOOM_IN和STATUS_MOVE
    private int width;//ZoomImageView控件的寬度
    private int height;//ZoomImageView控件的高度
    private float centerPointX;//記錄兩指同時(shí)放在屏幕上時(shí)父叙，中心點(diǎn)的橫坐標(biāo)值
    private float centerPointY;//記錄兩指同時(shí)放在屏幕上時(shí)，中心點(diǎn)的縱坐標(biāo)值
    private float currentBitmapWidth;//記錄當(dāng)前圖片的寬度肴裙，圖片被縮放時(shí)趾唱，這個(gè)值會(huì)一起變動(dòng)
    private float currentBitmapHeight;//記錄當(dāng)前圖片的高度，圖片被縮放時(shí)蜻懦，這個(gè)值會(huì)一起變動(dòng)
    private float lastXMove = -1;//記錄上次手指移動(dòng)時(shí)的橫坐標(biāo)
    private float lastYMove = -1;//記錄上次手指移動(dòng)時(shí)的縱坐標(biāo)
    private float movedDistanceX;//記錄手指在橫坐標(biāo)方向上的移動(dòng)距離
    private float movedDistanceY;//記錄手指在縱坐標(biāo)方向上的移動(dòng)距離
    private float totalTranslateX;//記錄圖片在矩陣上的橫向偏移值
    private float totalTranslateY;//記錄圖片在矩陣上的縱向偏移值
    private float totalRatio;//記錄圖片在矩陣上的總縮放比例
    private float scaledRatio;//記錄手指移動(dòng)的距離所造成的縮放比例
    private float initRatio;//記錄圖片初始化時(shí)的縮放比例
    private double lastFingerDis;//記錄上次兩指之間的距離


    /**
     * ZoomImageView構(gòu)造函數(shù)甜癞，將當(dāng)前操作狀態(tài)設(shè)為STATUS_INIT。
     *
     * @param context
     * @param attrs
     */
    public ZoomImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        currentStatus = STATUS_INIT;
    }


    /*將待展示的圖片設(shè)置進(jìn)來(lái)宛乃。
    * @param bitmap
    * 待展示的Bitmap對(duì)象
    */
    public void setImageBitmap(Bitmap bitmap) {
        sourceBitmap = bitmap;
        invalidate();
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right,
                            int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        if (changed) {
// 分別獲取到ZoomImageView的寬度和高度
            width = getWidth();
            height = getHeight();
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (initRatio == totalRatio) {
            getParent().requestDisallowInterceptTouchEvent(false);
        } else {
            getParent().requestDisallowInterceptTouchEvent(true);
        }
        switch (event.getActionMasked()) {
            case MotionEvent.ACTION_POINTER_DOWN:
                if (event.getPointerCount() == 2) {
// 當(dāng)有兩個(gè)手指按在屏幕上時(shí)悠咱，計(jì)算兩指之間的距離
                    lastFingerDis = distanceBetweenFingers(event);
                }
                break;
            case MotionEvent.ACTION_CANCEL:
            case MotionEvent.ACTION_MOVE:
                if (event.getPointerCount() == 1) {
// 只有單指按在屏幕上移動(dòng)時(shí)，為拖動(dòng)狀態(tài)
                    float xMove = event.getX();
                    float yMove = event.getY();
                    if (lastXMove == -1 && lastYMove == -1) {
                        lastXMove = xMove;
                        lastYMove = yMove;
                    }
                    currentStatus = STATUS_MOVE;
                    movedDistanceX = xMove - lastXMove;
                    movedDistanceY = yMove - lastYMove;
// 進(jìn)行邊界檢查征炼，不允許將圖片拖出邊界
                    if (totalTranslateX + movedDistanceX > 0) {
                        movedDistanceX = 0;
                    } else if (width - (totalTranslateX + movedDistanceX) > currentBitmapWidth) {
                        movedDistanceX = 0;
                    }
                    if (totalTranslateY + movedDistanceY > 0) {
                        movedDistanceY = 0;
                    } else if (height - (totalTranslateY + movedDistanceY) > currentBitmapHeight) {
                        movedDistanceY = 0;
                    }
// 調(diào)用onDraw()方法繪制圖片
                    invalidate();
                    lastXMove = xMove;
                    lastYMove = yMove;
                } else if (event.getPointerCount() == 2) {
// 有兩個(gè)手指按在屏幕上移動(dòng)時(shí)析既，為縮放狀態(tài)
                    centerPointBetweenFingers(event);
                    double fingerDis = distanceBetweenFingers(event);
                    if (fingerDis > lastFingerDis) {
                        currentStatus = STATUS_ZOOM_OUT;
                    } else {
                        currentStatus = STATUS_ZOOM_IN;
                    }
// 進(jìn)行縮放倍數(shù)檢查，最大只允許將圖片放大6倍谆奥，最小可以縮小到初始化比例
                    if ((currentStatus == STATUS_ZOOM_OUT && totalRatio < 6 * initRatio)
                            || (currentStatus == STATUS_ZOOM_IN && totalRatio > initRatio)) {
                        scaledRatio = (float) (fingerDis / lastFingerDis);
                        totalRatio = totalRatio * scaledRatio;
                        if (totalRatio > 6 * initRatio) {
                            totalRatio = 6 * initRatio;
                        } else if (totalRatio < initRatio) {
                            totalRatio = initRatio;
                        }
// 調(diào)用onDraw()方法繪制圖片
                        invalidate();
                        lastFingerDis = fingerDis;
                    }
                }
                break;
            case MotionEvent.ACTION_POINTER_UP:
                if (event.getPointerCount() == 2) {
// 手指離開(kāi)屏幕時(shí)將臨時(shí)值還原
                    lastXMove = -1;
                    lastYMove = -1;
                }
                break;
            case MotionEvent.ACTION_UP:
// 手指離開(kāi)屏幕時(shí)將臨時(shí)值還原
                lastXMove = -1;
                lastYMove = -1;
                break;
            default:
                break;
        }
        return true;
    }

    /*根據(jù)currentStatus的值來(lái)決定對(duì)圖片進(jìn)行什么樣的繪制操作渡贾。*/
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        switch (currentStatus) {
            case STATUS_ZOOM_OUT:
            case STATUS_ZOOM_IN:
                zoom(canvas);
                break;
            case STATUS_MOVE:
                move(canvas);
                break;
            case STATUS_INIT:
                initBitmap(canvas);
            default:
                if (sourceBitmap != null) {
                    canvas.drawBitmap(sourceBitmap, matrix, null);
                }
                break;
        }
    }


    /**
     * 對(duì)圖片進(jìn)行縮放處理。
     *
     * @param canvas
     */
    private void zoom(Canvas canvas) {
        matrix.reset();
// 將圖片按總縮放比例進(jìn)行縮放
        matrix.postScale(totalRatio, totalRatio);
        float scaledWidth = sourceBitmap.getWidth() * totalRatio;
        float scaledHeight = sourceBitmap.getHeight() * totalRatio;
        float translateX = 0f;
        float translateY = 0f;
// 如果當(dāng)前圖片寬度小于屏幕寬度雄右，則按屏幕中心的橫坐標(biāo)進(jìn)行水平縮放空骚。否則按兩指的中心點(diǎn)的橫坐標(biāo)進(jìn)行水平縮放
        if (currentBitmapWidth < width) {
            translateX = (width - scaledWidth) / 2f;
        } else {
            translateX = totalTranslateX * scaledRatio + centerPointX
                    * (1 - scaledRatio);
// 進(jìn)行邊界檢查，保證圖片縮放后在水平方向上不會(huì)偏移出屏幕
            if (translateX > 0) {
                translateX = 0;
            } else if (width - translateX > scaledWidth) {
                translateX = width - scaledWidth;
            }
        }
// 如果當(dāng)前圖片高度小于屏幕高度擂仍，則按屏幕中心的縱坐標(biāo)進(jìn)行垂直縮放囤屹。否則按兩指的中心點(diǎn)的縱坐標(biāo)進(jìn)行垂直縮放
        if (currentBitmapHeight < height) {
            translateY = (height - scaledHeight) / 2f;
        } else {
            translateY = totalTranslateY * scaledRatio + centerPointY
                    * (1 - scaledRatio);
// 進(jìn)行邊界檢查，保證圖片縮放后在垂直方向上不會(huì)偏移出屏幕
            if (translateY > 0) {
                translateY = 0;
            } else if (height - translateY > scaledHeight) {
                translateY = height - scaledHeight;
            }
        }
// 縮放后對(duì)圖片進(jìn)行偏移逢渔，以保證縮放后中心點(diǎn)位置不變
        matrix.postTranslate(translateX, translateY);
        totalTranslateX = translateX;
        totalTranslateY = translateY;
        currentBitmapWidth = scaledWidth;
        currentBitmapHeight = scaledHeight;
        canvas.drawBitmap(sourceBitmap, matrix, null);
    }


    /**
     * 對(duì)圖片進(jìn)行平移處理
     *
     * @param canvas
     */
    private void move(Canvas canvas) {
        matrix.reset();
// 根據(jù)手指移動(dòng)的距離計(jì)算出總偏移值
        float translateX = totalTranslateX + movedDistanceX;
        float translateY = totalTranslateY + movedDistanceY;
// 先按照已有的縮放比例對(duì)圖片進(jìn)行縮放
        matrix.postScale(totalRatio, totalRatio);
// 再根據(jù)移動(dòng)距離進(jìn)行偏移
        matrix.postTranslate(translateX, translateY);
        totalTranslateX = translateX;
        totalTranslateY = translateY;
        canvas.drawBitmap(sourceBitmap, matrix, null);
    }


    /**
     * 對(duì)圖片進(jìn)行初始化操作肋坚，包括讓圖片居中，以及當(dāng)圖片大于屏幕寬高時(shí)對(duì)圖片進(jìn)行壓縮肃廓。
     *
     * @param canvas
     */
    private void initBitmap(Canvas canvas) {
        if (sourceBitmap != null) {
            matrix.reset();
            int bitmapWidth = sourceBitmap.getWidth();
            int bitmapHeight = sourceBitmap.getHeight();
            if (bitmapWidth > width || bitmapHeight > height) {
                if (bitmapWidth - width > bitmapHeight - height) {
// 當(dāng)圖片寬度大于屏幕寬度時(shí)智厌，將圖片等比例壓縮，使它可以完全顯示出來(lái)
                    float ratio = width / (bitmapWidth * 1.0f);
                    matrix.postScale(ratio, ratio);
                    float translateY = (height - (bitmapHeight * ratio)) / 2f;
// 在縱坐標(biāo)方向上進(jìn)行偏移盲赊，以保證圖片居中顯示
                    matrix.postTranslate(0, translateY);
                    totalTranslateY = translateY;
                    totalRatio = initRatio = ratio;
                } else {
// 當(dāng)圖片高度大于屏幕高度時(shí)铣鹏，將圖片等比例壓縮，使它可以完全顯示出來(lái)
                    float ratio = height / (bitmapHeight * 1.0f);
                    matrix.postScale(ratio, ratio);
                    float translateX = (width - (bitmapWidth * ratio)) / 2f;
// 在橫坐標(biāo)方向上進(jìn)行偏移哀蘑，以保證圖片居中顯示
                    matrix.postTranslate(translateX, 0);
                    totalTranslateX = translateX;
                    totalRatio = initRatio = ratio;
                }
                currentBitmapWidth = bitmapWidth * initRatio;
                currentBitmapHeight = bitmapHeight * initRatio;
            } else {
// 當(dāng)圖片的寬高都小于屏幕寬高時(shí)诚卸，直接讓圖片居中顯示
                float translateX = (width - sourceBitmap.getWidth()) / 2f;
                float translateY = (height - sourceBitmap.getHeight()) / 2f;
                matrix.postTranslate(translateX, translateY);
                totalTranslateX = translateX;
                totalTranslateY = translateY;
                totalRatio = initRatio = 1f;
                currentBitmapWidth = bitmapWidth;
                currentBitmapHeight = bitmapHeight;
            }
            canvas.drawBitmap(sourceBitmap, matrix, null);
        }
    }


    /**
     * 計(jì)算兩個(gè)手指之間的距離。
     *
     * @param event
     * @return 兩個(gè)手指之間的距離
     */
    private double distanceBetweenFingers(MotionEvent event) {
        float disX = Math.abs(event.getX(0) - event.getX(1));
        float disY = Math.abs(event.getY(0) - event.getY(1));
        return Math.sqrt(disX * disX + disY * disY);
    }


    /**
     * 計(jì)算兩個(gè)手指之間中心點(diǎn)的坐標(biāo)绘迁。
     *
     * @param event
     */
    private void centerPointBetweenFingers(MotionEvent event) {
        float xPoint0 = event.getX(0);
        float yPoint0 = event.getY(0);
        float xPoint1 = event.getX(1);
        float yPoint1 = event.getY(1);
        centerPointX = (xPoint0 + xPoint1) / 2;
        centerPointY = (yPoint0 + yPoint1) / 2;
    }
}

這里推薦一個(gè)第三方組件

android PhotoView圖片控件合溺，手勢(shì)放大縮小的簡(jiǎn)單用法
在我們項(xiàng)目module build.gradle中配置

compile 'com.bm.photoview:library:1.4.1'

然后右上角Sync Now一下，去下載這個(gè)包缀台。
直接在布局文件里面添加

<com.bm.library.PhotoView
    android:id="@+id/photoview"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

在初始化的時(shí)候默認(rèn)這個(gè)控件是不縮放的棠赛，加上

     ptotoview.enable();