Android 点击图片，放大查看，实现缩放拖动等功能

实现方法：点击图片时，把图片url传到另一个activity中实现放大拖动，

图片点击事件触发：
Intent intent = new Intent();
intent.setClass(mContext, PictureActivity.class);
intent.putExtra(“url”,R.drawable.ic_logo);
mContext.startActivity(intent);

然后创建一个activity的内容如下：
public class PictureActivity extends AppCompatActivity {
private ZoomImageView zoomView;
private GestureDetector gestureDetector;
private LinearLayout layout;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);
    setContentView(R.layout.activity_picture_preview);

    zoomView = (ZoomImageView) findViewById(R.id.zoom_view);
    zoomView.getActivity(PicturePreviewActivity.this);
    layout = (LinearLayout) this.findViewById(R.id.layout_picture_preview);
    //这里把intent收到的资源文件下的图片转成bitmap。
    Bitmap url = BitmapFactory.decodeResource(getResources(),
            getIntent().getIntExtra("url", 0), null);

    layout.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            PicturePreviewActivity.this.finish();
        }
    });
    //若图片模糊，根据原图比例调整这里的宽高即可
    zoomView.setImageBitmap(zoomBitmap(url, 4080,
            1920));

    gestureDetector = new GestureDetector(this,
            new GestureDetector.SimpleOnGestureListener() {
                @Override
                public boolean onFling(MotionEvent e1, MotionEvent e2,
                                       float velocityX, float velocityY) {
                    float x = e2.getX() - e1.getX();
                    if (x > 0) {
                        prePicture();
                    } else if (x < 0) {

                        nextPicture();
                    }
                    return true;
                }
            });



}

protected void nextPicture() {
    // TODO Auto-generated method stub

}

protected void prePicture() {
    // TODO Auto-generated method stub

}

@Override
public void onResume() {
    super.onResume();
    // recycle();
}

public void recycle() {
    if (zoomView != null && zoomView.getDrawable() != null) {
        BitmapDrawable bitmapDrawable = (BitmapDrawable) zoomView
                .getDrawable();
        if (bitmapDrawable != null && bitmapDrawable.getBitmap() != null
                && !bitmapDrawable.getBitmap().isRecycled()) {
            bitmapDrawable.getBitmap().recycle();
        }
    }
}


public Bitmap getBitMapFromUrl(String url) {
    Bitmap bitmap = null;
    URL u = null;
    HttpURLConnection conn = null;
    InputStream is = null;
    try {
        u = new URL(url);
        conn = (HttpURLConnection) u.openConnection();
        is = conn.getInputStream();
        bitmap = BitmapFactory.decodeStream(is);
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            if (is != null) {
                is.close();
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
        conn.disconnect();
    }
    return bitmap;
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    return gestureDetector.onTouchEvent(event);
}

/**
 * Resize the bitmap
 *
 * @param bitmap
 * @param width
 * @param height
 * @return
 */
public static Bitmap zoomBitmap(Bitmap bitmap, int width, int height) {
    if (bitmap == null)
        return bitmap;
    int w = bitmap.getWidth();
    int h = bitmap.getHeight();
    Matrix matrix = new Matrix();
    float scaleWidth = ((float) width / w);
    float scaleHeight = ((float) height / h);
    if (scaleWidth < scaleHeight) {
        matrix.postScale(scaleWidth, scaleWidth);
    } else {
        matrix.postScale(scaleHeight, scaleHeight);
    }
    Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);
    return newbmp;
}


public static boolean checkSDCardAvailable() {
    return android.os.Environment.getExternalStorageState().equals(
            android.os.Environment.MEDIA_MOUNTED);
}

public void closeActivity() {
    this.finish();
}

xml中代码
<com.hekang.EM.utils.ZoomImageView
android:id=“@+id/zoom_view”
android:layout_width=“wrap_content”
android:layout_height=“wrap_content”/>

自定义ZoomImageView类全部代码:

@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 = 4.0f;
private static final float SCALE_MID = 2.0f;

/**
 * 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;

private PicturePreviewActivity activity;


public void getActivity(PicturePreviewActivity activity) {
    this.activity = activity;
}

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) {
                        ZoomImageView.this.postDelayed(
                                new AutoScaleRunnable(SCALE_MID, x, y), 16);
                        isAutoScale = true;
                    } else if (getScale() >= SCALE_MID
                            && 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;
                }

                @Override
                public boolean onSingleTapConfirmed(MotionEvent e) {
                    Log.i(TAG, "single");
                    activity.closeActivity();
                    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;
        }

    }
}

@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) {
}

@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;
                    }


                    mScaleMatrix.postTranslate(dx, dy);
                    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);
}

@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;
}

}