Android实现图片查看功能

/**
 * 缩放手势监听
 */
private ScaleGestureDetector.OnScaleGestureListener mOnScaleGestureListener= new ScaleGestureDetector.SimpleOnScaleGestureListener() {

  @Override
  public boolean onScale(ScaleGestureDetector detector) {
    float scaleFactor = detector.getScaleFactor();
    float wantScale = mScale * scaleFactor;
    if (wantScale >= MIN_SCALE) {
      mScale = wantScale;
      focusX = detector.getFocusX();
      focusY = detector.getFocusY();
      mMatrix.postScale(scaleFactor, scaleFactor, focusX, focusY);
      invalidate();
    }
    return true;
  }
};

/**
 * 简单手势监听
 */
private GestureDetector.SimpleOnGestureListener mOnGestureListener= new GestureDetector.SimpleOnGestureListener() {

  ...

  @Override
  public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
    if (!isAlwaysSingleTouch) {
      return true;
    }
    mMatrix.postTranslate(-distanceX, -distanceY);
    invalidate();
    return false;
  }

  ...
};

@Override
protected void onDraw(Canvas canvas) {
  int saveCount = canvas.save();
  canvas.concat(mMatrix);
  super.onDraw(canvas);
  canvas.restoreToCount(saveCount);
}

OverScroller.fling(int startX, int startY, int velocityX, int velocityY,int minX, int maxX, int minY, int maxY)

/**
 * 惯性滑动工具类
 * 使用fling方法开始滑动
 * 使用stop方法停止滑动
 */
private class FlingUtil implements Runnable {
  private int mLastFlingX = 0;
  private int mLastFlingY = 0;
  private OverScroller mScroller;
  private boolean mEatRunOnAnimationRequest= false;
  private boolean mReSchedulePostAnimatiOnCallback= false;

  /**
   * RecyclerView使用的惯性滑动插值器
   * f(x) = (x-1)^5 + 1
   */
  private final Interpolator sQuinticInterpolator = new Interpolator() {
    @Override
    public float getInterpolation(float t) {
      t -= 1.0f;
      return t * t * t * t * t + 1.0f;
    }
  };

  public FlingUtil() {
    mScroller = new OverScroller(getContext(), sQuinticInterpolator);
  }

  @Override
  public void run() {
    disableRunOnAnimationRequests();
    final OverScroller scroller = mScroller;
    if (scroller.computeScrollOffset()) {
      final int y = scroller.getCurrY();
      int dy = y - mLastFlingY;
      final int x = scroller.getCurrX();
      int dx = x - mLastFlingX;
      mLastFlingY = y;
      mLastFlingX = x;
      constrainScrollBy(dx, dy);
      postOnAnimation();
    }
    enableRunOnAnimationRequests();
  }

  public void fling(int velocityX, int velocityY) {
    mLastFlingX = 0;
    mLastFlingY = 0;
    mScroller.fling(0, 0, velocityX, velocityY, Integer.MIN_VALUE, Integer.MAX_VALUE, Integer.MIN_VALUE, Integer.MAX_VALUE);
    postOnAnimation();
  }

  public void stop() {
    removeCallbacks(this);
    mScroller.abortAnimation();
  }

  private void disableRunOnAnimationRequests() {
    mReSchedulePostAnimatiOnCallback= false;
    mEatRunOnAnimationRequest= true;
  }

  private void enableRunOnAnimationRequests() {
    mEatRunOnAnimationRequest= false;
    if (mReSchedulePostAnimationCallback) {
      postOnAnimation();
    }
  }

  void postOnAnimation() {
    if (mEatRunOnAnimationRequest) {
      mReSchedulePostAnimatiOnCallback= true;
    } else {
      removeCallbacks(this);
      ViewCompat.postOnAnimation(ZoomImageView.this, this);
    }
  }
}

/**
 * 获得缩放移动后的图片内容的位置区域
 *
 * @param matrix
 * @return RectF
 */
private RectF getScaledRect(Matrix matrix) {
  RectF rectF = new RectF(mImageRectF);
  //转化为缩放后的相对位置
  matrix.mapRect(rectF);
  return rectF;
}

/**
 * 针对边缘问题，约束移动
 *
 * @param dx
 * @param dy
 */
private void constrainScrollBy(float dx, float dy) {
  RectF rectF = getScaledRect(mMatrix);
  float scaleImageWidth = rectF.width();
  float scaleImageHeight = rectF.height();

  if (scaleImageWidth > mWidth) {
    //right
    if (rectF.right + dx  0) {
      dx = -rectF.left;
    }
  } else {
    //center
    dx = -rectF.left + ((float) mWidth - scaleImageWidth) / 2;
  }

  if (scaleImageHeight > mHeight) {
    //bottom
    if (rectF.bottom + dy  0) {
      dy = -rectF.top;
    }
  } else {
    //center
    dy = -rectF.top + ((float) mHeight - scaleImageHeight) / 2;
  }

  mMatrix.postTranslate(dx, dy);
  invalidate();
  checkBorder();
}

private ControllerListener cOntrollerListener= new BaseControllerListener() {
  @Override
  public void onFinalImageSet(String id, @Nullable ImageInfo imageInfo, @Nullable Animatable anim) {
    if (imageInfo == null) {
      return;
    }
    int preWidth = imageInfo.getWidth();
    int preHeight = imageInfo.getHeight();
    if (preWidth != mWidth || preHeight != mHeight) {
      //获取到最新的图片内容的宽高
      mWidth = preWidth;
      mHeight = preHeight;
    }
  }

  @Override
  public void onIntermediateImageSet(String id, @Nullable ImageInfo imageInfo) {
    Log.d("zhufeng", "Intermediate image received");
  }

  @Override
  public void onFailure(String id, Throwable throwable) {
    throwable.printStackTrace();
  }
};

public void loadImage(int resizeX, int resizeY, Uri uri) {
  ImageRequest request = ImageRequestBuilder
      .newBuilderWithSource(uri)
      .setResizeOptions(new ResizeOptions(resizeX, resizeY))
      .build();
  PipelineDraweeController cOntroller= (PipelineDraweeController) Fresco.newDraweeControllerBuilder().setControllerListener(controllerListener).setOldController(getController()).setImageRequest(request).build();
  setController(controller);
}

/**
 * 用于ViewPager滑动拦截
 *
 * @param direction
 * @return
 */
public boolean canScroll(int direction) {
  return !((direction <0 && isRightSide()) || (direction > 0 && isLeftSide()));
}

/**
 * 相册ViewPager
 *
 * @author zhufeng on 2017/10/22
 */
public class AlbumViewPager extends ViewPager {

  ...

  @Override
  protected boolean canScroll(View v, boolean checkV, int dx, int x, int y) {
    if (v instanceof ZoomImageView) {
      return ((ZoomImageView) v).canScroll(dx) || super.canScroll(v, checkV, dx, x, y);
    }
    return super.canScroll(v, checkV, dx, x, y);
  }

  ...

}