Question

我在自定义视图中使用DraweeHolder来显示图像。当我想用新资源更新图像时，我创建一个新的DraweeController，然后将setController创建为DraweeHolder。

我想要实现的是前一个图像和新图像之间的交叉淡化效果。对于淡入/淡出，我将setAlpha递归到drawable。

void handleTransition(DraweeHolder draweeHolder, long startingTime) {
    Drawable drawable = draweeHolder.getTopLevelDrawable().mutate();
    int duration = 2000;
    long currTime = System.currentTimeMillis();
    int diff = (int) (currTime - startingTime);
    int toAlpha = Math.max(0, 255 - (255 * diff / duration));
    drawable.setAlpha(toAlpha);
    invalidate();
}


@Override
protected void onDraw(Canvas canvas) {
    Log.d(TAG, "onDraw()");
    super.onDraw(canvas);
    synchronized (this) {
        handleTransition(draweeHolder, mCurrentTransStartTime);
    }
}

似乎工作正常，但onDraw会被调用太多次。但是，我不知道怎么能在这个DraweeHolder中同时出现两个图像（交叉淡入淡出）。即使为DraweeHolder设置高/低分辨率图像也不能选择交叉渐变。

Answer 1

你走在正确的轨道上。您必须编写自定义视图（例如，通过扩展ImageView）。请记住，为了让Drawee正常工作，您需要连接一些东西，请阅读here如何做到这一点。

您需要两个DraweeHolders。使用多个持有者时，最好将它们保存在MultiDraweeHolder：

中

  private void init() {
    mMultiDraweeHolder = new MultiDraweeHolder<GenericDraweeHierarchy>();
    // holders for the two images to cross-fade between
    Drawable drawables[] = new Drawable[2];
    for (int i = 0; i < drawables.length; i++) {
      GenericDraweeHierarchy hierarchy = createDraweeHierarchy();
      mMultiDraweeHolder.add(DraweeHolder.create(hierarchy, getContext()));
      drawables[i] = hierarchy.getTopLevelDrawable();
    }
    mFadeDrawable = new FadeDrawable(drawables);
    // no need to override onDraw, ImageView superclass will correctly draw our fade drawable if we set it like this:
    super.setImageDrawable(mFadeDrawable);
    mCurrentIndex = 0;
  }

  void loadNextImage(DraweeController controller) {
    mCurrentIndex = (mCurrentIndex + 1) % 2;
    mMultiDraweeHolder.get(mCurrentIndex).setController(controller);
    mFadeDrawable.fadeToLayer(mCurrentIndex);
  }

  GenericDraweeHierarchy createDraweeHierarchy() {
    // create a new drawee hierarchy here,
    // as each image needs to have its own instance
  }

DraweeHolder内的壁画交叉淡化

1 个答案: