android - Youtube 缩略图在使用官方 YouTube Android Player API 的 ListView 中闪烁

Question

我的问题不容易用语言描述，但我会尽力而为。我有一个显示 YouTube 视频缩略图的 ListView。基本上这些缩略图确实加载正确(意味着每个缩略图都显示在 ListView 的相应行中)，但是在列表中滑动时会发生奇怪的事情。向下滑动列表(= 从列表顶部向其末尾滑动)时，只要有新缩略图进入屏幕，它就会显示错误的缩略图几毫秒，然后再更改为正确的缩略图。错误的缩略图总是之前两行或三行的缩略图。向上/向后滑动列表时，所有内容都会立即以正确的方式显示。

我完全不知道从哪里开始搜索这个，但我想我的 ListView 适配器可能会感兴趣:

private final Map<View, YouTubeThumbnailLoader> thumbnailViewToLoaderMap;

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    SuggestionViewHolder holder;

    Suggestion suggestion = getItem(position);
    String videoId = suggestion.getYoutubeId();

    // There are three cases here:
    if (convertView == null) {
        convertView = layoutInflater.inflate(R.layout.row_suggestion, parent, false);

        holder = new SuggestionViewHolder();

        // 1) The view has not yet been created - we need to initialize the YouTubeThumbnailView.
        holder.thumbnailView = (YouTubeThumbnailView) convertView.findViewById(R.id.youtubeThumbnail);
        holder.thumbnailView.setTag(videoId);
        holder.thumbnailView.initialize(DeveloperKey.DEVELOPER_KEY, this);

        convertView.setTag(holder);

    } else {

        holder = (SuggestionViewHolder) convertView.getTag();

        // 2) and 3) The view is already created...
        YouTubeThumbnailLoader loader = thumbnailViewToLoaderMap.get(holder.thumbnailView);

        // ...and is currently being initialized. We store the current videoId in the tag.
        if (loader == null) {
            holder.thumbnailView.setTag(videoId);

        // ...and already initialized. Simply set the right videoId on the loader.
        } else {
            loader.setVideo(videoId);

        }
    }

    return convertView;
}


@Override
public void onInitializationSuccess(YouTubeThumbnailView youTubeThumbnailView, YouTubeThumbnailLoader youTubeThumbnailLoader) {
    String videoId = (String) youTubeThumbnailView.getTag();

    thumbnailViewToLoaderMap.put(youTubeThumbnailView, youTubeThumbnailLoader);

    youTubeThumbnailLoader.setOnThumbnailLoadedListener(this);
    youTubeThumbnailLoader.setVideo(videoId);
}


private static class SuggestionViewHolder {
    public YouTubeThumbnailView thumbnailView;
}

知道为什么会这样吗？也许是 ListView 的一些缓存内容(因为在切换图像之前它总是显示以前的缩略图之一)？

Answer 1

发生这种情况是因为加载程序需要时间来显示缩略图。当单元格被重复使用时，它会保留前一个单元格的图像，因此如果加载程序需要时间，它会在加载新图像之前显示旧图像一段时间。你必须在调用加载程序之前清除它。

    holder = (SuggestionViewHolder) convertView.getTag();

    // 2) and 3) The view is already created...
    YouTubeThumbnailLoader loader = thumbnailViewToLoaderMap.get(holder.thumbnailView);

    // ...and is currently being initialized. We store the current videoId in the tag.
    if (loader == null) {
        holder.thumbnailView.setTag(videoId);

    // ...and already initialized. Simply set the right videoId on the loader.
    } else {
        holder.thumbnailView.setImageBitmap(null);
        loader.setVideo(videoId);

    }