Question

我的问题用文字描述并不容易，但我会尽我所能。我有一个ListView，显示YouTube视频的缩略图。基本上这些缩略图确实正确加载（意味着每个缩略图都显示在ListView的相应行中），但是在浏览列表时会发生奇怪的事情。每当新的缩略图进入屏幕时向下滑动列表（=从列表的顶部向其末端），在更改为正确的缩略图之前，它会显示错误的缩略图几毫秒。 错误的缩略图始终是前两行或三行的缩略图。在向上/向后滑动列表的同时，所有内容都会以正确的方式立即显示。

我完全不知道从哪里开始搜索，但我想我的listview适配器可能会引起关注：

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;
}

为什么会这样？也许是列表视图的一些缓存（因为它在切换图像之前总是显示以前的缩略图之一）？

Answer 1

这是因为加载程序需要时间来显示缩略图。当重复使用单元格时，它会保留前一个单元格中的图像，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。你必须在调用加载器之前清除它。

    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);

    }

Youtube缩略图使用官方YouTube Android Player API在ListView中闪烁

1 个答案: