android - Textview 延迟加载，setText 在 gridview 中的错误位置？

Question

我创建了一个 gridview，它显示来自服务器的视频。 GridItem 有视频缩略图和视频持续时间。为了加载视频的缩略图，我正在使用 UniversalImageloader 并通过使用 asynctask 创建延迟加载来加载视频持续时间。延迟加载工作正常。但如果有人频繁滚动 gridview，则视频持续时间显示在错误的位置。为了创建延迟加载，我在下面关注 link

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    final TextView durationTextView;

    View view = null;
    if (convertView == null) {
        view = mInflater.inflate(R.layout.camera_roll_item, parent, false);

        MediaItemViewHolder mediaItemViewHolder = new MediaItemViewHolder();
        mediaItemViewHolder.highlightTagIcon = (ImageView) view.findViewById(R.id.iv_media_grid_item_highlight_tag);
        mediaItemViewHolder.mediaTypeIcon = (ImageView) view.findViewById(R.id.iv_media_grid_item_type);
        mediaItemViewHolder.mediaClipLength = (TextView) view.findViewById(R.id.tv_media_grid_item_length);
        mediaItemViewHolder.mediaThumbnail = (ImageView) view.findViewById(R.id.iv_media_grid_item_thumbnail);
        mediaItemViewHolder.cameraItemSelectedView = (RelativeLayout) view.findViewById(R.id.rl_item_selection_parent);
        mediaItemViewHolder.progressContainer = (RelativeLayout) view.findViewById(R.id.rl_grid_loader_parent);
        view.setTag(mediaItemViewHolder);
    } else {
        view = convertView;//(MediaItemViewHolder) convertView.getTag();
        //mediaItemViewHolder.mediaClipLength.setText("");
        Log.i(TAG, "set blank to ");
    }
    MediaItemViewHolder mediaItemViewHolder = (MediaItemViewHolder) convertView.getTag();
    durationTextView = mediaItemViewHolder.mediaClipLength;
    if (position >= mCameraMediaItems.size()) {
        Log.d(TAG, "Index out of Bound, position:" + position + " - mCameraMediaItems.size():" + mCameraMediaItems.size());
        return convertView;
    }
    MediaItemBean mediaItemBean = CameraMediaController.getInstance().getMediaItemByPosition(position);
    mediaItemViewHolder.mediaClipLength.setVisibility(View.VISIBLE);
    mediaItemViewHolder.highlightTagIcon.setVisibility(View.GONE);

    if (mediaItemBean != null && mediaItemBean.getCameraMedia() != null) {
        switch (mediaItemBean.getCameraMedia().getType()) {
            case AppConstant.MEDIA_TYPE_VIDEO:
                mediaItemViewHolder.mediaTypeIcon.setImageResource(R.drawable.icn_thumb_vid);
                //VideoInfoAsyncTask loads data in this list
                int videoDuration = mediaItemBean.getVideoDuration();
                //mediaItemViewHolder.mediaClipLength.setTag(CameraMediaUtil.convertSecondsTimeToMinutesString(videoDuration));
                Log.i(TAG, "VideoDuration " + videoDuration);

                String resId = mediaItemBean.getCreatedId()+"video_media_duration_com.gopro.buckhorn";
                Log.i(TAG, "RESID "+resId);
                downloadDuration(resId, durationTextView, mediaItemViewHolder.highlightTagIcon, mediaItemBean);
                break;
            case MULTI_PHOTO:
                String mulCount = String.valueOf(Controller.getInstance().getPhotoCountAtPosition(position));
                Log.i("MULTI_SHOT_SECTION", "MultiShot "+mulCount);
                mediaItemViewHolder.mediaTypeIcon.setImageResource(R.drawable.icn_thumb_burst);
                mediaItemViewHolder.mediaClipLength.setText(mulCount);
                break;

        }
        //Load image into image view from URL
        String imageUri = mediaItemBean.getThumbnailUri().toString();
        Log.i(TAG, "Thumb url :" + imageUri);
        mediaItemViewHolder.progressContainer.setVisibility(View.VISIBLE);

        DownloadImageUtil.getLoadImageInsatnce().downloadGridImage(imageUri,
                mediaItemViewHolder.mediaThumbnail, R.drawable.thumb_load, mediaItemViewHolder.progressContainer);
    }

    return convertView;
}


private void downloadDuration(String resId, TextView textView, ImageView highlightTagIcon, MediaItemBean mediaItemBean) {
    String duration = getVideoDurationFromCache(String.valueOf(resId));
    Log.i(TAG, "downloadDuration " + duration);
    if (duration == null) {
        loadVideoDuration(resId, textView, highlightTagIcon, mediaItemBean);
        textView.setText("");
    } else {
        cancelVideoDurationDownloaderTask(resId, textView);
        if(mediaItemBean.getCameraMedia().getType() == AppConstant.MEDIA_TYPE_VIDEO){
            textView.setText(duration);
            if (mediaItemBean.isIsHighLightTags()) {
                highlightTagIcon.setVisibility(View.VISIBLE);
            }
        }
    }
}


private String getVideoDurationFromCache(String key) {
    // First try the hard reference cache
    synchronized (mMemoryCache) {
        final String duration = mMemoryCache.get(key);
        if (duration != null) {
            // Bitmap found in hard cache
            // Move element to first position, so that it is removed last
            mMemoryCache.remove(key);
            mMemoryCache.put(key, duration);
            return duration;
        }
    }
    return null;
}


private static class MediaItemViewHolder {
    ImageView highlightTagIcon, mediaTypeIcon, mediaThumbnail;
    TextView mediaClipLength;
    RelativeLayout cameraItemSelectedView;
    /* ProgressBar innerProgressBar;
     ProgressBar outerProgressBar;*/
    RelativeLayout progressContainer;
}

public class VideoDurationDownloaderTask extends AsyncTask<String, Void, String> {
    private final WeakReference<TextView> videoDurationReference;
    private final WeakReference<ImageView> hiliteTagImageViewWeakReference;
    private String data = "";
    private MediaItemBean mediaItemBean;

    public VideoDurationDownloaderTask(TextView textView, ImageView hiliteTagIcon, MediaItemBean mediaItemBean) {
        this.mediaItemBean = mediaItemBean;
        videoDurationReference = new WeakReference<>(textView);
        hiliteTagImageViewWeakReference = new WeakReference<>(hiliteTagIcon);
    }

    @Override
    protected String doInBackground(String... params) {
        data = params[0];
        Log.i(TAG, "data in task "+data);
        return downloadVideoDuration(mediaItemBean);
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        if (isCancelled()) {
            Log.i(TAG, "isCancelled " + result);
            result = "";
        }
        addDurationToMemoryCache(data, result);
        //noinspection ConstantConditions
        if (videoDurationReference != null) {
            TextView videoDuration = videoDurationReference.get();
            Log.i(TAG, "videoDuration " + videoDuration);
            VideoDurationDownloaderTask videoDurationDownloaderTask =
                    getTextViewDerationWorkerTask(videoDuration);
            Log.i(TAG, "videoDurationDownloaderTask " + videoDurationDownloaderTask);
            if (videoDuration != null) {
                if (this == videoDurationDownloaderTask) {
                    if(mediaItemBean.getCameraMedia().getType() == AppConstant.MEDIA_TYPE_VIDEO) {
                        Log.i(TAG, "TAG VAL "+videoDuration.getTag());
                        videoDuration.setText(result);
                        videoDuration.setTag(new TextView(context));
                        if (mediaItemBean.isIsHighLightTags()) {
                            ImageView highlightTagIcon = hiliteTagImageViewWeakReference.get();
                            if (highlightTagIcon != null)
                                highlightTagIcon.setVisibility(View.VISIBLE);
                        }
                    }
                }
            }
        }
    }
}

private String downloadVideoDuration(MediaItemBean mediaItemBean) {
    try {
        if (media != null && mediaItemBean.getMedia() != null) {
            int videoDuration = mediaItemBean.getVideoDuration();
            Log.i(TAG, "Video has duration = " + videoDuration);
            if (videoDuration == -1) {
                CommandResult<Integer> duration =
                        media.getVideoDuration(mediaItemBean.getCameraMedia().getFilePath());
                videoDuration = duration.getData();
                mediaItemBean.setVideoDuration(videoDuration);
                Log.i(TAG, "set Video Duration " + videoDuration);
            }
            return MediaUtil.convertSecondsTimeToMinutesString(videoDuration);
        }
    } catch (Exception e) {
        Log.e(TAG, "Exception Occure while Getting video info:" + e.getMessage());
    }
    Log.i(TAG, "not fetch duration ");
    return "";
}


public void loadVideoDuration(String resId, TextView textView, ImageView hiliteTagIcon, MediaItemBean mediaItemBean) {
    if (cancelVideoDurationDownloaderTask(resId, textView)) {
        final VideoDurationDownloaderTask task = new VideoDurationDownloaderTask(textView, hiliteTagIcon, mediaItemBean);
        AsyncTextView asyncTextView = new AsyncTextView(context, task);
        textView.setTag(asyncTextView);
        task.execute(resId);
    }
}

private boolean cancelVideoDurationDownloaderTask(String data, TextView textView) {
    final VideoDurationDownloaderTask durationWorkerTask = getTextViewDerationWorkerTask(textView);

    if (durationWorkerTask != null) {
        final String textViewData = durationWorkerTask.data;
        Log.i(TAG, textViewData + " textViewDataData, data " + data);
        if (data != null && !textViewData.equalsIgnoreCase(data)) {
            // Cancel previous task
            Log.i(TAG, "Cancel previous task " + data);
            durationWorkerTask.cancel(true);
        } else {
            // The same work is already in progress
            Log.i(TAG, "same work is already in progress " + false);
            return false;
        }
    }
    // No task associated with the ImageView, or an existing task was
    // cancelled
    Log.i(TAG, "cancelVideoDurationDownloaderTask true");
    return true;
}

static class AsyncTextView extends TextView {
    private final WeakReference<VideoDurationDownloaderTask> textviewWorkerTaskReference;

    public AsyncTextView(Context context, VideoDurationDownloaderTask textviewWorkerTask) {
        super(context);
        textviewWorkerTaskReference = new WeakReference<>(textviewWorkerTask);
    }

    public VideoDurationDownloaderTask getTextViewWorkerTask() {
        return textviewWorkerTaskReference.get();
    }
}

private static VideoDurationDownloaderTask getTextViewDerationWorkerTask(TextView textView) {
    if(textView.getTag() != null){
        Log.i(TAG, " textView.getTag() " + textView.getTag());
        if (textView.getTag() instanceof AsyncTextView) {
            Log.i(TAG, " Return Textview task");
            final AsyncTextView asyncTextView = (AsyncTextView) textView.getTag();
            return asyncTextView.getTextViewWorkerTask();
        }
    }
    return null;
}

public void addDurationToMemoryCache(String key, String duration) {
    if (getBitmapFromMemCache(key) == null) {
        mMemoryCache.put(key, duration);
    }
}

Answer 1

摆脱 view 并使用 convertView 从方法中接收。改成如下

//final is optional but if you need to use in thread
final MediaItemViewHolder mediaItemViewHolder = null;
if (convertView == null) {
    convertView = mInflater.inflate(R.layout.camera_roll_item, parent, false);

    mediaItemViewHolder = new MediaItemViewHolder();
    mediaItemViewHolder.highlightTagIcon = (ImageView) convertView.findViewById(R.id.iv_media_grid_item_highlight_tag);
    mediaItemViewHolder.mediaTypeIcon = (ImageView) convertView.findViewById(R.id.iv_media_grid_item_type);
    mediaItemViewHolder.mediaClipLength = (TextView) convertView.findViewById(R.id.tv_media_grid_item_length);
    mediaItemViewHolder.mediaThumbnail = (ImageView) convertView.findViewById(R.id.iv_media_grid_item_thumbnail);
    mediaItemViewHolder.cameraItemSelectedView = (RelativeLayout) convertView.findViewById(R.id.rl_item_selection_parent);
    mediaItemViewHolder.progressContainer = (RelativeLayout) convertView.findViewById(R.id.rl_grid_loader_parent);
    convertView.setTag(mediaItemViewHolder);
} else {
    mediaItemViewHolder = (MediaItemViewHolder)convertView.getTag();
    Log.i(TAG, "set blank to ");
}

现在使用 mediaItemViewHolder.durationTextView.setText(....)

更新 1: 我已经找到问题所在了。 为什么延迟加载会在错误的 gridview 位置更新视频持续时间。 如果需要，请丢弃以上内容

downloadDuration(resId, durationTextView, mediaItemViewHolder.highlightTagIcon, mediaItemBean);

是罪魁祸首。 downloadDuration 以异步模式运行，并且它事先有 durationTextView 的引用。假设 downloadDuration 未完成并且用户滚动 ListView。滚动 ListView downloadDuration 完成后，此 durationTextView 将更新为错误的 ListView 值项目位置，而不是这是在 downloadDuration 中传递的位置。制作 final TextView durationTextView；
final 也解决不了问题。解决方案可能是显示某种持续时间的空指示器，并让 downloadDuration 完成它的异步作业。删除 durationTextView 作为参数并添加 position 作为参数。异步作业完成后，您可以为该位置更新 MediaItemBean 类型的 bean 列表。现在通知适配器某些值已更改，ListView 将相应地更新自身。 仅供引用 RecyclerView 项目更新比 ListView 更优化。

更新 2:您可以提前获取项目并将其映射到 bean。只会运行一次异步。

更新 3:与此同时，您可以检查特定 ListView 项的 bean 是否为 0。如果在 durationTextView.setText("00:00:00") 中显示为 0，则调用 downloadDuration 并让它完成并更新 bean 中的持续时间值。但是您仍然需要通知更新项目。