Question

您刚才有一个关于为什么我的进度条没有更新的快速问题。我将在下面添加注释，以演示哪些有效，哪些无效。

据我所知，它应该工作，因为它在asynctask中更新。

@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    View view = convertView;
    if (!(data.get(position) instanceof TemporarySongInfomation)) {
        SongViewHolder holder;
        view = inflater.inflate(R.layout.music_list_format, null);
        holder = new SongViewHolder();
        holder.timesplayed = (TextView) view.findViewById(R.id.textView7);
        holder.artist = (TextView) view.findViewById(R.id.textView6);
        holder.title = (TextView) view.findViewById(R.id.textView5);
        holder.imagebutton = (ImageButton) view.findViewById(R.id.playbutton);
        holder.source = (TextView) view.findViewById(R.id.textView8);
        tempValue = (SongInfomation) data.get(position);
        String songName = tempValue.getName();
        holder.imagebutton.setBackgroundResource(R.drawable.playbutton1);
        holder.source.setText(tempValue.getVideoid());
        holder.title.setText(songName.length() > 45 ? songName.substring(0, 38) + "..." : songName);
        holder.timesplayed.setText("" + tempValue.getTimesplayed());
        holder.artist.setText(tempValue.getArtist());
        swipeDetector = new SwipeDetector();
        view.setOnClickListener(new SongListOnItemClickListener(position));
        view.setOnTouchListener(swipeDetector);
        holder.imagebutton.setOnClickListener(new OnPlayButtonClickListener(position));
    } else {
        TemporarySongViewHolder holder;
        view = inflater.inflate(R.layout.music_list_process_format, null);
        holder = new TemporarySongViewHolder();
        holder.artist = (TextView) view.findViewById(R.id.artisttemp);
        holder.bar = (ProgressBar) view.findViewById(R.id.ppbar);
        holder.title = (TextView) view.findViewById(R.id.titletemp);
        holder.source = (TextView) view.findViewById(R.id.sourcetemp);
        tempValue1 = (TemporarySongInfomation) data.get(position);
        String songName = tempValue1.getName();
        holder.source.setText(tempValue1.getVideoid());
        holder.title.setText(songName.length() > 45 ? songName.substring(0, 38) + "..." : songName);
        holder.artist.setText(tempValue1.getArtist());
        holder.bar.setMax(100);
// the below line starts the task!
        new UpdateProgressBar(holder.bar, tempValue1).execute();

    }

    return view;
}

private class UpdateProgressBar extends AsyncTask<Void, Void, Void> {
    private TemporarySongInfomation songinfo;
    private ProgressBar progress;

    UpdateProgressBar(ProgressBar bar, TemporarySongInfomation tp) {
        progress = bar;
        songinfo = tp;
    }

    @Override
    protected Void doInBackground(Void... params) {
        while (!songinfo.isCompleted()) {
            System.out.println("going " + (int) songinfo.getProgress());
// the above line prints different values for songinfo.getProgress()
            progress.setProgress((int) songinfo.getProgress());
            publishProgress();
            System.out.println("Progress "+progress.getProgress());
// the above line only prints "Progress 0"
// and obviously the ui doesnt update.
            try {
                Thread.sleep(500);
            } catch (Exception e) {

            }
        }
        return null;
    }
}

Answer 1

publishProgress（Progress ...）调用onProgressUpdate（Progress ...）

调用后，在UI线程上调用了
onProgressUpdate（Progress ...） publishProgress（进展...）。执行的时间是未定义。此方法用于显示任何形式的进度后台计算仍在执行时的用户界面。例如，它可用于为进度条设置动画或显示登录文本字段。

所以基本上你需要从onProgressUpdate方法更新UI线程。

这是一个例子：

private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
     protected Long doInBackground(URL... urls) {
         int count = urls.length;
         long totalSize = 0;
         for (int i = 0; i < count; i++) {
             totalSize += Downloader.downloadFile(urls[i]);
             publishProgress((int) ((i / (float) count) * 100));
             // Escape early if cancel() is called
             if (isCancelled()) break;
         }
         return totalSize;
     }

     protected void onProgressUpdate(Integer... progress) {
         setProgressPercent(progress[0]);
     }

     protected void onPostExecute(Long result) {
         showDialog("Downloaded " + result + " bytes");
     }
 }

Answer 2

这部分错了

progress.setProgress((int) songinfo.getProgress());
publishProgress();

您需要从UI线程更新进度条。因此，要更新进度，您必须覆盖在UI线程上运行的onProgressUpdate，并从那里更新进度条。

<{1>}中的

，执行此操作

doInBackground

然后，在publishProgress((int) songinfo.getProgress()); // this calls onProgressUpdate on the UI thread中，执行此操作

onProgressUpdate

您还需要更改progress.setProgress(values[0]); // called on UI thread班级定义

AsyncTask

ProgressBar - 不在AsyncTask中更新

2 个答案: