如何防止在下载文件时更新通知时UI滞后？

Question

protected String doInBackground(String... sUrl) {
        try {
            String destName = sUrl[1];
            file_Delete(destName); // Just to make sure!

            URL url = new URL(sUrl[0]);
            URLConnection connection = url.openConnection();
            connection.connect();
            int fileLength = connection.getContentLength();

            InputStream input = new BufferedInputStream(url.openStream());
            OutputStream output = new FileOutputStream(destName);

            byte data[] = new byte[1024];
            long total = 0;
            int count;
            while ((count = input.read(data)) != -1) {
                total += count;
                publishProgress((int) (total * 100 / fileLength));
                output.write(data, 0, count);
            }

            output.flush();
            output.close();
            input.close();

        } catch (Exception e) {
            Log.e(TAG, NAME + ": Error downloading file! " + e.getMessage());
            return e.getMessage();
        }

        return null;
    }

@Override protected void onProgressUpdate(Integer... progress) {
        super.onProgressUpdate(progress);
        DownloadImage.mProgressDialog.setProgress(progress[0]);


    }

这很好，但我现在想使用通知栏中的通知，以便跟踪下载（因为文件可能相当大，用户希望从应用程序之外跟踪）。

我已经尝试了下面的代码，但是UI开始严重滞后，我可以看到这是由于publishprogress被调用太多，所以我怎么才能改变后台代码，只每秒调用publishprogress

@Override protected void onProgressUpdate(Integer... progress) {
        super.onProgressUpdate(progress);
        DownloadImage.mProgressDialog.setProgress(progress[0]);

        DownloadImage.myNotification = new NotificationCompat.Builder(c)
        .setContentTitle("Downloading SlapOS")
        .setContentText("Download is " + progress[0] + "% done")
        .setTicker("Downloading...")
        .setOngoing(true)
        .setWhen(System.currentTimeMillis())
        .setProgress(100, progress[0], false)
        .setSmallIcon(R.drawable.icon)
        .build();

        DownloadImage.notificationManager.notify(1, DownloadImage.myNotification);

    }

Answer 1

那么，如何更改后台代码，使其只每秒调用一次publishProgress

我以前为一个在通知中显示%的上传函数做过这样的操作，但想法完全相同。让您的AsyncTask跟踪下载的PercentDone内容，并且只有在PercentDone更改时才调用Publisprogress。这样，只有当%downloaded发生更改时，才会调用publishprogress，因此通知需要更新。这应该可以解决UI滞后的问题。

我把它写成了我建议的实现，听起来OP已经让它工作了。但也许这会在未来帮助其他人：

    byte data[] = new byte[1024];
    long total = 0;
    int count, latestPercentDone;
    int percentDone = -1;
    while ((count = input.read(data)) != -1) {
        total += count;
        latestPercentDone = (int) Math.round(total / fileLength * 100.0);
        if (percentDone != latestPercentDone) {
            percentDone = latestPercentDone;
            publishProgress(percentDone);
        }
        output.write(data, 0, count);
    }