Question

private class DownloadTextTask extends AsyncTask<String,Long,Long> {

        CharSequence contentText;
        Context context;
        CharSequence contentTitle;
        PendingIntent contentIntent;
        int ID = 1;
        long time;
        int icon;
        CharSequence tickerText;

        @Override
        protected Long doInBackground(String... urls) {
            InputStream inputStream = null;
            try {
                HttpClient httpclient = new DefaultHttpClient();
                HttpResponse httpResponse = httpclient.execute(new HttpGet(urls[0]));
                inputStream = httpResponse.getEntity().getContent();
                byte[] buffer = IOUtils.toByteArray(inputStream);
                FileOutputStream fos = new FileOutputStream(MEDIA_PATH + "/fileName.mp3");
                fos.write(buffer);
                fos.flush();
                fos.close();    
            } catch (Exception e) {
            }
            return (long) 100;
        }

        @Override
        protected void onPostExecute(Long result) {
            contentText = result + "% complete";
            contentTitle="Downloading Finished!";
            notification.setLatestEventInfo(context, contentTitle, contentText, contentIntent);
            notificationManager.notify(ID, notification);
        }

        @Override
         protected void onPreExecute() {
                super.onPreExecute();
                downloadNotification();
         }

         @Override
         public void onProgressUpdate(Long... progress) {
                super.onProgressUpdate(progress);
                contentText = progress[0] + "% complete";
                notification.setLatestEventInfo(context, contentTitle, contentText, contentIntent);
                notificationManager.notify(ID, notification);
         }

           public void downloadNotification(){
                String ns = Context.NOTIFICATION_SERVICE;
                notificationManager = (NotificationManager) getSystemService(ns);

                icon = R.drawable.downicon;
                //the text that appears first on the status bar
                tickerText = "Downloading...";
                time = System.currentTimeMillis();

                notification = new Notification(icon, tickerText, time);

                context = getApplicationContext();
                //the bold font
                contentTitle = "Your download is in progress";
                //the text that needs to change
                contentText = "0% complete";
                Intent notificationIntent = new Intent(Intent.ACTION_VIEW);
               // notificationIntent.setType("audio/*");
                contentIntent = PendingIntent.getActivity(context, 0, notificationIntent,PendingIntent.FLAG_UPDATE_CURRENT);

                notification.setLatestEventInfo(context, contentTitle, contentText, contentIntent);
                notificationManager.notify(ID, notification);

            }
    }

我已经编写了这段代码来下载一个mp3文件，这里的问题是，它没有更新下载文件的进度！我正在使用IOUtils类将InputStream转换为byte []。我不知道如何在这种情况下发布进展！请帮助我。

Answer 1

您需要在doInBackground（）

中调用publishProgress（param）

http://developer.android.com/reference/android/os/AsyncTask.html

doInBackground（Params ...），在onPreExecute（）完成执行后立即在后台线程上调用。此步骤用于执行可能需要很长时间的后台计算。异步任务的参数将传递给此步骤。计算结果必须由此步骤返回，并将传递回最后一步。 此步骤还可以使用publishProgress（Progress ...）发布一个或多个进度单位。这些值发布在UI线程的onProgressUpdate（Progress ...）步骤中。
onProgressUpdate（Progress ...），在调用publishProgress（Progress ...）后在UI线程上调用。执行的时间是不确定的。 此方法用于在后台计算仍在执行时显示用户界面中的任何形式的进度。例如，它可用于为进度条设置动画或在文本字段中显示日志。

示例@ http://www.androidhive.info/2012/04/android-downloading-file-by-showing-progress-bar/

        OutputStream output = new FileOutputStream("/sdcard/file_name.extension")
        long total = 0;
        int count;
        while ((count = inputStream.read(buffer) != -1) {
            total += count;
            // publishing the progress....
            publishProgress((int) (total * 100 / fileLength));
            output.write(buffer, 0, count);
        }

Answer 2

AsyncTask的所有功能都有访问说明符protected。

所以它应该是：

@Override
     protected void onProgressUpdate(Long... progress) {
            super.onProgressUpdate(progress);
            contentText = progress[0] + "% complete";
            notification.setLatestEventInfo(context, contentTitle, contentText, contentIntent);
            notificationManager.notify(ID, notification);
     }

Answer 3

我认为IOUtils.toByteArray(..)无法提供进度更新。如果文件很大，你可能不想将整个内容读入内存。您可以使用CountingInputStream来跟踪读取的总字节数。

public long countContent(URL urls) {
  try {
     //...
     CountingInputStream counter = new CountingInputStream(httpResponse.getEntity().getContent());
     FileOutputStream os = new FileOutputStream(MEDIA_PATH + "/fileName.mp3");

     int read;
     byte[] buffer = new byte[1028];
     while ((read = counter.read(buffer)) != -1) {
        os.write(buffer, 0, read);
        publishProgress(counter.getByteCount()/size);
     }
     // ...
     return counter.getByteCount()/size;
  } catch (IOException ex) {
     throw new RuntimeException(ex);
  }
}

onProgressUpdate不起作用

3 个答案: