19

我在我的活动中使用了下载管理器类来执行下载；它工作正常，我的下一个任务是在我的活动中显示相同的进度百分比。我不知道该怎么做。

到目前为止我的代码

public class DownloadSampleBook extends Activity{

private long enqueue;
private DownloadManager dm;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_sample_download);

    BroadcastReceiver receiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (DownloadManager.ACTION_DOWNLOAD_COMPLETE.equals(action)) {
                long downloadId = intent.getLongExtra(
                        DownloadManager.EXTRA_DOWNLOAD_ID, 0);
                Query query = new Query();
                query.setFilterById(enqueue);
                Cursor c = dm.query(query);
                if (c.moveToFirst()) {
                    int columnIndex = c
                            .getColumnIndex(DownloadManager.COLUMN_STATUS);
                    if (DownloadManager.STATUS_SUCCESSFUL == c
                            .getInt(columnIndex)) {

                       view.setImageURI(Uri.parse(uriString));
                    }
                }
            }
        }
    };

    registerReceiver(receiver, new IntentFilter(
            DownloadManager.ACTION_DOWNLOAD_COMPLETE));
}

public void onClick(View view) {
    dm = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
    Request request = new Request(
            Uri.parse("http://abc.com/a.png"));
    enqueue = dm.enqueue(request);

}

public void showDownload(View view) {
    Intent i = new Intent();
    i.setAction(DownloadManager.ACTION_VIEW_DOWNLOADS);
    startActivity(i);
}
}

有没有什么方法可以给出进度下载百分比？

4

3 回答 3

26

如果您正在寻找一种合适的方式来确定何时查询DownloadManager进度更新，请考虑ContentObserver为 uri注册content://downloads/my_downloads

例子：

DownloadManager manager = (DownloadManager) getSystemService( Context.DOWNLOAD_SERVICE );
manager.enqueue( myRequest );

Uri myDownloads = Uri.parse( "content://downloads/my_downloads" );
getContentResolver().registerContentObserver( myDownloads, true, new DownloadObserver() );

...

public static class DownloadObserver extends ContentObserver {
   @Override
   public void onChange( boolean selfChange, Uri uri ) {
      Log.d( "DownloadObserver", "Download " + uri + " updated" );
   }

当接收到长时间运行的下载的每个块时，这会产生以下输出

D/DownloadObserver(15584): Download content://downloads/my_downloads/437 updated
D/DownloadObserver(15584): Download content://downloads/my_downloads/437 updated
D/DownloadObserver(15584): Download content://downloads/my_downloads/437 updated
D/DownloadObserver(15584): Download content://downloads/my_downloads/437 updated

其中“437”是您下载的 ID。

请注意，这遵循类android.provider.Downloads中定义的内容 URI，该 URI 似乎隐藏在框架中，并且可能无法在所有设备上一致地工作。（https://android.googlesource.com/platform/frameworks/base/+/refs/heads/master/core/java/android/provider/Downloads.java#89）

于 2014-07-22T18:50:48.630 回答
23

您可以使用该方法查询到目前为止已下载的字节数以及需要下载的总字节数，其query方式与您在示例代码中查询状态的方式大致相同。一旦有了这些值，就很容易将进度计算为百分比。

收到新数据时似乎没有任何方法可以通知您，因此您需要定期轮询下载管理器以确定您要监控的任何下载的当前状态。

Query query = new Query();
query.setfilterById(downloadId);

Cursor c = dm.query(query);
if (c.moveToFirst()) {
  int sizeIndex = c.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES);
  int downloadedIndex = c.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR);
  long size = c.getInt(sizeIndex);
  long downloaded = c.getInt(downloadedIndex);
  double progress = 0.0;
  if (size != -1) progress = downloaded*100.0/size;  
  // At this point you have the progress as a percentage.
}

请注意，总大小最初为 -1，只有在下载开始后才会填写。因此，在上面的示例代码中，我检查了 -1，如果尚未设置大小，则将进度设置为 0。

但是，您可能会发现在某些情况下总大小永远不会返回（例如，在 HTTP 分块传输中，将没有 Content-Length 标头可以确定大小）。如果您需要支持这种服务器，您可能应该向用户提供某种指示下载正在进行中，而不仅仅是卡在零的进度条。

于 2013-06-06T19:58:31.070 回答
5

我需要跟踪多个文件的下载。经过大量的思考和实验，我想出了以下代码：

private void startDownloadThread(final List<DownloadFile> list) {

        // Initializing the broadcast receiver ...
        mBroadCastReceiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                mFinishedFilesFromNotif.add(intent.getExtras()
                        .getLong(DownloadManager.EXTRA_DOWNLOAD_ID));
            }
        };

        IntentFilter intentFilter = new IntentFilter(
                "android.intent.action.DOWNLOAD_COMPLETE");
        DownloadProgressUIFragment.this.getActivity().registerReceiver(mBroadCastReceiver,
                intentFilter);

        // initializing the download manager instance ....
        mDownloadManager = (DownloadManager) getActivity()
                .getSystemService(Context.DOWNLOAD_SERVICE);

        // adding files to the download manager list ...
        for(DownloadFile f: list) {
            mDownloadIds.add(FileUtils.addFileForDownloadInBkg(getApplicationContext(),
                    f.getUrl(),
                    f.getPath()));
        }

        // starting the thread to track the progress of the download ..
        mProgressThread = new Thread(new Runnable() {
            @Override
            public void run() {

                // Preparing the query for the download manager ...
                DownloadManager.Query q = new DownloadManager.Query();
                long[] ids = new long[mDownloadIds.size()];
                final List<Long> idsArrList= new ArrayList<>();
                int i = 0;
                for (Long id: mDownloadIds) {
                    ids[i++] = id;
                    idsArrList.add(id);
                }
                q.setFilterById(ids);

                // getting the total size of the data ...
                Cursor c;

                while(true) {

                    // check if the downloads are already completed ...
                    // Here I have created a set of download ids from download manager to keep
                    // track of all the files that are dowloaded, which I populate by creating
                    //
                    if(mFinishedFilesFromNotif.containsAll(idsArrList)) {
                        isDownloadSuccess = true;

                        // TODO - Take appropriate action. Download is finished successfully
                        return;
                    }

                    // start iterating and noting progress ..
                    c = mDownloadManager.query(q);
                    if(c != null) {
                        int filesDownloaded = 0;
                        float fileFracs = 0f; // this stores the fraction of all the files in
                        // download
                        final int columnTotalSize = c.getColumnIndex
                                (DownloadManager.COLUMN_TOTAL_SIZE_BYTES);
                        final int columnStatus = c.getColumnIndex(DownloadManager.COLUMN_STATUS);
                        //final int columnId = c.getColumnIndex(DownloadManager.COLUMN_ID);
                        final int columnDwnldSoFar =
                                c.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR);

                        while (c.moveToNext()) {
                            // checking the progress ..
                            if(c.getInt(columnStatus) == DownloadManager.STATUS_SUCCESSFUL) {
                                filesDownloaded++;
                            }
                            // If the file is partially downloaded, take its fraction ..
                            else if(c.getInt(columnTotalSize) > 0) {
                                fileFracs += ((c.getInt(columnDwnldSoFar) * 1.0f) /
                                        c.getInt(columnTotalSize));
                            } else if(c.getInt(columnStatus) == DownloadManager.STATUS_FAILED) {
                                // TODO - Take appropriate action. Error in downloading one of the
                                // files.
                                return;
                            }
                        }

                        c.close();

                        // calculate the progress to show ...
                        float progress = (filesDownloaded + fileFracs)/ids.length;

                        // setting the progress text and bar...
                        final int percentage = Math.round(progress * 100.0f);
                        final String txt = "Loading ... " + percentage + "%";

                        // Show the progress appropriately ...
                    }
                }
            }
        });

        mProgressThread.start();
    }

入队文件的功能是：

public static long addFileForDownloadInBkg(Context context, String url, String savePath) {
        Uri uri = Uri.parse(url);
        DownloadManager.Request request = new DownloadManager.Request(uri);
        request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_HIDDEN);
        request.setDestinationUri(Uri.fromFile(new File(savePath)));

        final DownloadManager m = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
        return m.enqueue(request);
    }

基本上，我会为每个已完成下载的文件单独收到通知，然后将它们添加到一个集合中，该集合基本上是帮助我确定所有下载是否已完成的集合。我根据文件的数量和每个文件完成的比例来跟踪进度。我希望这有帮助。

于 2017-02-17T10:41:34.330 回答