DownloadManager 在 INSUFFICIENT_SPACE_ERROR 之后不发送广播

问题

If the cache目录已满，尝试执行简单请求将失败而不发送DownloadManager.ACTION_DOWNLOAD_COMPLETE播送。

Note:该问题很普遍，但大部分可以在缓存有限的低端设备上重现（/data/data/com.android.providers.downloads/cache) size.

The code

接收器配置正确，因为当操作成功并因其他原因失败时我仍然收到广播。

    DownloadManager.Request request = new DownloadManager.Request(Uri.parse("http://www.apkmirror.com/wp-content/themes/APKMirror/download.php?id=44753"));

    request.setTitle("Facebook");

    DownloadManager downloadManager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);

    downloadManager.enqueue(request);

所需的解决方案

我对以下问题的解决方案感兴趣specific问题，或更多信息（如果您也遇到过）。
I'm not寻找一个需要我停止使用的解决方案DownloadManager或添加WRITE_EXTERNAL_STORAGE允许。

Logs

当缓存已满并且最后无法再容纳时，您可以观察以下日志入口（通过过滤）downloadmanager)

11-08 08:47:06.079 830-14261/? I/DownloadManager: Download 135 starting
11-08 08:47:06.989 830-14261/? W/DownloadManager: Downloads data dir: /data/data/com.android.providers.downloads/cache is running low on space. space available (in bytes): -6994124
11-08 08:47:06.999 830-14261/? I/DownloadManager: discardPurgeableFiles: destination = 2, targetBytes = 10485760
11-08 08:47:06.999 830-14261/? I/DownloadManager: Purged files, freed 0 for 10485760 requested
11-08 08:47:07.309 830-14261/? W/DownloadManager: Aborting request for download 135: not enough free space in the filesystem rooted at: /data/data/com.android.providers.downloads/cache and unable to free any more
11-08 08:47:07.319 830-14261/? I/DownloadManager: Download 135 finished with status INSUFFICIENT_SPACE_ERROR

这里有一个演示项目 https://github.com/furmana/TestDownloadManager这可以证明这个问题。请记住，此时缓存目录必须已满（不可清除的项目，根据我的经验，这基本上意味着下载中止）

由于DownloadManager本质上是一个系统ContentProvider，所以你可以向它注册自己的ContentObserver， 因此，当下载提供程序更新时，它会选择在 INSUFFICIENT_SPACE 的情况下通知观察者。

final DownloadManager downloadManager = (DownloadManager)context.getSystemService(Context.DOWNLOAD_SERVICE);
        context.getContentResolver().registerContentObserver(Uri.parse("content://downloads/my_downloads"),
                true, new ContentObserver(null) {
                    @Override
                    public void onChange(boolean selfChange) {
                        super.onChange(selfChange);
                        Cursor localCursor = downloadManager.query(
                                new DownloadManager.Query());
                        if (localCursor.getCount() == 0) {
                            localCursor.close();
                        }
                        localCursor.moveToFirst();
                        do {
                            if ((localCursor.getInt(localCursor.getColumnIndex(DownloadManager.COLUMN_STATUS)) & DownloadManager.STATUS_FAILED )!=0) {
                                // Download failed, go see why
                                if (localCursor.getInt(localCursor.getColumnIndex(DownloadManager.COLUMN_REASON)) == DownloadManager.ERROR_INSUFFICIENT_SPACE){
                                    Log.w("DownloadStatus", " Download failed with ERROR_INSUFFICIENT_SPACE");
                                }
                            }
                        }while (localCursor.moveToNext());
                    }
                });

请注意，不要设置状态为 DownloadManager.STATUS_FAILED 的查询过滤器，因为 DownloadManager 奇怪地只将 400 到 600 之间的状态视为失败状态， 但 INSUFFICIENT_SPACE 的错误代码为 198...

android.app.DownloadManager.Request：

Cursor runQuery(ContentResolver resolver, String[] projection, Uri baseUri) {
 .....
 if ((mStatusFlags & STATUS_FAILED) != 0) {
                    parts.add("(" + statusClause(">=", 400)
                              + " AND " + statusClause("<", 600) + ")");
                }
}