android - 如何获得下载状态？

我使用downloadmanager获取下载状态，但它仍然不起作用，它从不跳转到条件if(c.moveToFirst())并且我不知道为什么。有人能帮我吗？

private final BroadcastReceiver myReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();

            if(Intent.ACTION_SCREEN_OFF.equals(action)) {

                DownloadManager downloadMgr = (DownloadManager)getSystemService(DOWNLOAD_SERVICE);
                DownloadManager.Query query = new DownloadManager.Query();
                query.setFilterByStatus(DownloadManager.STATUS_FAILED|DownloadManager.STATUS_PENDING|DownloadManager.STATUS_RUNNING|DownloadManager.STATUS_SUCCESSFUL);
                Cursor c = downloadMgr.query(query);
                if(c==null) {
                    //
                }
                else {
                    if(c.moveToFirst()) {
                        int columnIndex = c.getColumnIndex(DownloadManager.COLUMN_STATUS);
                        int status = c.getInt(columnIndex);
                        if(status == DownloadManager.STATUS_RUNNING){
                        //do something
                        }
                    }
                }
            }
        }
    };

最佳答案

这里有几个链接。
LINK1
LINK2
示例代码如下：

DownloadManager.Query query = null;
    Cursor c = null;
    DownloadManager downloadManager = null;
    downloadManager = (DownloadManager)getSystemService(Context.DOWNLOAD_SERVICE);
    query = new DownloadManager.Query();
     if(query!=null) {
                query.setFilterByStatus(DownloadManager.STATUS_FAILED|DownloadManager.STATUS_PAUSED|DownloadManager.STATUS_SUCCESSFUL|
                        DownloadManager.STATUS_RUNNING|DownloadManager.STATUS_PENDING);
            } else {
                return;
            }
    c = downloadManager.query(query);
    if(c.moveToFirst()) {
    int status = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));
    switch(status) {
    case DownloadManager.STATUS_PAUSED:
    break;
    case DownloadManager.STATUS_PENDING:
    break;
    case DownloadManager.STATUS_RUNNING:
    break;
    case DownloadManager.STATUS_SUCCESSFUL:
    break;
    case DownloadManager.STATUS_FAILED:
    break;
    }
}