ContentResolver openInputStream 在后台下载文件

Question

所以我正在尝试下载一个大文件。所以很自然我的第一步就是打开流

RNFetchBlob.RCTContext.getContentResolver().openInputStream(Uri.parse(fromUri));

我的问题是，它实际上不是快速工作并只是打开流，而是在后台下载东西。我怎么知道？好吧，这个命令会阻塞 5 分钟，然后当我从流中读取时，它是瞬时的。

我可以让这个动作阻止在后台下载吗？我想通知用户进度而不是等待。

编辑：为了清楚起见，我使用 content:// URI 作为资源

Answer 1

这是通过网络读取文件的错误方法，您需要使用特定于网络的方法。

HttpURLConnection request = 
    (HttpURLConnection)(new URL(Uri.parse(fromUri)).openConnection());
// Connect to the server, expect a delay and draw a progress bar
request.connect();
// This will read HTTP headers with content length, expect another delay
// Must be called before request.getContentLength()
request.getInputStream();
// Get the size of your file, to draw your progress bar properly
long total = request.getContentLength();
// Now you can finally start reading the data
InputStream input = request.getInputStream();

Answer 2

对于长时间运行的 HTTP 下载，您可以使用 DownloadManager 并显示下载进度，例如比如thisVictor Laerte的问题：

    String urlDownload = <YOUR_URL>;
    DownloadManager.Request request = new DownloadManager.Request(Uri.parse(urlDownload));

    request.setDescription("Testando");
    request.setTitle("Download");
    request.allowScanningByMediaScanner();
    request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
    request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,"teste.zip");

    final DownloadManager manager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);

    final long downloadId = manager.enqueue(request);

    final ProgressBar mProgressBar = (ProgressBar) findViewById(R.id.progressBar1);

    new Thread(new Runnable() {

        @Override
        public void run() {

            boolean downloading = true;

            while (downloading) {

                DownloadManager.Query q = new DownloadManager.Query();
                q.setFilterById(downloadId);

                Cursor cursor = manager.query(q);
                cursor.moveToFirst();
                int bytes_downloaded = cursor.getInt(cursor
                        .getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));
                int bytes_total = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));

                if (cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS)) == DownloadManager.STATUS_SUCCESSFUL) {
                    downloading = false;
                }

                final int dl_progress = (int) ((bytes_downloaded * 100l) / bytes_total);

                runOnUiThread(new Runnable() {

                    @Override
                    public void run() {

                        mProgressBar.setProgress((int) dl_progress);

                    }
                });

                Log.d(Constants.MAIN_VIEW_ACTIVITY, statusMessage(cursor));
                cursor.close();
            }

        }
    }).start();