DownloadManager正在下载时显示进度对话框？

Question

我有一个下载管理器，可以下载多个文件。 当管理员启动第一个请求并在最后一个请求完成下载后关闭对话框时，如何显示进度对话框？

我想我需要使用ACTION_DOWNLOAD_COMPLETE进行检查，但我不确定如何实现。 感谢您的帮助。

Answer 1

这是我编写的一些实用程序代码，用于使用DownloadManager执行下载并将结果传递给回调

public static void downloadPdf(Context context, String url, String name, final Callback callback){
    Uri uri;
    try{
        uri = Uri.parse(url);
    }
    catch(Exception e){
        Log.e(LogTags.UI, "Error parsing pdf url " + url, e);
        callback.onError();
        return;
    }

    DownloadManager.Request r = new DownloadManager.Request(uri);

    // This put the download in the same Download dir the browser uses
    r.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, name);

    // When downloading music and videos they will be listed in the player
    // (Seems to be available since Honeycomb only)
    r.allowScanningByMediaScanner();

    // Notify user when download is completed
    // (Seems to be available since Honeycomb only)
    r.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);

    // Start download
    final DownloadManager dm = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
    final long downloadId = dm.enqueue(r);

    BroadcastReceiver receiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (DownloadManager.ACTION_DOWNLOAD_COMPLETE.equals(action)) {
                if(intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, 0) != downloadId){
                    // Quick exit - its not our download!
                    return;
                }

                DownloadManager.Query query = new DownloadManager.Query();
                query.setFilterById(downloadId);
                Cursor c = dm.query(query);
                if (c.moveToFirst()) {
                    int columnIndex = c
                            .getColumnIndex(DownloadManager.COLUMN_STATUS);
                    if (DownloadManager.STATUS_SUCCESSFUL == c
                            .getInt(columnIndex)) {

                        String uriString = c
                                .getString(c
                                        .getColumnIndex(DownloadManager.COLUMN_LOCAL_URI));
                        Uri uri = Uri.parse(uriString);

                        intent = new Intent();
                        intent.setAction(Intent.ACTION_VIEW);
                        intent.setDataAndType(uri, "application/pdf");

                        callback.onSuccess();

                        context.startActivity(intent);

                    }
                    else{
                        callback.onError();
                    }
                }
                else{
                    callback.onError();
                }
                context.unregisterReceiver(this);
            }
        }
    };

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

您可以在回调中执行所需的任何UI工作-就我而言，在开始下载之前，我先启动一个不确定的进度对话框，然后将其隐藏起来：

    String filename =  "Some Notes.pdf";
    final ProgressDialog dialog = ProgressDialog.show(this,
            "Downloading PDF",
            "Donwloading " + filename, true, true);

   downloadPdf(this,
            "http://some-url.com/with_pdf.pdf",
            filename,
            new Callback() {
                @Override
                public void onSuccess() {
                    dialog.dismiss();
                }

                @Override
                public void onError() {
                    dialog.dismiss();
                }
            });

PS。 我正在使用有用的Picasso库中的Callback接口-您可以轻松定义自己的接口，它只有两个onSuccess和onError方法。