如何在 Android 中检索并打开通过 MediaStore API 保存下载的 PDF 文件？

Question

我正在从服务器下载 PDF 文件并将响应正文字节流传递到下面的函数中，该函数将 PDF 文件成功存储在用户下载文件夹中。

@RequiresApi(Build.VERSION_CODES.Q)
fun saveDownload(pdfInputStream: InputStream) {
    val values = ContentValues().apply {
        put(MediaStore.Downloads.DISPLAY_NAME, "test")
        put(MediaStore.Downloads.MIME_TYPE, "application/pdf")
        put(MediaStore.Downloads.IS_PENDING, 1)
    }

    val resolver = context.contentResolver
    val collection = MediaStore.Downloads.getContentUri(MediaStore.VOLUME_EXTERNAL_PRIMARY)
    val itemUri = resolver.insert(collection, values)
    if (itemUri != null) {
        resolver.openFileDescriptor(itemUri, "w").use { parcelFileDescriptor ->
            ParcelFileDescriptor.AutoCloseOutputStream(parcelFileDescriptor)
                .write(pdfInputStream.readBytes())
        }
        values.clear()
        values.put(MediaStore.Downloads.IS_PENDING, 0)
        resolver.update(itemUri, values, null, null)
    }
}

现在，一旦该函数返回，我想打开保存的 PDF 文件。我尝试了多种方法来使其正常工作，但选择器总是说没有任何内容可以打开文件。我认为要么仍然存在权限问题（也许我使用的 FileProvider 错误？），要么路径错误，或者可能完全是其他问题。

以下是我尝试过的几个示例：

fun uriFromFile(context: Context, file: File): Uri {
    return FileProvider.getUriForFile(context, BuildConfig.APPLICATION_ID + ".provider", file)
}

A）

val openIntent = Intent(Intent.ACTION_VIEW)
openIntent.putExtra(Intent.EXTRA_STREAM, uriFromFile(this, File(this.getExternalFilesDir(DIRECTORY_DOWNLOADS)?.absolutePath.toString(), "test")))
openIntent.flags = Intent.FLAG_GRANT_READ_URI_PERMISSION
openIntent.type = "application/pdf"
startActivity(Intent.createChooser(openIntent, "share.."))

b)

val shareIntent = Intent(Intent.ACTION_SEND)
shareIntent.putExtra(Intent.EXTRA_STREAM,  uriFromFile(this, File(this.getExternalFilesDir(null)?.absolutePath.toString(), "test.pdf")))
shareIntent.flags = Intent.FLAG_GRANT_READ_URI_PERMISSION
shareIntent.type = "application/pdf"
startActivity(Intent.createChooser(shareIntent, "share.."))

C）

val file = File(itemUri.toString()) //itemUri from the saveDownload function
val target = Intent(Intent.ACTION_VIEW)
val newFile = FileProvider.getUriForFile(this, BuildConfig.APPLICATION_ID + ".provider", file);
target.setDataAndType(newFile, "application/pdf")
target.flags = Intent.FLAG_ACTIVITY_NO_HISTORY
val intent = Intent.createChooser(target, "Open File")
intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
ContextCompat.startActivity(this, intent, null)

d)

val target = Intent(Intent.ACTION_VIEW)
target.setDataAndType(Uri.parse("content://media/external_primary/downloads/2802"), "application/pdf"
target.flags = Intent.FLAG_ACTIVITY_NO_HISTORY
val intent = Intent.createChooser(target, "Open File")
intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
ContextCompat.startActivity(this, intent, null)

（还尝试在此 URI 末尾添加 /test.pdf，并用我的权威名称替换 media）

我还将其添加到应用程序标签内的清单文件中：

<provider
    android:name="androidx.core.content.FileProvider"
    android:authorities="${applicationId}.provider"
    android:exported="false"
    android:grantUriPermissions="true">
    <meta-data
        android:name="android.support.FILE_PROVIDER_PATHS"
        android:resource="@xml/provider_paths" />
</provider>

@xml/provider_paths 如下，尽管我还尝试了除此之外的各种组合，包括路径为“.”：

<?xml version="1.0" encoding="utf-8"?>
<paths>
    <external-files-path name="files_root" path="/"/>
    <files-path name="files_root" path="/"/>
    <external-path name="files_root" path="/"/>
</paths>

顺便说一句，肯定有可以打开 PDF 的选择器，进入文件资源管理器并从那里打开它效果很好。当尝试共享而不是打开时，共享也会失败。

Answer 1

按照此步骤和代码，它将管理从下载 pdf 到打开它的所有内容。

创建一个类名为DownloadTask并放入下面给出的完整代码

public class DownloadTask {

    private static final String TAG = "Download Task";
    private Context context;

    private String downloadFileUrl = "", downloadFileName = "";
    private ProgressDialog progressDialog;
    long downloadID;

    private BroadcastReceiver onDownloadComplete = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            //Fetching the download id received with the broadcast
            long id = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
            //Checking if the received broadcast is for our enqueued download by matching download id
            if (downloadID == id) {
                downloadCompleted(downloadID);
            }
        }
    };

    public DownloadTask(Context context, String downloadUrl) {
        this.context = context;

        this.downloadFileUrl = downloadUrl;


        downloadFileName = downloadFileUrl.substring(downloadFileUrl.lastIndexOf('/') + 1);//Create file name by picking download file name from URL
        Log.e(TAG, downloadFileName);

        context.registerReceiver(onDownloadComplete, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
        downloadFile(downloadFileUrl);

    }

    public void downloadFile(String url) {

        try {
            File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getAbsolutePath(), downloadFileName);

            DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url))
                    .setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED)// Visibility of the download Notification
                    .setDestinationInExternalPublicDir(
                            Environment.DIRECTORY_DOWNLOADS,
                            downloadFileName
                    )
                    .setDestinationUri(Uri.fromFile(file))
                    .setTitle(downloadFileName)// Title of the Download Notification
                    .setDescription("Downloading")// Description of the Download Notification
                    .setAllowedOverMetered(true)// Set if download is allowed on Mobile network
                    .setAllowedOverRoaming(true);// Set if download is allowed on roaming network


            request.allowScanningByMediaScanner();
            DownloadManager downloadManager = (DownloadManager) context.getSystemService(DOWNLOAD_SERVICE);
            downloadID = downloadManager.enqueue(request);// enqueue puts the download request in the queue.

            progressDialog = new ProgressDialog(context);
            progressDialog.setMessage("Downloading...");
            progressDialog.setCancelable(false);
            progressDialog.show();
        } catch (Exception e) {
            Log.d("Download", e.toString());
        }


    }

    void downloadCompleted(long downloadID) {

        progressDialog.dismiss();

        new AlertDialog.Builder(context)
                .setTitle("Document")
                .setMessage("Document Downloaded Successfully")

                .setPositiveButton("Open", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {

                        openDownloadedAttachment(downloadID);
                    }
                })

                // A null listener allows the button to dismiss the dialog and take no further action.
                .setNegativeButton(android.R.string.no, null)
                .setIcon(android.R.drawable.ic_dialog_alert)
                .show();

        context.unregisterReceiver(onDownloadComplete);

    }

    Uri path;

    private void openDownloadedAttachment(final long downloadId) {
        DownloadManager downloadManager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
        DownloadManager.Query query = new DownloadManager.Query();
        query.setFilterById(downloadId);
        Cursor cursor = downloadManager.query(query);
        if (cursor.moveToFirst()) {
            int downloadStatus = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS));
            String downloadLocalUri = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI));
            String downloadMimeType = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_MEDIA_TYPE));
            if ((downloadStatus == DownloadManager.STATUS_SUCCESSFUL) && downloadLocalUri != null) {
                path = FileProvider.getUriForFile(context, context.getApplicationContext().getPackageName() + ".provider", new File(Uri.parse(downloadLocalUri).getPath()));
                //path = Uri.parse(downloadLocalUri);
                Intent pdfIntent = new Intent(Intent.ACTION_VIEW);

                pdfIntent.setDataAndType(path, downloadMimeType);

                pdfIntent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_ACTIVITY_CLEAR_TOP);
                try {
                    context.startActivity(pdfIntent);
                } catch (ActivityNotFoundException e) {
                    Toast.makeText(context, "No Application available to view PDF", Toast.LENGTH_SHORT).show();
                }
            }
        }
        cursor.close();
    }
}

然后从您的活动中下载您的 pdf 文件。

new DownloadTask(this, "PDF_URL");

从你的片段中

new DownloadTask(getContext(), "PDF_URL");

下载完成后，它将自动打开您的 pdf 文件。