如何在 Android 中通过 MediaStore API 检索和打开保存到下载的 PDF 文件?

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【中文标题】如何在 Android 中通过 MediaStore API 检索和打开保存到下载的 PDF 文件?【英文标题】:How to retrieve and open PDF file saved to downloads through MediaStore API in Android? 【发布时间】:2021-04-25 01:15:04 【问题描述】:

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,一旦此函数返回,我想打开保存的 PDF 文件。我已经尝试了几种方法来让它工作,但选择器总是说没有什么可以打开文件。我认为仍然存在权限问题(也许我使用 FileProvider 错误?),或者路径错误,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)

一)

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)

(也尝试在此 URI 末尾添加 /test.pdf,并将 media 替换为我的权限名称)

我还在应用程序标签内的清单文件中添加了这个:

<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>

附带说明,肯定有可用的选择器能够打开 PDF,然后进入文件资源管理器并从那里打开它可以正常工作。尝试共享而不是打开共享时也会失败。

【问题讨论】:

不用加粗,不用加粗也能正常阅读:) @a_local_nobody 哈哈,对不起,我的错 :) 很遗憾,我无法真正帮助您解决问题,所以我能做的最好的就是编辑,但我相信您会找到答案 你为什么会选择?你已经有一个uri。这个:val itemUri = resolver.insert(collection...... @blackapps 我尝试使用该 Uri,但它不起作用,请参阅 (c) 【参考方案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DownloadTask,并把完整的代码放在下面

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();
    

然后像这样从您的活动中下载您的 pdf。

new DownloadTask(this, "PDF_URL");

从你的片段中

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

下载完成后会自动打开你的pdf。

【讨论】:

您的课程中有一些已弃用的调用:Environment.getExternalStoragePublicDirectory、ProgressDialog 和 request.allowScanningByMediaScanner(),如果可能,您应该避免这种情况,谢谢。 android deprecation 也是这个工具的另一个令人头疼的问题。 支持这项工作。但如果可能,请避免不推荐使用的调用。【参考方案2】:

根据Android Developer,MediaStore 未用于访问非媒体文件,例如 pdf 文件:

如果您的应用可以处理非独占性的文档和文件 包含媒体内容,例如使用 EPUB 或 PDF 文件的文件 扩展,使用 ACTION_OPEN_DOCUMENT 意图操作,如中所述 存储指南和access documents and other files。

此外,通过CursorContent Provider访问非媒体文件也没有任何官方解决方案。但是,我已经在 Android 11 上对其进行了测试,并按预期工作了一种官方且干净的代码方法。这里是:

public class retrieve_pdf_file 
    @RequiresApi(Build.VERSION_CODES.Q)
    public static void get(Activity activity) 
        Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.setType("application/pdf");
        // Optionally, specify a URI for the file that should appear in the
        // system file picker when it loads.
        intent.putExtra(DocumentsContract.EXTRA_INITIAL_URI, MediaStore.Downloads.EXTERNAL_CONTENT_URI);
        activity.startActivityForResult(intent, main_activity.PICK_PDF_FILE);
    

    public static void get(Activity activity, String filename)  // filename is used for lower that API level 29
        // older that  API level 29 approaches
        File file = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
        // TODO
    

此外,要获取所选 pdf 文件的 Uri,您必须监听活动的结果:

@Override
public void onActivityResult(int requestCode, int resultCode, Intent resultData) 
    if (requestCode == PICK_PDF_FILE && resultCode == Activity.RESULT_OK) 
        System.out.println("request code: PICK_PDF_FILE && result code: OK");
        // The result data contains a URI for the document or directory that
        // the user selected.
        Uri uri = null;
        if (resultData != null) 
            uri = resultData.getData();
            // Perform operations on the document using its URI.
            System.out.println(uri);
         else 
            System.out.println("resultData is null");
        
     else 
        System.out.println("result code: NOT OK");
    

这是 API 级别 29 或更高级别的官方解决方案,可在 Android Developer 中找到。

【讨论】:

【参考方案3】:

这是我用 Uri 打开 doc 文件的代码。

fun viewPDFIntent(fileUri: Uri?, context: Context, title: String?, type: String) 
        val viewPDFIntent = Intent(Intent.ACTION_VIEW).apply 
            setDataAndType(fileUri, type)
            flags = Intent.FLAG_GRANT_READ_URI_PERMISSION
        
        context.startActivity(Intent.createChooser(viewPDFIntent, title))
    

这里 type for pdf 是 "application/pdf"。 您正在 itemUri 变量中创建 pdf uri,将其传递给此函数的第一个参数。

【讨论】:

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