我正在从服务器下载一个PDF文件，并将响应体字节流传递给下面的函数，该函数将PDF文件成功地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，一旦这个函数返回，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。我认为仍然有一个权限问题正在进行(也许我使用错误的文件提供程序?)，或者可能路径是错误的，或者它可能是其他东西完全。
下面是我尝试过的几个例子:
fun uriFromFile(context: Context, file: File): Uri {
return FileProvider.getUriForFile(context, BuildConfig.APPLICATION_ID + ".provider", file)
}
)
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)
(也尝试了/test.pdf在这个URI的末尾，并将media替换为我的权限名称)
我还将此添加到我的manifest文件中的应用程序标签:
<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如下所示，尽管除此之外我还尝试了各种组合，包括路径".":
<?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>
作为旁注，肯定有能够打开pdf的选择器，进入文件资源管理器并从那里打开它很好。当尝试共享而不是打开共享时，共享也失败。
按照这个步骤和代码，它将管理从下载pdf到打开它的一切。
创建一个类名为DownloadTask并将完整的代码放在
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activity下载pdf。
new DownloadTask(this, "PDF_URL");
从你的片段
new DownloadTask(getContext(), "PDF_URL");
下载完成后会自动打开你的pdf文件。
根据Android Developer,MediaStore不被用于访问非媒体文件，如pdf文件:
如果你的应用程序处理的文档和文件不是排他的包含媒体内容，例如使用EPUB或PDF格式的文件扩展时，使用ACTION_OPEN_DOCUMENT意图动作，如关于如何存储和访问文档和其他文件的指南。
此外，使用Cursor和Content Provider访问非媒体文件没有任何官方解决方案。然而，有一个官方的和干净的代码方法，我已经测试了它在Android 11效果如预期。这是:
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
}
}
而且，要获得所选pdf文件的Uri，您必须侦听活动的结果:
@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");
}
}
这是官方的解决方案，可以在Android开发人员的API级别29或更高。
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))
}
这里的类型下载pdf文件"application/pdf">．您将在itemUri中创建pdf uri变量，将其传递给函数的第一个参数。