Question

    DownloadManager.Request request = new DownloadManager.Request(uri);
      request.setDestinationInExternalPublicDir(Environment.
                        DIRECTORY_DOWNLOADS, nameOfFile)

打开它

       File file = new File(Environment.
                    DIRECTORY_DOWNLOADS, nameOfFile);
            MimeTypeMap map = MimeTypeMap.getSingleton();
            String ext = MimeTypeMap.getFileExtensionFromUrl(file.getName());
            String type = map.getMimeTypeFromExtension(ext);

但我收到一条错误消息，指出无法访问该文件。检查位置

Answer 1

尝试使用读取权限：

android.permission.READ_EXTERNAL_STORAGE

Answer 2

试试这个......

protected void openFile(String fileName) {
    Intent install = new Intent(Intent.ACTION_VIEW);
    install.setDataAndType(Uri.fromFile(new File(fileName)),
            "MIME-TYPE");
    startActivity(install);
}

Answer 3

这是一个有效的解决方案。注意：不要使用DownloadManager.COLUMN_LOCAL_FILENAME，因为它在API 24中已弃用。请改用DownloadManager.COLUMN_LOCAL_URI。

创建字段下载管理器和长变量以保存下载ID。

DownloadManager dm;
long downloadId;
String  pendingDownloadUrl = url;
fial int storagePermissionRequestCode = 101;

创建下载管理器 dm = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);

注册广播接收器以便下载完成

 BroadcastReceiver downloadCompleteReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(final Context context, final Intent intent) {
        Cursor c = dm.query(new DownloadManager.Query().setFilterById(downloadId));
        if (c != null) {
            c.moveToFirst();
            try {
                String fileUri = c.getString(c.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI));
                File mFile = new File(Uri.parse(fileUri).getPath());
                String fileName = mFile.getAbsolutePath();
                openFile(fileName);
            }catch (Exception e){
                Log.e("error", "Could not open the downloaded file");
            }
        }
    }
};

//注册boradcast以下载完成

registerReceiver(downloadCompleteReceiver, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));

开始下载

开始下载

private  void onDownloadStart(String url) {
if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
    downloadFile(url);
} else {
    pendingDownloadUrl = url;
    ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, storagePermissionRequestCode);
} }

//使用下载管理器下载文件

private void downlaodFile(String url){
    DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
    String filename = URLUtil.guessFileName(url, null, null);
    request.allowScanningByMediaScanner();
    request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
    request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,filename);
    downloadId = dm.enqueue(request);//save download id for later reference }

//权限状态

@Override public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    if(requestCode == storagePermissionRequestCode){
        boolean canDownload = true;
        for (int grantResult : grantResults) {
            if (grantResult == PackageManager.PERMISSION_DENIED) {
                canDownload = false;
                break;
            }
        }
        if(canDownload){
            downlaodFile(pendingDownloadUrl);
        }
    }        }

打开下载的文件

private void openFile(String file) {
try {
    Intent i = new Intent(Intent.ACTION_VIEW);
    i.setDataAndType(Uri.fromFile(new File(file)), "application/pdf");//this is for pdf file. Use appropreate mime type
    startActivity(i);
} catch (Exception e) {           
    Toast.makeText(this,"No pdf viewing application detected. File saved in download folder",Toast.LENGTH_SHORT).show();
}
}

现在尝试通过调用downladFile(String url);方法

下载后如何打开下载的文件？

3 个答案: