DownloadManager not working for Android 10 (Q)

问题

I've been beating my head against this issue for quite awhile... I am updating an app that uses DownloadManger to do a simple task like downloading a file to the external storage public directory i.e:

Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS)

Everything works fine here from Android api 19-28. Its when testing on API 29 (Q/10) is where issues occur. Android implemented scoped storage and so deprecated the getExternalStoragePublicDirectory... As a result I need to figure out a compatible solution to support APIs 19-29. I cannot use internal application storage since DownloadManager will throw a SecurityException. Androids documentation states that I can use the DownloadManager.Request setDestinationUri and it even mentions for Android Q that I can use Context.getExternalFilesDir(String). When I do this though, the path is still the emulated path:

/storage/emulated/0/Android/data/com.my.package.name/files/Download/myFile.xml

I get a callback from the download manager that the download is complete (with right ID) but then I cannot grab the download from the area I saved it to. I check to see if the file exists and it returns false:

new File("/storage/emulated/0/Android/data/com.my.package.name/files/Download/myFile.xml").exists();

Any help is appreciated

Adding code for context. So setting up download manager

    private void startDownload() {
        IntentFilter filter = new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE);
        registerReceiver(downloadReceiver, filter);

        String remoteURL= getString(R.string.remote_url);

        DownloadManager.Request request = new DownloadManager.Request(Uri.parse(remoteUrl));
        request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE);
        request.setTitle(getString(R.string.download_title));
        request.setDescription(getString(R.string.download_description));
        request.setDestinationUri(Uri.fromFile(new File(getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS), "myFile.xml")));

        DownloadManager manager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
        mainDownloadID= manager.enqueue(request);
    }

checking file if it exists:

new File(getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS), "myFile.xml").exists(); //this returns false in the onReceive (and download IDs match)

回答1:

Try add this into your manifest file in application tag

android:requestLegacyExternalStorage="true"

回答2:

File Paths outside of the App's private directories in Android Q and above useless.

See https://developer.android.com/training/data-storage#scoped-storage

You need to ask the user where to download the files too, this will get you a URI for the DownloadManager destination.

https://developer.android.com/training/data-storage/shared/documents-files#grant-access-directory

You will probably want to persist this permission

https://developer.android.com/training/data-storage/shared/documents-files#persist-permissions

回答3:

Yeah Its scope storage but even though you can download file in Q+ using downloadmanger no need to do android:requestLegacyExternalStorage="true"

I am doing this way.

1. manifest

• -->

2. Downloadmanger

    val fileName =
        Constants.FILE_NAME + Date().time
   
    val downloadUri = Uri.parse(media.url)
    val request = DownloadManager.Request(
        downloadUri
    )
    request.setAllowedNetworkTypes(
        DownloadManager.Request.NETWORK_WIFI or DownloadManager.Request.NETWORK_MOBILE
    )
        .setAllowedOverRoaming(true).setTitle("Some name")
        .setDescription("Downloading file")
        .setDestinationInExternalPublicDir(
            Environment.DIRECTORY_DOWNLOADS, File.separator + FOLDER + File.separator + fileName
        )
   
   
    Toast.makeText(
        context,
        "Download successfully to ${downloadUri?.path}",
        Toast.LENGTH_LONG
    ).show()
   
    downloadManager.enqueue(request)
   

Hence it will ask write permission below Q, but in Q and Q+ it will download without asking permission in /Download/folder dir.

来源：https://stackoverflow.com/questions/59177136/downloadmanager-not-working-for-android-10-q