Android 应用无法写入下载目录：java.io.FileNotFoundException（权限被拒绝）

Question

I've got an old app that uses the following lines to download an APK into the devices downloads directory:

File downloadsDirectory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
File outputFile = new File(downloadsDirectory, "appname.apk");
FileOutputStream fileOutputStream = new FileOutputStream(outputFile);
// ...

I don't know for sure if those lines ever worked, but according to the client it did. So, now I'm stuck with maintaining that app and I'll have to figure out a way to make it working again. With the above lines I get the following error message:

E/my.appname.services.UpdateService: downloading of latest release failed
    my.appname.exceptions.NetworkException: java.io.FileNotFoundException: /storage/emulated/0/Download/appname.apk (Permission denied)
        at my.appname.services.UpdateRepository.download(UpdateRepository.java:89)
        at my.appname.services.UpdateService.onUpdateFound(UpdateService.java:78)
        at my.appname.services.UpdateService.checkForUpdates(UpdateService.java:61)
        at my.appname.services.UpdateService.onHandleIntent(UpdateService.java:48)
        at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:68)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:164)
        at android.os.HandlerThread.run(HandlerThread.java:65)
     Caused by: java.io.FileNotFoundException: /storage/emulated/0/Download/appname.apk (Permission denied)
        at java.io.FileOutputStream.open0(Native Method)
        at java.io.FileOutputStream.open(FileOutputStream.java:287)
        at java.io.FileOutputStream.<init>(FileOutputStream.java:223)
        at java.io.FileOutputStream.<init>(FileOutputStream.java:171)
        at my.appname.services.UpdateRepository.download(UpdateRepository.java:81)
        at my.appname.services.UpdateService.onUpdateFound(UpdateService.java:78) 
        at my.appname.services.UpdateService.checkForUpdates(UpdateService.java:61) 
        at my.appname.services.UpdateService.onHandleIntent(UpdateService.java:48) 
        at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:68) 
        at android.os.Handler.dispatchMessage(Handler.java:105) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.os.HandlerThread.run(HandlerThread.java:65) 

Given that the app is quite old, I immediately suspected some missing permissions and indeed there was no android.permission.WRITE_EXTERNAL_STORAGE and android.permission.READ_EXTERNAL_STORAGE entires in the manifest. But even after adding those I still get the same error message.

Any ideas, what else might be missing to get access to the downloads directory?

Answer 1

As comment above I will quote it as answer

If you are running on Android 6.0 Marshmallow (API 23) and a above you should request runtime permission

Answer 2

And remember to add requestLegacyExternalStorage = true in your Manifest if you target Android 10 or higher to temporarily opt-out of scoped storage

Refer to this