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

Question

我有一个旧应用程序使用以下行将 APK 下载到设备下载目录中：

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

我不确定这些线路是否有效，但根据客户的说法是有效的。所以，现在我一直在维护那个应用程序，我必须想办法让它再次工作。通过以上几行，我收到以下错误消息：

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)

鉴于该应用程序很旧，我立即怀疑缺少某些权限，而且清单中确实没有 android.permission.WRITE_EXTERNAL_STORAGE 和 android.permission.READ_EXTERNAL_STORAGE 的完整内容。但即使添加了这些，我仍然收到相同的错误消息。

任何想法，还有什么可能缺少访问下载目录？

Answer 1

如上评论，我会引用它作为答案

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

Answer 2

并且如果您将Android 10 或更高目标临时 opt-out 范围存储

，请记住在您的清单中添加 requestLegacyExternalStorage = true ]

Refer to this

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

Android app fails to write to downloads directory: java.io.FileNotFoundException (Permission denied)

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android-permissions