Java Can'；即使设置了Android 11上的Android 10和requestLegacyExternalStorage，也无法访问/Android/数据

我正在尝试读取/写入Android 11上我的应用程序中的

/Android/data

和

/Android/obb

文件夹。我已经知道针对Android 11是不可能的，所以我在build.gradle中写了以下内容：

 compileSdkVersion 29
    buildToolsVersion "29.0.3"
    defaultConfig {
        applicationId "bla.bla.bla"
        minSdkVersion 21
        //noinspection OldTargetApi
        targetSdkVersion 29

        . . .
}

在AndroidManifist.xml中：

<application
        . . .

        android:requestLegacyExternalStorage="true">

        . . .
<application/>

目前，

Environment.isExternalStorageLegacy（）

返回true

2021-05-10 23:20:32.737 31921-31921/com.fqxd.gftools D/Storage: Legacy true

但不幸的是，在获取文件列表时，我得到了java.lang.NullPointerException

/Android/data

：

2021-05-10 23:20:32.739 31921-31921/com.fqxd.gftools D/AndroidRuntime: Shutting down VM
2021-05-10 23:20:32.740 31921-31921/com.fqxd.gftools E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.fqxd.gftools, PID: 31921
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.fqxd.gftools/com.fqxd.gftools.MainActivity}: java.lang.NullPointerException: Attempt to get length of null array
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3431)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7660)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: java.lang.NullPointerException: Attempt to get length of null array
        at com.fqxd.gftools.MainActivity.onCreate(MainActivity.java:53)
        at android.app.Activity.performCreate(Activity.java:8000)
        at android.app.Activity.performCreate(Activity.java:7984)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3404)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:223) 
        at android.app.ActivityThread.main(ActivityThread.java:7660) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) 
2021-05-10 23:20:33.268 31921-31937/com.fqxd.gftools W/System: A resource failed to call close. 

这似乎阻止了对Android本身上的

/Android/data

文件夹的访问

---

请告诉我如何解决此问题。

在Android 10设备上，如果您在清单文件中请求旧版外部存储，您可以完全访问/storage/simulated/0/Android/data。根据：“在Android 11上，应用程序无法再访问外部存储中任何其他应用程序专用、特定于应用程序的目录中的文件。”这可能适用于任何版本的Android应用程序。对不起。这是我的错。它不是

环境。getExternalStorageDirectory（）

。它是Environment.isExternalStorageLegacy（）。

2021-05-10 23:20:32.739 31921-31921/com.fqxd.gftools D/AndroidRuntime: Shutting down VM
2021-05-10 23:20:32.740 31921-31921/com.fqxd.gftools E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.fqxd.gftools, PID: 31921
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.fqxd.gftools/com.fqxd.gftools.MainActivity}: java.lang.NullPointerException: Attempt to get length of null array
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3431)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7660)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: java.lang.NullPointerException: Attempt to get length of null array
        at com.fqxd.gftools.MainActivity.onCreate(MainActivity.java:53)
        at android.app.Activity.performCreate(Activity.java:8000)
        at android.app.Activity.performCreate(Activity.java:7984)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3404)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:223) 
        at android.app.ActivityThread.main(ActivityThread.java:7660) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) 
2021-05-10 23:20:33.268 31921-31937/com.fqxd.gftools W/System: A resource failed to call close.