保存文本文件 - 分区存储 Android 11

Question

有没有办法在外部存储的 Android/data 文件夹之外创建和保存文本文件？我正在创建一个音乐应用程序，并添加了一个预设管理器，以便用户可以保存、加载和编辑预设文件（在 Android 11 之前工作得很好），我不希望这些文件在应用程序出现时自动删除被卸载。这就像如果 Photoshop 在卸载 Photoshop 时删除了所有 Photoshop 文档，那太糟糕了！这些是用户保存的文件，如果用户愿意，可以单独删除它们。

一定有办法解决这个问题，但我一直没能找到任何有效的方法。 ACTION_OPEN_DOCUMENT_TREE 看起来很有前途，直到我看到 Android 也删除了这个选项。

https://developer.android.com/about/versions/11/privacy/storage

You can no longer use the ACTION_OPEN_DOCUMENT_TREE intent action to request access to the following directories:

The root directory of the internal storage volume.

The root directory of each SD card volume that the device manufacturer considers to be reliable, regardless of whether the card is emulated or removable. A reliable volume is one that an app can successfully access most of the time.

The Download directory.

我读过 Google Play 仅允许 MANAGE_EXTERNAL_STORAGE 在需要它的应用程序（如文件浏览器或防病毒软件等）中使用，这可能不适用于我的情况。我不想只针对年龄较大的 API，所以 requestLegacyExternalStorage 也行不通。

我调查过的一切似乎都是死胡同。还有什么我可以做的吗？

这里是一个简短的测试程序（我用的是LibGDX），目前只能保存到根目录：

Android/data/com.mygdx.filetest/files/

[核心]FileTest.java

package com.mygdx.filetest;

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Files;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.files.FileHandle;
import com.badlogic.gdx.utils.ScreenUtils;

public class FileTest implements ApplicationListener {
    private NativePermissions permissions;
    private Files.FileType fileType;
    private String directory = "TestDir/";
    private String name = "text.txt";
       
    public FileTest(final NativePermissions permissions){     
        this.permissions = permissions;
    }
    
    @Override
    public void create(){
        fileType = getFileType();
        if (permissions != null){
            permissions.checkExternalStoragePermission();
        } else {
            permissionGranted();
        }
    }
    private Files.FileType getFileType(){
        switch(Gdx.app.getType()) {
            case Android:
                return Files.FileType.External;
            default:
                return Files.FileType.Local;
        }
    }
    
    @Override public void render(){ ScreenUtils.clear(0.4f, 0.4f, 0.4f, 1); }
    @Override public void resize(int width, int height) {}
    @Override public void pause(){}
    @Override public void resume(){}
    @Override public void dispose (){}
    
    public void permissionGranted() {
        FileHandle fileHandle = Gdx.files.getFileHandle(directory+name, fileType); 
        if (fileHandle!=null) fileHandle.writeString("test", false);
    }
}

[android] AndroidLauncher.java

package com.mygdx.filetest;

import android.Manifest;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.widget.Toast;

import androidx.core.app.ActivityCompat;

import com.badlogic.gdx.backends.android.AndroidApplication;
import com.badlogic.gdx.backends.android.AndroidApplicationConfiguration;

public class AndroidLauncher extends AndroidApplication {
    private final FileTest application;
    private final int STORAGE_PERMISSION_CODE = 1;
    private boolean dialogBoxShowing = false;
    
    public AndroidLauncher(){
        final AndroidPermissions permissions = new AndroidPermissions(this);
        application = new FileTest(permissions);
    }
    
    @Override
    protected void onCreate (Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        AndroidApplicationConfiguration config = new AndroidApplicationConfiguration();
        initialize(application, config);
    }
    @Override
    public void onRequestPermissionsResult(final int requestCode, final String permissions[], final int[] grantResults) {
        dialogBoxShowing = false;
        if (requestCode == STORAGE_PERMISSION_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this, "Permission GRANTED", Toast.LENGTH_SHORT).show();
                permissionGranted();
            } else {
                Toast.makeText(this, "Permission DENIED", Toast.LENGTH_SHORT).show();
            }
        }
    }
    public void promptExternalStoragePermission() {
        if (dialogBoxShowing) return;
        dialogBoxShowing = true;
        this.runOnUiThread(new Runnable() {
            @Override
            public void run() {
                final AlertDialog.Builder builder = new AlertDialog.Builder(AndroidLauncher.this);
                builder.setMessage("To save user presets and custom settings, allow access to your phone’s storage.");
                builder.setCancelable(false);
                // reverse these buttons to put "NO" on left and "YES" on right
                builder.setPositiveButton("NOT NOW", new DialogInterface.OnClickListener(){
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialogBoxShowing = false;
                        dialog.dismiss();
                    }
                });
                builder.setNegativeButton("CONTINUE", new DialogInterface.OnClickListener(){
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        ActivityCompat.requestPermissions(AndroidLauncher.this, new String[] {Manifest.permission.WRITE_EXTERNAL_STORAGE}, STORAGE_PERMISSION_CODE);
                    }
                });
                builder.create().show();
            }
        });
    }
    public void permissionGranted(){ application.permissionGranted(); }
}

[核心]NativePermissions.java

package com.mygdx.filetest;

public interface NativePermissions {
    public void checkExternalStoragePermission();
}

[android] AndroidPermissions.java

package com.mygdx.filetest;

import android.Manifest;
import android.content.pm.PackageManager;

import androidx.core.content.ContextCompat;

public class AndroidPermissions implements NativePermissions {
    private final AndroidLauncher context;
    
    public AndroidPermissions(final AndroidLauncher context){
        this.context = context;
    }
    
    @Override
    public void checkExternalStoragePermission() {
        if (ContextCompat.checkSelfPermission(context, Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED){
            context.permissionGranted();
        } else {
            context.promptExternalStoragePermission();
        }
    }
}

[android] AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.mygdx.filetest">
    
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:isGame="true"
        android:appCategory="game"
        android:label="@string/app_name"
        android:theme="@style/GdxTheme" >
        <activity
            android:name="com.mygdx.filetest.AndroidLauncher"
            android:label="@string/app_name" 
            android:screenOrientation="fullUser"
            android:configChanges="keyboard|keyboardHidden|navigation|orientation|screenSize|screenLayout">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

Answer 1

大惊小怪。

您可以以经典方式将文件保存到 public Documents 目录。

或者对该目录使用带 ACTION_OPEN_DOCUMENT_TREE 的 SAF。

两者都不需要 'all files access'。

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