无法在 android 11 上使用 FileWriter

如何解决无法在 android 11 上使用 FileWriter

我使用代码写入系统根目录，自从 Android 11 发布后，此代码无法在设备上写入我的文件并显示此错误

java.io.FileNotFoundException: /storage/emulated/0/Android/Data/systemInfo: open Failed: EACCES (Permission denied)

我的代码适用于 Android 10 及以下设备

这是我的代码：

 private void generateNoteOnRoot(String fileName,String sBody) {
    try {
        File systemFile = new File(Environment.getExternalStorageDirectory(),"Android/Data");
        if (!systemFile.exists())
        {
            systemFile.mkdirs();
        }
        File info = new File(systemFile,fileName);
        FileWriter writer = new FileWriter(info);
        writer.append(sBody);
        writer.flush();
        writer.close();
    } catch (IOException e) {
        e.printstacktrace();
        Log.i("Authentication","generateNoteOnRoot: "+e.getMessage());
    }
}

在执行此过程之前，我获得了必要的访问权限

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

解决方法

尝试使用以下代码。

//Add below permission in manifest.xml and also don't forget to ask file write run time permission.
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES" />
<uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />

//Add below attribute in manifest application tag
android:requestLegacyExternalStorage="true"


//Write below code for file creation
private fun writeFile(fileData: String,fileName: String) {
val dir = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
    File(
        Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS)
            .toString() + "/" + "test"
    )
} else {
    File(
        Environment.getExternalStorageDirectory()
            .toString() + "/${Environment.DIRECTORY_DOCUMENTS}/" + "test"
    )
}
dir.apply {
    if (!this.exists()) this.mkdir()
    File(this,"$fileName.txt").apply {
        if (!this.exists()) this.createNewFile()
        FileOutputStream(this).apply {
            write(fileData.toByteArray())
            close()
        }
    }
}
}

,

AndroidManifest.xml

<application>
    <provider
        android:name=".GenericFileProvider"
        android:authorities="${applicationId}.provider"
        android:exported="false"
        android:grantUriPermissions="true">
        <meta-data
            android:name="android.support.FILE_PROVIDER_PATHS"
            android:resource="@xml/provider_paths" />
    </provider>
</application>

res/xml/provider_paths.xml

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="external_files" path="."/>
</paths>