即使已授予权限，也无法在外部存储中创建目录

Question

我有问题在Android Studio中创建外部存储的新目录。它可能必须做一些有权限的事情，但据我所知，一切似乎都很好。

我想做的是：

1. 检查目录“/storage/emulated/0/Recordings”是否存在，如果不存在-创建目录
2. 检查文件“/storage/simulated/0/Recordings/tempFile.raw”是否存在，如果存在-将其删除
3. 使用“new FileOutputStream（filename）；”在目录内创建文件

代码im使用（简化）：

String filepath = Environment.getExternalStorageDirectory().getPath();
//returns "/storage/emulated/0"
File file = new File(filepath,"Recordings");

if(!file.exists()){
   file.mkdirs();
}else{
   Log.w(TAG, "Didn't work");
}

fileName= "Recording #" + recordingNumber; //int recordingNumber = 1
recordingNumber++;
absolutePath = file.getAbsolutePath() + "/" + fileName + "tempFile.raw";

try {
   os = new FileOutputStream(absolutePath);
} catch (FileNotFoundException e) {
   e.printStackTrace();
}

我得到的错误：

java.io.FileNotFoundExc0019： /storage/emulated/0/Recordings/tempFile.raw（没有这样的文件或目录）

注意：logcat中没有“未工作”，这意味着执行了file.mkdirs（）。

清单权限：

<uses-permission android:name="android.permission.RECORD_AUDIO"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS"/>
<uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS"/>
<uses-permission android:name="android.permission.FOREGROUND_SERVICE"/>

权限：

虚拟设备上的外部存储：

Build.gradle：

android {
    compileSdkVersion 28
    buildToolsVersion "29.0.2"
    defaultConfig {
        applicationId "com.example.soundrecorder"
        minSdkVersion 22
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

Answer 1

首先，你错过了另一个许可：

写入外部存储器

此外，在你的活动中，你必须明确请求许可。检查此链接：

https://developer.android.com/training/permissions/requesting

if (ContextCompat.checkSelfPermission(thisActivity,
        Manifest.permission.WRITE_EXTERNAL_STORAGE)
        != PackageManager.PERMISSION_GRANTED) {

    // Permission is not granted
    // Should we show an explanation?
    if (ActivityCompat.shouldShowRequestPermissionRationale(thisActivity,
            Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
        // Show an explanation to the user *asynchronously* -- don't block
        // this thread waiting for the user's response! After the user
        // sees the explanation, try again to request the permission.
    } else {
        // No explanation needed; request the permission
        ActivityCompat.requestPermissions(thisActivity,
                new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                MY_PERMISSIONS_REQUEST_READ_CONTACTS);

        // MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
        // app-defined int constant. The callback method gets the
        // result of the request.
    }
} else {
    // Permission has already been granted
}