如何在android下使用superpowered SDK将文件写到外部存储？

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

import android.os.Environment;
import com.superpowered.sdk.audio.SuperpoweredRecorder;

// 获取外部存储的根目录路径
String externalStoragePath = Environment.getExternalStorageDirectory().getAbsolutePath();

// 创建文件保存路径
String filePath = externalStoragePath + "/myfolder/myfile.txt";

// 创建SuperpoweredRecorder对象
SuperpoweredRecorder recorder = new SuperpoweredRecorder(filePath, 44100, 1, false);

// 开始录制
recorder.start();

// 停止录制
recorder.stop();