使用 Kotlin 创建新目录，Mkdir() 不起作用

var filename = "blesson.txt"
var wallpaperDirectory = File("/sdcard/Wallpaper")
 wallpaperDirectory.mkdirs()
val outputFile = File(wallpaperDirectory, filename)
val fos = FileOutputStream(outputFile)

我正在尝试使用 Kotlin 在 Android 设备上创建一个新目录，但是该函数mkdirs()不起作用。

var filename = "blesson.txt"
var wallpaperDirectory = File(Environment.getExternalStorageDirectory().absolutePath)//("/sdcard/Wallpaper")
wall
val outputFile = File(wallpaperDirectory, filename)
val fos = FileOutputStream(outputFile)

我也尝试过，它没有创建新目录 欢迎任何帮助

这在 Kotlin 上完美运行

class MainActivity : AppCompatActivity() {

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    var filename = "blesson.txt"
    // create a File object for the parent directory
    val wallpaperDirectory = File("/sdcard/Wallpaper/")
    // have the object build the directory structure, if needed.
    wallpaperDirectory.mkdirs()
    // create a File object for the output file
    val outputFile = File(wallpaperDirectory, filename)
    // now attach the OutputStream to the file object, instead of a String representation
    try {
      val fos = FileOutputStream(outputFile)
    } catch (e: FileNotFoundException) {
      e.printStackTrace()
    }

  }
}