GoogleMap Fragment，当我想获取我的位置的屏幕截图时出现黑屏

Question

我希望将Google地图的屏幕快照保存在列表视图中，但是当我执行该操作时，它只显示地图的黑屏，但是我得到了屏幕

    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    var t = inflater.inflate(R.layout.fragment_map, container, false)
    var download = t.findViewById(R.id.download) as FloatingActionButton
    var imageView=t.findViewById(R.id.imageView) as ImageView
    mapFragment = childFragmentManager.findFragmentById(R.id.map) as SupportMapFragment?
    mapFragment!!.getMapAsync(this)
     download.setOnClickListener(){

             var bitmap: Bitmap? = getBitmapRootView(it)
             imageView.setImageBitmap(bitmap)
             createImage(bitmap!!)

     }
    return t
}


}
private fun getBitmapRootView(v: View): Bitmap {
    val rootView = v.rootView
    rootView.isDrawingCacheEnabled = true
    return rootView.drawingCache
}

private fun createImage(bmp: Bitmap) {
    val bytes = ByteArrayOutputStream()
    bmp.compress(Bitmap.CompressFormat.JPEG, 40, bytes)
    val file = File(Environment.getExternalStorageDirectory().toString().plus("/captured_screen_shot.jpg"))
    try {
        file.createNewFile()
        val outputStream = FileOutputStream(file)
        outputStream.write(bytes.toByteArray())
        outputStream.close()
    } catch (e: Exception) {
        e.printStackTrace()
    }
}

}

我希望获得我的googlemap的屏幕截图，但实际上只是黑屏
文件：///home/khouloud/T%C3%A9l%C3%A9chargements/Screenshot_2019-04-23-09-29-37.png