WallpaperFragment.kt

private fun checkPermissionForImageSave() {
      if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M ||
              activity!!.checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
          saveImageToGallery()
      } else {
          requestPermissions(arrayOf(Manifest.permission.WRITE_EXTERNAL_STORAGE), REQUEST_STORAGE_PERMISSION_CODE)
      }
  }

  override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
      if (requestCode == REQUEST_STORAGE_PERMISSION_CODE && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
          saveImageToGallery()
      } else {
          toast(R.string.unable_to_save_permission)
      }
      super.onRequestPermissionsResult(requestCode, permissions, grantResults)
  }

  private fun saveImageToGallery() {
      val dialog = ProgressDialog()
      dialog.isCancelable = false
      dialog.title = getString(R.string.save_image)
      dialog.show(fragmentManager, "")
      runInBackground {
          MediaStore.Images.Media.insertImage(context!!.contentResolver, imageFile.path, "wallpaper", "")
          runInMainThread {
              dialog.dismiss()
              toast(R.string.saved)
          }
      }
  }