在 Kotlin 中未调用 CallBack

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:orientation="horizontal">
    <fragment
          android:id="@+id/map"
          android:name="com.google.android.gms.maps.SupportMapFragment"
          android:layout_width="match_parent"
          android:layout_height="match_parent"/>
</LinearLayout>

-

 val supportMapFragment = map as SupportMapFragment
        supportMapFragment.getMapAsync { this }

我究竟做错了什么。不调用回调。 this显示错误The expression is unused

简而言之，这样反编译，垃圾结果

protected void onCreate(@Nullable Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      this.setContentView(2131296283);
      Fragment var10000 = this.getSupportFragmentManager().findFragmentById(id.map);
      if(var10000 == null) {
         throw new TypeCastException("null cannot be cast to non-null type com.google.android.gms.maps.SupportMapFragment");
      } else {
         SupportMapFragment supportMapFragment = (SupportMapFragment)var10000;
         supportMapFragment.getMapAsync((OnMapReadyCallback)(new OnMapReadyCallback() {
            public final void onMapReady(GoogleMap it) {
               MapsActivity var10000 = MapsActivity.this;
            }
         }));
      }
   }

为什么要创建 Android Studionew OnMapReadyCallback我已经创建了它并添加了这个......