如何在 Android 中使用 Java 以编程方式构建 NavGraph

Question

我知道用XML构建NavGraph很容易，但是如何使用java代码实现它呢？

不带"app：navGraph"属性的片段XML定义：

<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
/>
<!-- app:navGraph="@navigation/mobile_navigation" -->

测试活动.java

NavController navController = Navigation.findNavController(activity, R.id.nav_host_fragment);
// How to pass the Class argument into the getNavigator?
NavGraph navGraph = new NavGraph(navController.getNavigatorProvider().getNavigator(???));

问题： 如何在此处创建新的导航图对象？ 哪个 navigatorClass 应该用作方法 "getNavigator(Class(" 的参数？

androidx.navigation.NavigatorProvider.java

/**
* Retrieves a registered {@link Navigator} using the name provided by the
* {@link Navigator.Name Navigator.Name annotation}.
*
* @param navigatorClass class of the navigator to return
* @return the registered navigator with the given {@link Navigator.Name}
*
* @throws IllegalArgumentException if the Navigator does not have a
* {@link Navigator.Name Navigator.Name annotation}
* @throws IllegalStateException if the Navigator has not been added
*
* @see #addNavigator(Navigator)
*/
@NonNull
public final <T extends Navigator<?>> T getNavigator(@NonNull Class<T> navigatorClass) {
String name = getNameForNavigator(navigatorClass);
return getNavigator(name);
}

谢谢。

Answer 1

请在此处查看 java 代码：

NavHostFragment myNavHostFragment = (NavHostFragment) findViewById(R.id.my_nav_host_fragment);
NavInflater inflater = myNavHostFragment.getNavController().getNavInflater();
NavGraph graph = inflater.inflate(R.navigation.my_nav_graph);
myNavHostFragment.getNavController().setGraph(graph);