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，但是如何用 java 代码来实现呢？

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" -->

TestActivity.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： 如何在这里创建一个新的 NavGraph 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

请看这里的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);