如何在Android中用Java编程构建NavGraph

Question

我知道用XML构建NavGraph很容易，但是如何用java代码实现它呢？

片段XML定义，没有“app:导航图”属性：

@+id/nav_host_片段“android:name="androidx.navigation.fragment.NavHostFragment”android:layout_width="match_parent“android:layout_height="match_parent”app:defaultNavHost=“真”app:layout_constraintLeft_toLeftOf=“父”app:layout_constraintRight_toRightOf=“父”app:layout_constraintTop_toTopOf=“父”/>“

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？应该使用哪个navigatorClass作为“getNavigator(类)”方法的参数？

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

请参阅这里的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);