带有 CoordinatorLayout 的 Android NavHostFragment

Question

我想在我的应用中实现新的 Android 导航组件。据我所知，基本上用于托管片段（NavHostFragment）的片段默认使用 FrameLayout。但是，不幸的是，FrameLayout 对窗口插图一无所知，因为它是在 Android 4.4 之前开发的。所以我想知道如何创建我自己的 NavHostFragment，它将使用 CoordinatorLayout 作为根元素，在视图层次结构中传递窗口插图。

Answer 1

要将 FrameLayout 替换为 CoordinatorLayout，您可以创建自定义 NavHostFrament 并覆盖 onCreateView 方法。

NavHostFragment 内部：

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    FrameLayout frameLayout = new FrameLayout(inflater.getContext());
    // When added via XML, this has no effect (since this FrameLayout is given the ID
    // automatically), but this ensures that the View exists as part of this Fragment's View
    // hierarchy in cases where the NavHostFragment is added programmatically as is required
    // for child fragment transactions
    frameLayout.setId(getId());
    return frameLayout;
}

如您所见，FrameLayout 是通过编程方式创建的，并且在返回之前设置了它的 id。

CustomNavHostFragment：

class CustomNavHostFragment : NavHostFragment() {
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        // change it to CoordinatorLayout
        val view = CoordinatorLayout(inflater.context)
        view.id = id
        return view
    }
}

但是，您不需要将 NavHostFragment 的默认 FrameLayout 替换为 CoordinatorLayout。根据 Ian Lake 的answer 也可以实现ViewCompat.setOnApplyWindowInsetsListener() 来拦截对窗口插入的调用并进行必要的调整。

coordinatorLayout?.let {
    ViewCompat.setOnApplyWindowInsetsListener(it) { v, insets ->
        ViewCompat.onApplyWindowInsets(
            v, insets.replaceSystemWindowInsets(
                insets.systemWindowInsetLeft, 0,
                insets.systemWindowInsetRight, insets.systemWindowInsetBottom
            )
        )
        insets // return original insets to pass them down in view hierarchy or remove this line if you want to pass modified insets down the stream.
        // or
        // insets.consumeSystemWindowInsets()
    }
}