如何以编程方式更改导航图的起始目的地 [Jetpack] [英] How to change start destination of a navigation graph programmatically [Jetpack]

问题描述

基本上，我有以下导航图:

我想在到达它后立即将导航图中的起点更改为 fragment 2(以防止在按下后退按钮时返回到 fragment 1 - 例如与启动画面).

这是我的代码:

navGraph = navController.getGraph();navGraph.setStartDestination(R.id.fragment2);navController.setGraph(navGraph);

但是，显然它不起作用，按下后退按钮后它返回到fragment 1.

我做错了吗?还有其他解决办法吗?

解决方案

更新:

当你有这样的导航图时:

<片段android:id="@+id/firstFragment"android:name="com.appname.package.FirstFragment" ><动作android:id="@+id/action_firstFragment_to_secondFragment"app:destination="@id/secondFragment"/></片段><片段android:id="@+id/secondFragment"android:name="com.appname.package.SecondFragment"/>

并且您想导航到第二个片段并使其成为图形的根，指定下一个 NavOptions:

NavOptions navOptions = new NavOptions.Builder().setPopUpTo(R.id.firstFragment, true).建造();

并将它们用于导航:

Navigation.findNavController(view).navigate(R.id.action_firstFragment_to_secondFragment, bundle, navOptions);

<块引用>

setPopUpTo(int destinationId, boolean inclusive) - 在导航前弹出给定的目的地.这将从返回堆栈中弹出所有不匹配的目的地，直到找到该目的地.

destinationId - 要弹出的目的地，清除所有中间目的地.

inclusive - true 也从返回堆栈中弹出给定的目的地.

替代方案:

<片段android:id="@+id/firstFragment"android:name="com.appname.package.FirstFragment" ><动作android:id="@+id/action_firstFragment_to_secondFragment"应用程序:目的地=@id/secondFragment"app:popUpTo="@+id/firstFragment"app:popUpToInclusive="true"/></片段><片段android:id="@+id/secondFragment"android:name="com.appname.package.SecondFragment"/>

然后在你的代码上:

findNavController(fragment).navigate(FirstFragmentDirections.actionFirstFragmentToSecondFragment())

旧答案

已弃用:NavOptions 中用于操作和关联 API 的 clearTask 属性已被弃用.>

来源:https://developer.android.com/jetpack/docs/release-笔记

如果您想将根片段更改为 fragment 2(例如，在按 fragment 2 上的后退按钮后，您将退出应用程序)，您应该放置下一个属性到您的 action 或 destination:

app:clearTask="true"

实际上它的外观如下:

<片段android:id="@+id/firstFragment"android:name="com.appname.package.FirstFragment"android:label="fragment_first" ><动作android:id="@+id/action_firstFragment_to_secondFragment"应用程序:目的地=@id/secondFragment"应用程序:clearTask="true"/></片段><片段android:id="@+id/secondFragment"android:name="com.appname.package.SecondFragment"android:label="fragment_second"/>

我已将 app:clearTask="true" 添加到操作中.

现在，当您执行从 fragment 1 到 fragment 2 的导航时，请使用下一个代码:

Navigation.findNavController(view).navigate(R.id.action_firstFragment_to_secondFragment);

Basically, I have the following navigation graph:

I want to change my starting point in navigation graph to fragment 2 right after reaching it (in order to prevent going back to fragment 1 when pressing back button - like with the splash screen).

This is my code:

navGraph = navController.getGraph();
navGraph.setStartDestination(R.id.fragment2);
navController.setGraph(navGraph);

But, obviously it's not working and it gets back to fragment 1 after pressing back button.

Am I doing it wrong? Is there any other solution?

解决方案

UPDATE:

When you have nav graph like this:

<fragment
    android:id="@+id/firstFragment"
    android:name="com.appname.package.FirstFragment" >
    <action
        android:id="@+id/action_firstFragment_to_secondFragment"
        app:destination="@id/secondFragment" /> 
</fragment>

<fragment
    android:id="@+id/secondFragment"
    android:name="com.appname.package.SecondFragment"/>

And you want to navigate to the second fragment and make it root of your graph, specify the next NavOptions:

NavOptions navOptions = new NavOptions.Builder()
        .setPopUpTo(R.id.firstFragment, true)
        .build();

And use them for the navigation:

Navigation.findNavController(view).navigate(R.id.action_firstFragment_to_secondFragment, bundle, navOptions);

setPopUpTo(int destinationId, boolean inclusive) - Pop up to a given destination before navigating. This pops all non-matching destinations from the back stack until this destination is found.

destinationId - The destination to pop up to, clearing all intervening destinations.

inclusive - true to also pop the given destination from the back stack.

ALTERNATIVE:

<fragment
    android:id="@+id/firstFragment"
    android:name="com.appname.package.FirstFragment" >
<action
    android:id="@+id/action_firstFragment_to_secondFragment"
    app:destination="@id/secondFragment"
    app:popUpTo="@+id/firstFragment"
    app:popUpToInclusive="true" /> 
</fragment>

<fragment
    android:id="@+id/secondFragment"
    android:name="com.appname.package.SecondFragment"/>

And then on your code:

findNavController(fragment).navigate(
    FirstFragmentDirections.actionFirstFragmentToSecondFragment())

Old answer

Deprecated: The clearTask attribute for actions and the associated API in NavOptions has been deprecated.

Source: https://developer.android.com/jetpack/docs/release-notes

If you want to change your root fragment to fragment 2 (e.g. after pressing back button on fragment 2 you will exit the app), you should put the next attribute to your action or destination:

app:clearTask="true"

Practically it looks in a next way:

<fragment
    android:id="@+id/firstFragment"
    android:name="com.appname.package.FirstFragment"
    android:label="fragment_first" >
    <action
        android:id="@+id/action_firstFragment_to_secondFragment"
        app:destination="@id/secondFragment"
        app:clearTask="true" /> 
</fragment>

<fragment
    android:id="@+id/secondFragment"
    android:name="com.appname.package.SecondFragment"
    android:label="fragment_second"/>

I've added app:clearTask="true" to action.

Now when you perform navigation from fragment 1 to fragment 2 use the next code:

Navigation.findNavController(view)
        .navigate(R.id.action_firstFragment_to_secondFragment);

这篇关于如何以编程方式更改导航图的起始目的地 [Jetpack]的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！