Navigation组件

发表于 | Edited on | 分类于

Navigation

Navigation是一个可简化Android导航的库和插件。

Navigation是用来管理Fragment的切换，并且可以通过可视化的方式，看见App的交互流程。

实战

名称 用途
Navigation graph XML资源文件，包含所有的navigation关联信息，用户在可视化界面可以看出他能够到达的destination，以及流程关系
NavHost 在navigation graph展示destination的空容器，NavHostFragment为展示fragment destination的具体实现
NavController 导航控制者

创建Navigation graph

1
2
3
4
5
6
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/nav_graph"
    app:startDestination="@id/tasks_fragment_dest">

</navigation>

新建NavHostFragment

1
2
3
4
5
6
7
8
9
<fragment
           android:id="@+id/nav_host_fragment"
           android:name="androidx.navigation.fragment.NavHostFragment" //值是固定的，声明这是一个NavHostFragment
           android:layout_width="match_parent"
           android:layout_height="match_parent"

           app:defaultNavHost="true" //与系统的返回按钮相关联
           app:navGraph="@navigation/nav_graph"//存放Navigation graph
            />

界面跳转、参数传递和动画

利用id导航

1
2
fun Fragment.findNavController(): NavController =
        NavHostFragment.findNavController(this)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
btnLogin.setOnClickListener {
            // 设置动画参数
            val navOption = navOptions {
                anim {
                    enter = R.anim.slide_in_right
                    exit = R.anim.slide_out_left
                    popEnter = R.anim.slide_in_left
                    popExit = R.anim.slide_out_right
                }
            }
            // 参数设置
            val bundle = Bundle()
            bundle.putString("name","TeaOf")
            findNavController().navigate(R.id.login, bundle,navOption)
}

利用Safe Args

action标签：

属性 作用
app:destination 跳转完成到达的fragment的id
app:popUpTo 将fragment从栈中弹出，直到某个Id的fragment

argument标签：

|属性|作用|
|android:name|标签名字|
|app:argType|标签的类型|
|android:defaultValue|默认值|

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
<fragment
    android:id="@+id/tasks_fragment_dest"
    android:name="com.example.android.architecture.blueprints.todoapp.tasks.TasksFragment"
    android:label="@string/app_name">
    <action
        android:id="@+id/action_tasksFragment_to_statisticsFragment"
        app:destination="@id/statistics_fragment_dest" />
    <action
        android:id="@+id/action_tasksFragment_to_taskDetailFragment"
        app:destination="@id/task_detail_fragment_dest" />
    <action
        android:id="@+id/action_tasksFragment_to_addEditTaskFragment"
        app:destination="@id/add_edit_task_fragment_dest" />
    <argument
        android:name="userMessage"
        app:argType="integer"
        android:defaultValue="0" />
</fragment>

自动生成两个文件：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
class TasksFragmentDirections private constructor() {
    private data class ActionTasksFragmentToTaskDetailFragment(val taskId: String) : NavDirections {
        override fun getActionId(): Int = R.id.action_tasksFragment_to_taskDetailFragment

        override fun getArguments(): Bundle {
            val result = Bundle()
            result.putString("taskId", this.taskId)
            return result
        }
    }

    private data class ActionTasksFragmentToAddEditTaskFragment(val taskId: String?, val title:
            String) : NavDirections {
        override fun getActionId(): Int = R.id.action_tasksFragment_to_addEditTaskFragment

        override fun getArguments(): Bundle {
            val result = Bundle()
            result.putString("taskId", this.taskId)
            result.putString("title", this.title)
            return result
        }
    }

    companion object {
        fun actionTasksFragmentToStatisticsFragment(): NavDirections =
                ActionOnlyNavDirections(R.id.action_tasksFragment_to_statisticsFragment)

        fun actionTasksFragmentToTaskDetailFragment(taskId: String): NavDirections =
                ActionTasksFragmentToTaskDetailFragment(taskId)

        fun actionTasksFragmentToAddEditTaskFragment(taskId: String?, title: String): NavDirections
                = ActionTasksFragmentToAddEditTaskFragment(taskId, title)
    }
}

你还是得写点击事件来完成导航：

1
2
3
clsss TasksFragment : Fragment() {
    private val args: TasksFragmentArgs by navArgs();
}

总结

navigation总结

0%