Navigation

Navigation是用來管理Fragment的切換，重點是為了讓APP只有單個Activity多個Fragment。

name:必须是androidx.navigation.fragment.NavHostFragment。
navGraph="@navigation":創建好的navigation。
defaultNavHost="true":與返回鍵綁定。

navigation
startDestination:設置起始頁面。
1.fragment
name="class"綁定的Fragment類。
layout="@layout":顯示預覽圖。
2.action 
popUpTo="@id":清除自己用。
popUpToInclusive="true":清除自己用。
destination="@id":要跳轉的頁面。

Gradle(Project)

classpath "androidx.navigation:navigation-safe-args-gradle-plugin:2.3.0"

Gradle(Module)

apply plugin: "androidx.navigation.safeargs.kotlin"

android {
    kotlinOptions { jvmTarget = "1.8" }
}

dependencies {
    def nav_version = "2.3.0"
    implementation "androidx.navigation:navigation-fragment-ktx:$nav_version"
    implementation "androidx.navigation:navigation-ui-ktx:$nav_version"
}

layout

<androidx.fragment.app.FragmentContainerView
    android:id="@+id/navHost"
    android:name="androidx.navigation.fragment.NavHostFragment"    
    app:defaultNavHost="true"
    app:navGraph="@navigation/nav_graph"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

AFragment

class AFragment : Fragment() {
    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_a, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        
        toB.setOnClickListener {
            //通常要執行一次才會自動生成Directions這個方法
            findNavController().navigate(AFragmentDirections.toB())
        }
    }
}

BFragment

class BFragment : Fragment() {
    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_b, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
    }
}

創建navigation(nav_graph.xml)

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/nav_graph.xml"
    app:startDestination="@id/fragmentA"
    tools:ignore="UnusedNavigation">

    <fragment
        android:id="@+id/fragmentA"
        android:name="com.example.app_navigation_test.AFragment"
        tools:layout="@layout/fragment_a">

        <action
            android:id="@+id/toB"
            app:destination="@+id/fragmentB" />
    </fragment>

    <fragment
        android:id="@+id/fragmentB"
        android:name="com.example.app_navigation_test.BFragment"
        tools:layout="@layout/fragment_b" />
</navigation>

刪除自己AFragment

<action
    android:id="@+id/toB"
    app:popUpTo="@id/AFragment"
    app:popUpToInclusive="true"
    app:destination="@id/BFragment" />