Android Jetpack -- navigation

看到这些博客的时候，相信小伙伴们已经看了不少的有关于Android Jetpack的知识了，关于Jetpack的原理，有些文章讲的很好，这里就不重复了，此系列的博客，旨在通过一些很简单的小demo，和大家一起熟悉最基本的用法~

Android Jetpack -- Lifecycle

Android Jetpack -- ViewModel & LiveData

Android Jetpack -- paging & room

Android Jetpack -- navigation

项目git地址：https://github.com/zhangtiansimple/jetpack_demo

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Navigation的引入在一定程度上优化了传统的对于Fragment的控制，接下来看看Navigation的使用。

首先建立三个Fragment和它们的布局文件

class Fragment1 : Fragment() { override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? { return inflater.inflate(R.layout.fragment1, container, false) } override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) btn.setOnClickListener { Navigation.findNavController(it).navigate(R.id.action_page2) } } } class Fragment2 : Fragment() { override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? { return inflater.inflate(R.layout.fragment2, container, false) } override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) btn_return.setOnClickListener { Navigation.findNavController(it).navigateUp() } btn_go.setOnClickListener { Navigation.findNavController(it).navigate(R.id.action_page3) } } } class Fragment3 : Fragment() { override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? { return inflater.inflate(R.layout.fragment3, container, false) } override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) //点击返回page2 btn.setOnClickListener { Navigation.findNavController(it).navigateUp() } } } <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent"> <TextView android:id="@+id/btn" android:layout_centerInParent="true" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="current page1, click to go page2"/> </RelativeLayout> <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent"> <TextView android:id="@+id/btn_return" android:layout_centerInParent="true" android:layout_width="wrap_content" android:text="current page2, click to return page1" android:layout_height="wrap_content"/> <TextView android:id="@+id/btn_go" android:layout_centerInParent="true" android:layout_width="wrap_content" android:text="current page2, click to go page3" android:layout_below="@+id/btn_return" android:layout_marginTop="20dp" android:layout_height="wrap_content"/> </RelativeLayout> <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent"> <TextView android:id="@+id/btn" android:layout_centerInParent="true" android:text="current page3, click to return page2" android:layout_width="wrap_content" android:layout_height="wrap_content"/> </RelativeLayout>

接着在res资源目录下建立navigation路径，并且建立nav_graph.xml文件，xml文件里配置了fragment的行为关系

<?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" app:startDestination="@id/page1Fragment" tools:ignore="UnusedNavigation"> <fragment android:id="@+id/page1Fragment" android:name="com.study.jetpacktest.navigation.Fragment1" android:label="fragment_page1" tools:layout="@layout/fragment1"> <action android:id="@+id/action_page2" app:destination="@id/page2Fragment"/> </fragment> <fragment android:id="@+id/page2Fragment" android:name="com.study.jetpacktest.navigation.Fragment2" android:label="fragment_page2" tools:layout="@layout/fragment2"> <action android:id="@+id/action_page1" app:popUpTo="@id/page1Fragment"/> <action android:id="@+id/action_page3" app:destination="@id/nav_graph_page3"/> </fragment> <navigation android:id="@+id/nav_graph_page3" app:startDestination="@id/page3Fragment"> <fragment android:id="@+id/page3Fragment" android:name="com.study.jetpacktest.navigation.Fragment3" android:label="fragment_page3" tools:layout="@layout/fragment3"/> </navigation> </navigation>

最后是Activity，在Activity的布局文件里引入一个fragment作为根容器

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:id="@+id/container" android:layout_width="match_parent" android:layout_height="match_parent"> <fragment android:id="@+id/my_nav_host_fragment" android:name="androidx.navigation.fragment.NavHostFragment" android:layout_width="match_parent" android:layout_height="match_parent" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toTopOf="parent" app:defaultNavHost="true" app:navGraph="@navigation/nav_graph"/> </LinearLayout> class NavigationActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_navigation) } override fun onSupportNavigateUp() = findNavController(this, R.id.my_nav_host_fragment).navigateUp() }

一个简单的Navigation demo就写好了