Jetpack组件常用架构

常用UI架构

第一步：布局文件如下

<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">


    <fragment
        android:id="@+id/my_nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_marginBottom="10dp"
        android:layout_weight="1"
        app:defaultNavHost="true"
        app:navGraph="@navigation/main_navigation" />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/nv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:itemIconTint="@drawable/main_bottom_navigation"
        app:itemTextColor="@drawable/main_bottom_navigation"
        app:menu="@menu/navigation" />

</LinearLayout>

其中、main_navigation 如下

内部主要是几个Fragment

<?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/main_navigation.xml"
    app:startDestination="@id/fragment_info">

    <fragment
        android:id="@+id/fragment_info"
        android:name="com.example.jetpackdemo.fragment.ShoeFragment"
        android:label="fagment_info"
        tools:layout="@layout/fragment_shoe" />

    <fragment
        android:id="@+id/fragment_market"
        android:name="com.example.jetpackdemo.fragment.MarketFragment"
        android:label="fragment_market3"
        tools:layout="@layout/fragment_market" />

    <fragment
        android:id="@+id/fragment_me"
        android:name="com.example.jetpackdemo.fragment.MeFragment"
        android:label="fragment_me"
        tools:layout="@layout/fragment_me" />

</navigation>

其中、main_bottom_navigation如下：

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
	<item android:color="@color/colorPrimary" android:state_checked="true"/>
	<item android:color="@color/textPrimary" android:state_checked="false"/>
</selector>

其中、menu_main 如下

关键：每一个item的id必须和fragment的id进行对应，这样才可以进行切换。

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/fragment_info"
        android:icon="@android:drawable/ic_dialog_info"
        android:title="首页" />
    <item
        android:id="@+id/fragment_market"
        android:icon="@android:drawable/ic_dialog_info"
        android:title="圈子" />
    <item
        android:id="@+id/fragment_me"
        android:icon="@android:drawable/ic_dialog_info"
        android:title="个人中心" />
</menu>

第二步：MainActivity的逻辑如下：

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main2)
        // 获取Fragment的导航栏
        val navHostFragment =
            supportFragmentManager.findFragmentById(R.id.my_nav_host_fragment) as NavHostFragment
        val navController = navHostFragment.navController
        // 获取底部导航栏
        val bottomNavigationView = findViewById<BottomNavigationView>(R.id.nv)
        // 底部导航栏和Fragment导航绑定起来
        bottomNavigationView.setupWithNavController(navController)
    }

}