BottomNavigationView底部导航条解析

矫情吗；* 2022-09-09 06:21 175阅读 0赞

1 新建一个fragment,设置id为navigation\_black

2 在menu文件bottom\_nav\_menu.xml里增加一项

<item
        android:id="@+id/navigation_black"                  //菜单项ID
        android:icon="@drawable/ic_launcher_foreground"     //图标
        android:title="@string/title_black" />              //菜单标题

3 在navigation文件mobile\_navigation.xml文件里增加一项

<fragment
        android:id="@+id/navigation_black"                     //碎片ID
        android:name="com.example.bottomnav.ui.BlankFragment"  //碎片类
        android:label="@string/title_black"                    //碎片标题
        tools:layout="@layout/fragment_blank" />               //碎片布局文件

4 再看主布局文件的构成

<?xml version="1.0" encoding="utf-8"?>
    <androidx.constraintlayout.widget.ConstraintLayout 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"
        android:paddingTop="?attr/actionBarSize">
    
        <com.google.android.material.bottomnavigation.BottomNavigationView
            android:id="@+id/nav_view"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="0dp"
            android:layout_marginEnd="0dp"
            android:background="?android:attr/windowBackground"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:menu="@menu/bottom_nav_menu" />             //菜单文件
    
        <fragment
            android:id="@+id/nav_host_fragment"
            android:name="androidx.navigation.fragment.NavHostFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:defaultNavHost="true"
            app:layout_constraintBottom_toTopOf="@id/nav_view"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:navGraph="@navigation/mobile_navigation" />     //导航布局文件
    
    </androidx.constraintlayout.widget.ConstraintLayout>

一个导航控件和一个碎片控件

5 主activity中的初始化代码

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        BottomNavigationView navView = findViewById(R.id.nav_view);
    
    
        // Passing each menu ID as a set of Ids because each
        // menu should be considered as top level destinations.
        AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
                R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications,
                R.id.navigation_black)     //新增加的id号
                .build();
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
        NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
        NavigationUI.setupWithNavController(navView, navController);
    }

本质上采用了静态绑定，全部采用配置文件，操作方便，但灵活性不足。