BottomNavigationView+Fragment==底部導航

介紹

BottomNavigationView是Google的material下的用于底部導航組件，總的來說就是方便、好用

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匯入

implementation 'com.google.android.material:material:1.2.1'(1.2.1目前是最新版)

使用

1、創建主頁面加入BottomNavigationView
activity_nav_bottom.xml:

<?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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    >
    <FrameLayout
        android:id="@+id/home_fragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_marginBottom="2dp"
        android:layout_weight="1"
        android:background="#ffffff" />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/nav_bottom"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:background="#ffffff"
        app:menu="@menu/menu_nav"
        />
</LinearLayout>

2、為BottomNavigationView創建導航用的選單項
設定其 id 、title、icon屬性

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
    android:id="@+id/menu_one"
    android:title="一"
    android:icon="@drawable/ic_find"
    />
    <item
        android:id="@+id/menu_two"
        android:title="二"
         android:icon="@drawable/ic_video"
        />
    <item
        android:id="@+id/menu_three"
        android:title="三"
        android:icon="@drawable/ic_my"
        />
    <item
        android:id="@+id/menu_four"
        android:title="四"
        android:icon="@drawable/ic_accunt"
        />
</menu>

3、為BottomNavigationView中的選單項創建Fragment及其布局
我一共創建了4個布局，簡單演示：

package com.example.myapplication.nav_bottom1;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import com.example.myapplication.R;

public class fragment_one extends Fragment {
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        return inflater.inflate(R.layout.fragment_one,container,false);
    }
}

<?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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="50sp"
        android:text="ONE"
        />
</LinearLayout>

4、為BottomNavigationView中的選單項設定監聽
（1）實作BottomNavigationView.OnNavigationItemSelectedListener

(2)、利用FragmentTransaction切換不同的Fragment

package com.example.myapplication.nav_bottom1;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.FragmentTransaction;
import android.os.Bundle;
import android.view.MenuItem;
import com.example.myapplication.R;
import com.google.android.material.bottomnavigation.BottomNavigationView;

public class nav_bottom extends AppCompatActivity implements BottomNavigationView.OnNavigationItemSelectedListener {
    private BottomNavigationView navigationView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_nav_bottom);
        navigationView = findViewById(R.id.nav_bottom);
        navigationView.setOnNavigationItemSelectedListener(this);
        navigationView.setSelectedItemId(R.id.menu_one);
    }

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        switch (item.getItemId()){
            case R.id.menu_one:
                fragmentTransaction.replace(R.id.home_fragment, new fragment_one()).commit();
                return true;
            case R.id.menu_two:
                fragmentTransaction.replace(R.id.home_fragment,new fragment_two()).commit();
                return true;
            case R.id.menu_three:
                fragmentTransaction.replace(R.id.home_fragment,new fragment_three()).commit();
                return true;
            case R.id.menu_four:
                fragmentTransaction.replace(R.id.home_fragment,new fragment_four()).commit();
                return true;
        }
        return true;
    }
}

總結

BottomNavigationView是比較流行和官方推薦的組件，還有很多屬性，用起來也是非常靈活的