2BottomNavigationView+Fragment+ButterKnife实现底部状态栏切换

1 MainActivity.java对应的布局文件activity_main

<?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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <FrameLayout
        android:id="@+id/main_page_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

<!-- itemIconTint 是被点击的图标时的颜色改变
     itemTextColor是被点击时文字的改变 -->
    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/main_navigation_bar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/white"
        app:layout_constraintBottom_toBottomOf="parent"
        app:itemIconTint="@drawable/navigation_bar_color"
        app:itemTextColor="@drawable/navigation_bar_color"
        app:menu="@menu/my_navigation_items"
        />

</androidx.constraintlayout.widget.ConstraintLayout>

给FrameLayout属性添加id，便于其他fragment替换该部分的内容。
给BottomNavigationView添加id，便于给底部状态栏添加单击监听事件。
2 先抽取Fragment的基类BaseFragment

package com.example.taobaounion.base;

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;


public abstract class BaseFragment extends Fragment {
    /**
     *
     * @param inflater 打气筒,加载布局
     * @param container
     * @param savedInstanceState
     * @return
     */
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        //绑定布局,第三个参数:是否绑定到container里面去,false表示不绑定,如果绑定过去就会有问题
        return loadRootView(inflater,container,savedInstanceState);
    }

    protected View loadRootView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        int resId = getRootViewResId();
        return inflater.inflate(resId,container,false);
    }

    protected abstract int getRootViewResId();
}

3 创建四个子类继承BaseFragment

（1）
package com.example.taobaounion.fragment;
import com.example.taobaounion.R;
import com.example.taobaounion.base.BaseFragment;

public class HomeFragment extends BaseFragment {
    @Override
    protected int getRootViewResId() {
        return R.layout.fragment_home;
    }
}

（2）
package com.example.taobaounion.fragment;

import androidx.fragment.app.Fragment;

import com.example.taobaounion.R;
import com.example.taobaounion.base.BaseFragment;

/**
 * A simple {@link Fragment} subclass.
 */
public class RedPacketFragment extends BaseFragment {

    @Override
    protected int getRootViewResId() {
        return R.layout.fragment_red_packet;
    }
}

（3）
package com.example.taobaounion.fragment;

import androidx.fragment.app.Fragment;

import com.example.taobaounion.R;
import com.example.taobaounion.base.BaseFragment;

/**
 * A simple {@link Fragment} subclass.
 */
public class SearchFragment extends BaseFragment {


    @Override
    protected int getRootViewResId() {
        return R.layout.fragment_search;
    }
}

（4）
package com.example.taobaounion.fragment;

import androidx.fragment.app.Fragment;

import com.example.taobaounion.R;
import com.example.taobaounion.base.BaseFragment;

/**
 * A simple {@link Fragment} subclass.
 */
public class SelectedFragment extends BaseFragment {

    @Override
    protected int getRootViewResId() {
        return R.layout.fragment_selected;
    }
}

3
(1)使用ButterKnife初始化mBottomNavigationView控件

//在MainActivity.java中
/*1 初始化底部导航栏控件,使用插件butterKnife
    * (1)bind方法绑定
    * (2)使用注解@BindView,注意该注解不可以是私有和静态,因为是通过反射去赋值*/
//第二步
@BindView(R.id.main_navigation_bar)
public BottomNavigationView mBottomNavigationView;

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //第一步
        ButterKnife.bind(this);
    }

(2)给底部导航栏添加事件监听

(3)实现主页面的切换

package com.example.taobaounion;

import android.os.Bundle;
import android.view.MenuItem;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;

import com.example.taobaounion.base.BaseFragment;
import com.example.taobaounion.fragment.HomeFragment;
import com.example.taobaounion.fragment.RedPacketFragment;
import com.example.taobaounion.fragment.SearchFragment;
import com.example.taobaounion.fragment.SelectedFragment;
import com.example.taobaounion.utils.LogUtils;
import com.google.android.material.bottomnavigation.BottomNavigationView;

import butterknife.BindView;
import butterknife.ButterKnife;

public class MainActivity extends AppCompatActivity {

    /*1 初始化底部导航栏控件,使用插件butterKnife
    * (1)bind方法绑定
    * (2)使用注解@BindView,注意该注解不可以是私有和静态,因为是通过反射去赋值*/
    //抽取成全局变量的快捷键:ctrl+alt+f
    @BindView(R.id.main_navigation_bar)
    public BottomNavigationView mBottomNavigationView;

    private FragmentManager mFm;
    private HomeFragment mHomeFragment;
    private SelectedFragment mSelectedFragment;
    private RedPacketFragment mRedPacketFragment;
    private SearchFragment mSearchFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);


        //2 给底部导航栏添加事件监听
        initListener();

        /*
        * 实现主页面的切换*/
        initFragment();

    }

    private void switchFragment(BaseFragment targetFragment) {
        FragmentTransaction fragmentTransaction = mFm.beginTransaction();//开启事务
        fragmentTransaction.replace(R.id.main_page_container,targetFragment); //替换fragment
        fragmentTransaction.commit();//提交事务
    }

    private void initFragment() {
        mHomeFragment = new HomeFragment();
        mSelectedFragment = new SelectedFragment();
        mRedPacketFragment = new RedPacketFragment();
        mSearchFragment = new SearchFragment();

        mFm = getSupportFragmentManager();//拿到一个支持包
        switchFragment(mHomeFragment); //默认选中第一页
    }

    private void initListener() {
        mBottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                //Log.d(TAG,"title -- > " + item.getTitle());
                if (item.getItemId() == R.id.home){
                    LogUtils.d(MainActivity.class,"切换到首页");
                    switchFragment(mHomeFragment);
                }else if (item.getItemId() == R.id.selected){
                    LogUtils.d(MainActivity.class,"切换到精选");
                    switchFragment(mSelectedFragment);
                }else if (item.getItemId() == R.id.red_packet){
                    LogUtils.d(MainActivity.class,"切换到特惠");
                    switchFragment(mRedPacketFragment);
                }else if (item.getItemId() == R.id.search){
                    LogUtils.d(MainActivity.class,"切换到搜索");
                    switchFragment(mSearchFragment);
                }

                return true;//这里写true,表示我们消费了这个事件
            }
        });
    }


//    private void initView() {
//        HomeFragment homeFragment = new HomeFragment();
//        FragmentManager fm = getSupportFragmentManager();//拿到一个支持包
//        FragmentTransaction transaction = fm.beginTransaction();//开启事务
//        transaction.add(R.id.main_page_container,homeFragment);//将fragment添加进事务中
//        transaction.commit(); //必须提交事务,不然添加Fragment不成功
//
//    }
}

贴上某个Fragment的布局文件,其他三个类似

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="首页"/>

</LinearLayout>

本文地址：https://blog.csdn.net/weixin_44021636/article/details/109962096