Android开发过程中，特别是新开的项目，底部状态栏的切换使用的频率非常的高，主要的实现方式有：

(1)、TabLayout + Fragment
    (2)、FragmentTabHost + Fragment
    (3)、BottomNavigationView + Fragment
    (4)、RidioGroup + Fragment

这里我先介绍前面两种实现方式，后面两种后期再贴出实现方式。

一、使用TabLayout + Fragment + ViewPager实现

1、实现步骤：

(1)、布局文件中定义TabLayout控件
    (2)、定义切换的每个Fragment布局文件
    (3)、定义切换的每个Fragment的Java类
    (4)、定义TabLayoutMainActivity类
    (5)、效果图演示

2、实现过程：

(1)、布局文件中定义TabLayout控件(activity_main.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"
 tools:context="com.showly.bottomnavigationbardemo.TabLayoutMainActivity">
 <android.support.v4.view.ViewPager
 android:id="@+id/viewpager_content_view"
 android:layout_width="match_parent"
 android:layout_height="0dp"
 android:layout_weight="1"
 android:scrollbars="none" />
 <android.support.design.widget.TabLayout
 android:id="@+id/tab_layout_view"
 android:layout_width="match_parent"
 android:layout_height="50dp"
 app:tabGravity="fill"
 app:tabIndicatorHeight="0dp"
 app:tabMode="fixed"
 app:tabSelectedTextColor="#FB8081"
 app:tabTextColor="#A0A0A0" />
</LinearLayout>

(2)、定义切换的每个Fragment布局文件(fragment_frist.xml)

这里有四个Tab类别(首页、娱乐、游戏、我的)，布局都类似，这里只贴出其中一个

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:background="#fff"
 android:orientation="vertical">
 <TextView
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_centerInParent="true"
 android:text="首页"
 android:textColor="#000"/>
</RelativeLayout>

(3)、定义切换的每个Fragment的Java类(FristFragment.class)

这里的Java 类实现方式也相似，贴出其中一个

package com.showly.bottomnavigationbardemo.fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.showly.bottomnavigationbardemo.R;
public class FristFragment extends Fragment {
 @Nullable
 @Override
 public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
 View view = inflater.inflate(R.layout.fragment_frist, null);
 return view;
 }
}

(4)、定义TabLayoutMainActivity类(TabLayoutMainActivity.class)

package com.showly.bottomnavigationbardemo;
import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import com.showly.bottomnavigationbardemo.fragment.FourthlyFragment;
import com.showly.bottomnavigationbardemo.fragment.FristFragment;
import com.showly.bottomnavigationbardemo.fragment.SecondFragment;
import com.showly.bottomnavigationbardemo.fragment.ThirtlyFragment;
public class TabLayoutMainActivity extends AppCompatActivity {
 //未选中的Tab图片
 private int[] unSelectTabRes = new int[]{R.drawable.i8live_menu_home_normal
  , R.drawable.i8live_menu_information_normal, R.drawable.i8live_menu_game_normal, R.drawable.i8live_menu_personl_normal};
 //选中的Tab图片
 private int[] selectTabRes = new int[]{R.drawable.i8live_menu_home_press, R.drawable.i8live_menu_information_press
  , R.drawable.i8live_menu_game_press, R.drawable.i8live_menu_personl_press};
 //Tab标题
 private String[] title = new String[]{"首页", "娱乐", "游戏", "我的"};
 private ViewPager viewPager;
 private TabLayout tabLayout;
 private TabLayout.Tab tabAtOne;
 private TabLayout.Tab tabAttwo;
 private TabLayout.Tab tabAtthree;
 private TabLayout.Tab tabAtfour;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 getSupportActionBar().hide();//隐藏掉整个ActionBar
 setContentView(R.layout.activity_main);
 initView();
 initData();
 initListener();
 }
 private void initView() {
 viewPager = (ViewPager) findViewById(R.id.viewpager_content_view);
 tabLayout = (TabLayout) findViewById(R.id.tab_layout_view);
 //使用适配器将ViewPager与Fragment绑定在一起
 viewPager.setAdapter(new MyFragmentPagerAdapter(getSupportFragmentManager()));
 //将TabLayout与ViewPager绑定
 tabLayout.setupWithViewPager(viewPager);
 /* //设置方式一：
 //获取底部的单个Tab
 tabAtOne = tabLayout.getTabAt(0);
 tabAttwo = tabLayout.getTabAt(1);
 tabAtthree = tabLayout.getTabAt(2);
 tabAtfour = tabLayout.getTabAt(3);
 //设置Tab图片
 tabAtOne.setIcon(R.drawable.i8live_menu_home_press);
 tabAttwo.setIcon(R.drawable.i8live_menu_information_normal);
 tabAtthree.setIcon(R.drawable.i8live_menu_game_normal);
 tabAtfour.setIcon(R.drawable.i8live_menu_personl_normal);*/
 //设置方式二：
 for (int i = 0; i < title.length; i++) {
  if (i == 0) {
  tabLayout.getTabAt(0).setIcon(selectTabRes[0]);
  } else {
  tabLayout.getTabAt(i).setIcon(unSelectTabRes[i]);
  }
 }
 }
 private void initData() {
 }
 private void initListener() {
 //TabLayout切换时导航栏图片处理
 tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
  @Override
  public void onTabSelected(TabLayout.Tab tab) {//选中图片操作
  for (int i = 0; i < title.length; i++) {
   if (tab == tabLayout.getTabAt(i)) {
   tabLayout.getTabAt(i).setIcon(selectTabRes[i]);
   viewPager.setCurrentItem(i);
   }
  }
  }
  @Override
  public void onTabUnselected(TabLayout.Tab tab) {//未选中图片操作
  for (int i = 0; i < title.length; i++) {
   if (tab == tabLayout.getTabAt(i)) {
   tabLayout.getTabAt(i).setIcon(unSelectTabRes[i]);
   }
  }
  }
  @Override
  public void onTabReselected(TabLayout.Tab tab) {
  }
 });
 }
 //自定义适配器
 public class MyFragmentPagerAdapter extends FragmentPagerAdapter {
 public MyFragmentPagerAdapter(FragmentManager fm) {
  super(fm);
 }
 @Override
 public Fragment getItem(int position) {
  if (position == 1) {
  return new SecondFragment();//娱乐
  } else if (position == 2) {
  return new ThirtlyFragment();//游戏
  } else if (position == 3) {
  return new FourthlyFragment();//我的
  }
  return new FristFragment();//首页
 }
 @Override
 public int getCount() {
  return title.length;
 }
 @Override
 public CharSequence getPageTitle(int position) {
  return title[position];
 }
 }
}

(5)、效果图演示

二、使用FragmentTabHost+ Fragment + ViewPager实现

1、实现步骤：

(1)、布局文件中定义FragmentTabHost控件
    (2)、定义底部菜单栏布局
    (3)、定义切换的每个Fragment布局文件
    (4)、定义切换的每个Fragment的Java类
    (5)、切换按钮的图片
    (6)、定义FragmentTabHostMainActivity类
    (7)、效果图演示

2、实现过程：

(1)、布局文件中定义FragmentTabHost控件(fragment_tabhost_activity.xml)

<?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:background="#fff"
 android:orientation="vertical">
 <android.support.v4.view.ViewPager
 android:id="@+id/vp_pager"
 android:layout_width="match_parent"
 android:layout_height="0dp"
 android:layout_weight="1"
 android:scrollbars="none" />
 <android.support.v4.app.FragmentTabHost
 android:id="@android:id/tabhost"
 android:layout_width="match_parent"
 android:background="#3000"
 android:layout_height="65dp">
 <FrameLayout
  android:id="@android:id/tabcontent"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content" />
 </android.support.v4.app.FragmentTabHost>
</LinearLayout>

(2)、定义底部菜单栏布局(tab_content.xml)

<?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:padding="2dp"
 android:orientation="vertical">

 <ImageView
 android:id="@+id/iv_imageview"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_gravity="center_horizontal"
 android:background="@drawable/i8live_menu_home_normal" />

 <TextView
 android:id="@+id/tv_item"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_gravity="center_horizontal"
 android:layout_marginTop="5dp"
 android:text="首页" />
</LinearLayout>

(3)、定义切换的每个Fragment布局文件(fragment_frist.xml)

这里有四个Tab类别(首页、娱乐、游戏、我的)，布局都类似，这里只贴出其中一个

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:background="#fff"
 android:orientation="vertical">
 <TextView
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_centerInParent="true"
 android:text="首页"
 android:textColor="#000"/>
</RelativeLayout>

(4)、定义切换的每个Fragment的Java类(FristFragment.class)

这里的Java 类实现方式也相似，贴出其中一个

package com.showly.bottomnavigationbardemo.fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.showly.bottomnavigationbardemo.R;
public class FristFragment extends Fragment {
 @Nullable
 @Override
 public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
 View view = inflater.inflate(R.layout.fragment_frist, null);
 return view;
 }
}

(5)、切换按钮的图片(tab_main.xml)

这里有四个是相似的，只贴出其中一个

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
 <!-- 切换选中之后的图片-->
 <item android:drawable="@drawable/i8live_menu_home_press" android:state_selected="true"/>
 <!-- 未选中的图片-->
 <item android:drawable="@drawable/i8live_menu_home_normal"/>
</selector>

(6)、定义FragmentTabHostMainActivity类（FragmentTabHostMainActivity.class）

package com.showly.bottomnavigationbardemo;
import android.graphics.Color;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentTabHost;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TabHost;
import android.widget.TabWidget;
import android.widget.TextView;
import com.showly.bottomnavigationbardemo.fragment.FourthlyFragment;
import com.showly.bottomnavigationbardemo.fragment.FristFragment;
import com.showly.bottomnavigationbardemo.fragment.SecondFragment;
import com.showly.bottomnavigationbardemo.fragment.ThirtlyFragment;
import java.util.ArrayList;
import java.util.List;
public class FragmentTabHostMainActivity extends FragmentActivity implements ViewPager.OnPageChangeListener, TabHost.OnTabChangeListener {
 private int[] selectTabRes = new int[]{R.drawable.tab_main, R.drawable.tab_infomation
  , R.drawable.tab_game, R.drawable.tab_personal};
 //Tab标题
 private String[] title = new String[]{"首页", "娱乐", "游戏", "我的"};
 private Class fragmentArry[] = {FristFragment.class, SecondFragment.class, ThirtlyFragment.class, FourthlyFragment.class};
 private List<Fragment> fragmentList = new ArrayList();
 private ViewPager viewPager;
 private FragmentTabHost tabHost;
 @Override
 protected void onCreate(@Nullable Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.fragment_tabhost_activity);
 initView();
 initData();
 initListener();
 }
 /**
 * 初始化Fragment并给ViewPager添加适配器
 */
 private void initVaper() {
 FristFragment fristFragment = new FristFragment();
 SecondFragment secondFragment = new SecondFragment();
 ThirtlyFragment thirtlyFragment = new ThirtlyFragment();
 FourthlyFragment fourthlyFragment = new FourthlyFragment();
 fragmentList.add(fristFragment);
 fragmentList.add(secondFragment);
 fragmentList.add(thirtlyFragment);
 fragmentList.add(fourthlyFragment);
 //ViewPager添加适配器
 viewPager.setAdapter(new MyFragmentAdapter(getSupportFragmentManager(), fragmentList));
 tabHost.getTabWidget().setDividerDrawable(null);
 }
 private void initView() {
 viewPager = (ViewPager) findViewById(R.id.vp_pager);
 tabHost = (FragmentTabHost) findViewById(android.R.id.tabhost);//绑定tabhost
 tabHost.setup(this, getSupportFragmentManager(), R.id.vp_pager);//TabHost绑定viewpager
 //获取item的个数
 int count = title.length;
 for (int i = 0; i < count; i++) {
  //设置每个TabHost布局
  TabHost.TabSpec tabSpec = tabHost.newTabSpec(title[i])
   .setIndicator(getTabItemView(i));
  //item与fragment关联
  tabHost.addTab(tabSpec, fragmentArry[i], null);
  tabHost.setTag(i);
 }
 //初始化TabHost文字颜色
 upDateTab(tabHost);
 //给ViewPager设置适配器
 initVaper();
 }
 /**
 * 更新文字颜色。
 *
 * @param mTabHost
 */
 private void upDateTab(FragmentTabHost mTabHost) {
 for (int i = 0; i < mTabHost.getTabWidget().getChildCount(); i++) {
  TextView tv = (TextView) mTabHost.getTabWidget().getChildAt(i).findViewById(R.id.tv_item);
  if (mTabHost.getCurrentTab() == i) {//选中
  tv.setTextColor(Color.parseColor("#FF5959"));
  } else {//不选中
  tv.setTextColor(Color.parseColor("#777777"));
  }
 }
 }
 /**
 * 设置每个Item布局
 */
 private View getTabItemView(int i) {
 View view = LayoutInflater.from(this).inflate(R.layout.tab_content, null);
 ImageView itemImg = (ImageView) view.findViewById(R.id.iv_imageview);
 TextView itemText = (TextView) view.findViewById(R.id.tv_item);
 itemImg.setBackgroundResource(selectTabRes[i]);
 itemText.setText(title[i]);
 return view;
 }
 private void initData() {
 }
 private void initListener() {
 viewPager.addOnPageChangeListener(this);
 tabHost.setOnTabChangedListener(this);
 }
 @Override
 public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
 }
 @Override
 public void onPageSelected(int position) {
 TabWidget widget = tabHost.getTabWidget();
 int oldFocusability = widget.getDescendantFocusability();
 widget.setDescendantFocusability(ViewGroup.FOCUS_BLOCK_DESCENDANTS);//设置View覆盖子类控件而直接获得焦点
 tabHost.setCurrentTab(position);//根据位置Postion设置当前的Tab
 widget.setDescendantFocusability(oldFocusability);//设置取消分割线
 }
 @Override
 public void onPageScrollStateChanged(int state) {
 }
 @Override
 public void onTabChanged(String tabId) {
 int position = tabHost.getCurrentTab();
 viewPager.setCurrentItem(position);//把选中的Tab的位置赋给适配器，让它控制页面切换
 upDateTab(tabHost);//设置TabHost文字颜色
 }
 /**
 * 适配器
 * */
 public class MyFragmentAdapter extends FragmentPagerAdapter {
 List<Fragment> list;
 public MyFragmentAdapter(FragmentManager fm, List<Fragment> list) {
  super(fm);
  this.list = list;
 }
 @Override
 public Fragment getItem(int position) {
  return list.get(position);
 }
 @Override
 public int getCount() {
  return list.size();
 }
 }

(7)、效果图演示

三、总结