安卓：ViewPager+Fragment+RadioButton实现底部菜单栏滑动切换移动开发CyrilKI的博客-

1.ViewPager简单介绍

ViewPager就是一个简单的页面切换组件，我们可以往里面填充多个View，然后我们可以左右滑动，从而切换不同的View，我们可以通过setPageTransformer()方法为我们的ViewPager> 设置切换时的动画效果。和ListView，GridView一样，我们也需要一个Adapter> (适配器)将我们的View和ViewPager进行绑定，而ViewPager则有一个特定的Adapter——> PagerAdapter！另外，Google官方是建议我们使用Fragment来填充ViewPager的，这样> 可以更加方便的生成每个Page，以及管理每个Page的生命周期！Google给我们提供了两个Fragment> 专用的Adapter：FragmentPageAdapter和FragmentStatePagerAdapter。

2.实现效果图以及工程目录结构：

3.代码实现：
1)、相关资源文件后续补上
2)、主界面布局文件：

<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"     xmlns:tools="https://schemas.android.com/tools"     android:layout_width="match_parent"     android:layout_height="match_parent"     tools:context=".MainActivity"> <RadioGroup         android:id="@+id/rg_tab_bar"         android:layout_width="match_parent"         android:layout_height="50dp"         android:layout_alignParentBottom="true"         android:background="@color/bg_white"         android:orientation="horizontal"> <RadioButton             android:id="@+id/rb_main"             style="@style/tab_menu_item"             android:drawableTop="@drawable/tab_menu_channel"             android:text="主页"             android:textSize="14sp"/> <RadioButton             android:id="@+id/rb_query"             style="@style/tab_menu_item"             android:drawableTop="@drawable/tab_menu_message"             android:text="查询"             android:textSize="14sp"/> <RadioButton             android:id="@+id/rb_predict"             style="@style/tab_menu_item"             android:drawableTop="@drawable/tab_menu_better"             android:text="预测"             android:textSize="14sp"/> <RadioButton             android:id="@+id/rb_user"             style="@style/tab_menu_item"             android:drawableTop="@drawable/tab_menu_setting"             android:text="个人中心"             android:textSize="14sp"/> </RadioGroup> <View         android:id="@+id/div_tab_bar"         android:layout_width="match_parent"         android:layout_height="2px"         android:layout_above="@id/rg_tab_bar"         android:background="@color/div_white" /> <androidx.viewpager.widget.ViewPager         android:id="@+id/vpager"         android:layout_width="match_parent"         android:layout_height="match_parent"         android:layout_above="@id/div_tab_bar"/> </RelativeLayout> 

3）、四个fragment及其布局文件
HomeFragment:

package com.example.buttommenubar; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.TextView; import androidx.annotation.NonNull; import androidx.annotation.Nullable; import androidx.fragment.app.Fragment; public class HomeFragment extends Fragment { private TextView textView; @Nullable @Override //类似于Activity里面的setContentView(); public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {         View view=inflater.inflate(R.layout.fragment_home,container,false); return view; } @Override public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState);         textView=view.findViewById(R.id.home); } } 

布局文件

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"     android:orientation="vertical"     android:layout_width="match_parent"     android:layout_height="match_parent"> <TextView         android:id="@+id/home"         android:layout_width="match_parent"         android:layout_height="match_parent"         android:text="这里是主界面"         android:textAlignment="center"         android:textSize="25sp"> </TextView> </LinearLayout> 

剩余三个改下名字就好了，这里就不列上代码了。

4)、极为关键的一步，自定义FragmentPagerAdapter
代码如下：

package com.example.buttommenubar; import android.view.ViewGroup; import androidx.annotation.NonNull; import androidx.fragment.app.Fragment; import androidx.fragment.app.FragmentManager; import androidx.fragment.app.FragmentPagerAdapter; public class MyFragmentPagerAdapter extends FragmentPagerAdapter { private final int PAGER_COUNT = 4; private HomeFragment homeFragment; private PredictFragment predictFragment; private QueryFragment queryFragment; private UserFragment userFragment; public MyFragmentPagerAdapter(FragmentManager fm) { super(fm);         homeFragment=new HomeFragment();         predictFragment=new PredictFragment();         queryFragment=new QueryFragment();         userFragment=new UserFragment(); } @Override public Fragment getItem(int position) {         Fragment fragment = null; switch (position) { case MainActivity.PAGE_ONE:                 fragment = homeFragment; break; case MainActivity.PAGE_TWO:                 fragment = queryFragment; break; case MainActivity.PAGE_THREE:                 fragment = predictFragment; break; case MainActivity.PAGE_FOUR:                 fragment = userFragment; break; } return fragment; } @Override public int getCount() { return PAGER_COUNT; } @Override public Object instantiateItem(@NonNull ViewGroup container, int position) { return super.instantiateItem(container, position); } @Override public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) { super.destroyItem(container, position, object); } } 

5）、MainActivity.java

package com.example.buttommenubar; import androidx.appcompat.app.AppCompatActivity; import androidx.viewpager.widget.ViewPager; import android.os.Bundle; import android.widget.RadioButton; import android.widget.RadioGroup; public class MainActivity extends AppCompatActivity implements RadioGroup.OnCheckedChangeListener,         ViewPager.OnPageChangeListener { private RadioGroup rg_tab_bar; private RadioButton rb_main; private RadioButton rb_query; private RadioButton rb_predict; private RadioButton rb_user; private ViewPager vpager; private MyFragmentPagerAdapter mAdapter; //代表页面的常量 public static final int PAGE_ONE = 0; public static final int PAGE_TWO = 1; public static final int PAGE_THREE = 2; public static final int PAGE_FOUR = 3; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); getSupportActionBar().hide(); setContentView(R.layout.activity_main);          mAdapter = new MyFragmentPagerAdapter(getSupportFragmentManager()); initViews();         rb_main.setChecked(true); } private void initViews() {         rg_tab_bar = findViewById(R.id.rg_tab_bar);         rb_main = findViewById(R.id.rb_main);         rb_query = findViewById(R.id.rb_query);         rb_predict = findViewById(R.id.rb_predict);         rb_user = findViewById(R.id.rb_user);         rg_tab_bar.setOnCheckedChangeListener(this);          vpager = findViewById(R.id.vpager);         vpager.setAdapter(mAdapter);         vpager.setCurrentItem(0);         vpager.addOnPageChangeListener(this); } @Override public void onCheckedChanged(RadioGroup group, int checkedId) { switch (checkedId) { case R.id.rb_main:                 vpager.setCurrentItem(PAGE_ONE); break; case R.id.rb_query:                 vpager.setCurrentItem(PAGE_TWO); break; case R.id.rb_predict:                 vpager.setCurrentItem(PAGE_THREE); break; case R.id.rb_user:                 vpager.setCurrentItem(PAGE_FOUR); break; } } @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { } @Override public void onPageSelected(int position) { } @Override public void onPageScrollStateChanged(int state) { if (state == 2) { switch (vpager.getCurrentItem()) { case PAGE_ONE:                     rb_main.setChecked(true); break; case PAGE_TWO:                     rb_query.setChecked(true); break; case PAGE_THREE:                     rb_predict.setChecked(true); break; case PAGE_FOUR:                     rb_user.setChecked(true); break; } } } @Override public void onPointerCaptureChanged(boolean hasCapture) { } }