RudioButton和ViewPager2联动

RudioButton必须搭配RudioGroup使用
1 创建 RgActivity ,直接复制名字即可

activity_rg.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".rudio.RgActivity">

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/vp_rg"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/rg_vp" />

    <RadioGroup
        android:id="@+id/rg_vp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_gravity="bottom"
        android:orientation="horizontal">

        <RadioButton
            android:id="@+id/rb_home"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:button="@null"
            android:checked="true"
            android:drawableTop="@drawable/selector_home"
            android:drawablePadding="5dp"
            android:gravity="center"
            android:paddingTop="5dp"
            android:paddingBottom="5dp"
            android:text="@string/home"
            android:textColor="@color/selector_rg"
            android:textSize="16sp" />

        <RadioButton
            android:id="@+id/rb_msg"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:button="@null"
            android:drawableTop="@drawable/selector_msg"
            android:drawablePadding="5dp"
            android:gravity="center"
            android:paddingTop="5dp"
            android:paddingBottom="5dp"
            android:text="@string/msg"
            android:textColor="@color/selector_rg"
            android:textSize="16sp" />

        <RadioButton
            android:id="@+id/rg_my"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:button="@null"
            android:drawableTop="@drawable/selector_my"
            android:drawablePadding="5dp"
            android:gravity="center"
            android:paddingTop="5dp"
            android:paddingBottom="5dp"
            android:text="@string/my"
            android:textColor="@color/selector_rg"
            android:textSize="16sp" />
    </RadioGroup>
</RelativeLayout>

颜色选择器，有按下效果
selector_rg.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:color="#1296db" android:state_checked="true" />
    <item android:color="#111111" android:state_checked="false" />
</selector>

图片选择器
selector_home.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/home_t" android:state_checked="true" />
    <item android:drawable="@drawable/home_f" android:state_checked="false" />
</selector>

通过适配器adapter(FragmentStateAdapter )进行关联

 RgAdapter adapter = new RgAdapter(this);

        RadioGroup radioGroup = findViewById(R.id.rg_vp);
        radioGroup.setOnCheckedChangeListener(this);

        viewPager2 = findViewById(R.id.vp_rg);
        viewPager2.setAdapter(adapter);
        adapter.addFragment(new HomeFragment());
        adapter.addFragment(new MessageFragment());
        adapter.addFragment(new MyFragment());

全代码

package com.ruhai.yibei.adapter;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.viewpager2.adapter.FragmentStateAdapter;

import java.util.ArrayList;
import java.util.List;

public class RgAdapter extends FragmentStateAdapter {

    private List<Fragment> fragments;

    public RgAdapter(@NonNull FragmentActivity fragmentActivity) {
        super(fragmentActivity);
        if (fragments == null) {
            fragments = new ArrayList<>();
        }
    }

    public void addFragment(Fragment fragment) {
        if (fragments != null) {
            fragments.add(fragment);
        }
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        return fragments.get(position);
    }

    @Override
    public int getItemCount() {
        return fragments.size();
    }
}

fragment

public class HomeFragment extends Fragment {


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_home, container, false);
    }

}

fragment_home

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:background="@color/holo_orange_dark"
    android:layout_height="match_parent"
    >

    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:text="@string/home"
        android:textSize="20sp"
        android:textColor="#ffffff" />

</FrameLayout>