RadioButton

<?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="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" tools:context=".MainActivity">


    <TextView android:id="@+id/textView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="性別" />

    <RadioGroup android:id="@+id/ra" android:layout_width="match_parent" android:layout_height="wrap_content">

        <RadioButton android:id="@+id/radioButton" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="男" />

        <RadioButton android:id="@+id/radioButton2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="女" />

    </RadioGroup>

    <TextView android:id="@+id/textView2" android:layout_width="match_parent" android:layout_height="wrap_content" />

</LinearLayout>

package com.example.radiobutton;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.widget.RadioGroup;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity { 
    private TextView tips;
    private RadioGroup sex;

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

        tips=(TextView)findViewById(R.id.textView2);
        sex=(RadioGroup)findViewById((R.id.ra));

        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() { 
            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId) { 
                if(checkedId==R.id.radioButton){ 
                    tips.setText("您已選擇了男");
                }else{ 
                    tips.setText("您已選擇了女");
                }
            }
        });
    }
}