<?xml version="1.0" encoding="utf-8"?>

<LinearLayout 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" android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:orientation="vertical"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context="helloworld.com.inspur.app5.MainActivity">

    <TextView android:layout_width="wrap_content"

        android:id="@+id/tv"

        android:layout_height="wrap_content"

        android:text="选择正确答案：" />

    <RadioGroup

        android:id="@+id/rg"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content">

        <RadioButton

            android:layout_width="match_parent"

            android:layout_height="wrap_content"

            android:id="@+id/rb1"

            android:text="2+1=2"/>

        <RadioButton

            android:layout_width="match_parent"

            android:layout_height="wrap_content"

            android:id="@+id/rb2"

            android:text="2+1=3"/>

        <RadioButton

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:id="@+id/rb3"

        android:text="2+1=4"/>

        <RadioButton

            android:layout_width="match_parent"

            android:layout_height="wrap_content"

            android:id="@+id/rb4"

            android:text="2+1=1"/>

    </RadioGroup>

</LinearLayout>

package helloworld.com.inspur.app5;

import android.support.v4.widget.TextViewCompat;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.widget.RadioButton;

import android.widget.RadioGroup;

import android.widget.TextView;

import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private TextView tv;

    private RadioGroup rg;

    private RadioButton rb1;

    private RadioButton rb2;

    private RadioButton rb4;

    private RadioButton rb3;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        tv=(TextView)findViewById(R.id.tv);

        rg=(RadioGroup)findViewById(R.id.rg);

        rb1=(RadioButton)findViewById(R.id.rb1);

        rb2=(RadioButton)findViewById(R.id.rb2);

        rb4=(RadioButton)findViewById(R.id.rb4);

        rb3=(RadioButton)findViewById(R.id.rb3);

        rg.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {

            @Override

            public void onCheckedChanged(RadioGroup group, int checkedId) {

                switch (checkedId)

                {

                    case R.id.rb1:

                        Toast.makeText(MainActivity.this,"false",Toast.LENGTH_LONG).show();

                        break;

                    case R.id.rb2:

                        Toast.makeText(MainActivity.this,"true",Toast.LENGTH_LONG).show();

                        break;

                    case R.id.rb3:

                    Toast.makeText(MainActivity.this,"false",Toast.LENGTH_LONG).show();

                    break;

                    case R.id.rb4:

                        Toast.makeText(MainActivity.this,"false",Toast.LENGTH_LONG).show();

                        break;

                }

            }

        });

    }

}

if(R.id.rb2==checkedId)

                {

                    Toast.makeText(MainActivity.this,"true",Toast.LENGTH_LONG).show();

                }

                else{

                    Toast.makeText(MainActivity.this,"false",Toast.LENGTH_LONG).show();

                }

RadioButton r=(RadioButton)findViewById(checkedId);

                if(rb2.equals(r))

                {

                    Toast.makeText(MainActivity.this,"true",Toast.LENGTH_LONG).show();

                }

                else{

                    Toast.makeText(MainActivity.this,"false",Toast.LENGTH_LONG).show();

                }