Руководство Android RadioGroup и RadioButton

1- RadioButton & RadioGroup

RadioButton это  view в  Android, обычно используется с  RadioGroup. При этом  RadioGroup это контейнер (container) и может содержать кнопки  RadioButton, когда вы нажимете выбрать кнопку radio button в одной группе, все другие выбранные radio button в группе будут отменены (deselect).

Ниже иллюстрируется  RadioButton группированные в разных группах.
RadioGroup может расположить кнопки  RadioButton по вертикали или горизонтали.

2- Пример с RadioGroup & RadioButtons

Создать project с названием  AndroidRadioDemo.
  • Name: AndroidRadioDemo
  • Package name: org.o7planning.androidradiodemo
Интерфейс приложения:
Если вас интересуют шаги дизайна интерфейса данного приложения, смотрите приложение в конце статьи.
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    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"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="50dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="19dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Game Settings"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="0dp"
        android:layout_height="30dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="19dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Game character"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <RadioGroup
        android:id="@+id/radioGroup_character"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="12dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2">

        <RadioButton
            android:id="@+id/radioButton_male"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Male" />

        <RadioButton
            android:id="@+id/radioButton_female"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Famale" />
    </RadioGroup>

    <TextView
        android:id="@+id/textView3"
        android:layout_width="0dp"
        android:layout_height="29dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Difficulty Level"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/radioGroup_character" />

    <RadioGroup
        android:id="@+id/radioGroup_diffLevel"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:orientation="horizontal"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView3">

        <RadioButton
            android:id="@+id/radioButton_easy"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="0"
            android:text="Easy" />

        <RadioButton
            android:id="@+id/radioButton_medium"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="0"
            android:text="Medium" />

        <RadioButton
            android:id="@+id/radioButton_hard"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="0"
            android:text="Hard" />
    </RadioGroup>

    <Button
        android:id="@+id/button_save"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="24dp"
        android:text="Save"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/radioGroup_diffLevel" />
</androidx.constraintlayout.widget.ConstraintLayout>
MainActivity.java
package org.o7planning.androidradiodemo;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private RadioGroup radioGroupCharacter;
    private RadioButton radioButtonMale;
    private RadioButton radioButtonFemale;

    private RadioGroup radioGroupDiffLevel;
    private RadioButton radioButtonEasy;
    private RadioButton radioButtonMedium;
    private RadioButton radioButtonHard;

    private Button buttonSave;

    private String LOGTAG = "AndroidRadioDemo";

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

        //
        this.radioGroupCharacter= (RadioGroup) this.findViewById(R.id.radioGroup_character);
        this.radioButtonMale = (RadioButton) this.findViewById(R.id.radioButton_male);
        this.radioButtonFemale  =  (RadioButton)this.findViewById(R.id.radioButton_female);
        this.radioButtonMale.setChecked(true);

        //
        this.radioGroupDiffLevel= (RadioGroup) this.findViewById(R.id.radioGroup_diffLevel);
        this.radioButtonEasy = (RadioButton) this.findViewById(R.id.radioButton_easy);
        this.radioButtonMedium  =  (RadioButton)this.findViewById(R.id.radioButton_medium);
        this.radioButtonHard =  (RadioButton)this.findViewById(R.id.radioButton_hard);
        this.radioButtonMedium.setChecked(true);

        this.buttonSave= (Button) this.findViewById(R.id.button_save);

        // When radio group "Difficulty Level" checked change.
        this.radioGroupDiffLevel.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId) {
                doOnDifficultyLevelChanged(group, checkedId);
            }
        });

        // When radio button "Female" checked change.
        this.radioButtonMale.setOnCheckedChangeListener(new RadioButton.OnCheckedChangeListener() {

            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                doOnGameCharacterChanged(buttonView,isChecked);
            }
        });

        // When radio button "Male" checked change.
        this.radioButtonFemale.setOnCheckedChangeListener(new RadioButton.OnCheckedChangeListener() {

            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                doOnGameCharacterChanged(buttonView,isChecked);
            }
        });

        // When button "Save" clicked.
        this.buttonSave.setOnClickListener(new Button.OnClickListener() {
            @Override
            public void onClick(View v) {
                doSave();
            }
        });
    }


    // When radio group "Difficulty Level" checked change.
    private void doOnDifficultyLevelChanged(RadioGroup group, int checkedId) {
        int checkedRadioId = group.getCheckedRadioButtonId();

        if(checkedRadioId== R.id.radioButton_easy) {
            Toast.makeText(this,"You choose the level of difficulty: Easy",Toast.LENGTH_SHORT).show();
        } else if(checkedRadioId== R.id.radioButton_medium ) {
            Toast.makeText(this,"You choose the level of difficulty: Medium",Toast.LENGTH_SHORT).show();
        } else if(checkedRadioId== R.id.radioButton_hard) {
            Toast.makeText(this,"You choose the level of difficulty: Hard",Toast.LENGTH_SHORT).show();
        }
    }

    // When radio button checked change.
    private void doOnGameCharacterChanged(CompoundButton buttonView, boolean isChecked)  {
        RadioButton radio =(RadioButton) buttonView;

        Log.i(LOGTAG, "RadioButton "+ radio.getText()+" : "+ isChecked);
    }

    // When button "Save" clicked.
    private void doSave()  {
        int difficultyLevel = this.radioGroupDiffLevel.getCheckedRadioButtonId();
        int gameCharacter = this.radioGroupCharacter.getCheckedRadioButtonId();

        RadioButton radioButtonDiffLevel = (RadioButton) this.findViewById(difficultyLevel);
        RadioButton radioButtonGameCharacter = (RadioButton) this.findViewById(gameCharacter);

        String message ="Difficulty Level: "+ radioButtonDiffLevel.getText()
                +", Game Character: " + radioButtonGameCharacter.getText() ;

        Toast.makeText(this,message,Toast.LENGTH_LONG).show();
    }
}
Запуск приложения:

3- Приложение: Дизайн интерфейса

Настроить размер шрифта для первого  TextView и настроить горизонтальное направление (orientation) для второго  RadioGroup.
Добавить  RadioButton в интерфейс:
Настроить  ID, Text для компонентов на интерфейсе.