RadioButton and RadioGroup in Andorid

A radio button is a two-states button that can be either checked or unchecked. When the radio button is unchecked, the user can press or click it to check it. However, contrary to a CheckBox, a radio button cannot be unchecked by the user once checked.

Radio buttons are normally used together in a RadioGroup. When several radio buttons live inside a radio group, checking one radio button unchecks all the others.

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

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    >

<TextView 

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:text="@string/hello"

    />

<RadioGroup

 android:layout_width="fill_parent"

 android:layout_height="wrap_content"

 android:checkedButton="@+id/option1"

 android:id="@+id/radiogrooup">

<RadioButton

 android:text="Option 1"

 android:id="@+id/option1"/>

<RadioButton

 android:text="Option 2"

 android:id="@+id/option2"/>

<RadioButton

 android:text="Option 3"

 android:id="@+id/option3"/>

<RadioButton

 android:text="Option 4"

 android:id="@+id/option4"/>

</RadioGroup>

</LinearLayout