Android Application Development Cookbook: 93 Recipes for Building Winning Apps

reCiPe 2.3 
using rADio buttons
Android Versions
Level 1 and above
permissions
None
source code to download from Wrox.com
RadioButtons.zip
Radio buttons enable users to select one item from a list of available options. This recipe shows how 
to use radio buttons in your Android application.
solution
Assume you have the following code snippet in your 
activity_main.xml
file:
android:layout_width="match_parent"
Figure 2-3 
Figure 2-4 
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---

 
Recipe 2.3 using Radio Buttons
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47
android:layout_height="match_parent"
android:orientation="vertical" >
android:id="@+id/rdbGp1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
android:id="@+id/rdb1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:drawableLeft="@drawable/ic_launcher"
android:text="Option 1" />
android:id="@+id/rdb2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:drawableLeft="@drawable/ic_launcher"
android:text="Option 2" 
android:checked="true"/>


The 
RadioButton
element represents a two-state button that can be either checked or unchecked. 
Once a radio button is checked, it cannot be unchecked by tapping on it. Instead, radio buttons are 
contained within a 
RadioGroup
element, which contains a set of radio buttons. Checking one radio 
button in a radio group unchecks the rest of the radio buttons in the same group. 
Figure 2-5 shows the result of the preceding code snippet in the Android emulator.