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. 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.
RadioGroup is used to create a multiple-exclusion scope for a set of radio buttons. Checking one radio button that belongs to a radio group unchecks any previously checked radio button within the same group.
Intially, all of the radio buttons are unchecked. While it is not possible to uncheck a particular radio button, the radio group can be cleared to remove the checked state.
main.xml with three RadioButton inside a RadioGroup.
<?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"
>
<RadioGroup
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<RadioButton
android:id="@+id/option1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Option 1" />
<RadioButton
android:id="@+id/option2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Option 2" />
<RadioButton
android:id="@+id/option3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Option 3" />
</RadioGroup>
</LinearLayout>
AndroidRadioGroup.java
package com.exercise.AndroidRadioGroup;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.RadioButton;
import android.widget.Toast;
public class AndroidRadioGroup extends Activity {
RadioButton myOption1, myOption2, myOption3;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
myOption1 = (RadioButton)findViewById(R.id.option1);
myOption2 = (RadioButton)findViewById(R.id.option2);
myOption3 = (RadioButton)findViewById(R.id.option3);
myOption1.setOnClickListener(myOptionOnClickListener);
myOption2.setOnClickListener(myOptionOnClickListener);
myOption3.setOnClickListener(myOptionOnClickListener);
myOption1.setChecked(true);
}
RadioButton.OnClickListener myOptionOnClickListener =
new RadioButton.OnClickListener()
{
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Toast.makeText(AndroidRadioGroup.this,
"Option 1 : " + myOption1.isChecked() + "\n"+
"Option 2 : " + myOption2.isChecked() + "\n" +
"Option 3 : " + myOption3.isChecked(),
Toast.LENGTH_LONG).show();
}
};
}
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