In android, Radio Button is a two-states button that can be either checked or unchecked and it’s the same as CheckBox control, except that it will allow only one option to select from the group of options.
The user can press or click on the radio button to make it select. In android, CheckBox control allow users to change the state of control either Checked or Unchecked but the radio button cannot be unchecked once it is checked.
Generally, we can use RadioButton controls in an android application to allow users to select only one option from the set of values.
Following is the pictorial representation of using RadioButton control in android applications.
In android, we use radio buttons with in a RadioGroup to combine multiple radio buttons into one group and it will make sure that users can select only one option from the group of multiple options.
By default, the android RadioButton will be in OFF (Unchecked) state. We can change the default state of RadioButton by using android:checked attribute.
In case, if we want to change the state of RadioButton to ON (Checked), then we need to set android:checked = “true” in our XML layout file.
In android, we can create RadioButton control in two ways either in the XML layout file or create it in the Activity file programmatically.
Following is the sample way to define RadioButton control using RadioGroup in the XML layout file in the android application.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent">
<RadioGroup
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<RadioButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Java"
android:checked="true"/>
</RelativeLayout>
If you observe above code snippet, here we defined RadioButton control and setting RadioButton state ON using android:checked attribute in xml layout file.
In android, we can create RadioButton control programmatically in activity file based on our requirements.
Following is the example of creating a RadioButton control dynamically in activity file.
LinearLayout layout = (LinearLayout)findViewById(R.id.l_layout);
RadioButton rd = new RadioButton(this);
rd.setText("Tutlane");
rd.setChecked(true);
layout.addView(rd);
This is how we can define RadioButton in XML layout file or programmatically in activity file based on our requirements.
Generally, whenever the user click on RadioButton to Select or Deselect the RadioButton object will receives an on-click event.
In android, we can define RadioButton click event in two ways either in the XML layout file or create it in Activity file programmatically.
We can define click event handler for button by adding the android:onClick attribute to the <RadioButton> element in our XML layout file.
The value of android:onClick attribute must be the name of the method which we need to call in response to a click event and the Activity file which hosting XML layout must implement the corresponding method.
Following is the example of defining a RadioButton click event using android:onClick attribute in XML layout file.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent">
<RadioGroup
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<RadioButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Java"
android:onClick="onRadioButtonClicked"/>
</RadioGroup>
</RelativeLayout>
In Activity that hosts our XML layout file, we need to implement click event method like as shown below.
public void onRadioButtonClicked(View view) {
// Is the view now checked?
boolean checked = ((RadioButton) view).isChecked();
// Check which RadioButton was clicked
switch(view.getId()) {
case R.id.chk1:
if (checked)
// Do your coding
else
// Do your coding
break;
// Perform your logic
}
}
In android, we can define RadioButton click event programmatically in Activity file rather than XML layout file.
To define RadioButton click event programmatically, create View.OnClickListener object and assign it to the button by calling setOnClickListener(View.OnClickListener) like as shown below.
This is how we can handle RadioButton click events in android applications based on our requirements.
Following are the some of commonly used attributes related to RadioButton control in android applications.
| Attribute | Description |
|---|---|
| android:id | It is used to uniquely identify the control |
| android:checked | It is used to specify the current state of radio button |
| android:gravity | It is used to specify how to align the text like left, right, center, top, etc. |
| android:text | It is used to set the text for the radio button. |
| android:textColor | It is used to change the color of text. |
| android:textSize | It is used to specify the size of the text. |
| android:textStyle | It is used to change the style (bold, italic, bolditalic) of text. |
| android:background | It is used to set the background color for radio button control. |
| android:padding | It is used to set the padding from left, right, top and bottom. |
| android:onClick | It’s the name of the method to invoke when the radio button clicked. |
| android:visibility | It is used to control the visibility of control. |
Following is the example of defining a multiple RadioButton controls, one TextView control and one Button control in RelativeLayout to get the selected values of RadioButton controls when we click on Button in the android application.
Create a new android application using android studio and give names as RadioButtonExample. In case if you are not aware of creating an app in android studio check this article Android Hello World App.
Now open an activity_main.xml file from \res\layout path and write the code like as shown below
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="150dp"
android:layout_marginLeft="100dp"
android:textSize="18dp"
android:text="Select Your Course"
android:textStyle="bold"
android:id="@+id/txtView"/>
<RadioGroup
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:id="@+id/rdGroup"
android:layout_below="@+id/txtView">
<RadioButton
android:id="@+id/rdbJava"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="10dp"
android:layout_marginLeft="100dp"
android:text="Java"
android:onClick="onRadioButtonClicked"/>
<RadioButton
android:id="@+id/rdbPython"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="10dp"
android:layout_marginLeft="100dp"
android:text="Python"
android:onClick="onRadioButtonClicked"/>
<RadioButton
android:id="@+id/rdbAndroid"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="10dp"
android:layout_marginLeft="100dp"
android:text="Android"
android:onClick="onRadioButtonClicked"/>
<RadioButton
android:id="@+id/rdbAngular"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="10dp"
android:layout_marginLeft="100dp"
android:text="AngularJS"
android:onClick="onRadioButtonClicked"/>
</RadioGroup>
<Button
android:id="@+id/getBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="100dp"
android:layout_below="@+id/rdGroup"
android:text="Get Course" />
</RelativeLayout>
If you observe above code we created a multiple RadioButton controls, one TextView control and one Button control in XML Layout file.
Once we are done with the creation of layout with required controls, we need to load the XML layout resource from our activity onCreate() callback method, for that open main activity file MainActivity.java from \java\com.tutlane.radiobuttonexample path and write the code like as shown below.
package com.tutlane.radiobuttonexample;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
RadioButton android, java, angular, python;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
android = (RadioButton)findViewById(R.id.rdbAndroid);
angular = (RadioButton)findViewById(R.id.rdbAngular);
java = (RadioButton)findViewById(R.id.rdbJava);
python = (RadioButton)findViewById(R.id.rdbPython);
Button btn = (Button)findViewById(R.id.getBtn);
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String result = "Selected Course: ";
result+= (android.isChecked())?"Android":(angular.isChecked())?"AngularJS":(java.isChecked())?"Java":(python.isChecked())?"Python":"";
Toast.makeText(getApplicationContext(), result, Toast.LENGTH_SHORT).show();
}
});
}
public void onRadioButtonClicked(View view) {
boolean checked = ((RadioButton) view).isChecked();
String str="";
// Check which radio button was clicked
switch(view.getId()) {
case R.id.rdbAndroid:
if(checked)
str = "Android Selected";
break;
case R.id.rdbAngular:
if(checked)
str = "AngularJS Selected";
break;
case R.id.rdbJava:
if(checked)
str = "Java Selected";
break;
case R.id.rdbPython:
if(checked)
str = "Python Selected";
break;
}
Toast.makeText(getApplicationContext(), str, Toast.LENGTH_SHORT).show();
}
}
If you observe above code we are calling our layout using setContentView method in the form of R.layout.layout_file_name in our activity file. Here our xml file name is activity_main.xml so we used file name activity_main and we are getting the status of RadiButton controls when they Select / Deselect and getting selected RadioButton control value on Button click.
Generally, during the launch of our activity, onCreate() callback method will be called by the android framework to get the required layout for an activity.
When we run the above example using android virtual device (AVD) we will get a result like as shown below.
If you observe the above result, we are able to select only one option from the set of values and getting the selected RadioButton value on button click.
This is how we can use RadioButton control in android applications to allow users to select only one option from a set of values based on our requirements.