RadioButton in Kotlin
Android Radio Button is bi-state button which can either be checked or unchecked. Also, it’s working is same as Checkbox except that radio button can not allow to be unchecked once it was selected.
Generally, we use RadioButton controls to allow users to select one option from multiple options.
By default, the RadioButton in OFF(Unchecked) state but we can change the default state of RadioButton by using android:checked attribute.
Following steps to create new project-
- Click on File,then New => New Project.
- Then, check Include Kotlin Support and click next button.
- Select minimum SDK, whatever you need.
- Select Empty activity and then click finish.
Different attributes of RadioButton widget
XML Attributes | Description |
---|---|
android:id | Used to uniquely identify the control |
android:gravity | Used to specify how to align the text like left, right, center, top, etc. |
android:checked | Used to specify the current state of radio button |
android:onClick | It’s a name of the method to invoke when the radio button clicked. |
android:textSize | Used to set size of the text. |
android:textColor | Used to set color of the text. |
android:textStyle | Used to set style of the text. For example, bold, italic, bolditalic etc. |
android:maxWidth | Used to make the view be at most this many pixels wide. |
android:minWidth | Used to make the view be at least this many pixels wide. |
android:background | Used to set the background of the radio button control. |
android:visibility | Used to control the visibility. |
Modify the strings.xml file
We can write the name of the application as RadioButtonInKotlin and write other strings which can be used.
<resources> <string name= "app_name" >RadioButtonInKotlin</string> <string name= "checked" >checked</string> <string name= "unchecked" >unchecked</string> </resources> |
Add RadioButtons in activity_main.xml file
In android, we use radio buttons inside RadioGroup to combine set of radio buttons into single group and it will make sure that user can select only button from the group of buttons.
<? xml version = "1.0" encoding = "utf-8" ?> < LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android" xmlns:tools = "http://schemas.android.com/tools" android:id = "@+id/root_layout" android:layout_width = "match_parent" android:layout_height = "match_parent" android:orientation = "vertical" android:padding = "16dp" > < RadioGroup android:id = "@+id/radio_group" android:layout_width = "match_parent" android:layout_height = "wrap_content" android:background = "#dbeceb" android:padding = "15dp" > < TextView android:id = "@+id/title" android:layout_width = "match_parent" android:layout_height = "wrap_content" android:text = "Which is your favorite color?" android:textStyle = "bold" android:textSize = "20sp" /> < RadioButton android:id = "@+id/red" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:text = "RED" android:onClick = "radio_button_click" /> < RadioButton android:id = "@+id/green" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:text = "GREEN" android:onClick = "radio_button_click" /> < RadioButton android:id = "@+id/yellow" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:text = "YELLOW" android:onClick = "radio_button_click" /> < RadioButton android:id = "@+id/pink" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:text = "PINK" android:onClick = "radio_button_click" /> </ RadioGroup > < Button android:id = "@+id/button" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:text = "Get Selected Color" /> </ LinearLayout > |
Here, we are trying to implement a scenario where you need to select your favorite color. So, in activity_main.xml file, we have added 4 radio buttons inside a radio group. Each button represent a color. Now, only one radio button can be selected at a time. *
Now, we will access this widget in kotlin file and show a proper message whenever a radio button is selected.
Now, Open MainActivity.kt file and add below code into it.
package com.w3wiki.myfirstkotlinapp import androidx.appcompat.app.AppCompatActivity import android.os.Bundle import android.view.View import android.widget.* import kotlinx.android.synthetic.main.activity_main.* import android.widget.RadioGroup class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super .onCreate(savedInstanceState) setContentView(R.layout.activity_main) // Get radio group selected item using on checked change listener radio_group.setOnCheckedChangeListener( RadioGroup.OnCheckedChangeListener { group, checkedId -> val radio: RadioButton = findViewById(checkedId) Toast.makeText(applicationContext, " On checked change :" + " ${radio.text}" , Toast.LENGTH_SHORT).show() }) // Get radio group selected status and text using button click event button.setOnClickListener{ // Get the checked radio button id from radio group var id: Int = radio_group.checkedRadioButtonId if (id!=- 1 ){ // If any radio button checked from radio group // Get the instance of radio button using id val radio:RadioButton = findViewById(id) Toast.makeText(applicationContext, "On button click :" + " ${radio.text}" , Toast.LENGTH_SHORT).show() } else { // If no radio button checked in this radio group Toast.makeText(applicationContext, "On button click :" + " nothing selected" , Toast.LENGTH_SHORT).show() } } } // Get the selected radio button text using radio button on click listener fun radio_button_click(view: View){ // Get the clicked radio button instance val radio: RadioButton = findViewById(radio_group.checkedRadioButtonId) Toast.makeText(applicationContext, "On click : ${radio.text}" , Toast.LENGTH_SHORT).show() } } |
In MainActivity.kt file, we have accessed radio group in which I have added four radio buttons. Then, we have set a listener to display toast message whenever radio button selection changes.
Since AndroidManifest.xml file is very important in any android application, we are also going to mention it here.
AndroidManifest.xml file
<?xml version= "1.0" encoding= "utf-8" ?> <manifest xmlns:android= "http://schemas.android.com/apk/res/android" package = "com.w3wiki.myfirstkotlinapp" > <application android:allowBackup= "true" android:icon= "@mipmap/ic_launcher" android:label= "@string/app_name" android:roundIcon= "@mipmap/ic_launcher_round" android:supportsRtl= "true" android:theme= "@style/AppTheme" > <activity android:name= ".MainActivity" > <intent-filter> <action android:name= "android.intent.action.MAIN" /> <category android:name= "android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest> |
When You run the application, you will get the output as shown below
Contact Us