RadioGroup in Kotlin

When working with the traditional Android View system (not Jetpack Compose), RadioGroup is the container for RadioButton views. It ensures that only one RadioButton can be selected at a time.

Here's a step-by-step guide to using RadioGroup in Kotlin for Android:

XML Layout: Firstly, create your layout with the RadioGroup and a few RadioButton views:

<!-- res/layout/activity_main.xml -->
<RadioGroup
    android:id="@+id/radioGroup"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <RadioButton
        android:id="@+id/radioButton1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Option 1" />

    <RadioButton
        android:id="@+id/radioButton2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Option 2" />

    <!-- Add more RadioButtons as required -->

</RadioGroup>

Kotlin Code: Next, in your Kotlin code, set an OnCheckedChangeListener on the RadioGroup to listen for changes to the selected RadioButton:

import android.os.Bundle
import android.widget.RadioButton
import android.widget.RadioGroup
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val radioGroup: RadioGroup = findViewById(R.id.radioGroup)

        radioGroup.setOnCheckedChangeListener { group, checkedId ->
            // Find the RadioButton that was selected by its ID
            val radioButton: RadioButton = findViewById(checkedId)
            when (checkedId) {
                R.id.radioButton1 -> {
                    // Handle option 1
                }
                R.id.radioButton2 -> {
                    // Handle option 2
                }
                // Add more cases as required
            }
        }
    }
}

With the code above, you can detect which RadioButton was selected and then perform an action accordingly.

Remember, RadioGroup ensures that only one RadioButton can be selected at a time. If you programmatically check one RadioButton by calling its setChecked(true) method, any previously selected button in the same group will automatically be unchecked.

Android RadioGroup example code in Kotlin:

<RadioGroup
    android:id="@+id/radioGroup"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

    <RadioButton
        android:id="@+id/radioButton1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Option 1" />

    <RadioButton
        android:id="@+id/radioButton2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Option 2" />
</RadioGroup>

val radioGroup: RadioGroup = findViewById(R.id.radioGroup)

// Set a listener for radio group changes
radioGroup.setOnCheckedChangeListener { group, checkedId ->
    // Handle radio group change
    when (checkedId) {
        R.id.radioButton1 -> {
            // Option 1 selected
        }
        R.id.radioButton2 -> {
            // Option 2 selected
        }
    }
}

Customizing RadioGroup in Kotlin:

Customize the appearance of the RadioGroup using XML attributes or programmatically in Kotlin.

<RadioGroup
    android:id="@+id/customRadioGroup"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/custom_background">

val customRadioGroup: RadioGroup = findViewById(R.id.customRadioGroup)

// Programmatically customize RadioGroup
customRadioGroup.setBackgroundResource(R.drawable.custom_background)

Dynamic creation of RadioGroup in Kotlin:

Programmatically create a RadioGroup instance and add it to a layout:

val dynamicRadioGroup = RadioGroup(this)
dynamicRadioGroup.layoutParams = ViewGroup.LayoutParams(
    ViewGroup.LayoutParams.WRAP_CONTENT,
    ViewGroup.LayoutParams.WRAP_CONTENT
)
parentLayout.addView(dynamicRadioGroup)

RadioGroup with AlertDialog in Kotlin example:

Use AlertDialog with a custom layout containing a RadioGroup:

val options = arrayOf("Option 1", "Option 2", "Option 3")

AlertDialog.Builder(this)
    .setTitle("Select an option")
    .setSingleChoiceItems(options, -1) { dialog, which ->
        // Handle selection
        dialog.dismiss()
    }
    .create()
    .show()

Kotlin RadioGroup with multiple columns:

Use GridLayout as the parent layout for the RadioGroup to achieve a multi-column layout:

<GridLayout
    android:id="@+id/gridLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:columnCount="2">

    <RadioGroup
        android:id="@+id/radioGroup"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="start"
        android:layout_column="0">
        <!-- RadioButtons go here -->
    </RadioGroup>

    <!-- Add another RadioGroup for the second column -->

</GridLayout>