Radio Buttons & Radio groups in Android: Choosing a single option

Radio Buttons allow you to give users the choice to choose a single option from a list of options. To make android recognise that all the options belong to the same group and that you can select only one option, create a RadioButton for each choice and enclose it with a RadioGroup.

<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>

Initially, none of the options in a RadioGroup are checked and once the user selects an option, only one RadioButton in a group can be checked at a time.

To handle the RadioGroup functionality in Java, you can use setOnCheckedChangeListener to listen to any selection of the RadioButton and then implement your functionality based on your chosen option.

A checkedID will be returned in the method which can be used to find the RadioButton by id. You can use the returned RadioButton view to get its value as shown below.

// Find the RadioGroup view by id
radioGroup = (RadioGroup) findViewById(R.id.radioGroup);
// Set a listener to check the state of RadioButton
radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
    @Override
    public void onCheckedChanged(RadioGroup group, int checkedId) {
        // Use checkedId to find the RadioButton view
        RadioButton radioButton = (RadioButton) findViewById(checkedId);
        // Get the value of the RadioButton and set it to textView
        String selectedOption = radioButton.getText().toString();
        textView.setText("Selected Option: ", selectedOption);
    }
});

As soon as an option is selected, the TextView gets updated and displays the value of the RadioButton.