GNOME.org

RadioButton

RadioButtons are named after old-style car radios, which had buttons for switching between channel presets. Because the radio could only be tuned to one station at a time, only one button could be pressed in at a time; if you pressed a new one, the one that was already pressed in would pop back out. That's how these buttons work, too.

Each RadioButton needs a text label and a group. Only one button in a group can be selected at a time. You don't name each group; you just set new RadioButtons to be part of the same group as an existing one. If you create a new one outside of a group, it automatically creates a new group for it to be part of.

Libraries to import

#!/usr/bin/gjs

const Gio = imports.gi.Gio;
const Gtk = imports.gi.Gtk;
const Lang = imports.lang;

These are the libraries we need to import for this application to run. Remember that the line which tells GNOME that we're using Gjs always needs to go at the start.

Creating the application window

const RadioButtonExample = new Lang.Class({
    Name: 'RadioButton Example',

    // Create the application itself
    _init: function() {
        this.application = new Gtk.Application({
            application_id: 'org.example.jsradiobutton',
            flags: Gio.ApplicationFlags.FLAGS_NONE
        });

    // Connect 'activate' and 'startup' signals to the callback functions
    this.application.connect('activate', Lang.bind(this, this._onActivate));
    this.application.connect('startup', Lang.bind(this, this._onStartup));
    },

    // Callback function for 'activate' signal presents window when active
    _onActivate: function() {
        this._window.present();
    },

    // Callback function for 'startup' signal builds the UI
    _onStartup: function() {
        this._buildUI ();
    },

All the code for this sample goes in the RadioButtonExample class. The above code creates a Gtk.Application for our widgets and window to go in.

    // Build the application's UI
    _buildUI: function() {

        // Create the application window
        this._window = new Gtk.ApplicationWindow({
            application: this.application,
            window_position: Gtk.WindowPosition.CENTER,
            border_width: 20,
            title: "Travel Planning"});

The _buildUI function is where we put all the code to create the application's user interface. The first step is creating a new Gtk.ApplicationWindow to put all our widgets into.

Creating the radiobuttons

        // Create a label for the first group of buttons
        this._placeLabel = new Gtk.Label ({label: "Where would you like to travel to?"});

We use a Gtk.Label to set each group of RadioButtons apart. Nothing will stop you from putting RadioButtons from all different groups wherever you want, so if you want people to know which ones go together you need to organize things accordingly.

        // Create three radio buttons three different ways
        this._place1 = new Gtk.RadioButton ({label: "The Beach"});

        this._place2 = Gtk.RadioButton.new_from_widget (this._place1);
        this._place2.set_label ("The Moon");

        this._place3 = Gtk.RadioButton.new_with_label_from_widget (this._place1, "Antarctica");
        // this._place3.set_active (true);

Here are three different ways to create RadioButtons. The first is the usual way, where we create a new Gtk.RadioButton and assign its properties at the same time. The second and third use functions which automatically handle some of the properties; new_from_widget takes a single argument, the RadioButton that you want to put this new one in the same group as. Meanwhile, new_with_label_from_widget takes that and the RadioButton's label at the same time.

The first RadioButton in a group is the one that's selected by default. Try uncommenting the last line in this sample code to see how you can set a different one to be the default selection.

        // Create a label for the second group of buttons
        this._thingLabel = new Gtk.Label ({label: "And what would you like to bring?" });

        // Create three more radio buttons
        this._thing1 = new Gtk.RadioButton ({label: "Penguins" });
        this._thing2 = new Gtk.RadioButton ({label: "Sunscreen", group: this._thing1 });
        this._thing3 = new Gtk.RadioButton ({label: "A spacesuit", group: this._thing1 });

Here we create the label for the second group of buttons, and then create them all the same way.

Creating the rest of the user interface

        // Create a stock OK button
        this._okButton = new Gtk.Button ({
            label: 'gtk-ok',
            use_stock: 'true',
            halign: Gtk.Align.END });

        // Connect the button to the function which handles clicking it
        this._okButton.connect ('clicked', Lang.bind (this, this._okClicked));

This code creates a Gtk.Button and binds it to a function which will show people a silly message when they click OK, depending on which RadioButtons were selected.

To make sure the button's "OK" label shows up properly in every language that GNOME is translated into, remember to use one of Gtk's stock button types.

        // Create a grid to put the "place" items in
        this._places = new Gtk.Grid ();

        // Attach the "place" items to the grid
        this._places.attach (this._placeLabel, 0, 0, 1, 1);
        this._places.attach (this._place1, 0, 1, 1, 1);
        this._places.attach (this._place2, 0, 2, 1, 1);
        this._places.attach (this._place3, 0, 3, 1, 1);

        // Create a grid to put the "thing" items in
        this._things = new Gtk.Grid ({ margin_top: 50 });

        // Attach the "thing" items to the grid
        this._things.attach (this._thingLabel, 0, 0, 1, 1);
        this._things.attach (this._thing1, 0, 1, 1, 1);
        this._things.attach (this._thing2, 0, 2, 1, 1);
        this._things.attach (this._thing3, 0, 3, 1, 1);

        // Create a grid to put everything in
        this._grid = new Gtk.Grid ({
            halign: Gtk.Align.CENTER,
            valign: Gtk.Align.CENTER,
            margin_left: 40,
            margin_right: 50 });

        // Attach everything to the grid
        this._grid.attach (this._places, 0, 0, 1, 1);
        this._grid.attach (this._things, 0, 1, 1, 1);
        this._grid.attach (this._okButton, 0, 2, 1, 1);

        // Add the grid to the window
        this._window.add (this._grid);

We use a separate Gtk.Grid to organize each group of radio buttons. This way we can change the layout with less fuss later on. The second Grid has a margin on top, to visually separate the two sets of choices.

After we've organized them, we put them into a third, master Grid, along with the OK button. Then we attach that to the window.

        // Show the window and all child widgets
        this._window.show_all();
    },

Finally, we tell the window and everything inside it to become visible when the application is run.

Function which handles your selection

    _okClicked: function () {

        // Create a popup that shows a silly message
        this._travel = new Gtk.MessageDialog ({
            transient_for: this._window,
            modal: true,
            message_type: Gtk.MessageType.OTHER,
            buttons: Gtk.ButtonsType.OK,
            text: this._messageText() });

        // Show the popup
        this._travel.show();

        // Bind the OK button to the function that closes the popup
        this._travel.connect ("response", Lang.bind (this, this._clearTravelPopUp));

    },

When you click OK, a Gtk.MessageDialog appears. This function creates and displays the popup window, then binds its OK button to a function that closes it. What text appears in the popup depends on the _messageText() function, which returns a different value depending on which set of options you chose.

    _messageText: function() {

        // Create a silly message for the popup depending on what you selected
        var stringMessage = "";

        if (this._place1.get_active()) {

            if (this._thing1.get_active())
                stringMessage = "Penguins love the beach, too!";

            else if (this._thing2.get_active())
                stringMessage = "Make sure to put on that sunscreen!";

            else stringMessage = "Are you going to the beach in space?";

        }

        else if (this._place2.get_active()) {

            if (this._thing1.get_active())
                stringMessage = "The penguins will take over the moon!";

            else if (this._thing2.get_active())
                stringMessage = "A lack of sunscreen will be the least of your problems!";

            else stringMessage = "You'll probably want a spaceship, too!";
        }

        else if (this._place3.get_active()) {

            if (this._thing1.get_active())
                stringMessage = "The penguins will be happy to be back home!";

            else if (this._thing2.get_active())
                stringMessage = "Antarctic sunbathing may be hazardous to your health!";

            else stringMessage = "Try bringing a parka instead!";
        }

        return stringMessage;

    },

The get_active() method is how we can tell which RadioButton's pressed in. This function returns a different silly message depending on which set of buttons was pressed. Its return value is used as the MessageDialog's text property.

    _clearTravelPopUp: function () {

        this._travel.destroy();

    }

});

This function is called when the MessageDialog's OK button is pressed. It simply makes the popup go away.

// Run the application
let app = new RadioButtonExample ();
app.application.run (ARGV);

Finally, we create a new instance of the finished RadioButtonExample class, and set the application running.

Complete code sample

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#!/usr/bin/gjs

imports.gi.versions.Gtk = '3.0';

const Gio = imports.gi.Gio;
const Gtk = imports.gi.Gtk;

class RadioButtonExample {

    // Create the application itself
    constructor() {
        this.application = new Gtk.Application({
            application_id: 'org.example.jsradiobutton',
            flags: Gio.ApplicationFlags.FLAGS_NONE
        });

        // Connect 'activate' and 'startup' signals to the callback functions
        this.application.connect('activate', this._onActivate.bind(this));
        this.application.connect('startup', this._onStartup.bind(this));
    }

    // Callback function for 'activate' signal presents window when active
    _onActivate() {
        this._window.present();
    }

    // Callback function for 'startup' signal builds the UI
    _onStartup() {
        this._buildUI();
    }

    // Build the application's UI
    _buildUI() {

        // Create the application window
        this._window = new Gtk.ApplicationWindow({
            application: this.application,
            window_position: Gtk.WindowPosition.CENTER,
            border_width: 20,
            title: "Travel Planning"});

        // Create a label for the first group of buttons
        this._placeLabel = new Gtk.Label ({label: "Where would you like to travel to?"});

        // Create three radio buttons three different ways
        this._place1 = new Gtk.RadioButton ({label: "The Beach"});

        this._place2 = Gtk.RadioButton.new_from_widget (this._place1);
        this._place2.set_label ("The Moon");

        this._place3 = Gtk.RadioButton.new_with_label_from_widget (this._place1, "Antarctica");
        // this._place3.set_active (true);

        // Create a label for the second group of buttons
        this._thingLabel = new Gtk.Label ({label: "And what would you like to bring?" });

        // Create three more radio buttons
        this._thing1 = new Gtk.RadioButton ({label: "Penguins" });
        this._thing2 = new Gtk.RadioButton ({label: "Sunscreen", group: this._thing1 });
        this._thing3 = new Gtk.RadioButton ({label: "A spacesuit", group: this._thing1 });

        // Create a stock OK button
        this._okButton = new Gtk.Button ({
            label: 'gtk-ok',
            use_stock: 'true',
            halign: Gtk.Align.END });

        // Connect the button to the function which handles clicking it
        this._okButton.connect ('clicked', this._okClicked.bind(this));

        // Create a grid to put the "place" items in
        this._places = new Gtk.Grid ();

        // Attach the "place" items to the grid
        this._places.attach (this._placeLabel, 0, 0, 1, 1);
        this._places.attach (this._place1, 0, 1, 1, 1);
        this._places.attach (this._place2, 0, 2, 1, 1);
        this._places.attach (this._place3, 0, 3, 1, 1);

        // Create a grid to put the "thing" items in
        this._things = new Gtk.Grid ({ margin_top: 50 });

        // Attach the "thing" items to the grid
        this._things.attach (this._thingLabel, 0, 0, 1, 1);
        this._things.attach (this._thing1, 0, 1, 1, 1);
        this._things.attach (this._thing2, 0, 2, 1, 1);
        this._things.attach (this._thing3, 0, 3, 1, 1);

        // Create a grid to put everything in
        this._grid = new Gtk.Grid ({
            halign: Gtk.Align.CENTER,
            valign: Gtk.Align.CENTER,
            margin_left: 40,
            margin_right: 50 });

        // Attach everything to the grid
        this._grid.attach (this._places, 0, 0, 1, 1);
        this._grid.attach (this._things, 0, 1, 1, 1);
        this._grid.attach (this._okButton, 0, 2, 1, 1);

        // Add the grid to the window
        this._window.add (this._grid);

        // Show the window and all child widgets
        this._window.show_all();
    }

    _okClicked() {

        // Create a popup that shows a silly message
        this._travel = new Gtk.MessageDialog ({
            transient_for: this._window,
            modal: true,
            message_type: Gtk.MessageType.OTHER,
            buttons: Gtk.ButtonsType.OK,
            text: this._messageText() });

        // Show the popup
        this._travel.show();

        // Bind the OK button to the function that closes the popup
        this._travel.connect ("response", this._clearTravelPopUp.bind(this));

    }

    _messageText() {

        // Create a silly message for the popup depending on what you selected
        var stringMessage = "";

        if (this._place1.get_active()) {

            if (this._thing1.get_active())
                stringMessage = "Penguins love the beach, too!";

            else if (this._thing2.get_active())
                stringMessage = "Make sure to put on that sunscreen!";

            else stringMessage = "Are you going to the beach in space?";

        }

        else if (this._place2.get_active()) {

            if (this._thing1.get_active())
                stringMessage = "The penguins will take over the moon!";

            else if (this._thing2.get_active())
                stringMessage = "A lack of sunscreen will be the least of your problems!";

            else stringMessage = "You'll probably want a spaceship, too!";
        }

        else if (this._place3.get_active()) {

            if (this._thing1.get_active())
                stringMessage = "The penguins will be happy to be back home!";

            else if (this._thing2.get_active())
                stringMessage = "Antarctic sunbathing may be hazardous to your health!";

            else stringMessage = "Try bringing a parka instead!";
        }

        return stringMessage;

    }

    _clearTravelPopUp() {
        this._travel.destroy();
    }
};

// Run the application
let app = new RadioButtonExample ();
app.application.run (ARGV);