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Getting Started Programming with Qt Quick

A tutorial for Qt Quick based on an alarms application.

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Publié le - Mis à jour le 26 janvier 2024 

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Getting Started Programming with Qt Quick▲

This tutorial shows how to develop a simple alarm application as an introduction to Qt Quick and Qt Quick Controls.

This application is similar to the alarm application usually found on an Android phone. Its features let you enter, edit, or delete alarms. An alarm can trigger on a given date, and you can set it to repeat on a series of subsequent days.

The main screen shows the list of saved alarms:

"Alarms application"

The detail screen lets you edit or delete existing alarms:

"Detail screen"

The dialog screen is used for adding new alarms. It pops up when you click on the "+" RoundButton on the bottom of the main screen:

"Add alarms"

The source files are located in the qtdoc repository. You can either fetch the Qt sources from the Qt Project, or install them as part of Qt. The application is also available in the example list of Qt Creator's Welcome mode.

Creating the Alarms Project▲

This section shows how to create the project in Qt Creator. It discusses the files generated automatically by Qt Creator, and the two files the programmer has to create in Qt Creator or some other editor. The latter two files are included with the source code for this tutorial.

The UI text in Qt Creator and the contents of the generated files depend on the Qt Creator version that you use.

Qt Creator▲

Setting up a new project in Qt Creator is aided by a wizard that guides you step-by-step through the project creation process. The wizard prompts you to enter the settings needed for that particular type of project and creates the project for you.

To create the Alarms project, select File > New Project > Application (Qt) > Qt Quick Application > Choose. Type alarms in the Name field, and follow the instructions of the wizard.

"Qt Creator New Project dialog"
"Project Location"

The Qt Quick application wizard creates a project that contains the following source files:

Source file

Purpose

CMakeLists.txt

The project file

main.cpp

The main C++ code file for the application.

main.qml

The main QML code file for the application. We will instantiate our custom QML types (AlarmDialog, AlarmModel, AlarmDelegate, and TumblerDelegate) in this file.

The wizard generates the code in the main.cpp file below. This code block enables High DPI scaling and declares app and engine. The engine then loads our main QML file.

 
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int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    const QUrl url(u"qrc:/alarms/main.qml"_s);
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated, &app,
                     [url](QObject *obj, const QUrl &objUrl) {
                         if (!obj && url == objUrl)
                             QCoreApplication::exit(-1);
                     },

Additional source files▲

Source file

Purpose

qtquickcontrols2.conf

Selects the Material style with the Dark theme.

AlarmDialog.qml

Defines the dialog for adding new alarms.

AlarmDelegate.qml

Defines the layout of the main screen of the app.

AlarmModel.qml

Defines the ListModel used for storing the alarms' data.

TumblerDelegate.qml

Defines the graphical layout of the Tumblers.

qml.qrc

The resource file, which contains the names of the source files, except main.cpp and the project file.

qtquickcontrols2.conf▲

The following snippet shows how to set the Dark theme in the Material style:

 
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[Controls]
Style=Material
[Material]
Theme=Dark
Accent=Red

main.qml▲

mainWindow, an ApplicationWindow QML type, is the root item in this app.

 
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ApplicationWindow {
    id: window
    width: 400
    height: 500
    visible: true

The ListView alarmListView combines the data from alarmModel with the layout defined in alarmDelegate.

 
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    ListView {
        id: alarmListView
        anchors.fill: parent
        model: AlarmModel {}
        delegate: AlarmDelegate {}
    }

New alarms can be added by clicking RoundButton addAlarmButton. Clicking it opens a Dialog screen alarmDialog.

 
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    RoundButton {
        id: addAlarmButton
        text: "+"
        anchors.bottom: alarmListView.bottom
        anchors.bottomMargin: 8
        anchors.horizontalCenter: parent.horizontalCenter
        onClicked: alarmDialog.open()
    }

    AlarmDialog {
        id: alarmDialog
        x: Math.round((parent.width - width) / 2)
        y: Math.round((parent.height - height) / 2)
        alarmModel: alarmListView.model
    }

AlarmDialog.qml▲

This dialog screen has a RowLayout with a Tumbler each for hours and minutes, and another RowLayout with a Tumbler each for day, month, and year.

 
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    contentItem: RowLayout {
        RowLayout {
            id: rowTumbler

            Tumbler {
                id: hoursTumbler
                model: 24
                delegate: TumblerDelegate {
                    text: formatNumber(modelData)
                }
            }
            Tumbler {
                id: minutesTumbler
                model: 60
                delegate: TumblerDelegate {
                    text: formatNumber(modelData)
                }
            }
        }

        RowLayout {
            id: datePicker

            Layout.leftMargin: 20

            property alias dayTumbler: dayTumbler
            property alias monthTumbler: monthTumbler
            property alias yearTumbler: yearTumbler

            readonly property var days: [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

            Tumbler {
                id: dayTumbler

                function updateModel() {
                    // Populate the model with days of the month. For example: [0, ..., 30]
                    var previousIndex = dayTumbler.currentIndex
                    var array = []
                    var newDays = datePicker.days[monthTumbler.currentIndex]
                    for (var i = 1; i <= newDays; ++i)
                        array.push(i)
                    dayTumbler.model = array
                    dayTumbler.currentIndex = Math.min(newDays - 1, previousIndex)
                }

                Component.onCompleted: updateModel()

                delegate: TumblerDelegate {
                    text: formatNumber(modelData)
                }
            }
            Tumbler {
                id: monthTumbler

                onCurrentIndexChanged: dayTumbler.updateModel()

                model: 12
                delegate: TumblerDelegate {
                    text: window.locale.standaloneMonthName(modelData, Locale.ShortFormat)
                }
            }
            Tumbler {
                id: yearTumbler

                // This array is populated with the next three years. For example: [2018, 2019, 2020]
                readonly property var years: (function() {
                    var currentYear = new Date().getFullYear()
                    return [0, 1, 2].map(function(value) { return value + currentYear; })
                })()

                model: years
                delegate: TumblerDelegate {
                    text: formatNumber(modelData)
                }
            }
        }
    }
}

If you click on OK in the dialog, the entered data will be added to alarmModel:

 
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    onAccepted: {
        alarmModel.append({
            "hour": hoursTumbler.currentIndex,
            "minute": minutesTumbler.currentIndex,
            "day": dayTumbler.currentIndex + 1,
            "month": monthTumbler.currentIndex + 1,
            "year": yearTumbler.years[yearTumbler.currentIndex],
            "activated": true,
            "label": "",
            "repeat": false,
            "daysToRepeat": [
                { "dayOfWeek": 0, "repeat": false },
                { "dayOfWeek": 1, "repeat": false },
                { "dayOfWeek": 2, "repeat": false },
                { "dayOfWeek": 3, "repeat": false },
                { "dayOfWeek": 4, "repeat": false },
                { "dayOfWeek": 5, "repeat": false },
                { "dayOfWeek": 6, "repeat": false }
            ],
        })
    }
    onRejected: alarmDialog.close()

AlarmDelegate.qml▲

Each alarm in the main screen is an ItemDelegate. The ItemDelegate root contains all fields on the main screen and the detail screen. The detail screen's fields are only visible after an alarm has been clicked on, i.e. when root.checked is true.

 
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ItemDelegate {
    id: root
    width: parent.width
    checkable: true

    onClicked: ListView.view.currentIndex = index

    contentItem: ColumnLayout {
        spacing: 0

        RowLayout {
            ColumnLayout {
                id: dateColumn

                readonly property date alarmDate: new Date(
                    model.year, model.month - 1, model.day, model.hour, model.minute)

                Label {
                    id: timeLabel
                    font.pixelSize: Qt.application.font.pixelSize * 2
                    text: dateColumn.alarmDate.toLocaleTimeString(window.locale, Locale.ShortFormat)
                }
                RowLayout {
                    Label {
                        id: dateLabel
                        text: dateColumn.alarmDate.toLocaleDateString(window.locale, Locale.ShortFormat)
                    }
                    Label {
                        id: alarmAbout
                        text: "⸱ " + model.label
                        visible: model.label.length > 0 && !root.checked
                    }
                }
            }
            Item {
                Layout.fillWidth: true
            }
            Switch {
                checked: model.activated
                Layout.alignment: Qt.AlignTop
                onClicked: model.activated = checked
            }
        }
        CheckBox {
            id: alarmRepeat
            text: qsTr("Repeat")
            checked: model.repeat
            visible: root.checked
            onToggled: model.repeat = checked
        }
        Flow {
            visible: root.checked && model.repeat
            Layout.fillWidth: true

            Repeater {
                id: dayRepeater
                model: daysToRepeat
                delegate: RoundButton {
                    text: Qt.locale().dayName(model.dayOfWeek, Locale.NarrowFormat)
                    flat: true
                    checked: model.repeat
                    checkable: true
                    Material.background: checked ? Material.accent : "transparent"
                    onToggled: model.repeat = checked
                }
            }
        }

        TextField {
            id: alarmDescriptionTextField
            placeholderText: qsTr("Enter description here")
            cursorVisible: true
            visible: root.checked
            text: model.label
            onTextEdited: model.label = text
        }
        Button {
            id: deleteAlarmButton
            text: qsTr("Delete")
            width: 40
            height: 40
            visible: root.checked
            onClicked: root.ListView.view.model.remove(root.ListView.view.currentIndex, 1)
        }
    }
}

AlarmModel.qml▲

This QML file contains the definition of alarmModel, the ListModel that manages the alarm data.

It creates five ListElements with example alarms.

 
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import QtQuick

// Populate the model with some sample data.
ListModel {
    id: alarmModel

    ListElement {
        hour: 6
        minute: 0
        day: 2
        month: 8
        year: 2018
        activated: true
        label: "Wake up"
        repeat: true
        daysToRepeat: [
            ListElement { dayOfWeek: 0; repeat: false },
            ListElement { dayOfWeek: 1; repeat: false },
            ListElement { dayOfWeek: 2; repeat: false },
            ListElement { dayOfWeek: 3; repeat: false },
            ListElement { dayOfWeek: 4; repeat: false },
            ListElement { dayOfWeek: 5; repeat: false },
            ListElement { dayOfWeek: 6; repeat: false }
        ]
    }
    ListElement {
        hour: 6
        minute: 0
        day: 3
        month: 8
        year: 2018
        activated: true
        label: "Wake up"
        repeat: true
        daysToRepeat: [
            ListElement { dayOfWeek: 0; repeat: true },
            ListElement { dayOfWeek: 1; repeat: true },
            ListElement { dayOfWeek: 2; repeat: true },
            ListElement { dayOfWeek: 3; repeat: true },
            ListElement { dayOfWeek: 4; repeat: true },
            ListElement { dayOfWeek: 5; repeat: false },
            ListElement { dayOfWeek: 6; repeat: false }
        ]
    }
    ListElement {
        hour: 7
        minute: 0
        day: 3
        month: 8
        year: 2018
        activated: false
        label: "Exercise"
        repeat: true
        daysToRepeat: [
            ListElement { dayOfWeek: 0; repeat: true },
            ListElement { dayOfWeek: 1; repeat: true },
            ListElement { dayOfWeek: 2; repeat: true },
            ListElement { dayOfWeek: 3; repeat: true },
            ListElement { dayOfWeek: 4; repeat: true },
            ListElement { dayOfWeek: 5; repeat: true },
            ListElement { dayOfWeek: 6; repeat: true }
        ]
    }
    ListElement {
        hour: 5
        minute: 15
        day: 1
        month: 9
        year: 2018
        activated: true
        label: ""
        repeat: false
        daysToRepeat: [
            ListElement { dayOfWeek: 0; repeat: false },
            ListElement { dayOfWeek: 1; repeat: false },
            ListElement { dayOfWeek: 2; repeat: false },
            ListElement { dayOfWeek: 3; repeat: false },
            ListElement { dayOfWeek: 4; repeat: false },
            ListElement { dayOfWeek: 5; repeat: false },
            ListElement { dayOfWeek: 6; repeat: false }
        ]
    }
    ListElement {
        hour: 5
        minute: 45
        day: 3
        month: 9
        year: 2018
        activated: false
        label: ""
        repeat: false
        daysToRepeat: [
            ListElement { dayOfWeek: 0; repeat: false },
            ListElement { dayOfWeek: 1; repeat: false },
            ListElement { dayOfWeek: 2; repeat: false },
            ListElement { dayOfWeek: 3; repeat: false },
            ListElement { dayOfWeek: 4; repeat: false },
            ListElement { dayOfWeek: 5; repeat: false },
            ListElement { dayOfWeek: 6; repeat: false }
        ]
    }
}

TumblerDelegate.qml▲

TumblerDelegate defines the graphical properties of the Tumblers.

 
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import QtQuick
import QtQuick.Controls
import QtQuick.Controls.Material

Text {
    text: modelData
    color: Tumbler.tumbler.Material.foreground
    font: Tumbler.tumbler.font
    opacity: 1.0 - Math.abs(Tumbler.displacement) / (Tumbler.tumbler.visibleItemCount / 2)
    horizontalAlignment: Text.AlignHCenter
    verticalAlignment: Text.AlignVCenter
}

Entering new alarms▲

At the bottom of the startup screen, you can see a Button for adding alarms. Click it to open the Add new alarm dialog.

 
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    RoundButton {
        id: addAlarmButton
        text: "+"
        anchors.bottom: alarmListView.bottom
        anchors.bottomMargin: 8
        anchors.horizontalCenter: parent.horizontalCenter
        onClicked: alarmDialog.open()
    }

The dialog for new alarms:

"Add alarms"

All fields are entered using Tumbler QML types. If you press OK, the values selected in the Tumblers are written to alarmModel.

 
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    contentItem: RowLayout {
        RowLayout {
            id: rowTumbler

            Tumbler {
                id: hoursTumbler
                model: 24
                delegate: TumblerDelegate {
                    text: formatNumber(modelData)
                }
            }
            Tumbler {
                id: minutesTumbler
                model: 60
                delegate: TumblerDelegate {
                    text: formatNumber(modelData)
                }
            }
        }

        RowLayout {
            id: datePicker

            Layout.leftMargin: 20

            property alias dayTumbler: dayTumbler
            property alias monthTumbler: monthTumbler
            property alias yearTumbler: yearTumbler

            readonly property var days: [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

            Tumbler {
                id: dayTumbler

                function updateModel() {
                    // Populate the model with days of the month. For example: [0, ..., 30]
                    var previousIndex = dayTumbler.currentIndex
                    var array = []
                    var newDays = datePicker.days[monthTumbler.currentIndex]
                    for (var i = 1; i <= newDays; ++i)
                        array.push(i)
                    dayTumbler.model = array
                    dayTumbler.currentIndex = Math.min(newDays - 1, previousIndex)
                }

                Component.onCompleted: updateModel()

                delegate: TumblerDelegate {
                    text: formatNumber(modelData)
                }
            }
            Tumbler {
                id: monthTumbler

                onCurrentIndexChanged: dayTumbler.updateModel()

                model: 12
                delegate: TumblerDelegate {
                    text: window.locale.standaloneMonthName(modelData, Locale.ShortFormat)
                }
            }
            Tumbler {
                id: yearTumbler

                // This array is populated with the next three years. For example: [2018, 2019, 2020]
                readonly property var years: (function() {
                    var currentYear = new Date().getFullYear()
                    return [0, 1, 2].map(function(value) { return value + currentYear; })
                })()

                model: years
                delegate: TumblerDelegate {
                    text: formatNumber(modelData)
                }
            }
        }
    }
}

Editing alarms▲

If you click on a particular alarm, you can edit it in the detail screen.

Image non disponible

Clicking on an alarm sets root.checked to true, which makes visible the fields of the detail screen.

 
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visible: root.checked

If you want the alarm to trigger also on other days, check alarmRepeat. The Repeater will display a checkable RoundButton for each day of the week.

 
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        Flow {
            visible: root.checked && model.repeat
            Layout.fillWidth: true

            Repeater {
                id: dayRepeater
                model: daysToRepeat
                delegate: RoundButton {
                    text: Qt.locale().dayName(model.dayOfWeek, Locale.NarrowFormat)
                    flat: true
                    checked: model.repeat
                    checkable: true
                    Material.background: checked ? Material.accent : "transparent"
                    onToggled: model.repeat = checked
                }
            }
        }

If you modify the description of the alarm, it will be reflected in the main screen afterwards.

 
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        TextField {
            id: alarmDescriptionTextField
            placeholderText: qsTr("Enter description here")
            cursorVisible: true
            visible: root.checked
            text: model.label
            onTextEdited: model.label = text
        }

Deleting alarms▲

The detail screen (see above) has a Button for deleting alarms. When onClicked is emitted, the current ListElement is deleted from alarmModel.

 
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        Button {
            id: deleteAlarmButton
            text: qsTr("Delete")
            width: 40
            height: 40
            visible: root.checked
            onClicked: root.ListView.view.model.remove(root.ListView.view.currentIndex, 1)
        }

Summary▲

The app has no code for adding sound or vibration to the alarm, nor does it store the alarms in any format or database. Maybe it could be an interesting coding project to add those features. Storing the data could be done quickly and easily in JSON format.

Example project▲

Example project @ code.qt.io

See Also▲

See also JSON Support in Qt

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