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 Controls2.

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:

The detail screen lets you edit or delete existing alarms:

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:

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.

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 File or Project > Application > Qt Quick Application - Empty > Choose. Type "alarms" in the Name field, and follow the instructions of the wizard.

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

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.

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

     QQmlApplicationEngine engine;
     engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
     if (engine.rootObjects().isEmpty())
         return -1;

     return app.exec();
 }

Additional source files

qtquickcontrols2.conf

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

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

main.qml

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

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

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

     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.

     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.

     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:

     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.

 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.

 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.

 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.

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

The dialog for new alarms:

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

     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.

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

 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.

         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.

         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.

         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.

Files:

• tutorials/alarms/AlarmDelegate.qml
• tutorials/alarms/AlarmDialog.qml
• tutorials/alarms/AlarmModel.qml
• tutorials/alarms/CMakeLists.txt
• tutorials/alarms/TumblerDelegate.qml
• tutorials/alarms/alarms.pro
• tutorials/alarms/main.cpp
• tutorials/alarms/main.qml
• tutorials/alarms/qml.qrc