Use Case - Responding To User Input in QML | Qt 6.4

- Qt 6.4
- Use Case - Responding To User Input in QML
- Qt 6.4.1 Reference Documentation

# Use Case - Responding To User Input in QML

## Supported types of user input

The Qt Quick module provides support for the most common types of user input, including mouse and touch events, text input, and key-press events. Other modules provide support for other types of user input.

This article covers how to handle basic user input. For information about audio-visual input, see the Qt Multimedia documentation.

### Mouse and touch events

The input handlers let QML applications handle mouse and touch events. For example, you could create a button by adding a TapHandler to an Image, or to a Rectangle with a Text object inside. The TapHandler responds to taps or clicks on any type of pointing device.

     import QtQuick

     Item {
         id: root

         width: 320
         height: 480

         Rectangle {
             color: "#272822"
             width: 320
             height: 480
         }

         Rectangle {
             id: rectangle
             x: 40
             y: 20
             width: 120
             height: 120
             color: "red"

             TapHandler {
                 onTapped: rectangle.width += 10
             }
         }
     }

Note: Some Item types have their own built-in input handling. For example, Flickable responds to mouse dragging, touch flicking, and mouse wheel scrolling.

### Keyboard and button events

Button and key presses, from buttons on a device, a keypad, or a keyboard, can all be handled using the Keys attached property. This attached property is available on all Item derived types, and works with the Item::focus property to determine which type receives the key event. For simple key handling, you can set the focus to true on a single Item and do all your key handling there.

     import QtQuick

     Item {
         id: root

         width: 320
         height: 480

         Rectangle {
             color: "#272822"
             width: 320
             height: 480
         }

         Rectangle {
             id: rectangle
             x: 40
             y: 20
             width: 120
             height: 120
             color: "red"

             focus: true
             Keys.onUpPressed: rectangle.y -= 10
             Keys.onDownPressed: rectangle.y += 10
             Keys.onLeftPressed: rectangle.x += 10
             Keys.onRightPressed: rectangle.x -= 10
         }
     }

For text input, we have several QML types to choose from. TextInput provides an unstyled single-line editable text, while TextField is more suitable for form fields in applications. TextEdit can handle multi-line editable text, but TextArea is a better alternative as it adds styling.

The following snippet demonstrates how to use these types in your application:

     import QtQuick
     import QtQuick.Controls
     import QtQuick.Layouts

     ApplicationWindow {
         width: 300
         height: 200
         visible: true

         ColumnLayout {
             anchors.fill: parent
             TextField {
                 id: singleline
                 text: "Initial Text"
                 Layout.alignment: Qt.AlignHCenter | Qt.AlignTop
                 Layout.margins: 5
                 background: Rectangle {
                    implicitWidth: 200
                    implicitHeight: 40
                    border.color: singleline.focus ? "#21be2b" : "lightgray"
                    color: singleline.focus ? "lightgray" : "transparent"
                 }
             }

             TextArea {
                 id: multiline
                 placeholderText: "Initial text\n...\n...\n"
                 Layout.alignment: Qt.AlignLeft
                 Layout.fillWidth: true
                 Layout.fillHeight: true
                 Layout.margins: 5
                 background: Rectangle {
                    implicitWidth: 200
                    implicitHeight: 100
                    border.color: multiline.focus ? "#21be2b" : "lightgray"
                    color: multiline.focus ? "lightgray" : "transparent"
                 }
             }
         }
     }