用例 - 响应 QML 用户输入

支持的用户输入类型

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 for example, the Qt Sensors module provides support for shake-gestures in QML applications.

This article covers how to handle basic user input; for further information about motion-gesture support, see the Qt Sensors documentation. For information about audio-visual input, see the Qt Multimedia 文档编制。

鼠标和触摸事件

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 采用 Text object inside. The TapHandler responds to taps or clicks on any type of pointing device.

import QtQuick 2.12
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
        }
    }
}

For more advanced use cases such as, drag, pinch and zoom gestures, see documentation for the DragHandler and PinchHandler 类型。

注意： Some types have their own built-in input handling. For example, Flickable responds to mouse dragging and mouse wheel scrolling. It handles touch dragging and flicking via synthetic mouse events that are created when the touch events are not handled.

键盘和按钮事件

Button and key presses, from buttons on a device, a keypad, or a keyboard, can all be handled using the 键 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 2.3
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 2.12
import QtQuick.Controls 2.4
import QtQuick.Layouts 1.3
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"
            }
        }
    }
}