用例 - QML 中的视觉元素

矩形类型

对于最基本视觉， Qt Quick 提供 Rectangle 类型来绘制矩形。这些矩形可以采用颜色或垂直渐变进行着色。 Rectangle 类型还可以绘制矩形边框。

为在矩形外绘制自定义形状，见 Canvas 类型或显示预渲染图像使用图像类型。

import QtQuick 2.3
Item {
    width: 320
    height: 480
    Rectangle {
        color: "#272822"
        width: 320
        height: 480
    }
    // This element displays a rectangle with a gradient and a border
    Rectangle {
        x: 160
        y: 20
        width: 100
        height: 100
        radius: 8 // This gives rounded corners to the Rectangle
        gradient: Gradient { // This sets a vertical gradient fill
            GradientStop { position: 0.0; color: "aqua" }
            GradientStop { position: 1.0; color: "teal" }
        }
        border { width: 3; color: "white" } // This sets a 3px wide black border to be drawn
    }
    // This rectangle is a plain color with no border
    Rectangle {
        x: 40
        y: 20
        width: 100
        height: 100
        color: "red"
    }
}

图像类型

Qt Quick 提供图像类型可用于显示图像。图像类型拥有 source property whose value can be a remote or local URL, or the URL of an image file embedded in a compiled resource file.

// This element displays an image. Because the source is online, it may take some time to fetch
Image {
    x: 40
    y: 20
    width: 61
    height: 73
    source: "http://codereview.qt-project.org/static/logo_qt.png"
}

对于更复杂图像，存在的其它类型类似图像 . BorderImage 采用栅格比例缩放绘制图像，适用于用作边框的图像。 AnimatedImage plays animated .gif and .mng images. AnimatedSprite and SpriteSequence play animations comprised of multiple frames stored adjacently in a non animated image format.

For displaying video files and camera data, see the Qt Multimedia 模块。

共享视觉特性

All visual items provided by Qt Quick are based on the Item type, which provides a common set of attributes for visual items, including opacity and transform attributes.

不透明度和可见性

The QML object types provided by Qt Quick have built-in support for opacity . Opacity can be animated to allow smooth transitions to or from a transparent state. Visibility can also be managed with the visible property more efficiently, but at the cost of not being able to animate it.

import QtQuick 2.3
Item {
    width: 320
    height: 480
    Rectangle {
        color: "#272822"
        width: 320
        height: 480
    }
    Item {
        x: 20
        y: 270
        width: 200
        height: 200
        MouseArea {
            anchors.fill: parent
            onClicked: topRect.visible = !topRect.visible
        }
        Rectangle {
            x: 20
            y: 20
            width: 100
            height: 100
            color: "red"
        }
        Rectangle {
            id: topRect
            opacity: 0.5
            x: 100
            y: 100
            width: 100
            height: 100
            color: "blue"
        }
    }
}

变换

Qt Quick types have built-in support for transformations. If you wish to have your visual content rotated or scaled, you can set the Item::rotation or Item::scale property. These can also be animated.

import QtQuick 2.3
Item {
    width: 320
    height: 480
    Rectangle {
        color: "#272822"
        width: 320
        height: 480
    }
    Rectangle {
        rotation: 45 // This rotates the Rectangle by 45 degrees
        x: 20
        y: 160
        width: 100
        height: 100
        color: "blue"
    }
    Rectangle {
        scale: 0.8 // This scales the Rectangle down to 80% size
        x: 160
        y: 160
        width: 100
        height: 100
        color: "green"
    }
}

更复杂变换，见 Item::transform 特性。