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接上文Qt5官方demo解析集32——Qt Quick Examples - Threading
来到我们Qt Quick Examples的第二个例子了，之所以挑这个demo，主要是我们使用Qt开发界面（尤其是跨平台界面）时，本地屏幕信息与窗口调用是不可避免的课题。
这个例子便向我们展示了在QML中获取本地屏幕信息的方法。
项目树如图，其中shared.qrc是很多QML示例共享的一些资源，包括按钮，滑块等。
此外，为了良好的跨平台，demo中添加了两种格式的图标文件(MAC支持的icns, 以及其他平台通用的png)。
程序运行如图，我们可以调用一个子窗口，以窗口化或最大化形式显示。下方是我的笔记本屏幕的一些信息，包括分辨率，像素密度，方向等等。
由于使用到图标，我们有必要将pro文件拿出来看看：
window.pro:
TEMPLATE = app QT += quick qml SOURCES += main.cpp RESOURCES += window.qrc ../shared/shared.qrc EXAMPLE_FILES = window.qml target.path = $$[QT_INSTALL_EXAMPLES]/quick/window INSTALLS += target ICON = resources/icon64.png // 设置ICON 图标 macx: ICON = resources/icon.icns // MAC平台额外定义图标 win32: RC_FILE = resources/window.rc
main.cpp：
#include <QtGui/QGuiApplication> // 个人比较推荐的头文件包含方式
#include <QtQml/QQmlEngine>
#include <QtQml/QQmlComponent>
#include <QtQuick/QQuickWindow>
#include <QtCore/QUrl>
#include <QDebug>
int main(int argc, char* argv[])
{
QGuiApplication app(argc, argv);
QQmlEngine engine; // 注意到在5.3以后我们大多使用QQmlApplicationEngine来加载qml文件 // 它实际也就是封装了这里QQmlEngine + QQmlComponent，并提供了一些其他的便利函数
QQmlComponent component(&engine);
QQuickWindow::setDefaultAlphaBuffer(true); // 如果我们需要应用透明窗体，需要在第一个QQuickWindow出现前设置该函数为true
component.loadUrl(QUrl("qrc:///window/window.qml"));
if ( component.isReady() )
component.create();
else
qWarning() << component.errorString();
return app.exec();
}
我们随着加载的顺序来看第一个qml文件
window.qml:
import QtQuick 2.0
import QtQuick.Window 2.1
import "../shared" as Shared
QtObject { // 非可视化的轻量顶层对象
property real defaultSpacing: 10 // 各对象间隔
property SystemPalette palette: SystemPalette { } // SystemPalette可以很方便地提供本地化的控件样式
property var controlWindow: Window { // 主窗口
width: visibilityLabel.implicitWidth * 1.2
height: col.implicitHeight + defaultSpacing * 2
color: palette.window
title: "Control Window"
Column {
id: col
anchors.fill: parent
anchors.margins: defaultSpacing
spacing: defaultSpacing
property real cellWidth: col.width / 3 - spacing // Grid 单元格宽度
Text { text: "Control the second window:" }
Grid {
id: grid
columns: 3
spacing: defaultSpacing
width: parent.width
Shared.Button { // 来自Shared 控件包的Button
id: showButton
width: col.cellWidth
text: testWindow.visible ? "Hide" : "Show"
onClicked: testWindow.visible = !testWindow.visible
}
//! [windowedCheckbox]
Shared.CheckBox { // CheckBox
text: "Windowed"
height: showButton.height
width: col.cellWidth
Binding on checked { value: testWindow.visibility === Window.Windowed } // 注意Binding是一个QML类型，而不是关键字 // 这个语句等于Binding{target: checked; value: testWindow.visibility === Window.Windowed} // 相对于checked: XXX 的属性绑定方式，这种方式更适用于var 类型的属性绑定 // 因此对于bool 型的checked 而言，checked: testWindow.visibility === Window.Windowed 也可行
onClicked: testWindow.visibility = Window.Windowed
}
//! [windowedCheckbox]
Shared.CheckBox {
height: showButton.height
width: col.cellWidth
text: "Full Screen"
Binding on checked { value: testWindow.visibility === Window.FullScreen }
onClicked: testWindow.visibility = Window.FullScreen
}
Shared.Button { // Window.AutomaticVisibility 根据所在平台调整显示方式，比如在Windows 上为窗口，Android 则为全屏
id: autoButton
width: col.cellWidth
text: "Automatic"
onClicked: testWindow.visibility = Window.AutomaticVisibility
}
Shared.CheckBox {
height: autoButton.height
text: "Minimized"
Binding on checked { value: testWindow.visibility === Window.Minimized }
onClicked: testWindow.visibility = Window.Minimized
}
Shared.CheckBox {
height: autoButton.height
text: "Maximized"
Binding on checked { value: testWindow.visibility === Window.Maximized }
onClicked: testWindow.visibility = Window.Maximized
}
}
function visibilityToString(v) { // 状态转换String 函数
switch (v) {
case Window.Windowed:
return "windowed";
case Window.Minimized:
return "minimized";
case Window.Maximized:
return "maximized";
case Window.FullScreen:
return "fullscreen";
case Window.AutomaticVisibility:
return "automatic";
case Window.Hidden:
return "hidden";
}
return "unknown";
}
Text {
id: visibilityLabel
text: "second window is " + (testWindow.visible ? "visible" : "invisible") +
" and has visibility " + parent.visibilityToString(testWindow.visibility)
}
Rectangle {
id: horizontalRule
color: "black"
width: parent.width
height: 1
}
ScreenInfo { } // 屏幕信息获取，实现代码在下方
}
} // !controlWindow
property var testWindow: Window { // 子窗口
width: 320
height: 240
color: "#215400" // 窗口背景色，但我们看到的颜色只在周围一圈，是因为中间为Rectangle，那一圈为间隔defaultSpacing
title: "Test Window with color " + color
flags: Qt.Window | Qt.WindowFullscreenButtonHint
Rectangle {
anchors.fill: parent
anchors.margins: defaultSpacing // 矩形与窗口间隔
Text {
anchors.centerIn: parent
text: "Second Window"
}
MouseArea { // 点击切换颜色
anchors.fill: parent
onClicked: testWindow.color = "#e0c31e"
}
Shared.Button {
anchors.right: parent.right
anchors.top: parent.top
anchors.margins: defaultSpacing
text: testWindow.visibility === Window.FullScreen ? "exit fullscreen" : "go fullscreen"
width: 150
onClicked: {
if (testWindow.visibility === Window.FullScreen)
testWindow.visibility = Window.AutomaticVisibility
else
testWindow.visibility = Window.FullScreen
}
}
Shared.Button {
anchors.left: parent.left
anchors.top: parent.top
anchors.margins: defaultSpacing
text: "X"
width: 30
onClicked: testWindow.visible = false // 窗口隐藏
}
}
} // !testWindow
property var splashWindow: Splash { // 启动窗口
onTimeout: controlWindow.visible = true // 自定义信号处理函数，显示主窗口
}
}
为了在QML获取屏幕信息，Qt为我们提供了Screen类型，它可以作为其他可视的QML类型的附加对象，指向该对象所显示的设备：
ScreenInfo.qml:
import QtQuick 2.1
import QtQuick.Window 2.1
Item {
id: root
width: 400
height: propertyGrid.implicitHeight + 16
function orientationToString(o) { // 状态转string 函数
switch (o) {
case Qt.PrimaryOrientation:
return "primary";
case Qt.PortraitOrientation:
return "portrait";
case Qt.LandscapeOrientation:
return "landscape";
case Qt.InvertedPortraitOrientation:
return "inverted portrait";
case Qt.InvertedLandscapeOrientation:
return "inverted landscape";
}
return "unknown";
}
Grid {
id: propertyGrid
columns: 2
spacing: 8
x: spacing
y: spacing
//! [screen]
Text {
text: "Screen \"" + Screen.name + "\":" // 显示设备名称
font.bold: true
}
Item { width: 1; height: 1 } // 设备名称右方的占位器
Text { text: "dimensions" } // 分辨率
Text { text: Screen.width + "x" + Screen.height }
Text { text: "pixel density" } // 像素密度
Text { text: Screen.pixelDensity.toFixed(2) + " dots/mm (" + (Screen.pixelDensity * 25.4).toFixed(2) + " dots/inch)" }
Text { text: "logical pixel density" } // 逻辑像素密度
Text { text: Screen.logicalPixelDensity.toFixed(2) + " dots/mm (" + (Screen.logicalPixelDensity * 25.4).toFixed(2) + " dots/inch)" }
Text { text: "available virtual desktop" } // 可用虚拟桌面，比分辨率的高度少了30 是因为Windows底下的状态栏
Text { text: Screen.desktopAvailableWidth + "x" + Screen.desktopAvailableHeight }
Text { text: "orientation" } // 屏幕方向
Text { text: orientationToString(Screen.orientation) + " (" + Screen.orientation + ")" }
Text { text: "primary orientation" } // 优先方向
Text { text: orientationToString(Screen.primaryOrientation) + " (" + Screen.primaryOrientation + ")" }
//! [screen]
}
}
最后是启动画面的实现
Splash.qml:
import QtQuick 2.0
import QtQuick.Window 2.1
//! [splash-properties]
Window {
id: splash
color: "transparent"
title: "Splash Window"
modality: Qt.ApplicationModal // 应用窗口模式
flags: Qt.SplashScreen // 启动画面
property int timeoutInterval: 2000
signal timeout // 自定义溢出信号
//! [splash-properties]
//! [screen-properties]
x: (Screen.width - splashImage.width) / 2 // 居中
y: (Screen.height - splashImage.height) / 2
//! [screen-properties]
width: splashImage.width // 窗口大小与图片大小一致
height: splashImage.height
Image {
id: splashImage
source: "../shared/images/qt-logo.png"
MouseArea {
anchors.fill: parent
onClicked: Qt.quit() // 点击退出
}
}
//! [timer]
Timer {
interval: timeoutInterval; running: true; repeat: false
onTriggered: {
visible = false // 2秒后隐藏，并发出timeout信号，以显示主窗口
splash.timeout()
}
}
//! [timer]
Component.onCompleted: visible = true
}
Qt5官方demo解析集33——Qt Quick Examples - Window and Screen
原文：http://blog.csdn.net/cloud_castle/article/details/39291069