QML設置窗口背景

import QtQuick 2.4  
import QtQuick.Controls 1.3  
import QtQuick.Window 2.2  
import QtQuick.Dialogs 1.2  

ApplicationWindow {  
    title: qsTr("Hello World")  
    width: 640  
    height: 480  
    visible: true  

    Image {  
        id: rocket  
        fillMode: Image.TileHorizontally  
        smooth: true  
        source: 'images/background.png'  
    }  

    menuBar: MenuBar {  
        Menu {  
            title: qsTr("&File")  
            MenuItem {  
                text: qsTr("&Open")  
                onTriggered: messageDialog.show(qsTr("Open action triggered"));  
            }  
            MenuItem {  
                text: qsTr("E&xit")  
                onTriggered: Qt.quit();  
            }  
        }  
    }  

    MainForm {  
        anchors.fill: parent  
        button1.onClicked: messageDialog.show(qsTr("Button 1 pressed"))  
        button2.onClicked: messageDialog.show(qsTr("Button 2 pressed"))  
        button3.onClicked: messageDialog.show(qsTr("Button 3 pressed"))  
    }  

    MessageDialog {  
        id: messageDialog  
        title: qsTr("May I have your attention, please?")  

        function show(caption) {  
            messageDialog.text = caption;  
            messageDialog.open();  
        }  
    }  
}