qml 暴露子组件信号

// Button.qml
import QtQuick 2.0

Rectangle{
    width: 200
    height: 30
    signal clicked
    MouseArea{
        anchors.fill: parent
        onClicked: parent.clicked()
    }
}

// main.qml
import QtQuick 2.12
import QtQuick.Window 2.12

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")
    Button{
        anchors.fill: parent
        color: "red"
        onClicked: {
            color = color == "#ff0000" ? "blue" : "red"
        }
    }
}