这个qml资料，为什么state下的onclicked，没有触发呢

这个qml文件，为什么state下的onclicked，没有触发呢？
这个qml，为什么state下onclicked，没有触发呢？

C/C++ code

import QtQuick 1.1Rectangle{    id:mainRec    width: 400    height: 400    Rectangle    {        id:topleftRec        width: 150        height: 150        anchors{left: parent.left;top: parent.top;leftMargin: 30;topMargin: 30;}        color: "red"        focus:true        MouseArea { anchors.fill: topleftRec; onClicked: topleftRec.state = '' }    }    Rectangle    {        id:toprightRec        width: 150        height: 150        anchors{right: parent.right;top: parent.top;rightMargin: 30;topMargin: 30;}        color: "blue"        MouseArea { anchors.fill: toprightRec; onClicked: toprightRec.state = 'topright' }    }    Rectangle    {        id:bottomleftRec        width: 150        height: 150        anchors{left: parent.left;bottom: parent.bottom;leftMargin: 30;bottomMargin: 30;}        color: "green"        MouseArea { anchors.fill: bottomleftRec; onClicked: bottomleftRec.state = 'bottomleft' }    }    Rectangle    {        id:bottomrightRec        width: 150        height: 150        anchors{right: parent.right;bottom: parent.bottom;rightMargin: 30;bottomMargin: 30;}        color: "yellow"        MouseArea { anchors.fill: bottomrightRec; onClicked: bottomrightRec.state = 'bottomright' }    }   states:    [        state        {            id:topleft            //name: "topleft"            PropertyChanges { target: topleftRec;color:"black" }        },        state        {            name: "topright"            PropertyChanges { target: toprightRec;color:"black" }        },        state        {            name: "bottomleft"            PropertyChanges { target: bottomleftRec;color:"black" }        },        state        {            name: "bottomright"            PropertyChanges { target: bottomrightRec;color:"black" }        }    ]}