我想将 QObject 的一个信号连接到由“Loader”qml 元素加载的各个页面。我的问题类似 Dead QML elements receiving signals?但加载的项目在调用“onDestruction”方法之前被销毁。
例如下面,如果在控制台中从 page1 切换到 page2 写:
"QML: Loading status: 1 Item: QDeclarativeRectangle(0x8dcd408, "page2")
QML Item: Loaded QDeclarativeRectangle(0x8dcd408, "page2") 1
qrc:/page1.qml:12: TypeError: Result of expression 'parent' [null] is not an object.
qrc:/page1.qml:15: ReferenceError: Can't find variable: page1text"
每一秒。所以不能断开信号,因为父对象被破坏了。
如何处理加载项中来自 QObject(根)的信号?或如何从卸载页面断开信号?
主文件
import QtQuick 1.1
Rectangle {
id: root
objectName: "root"
width: 360
height: 360
state: "page1"
color: "white"
Item {
width: parent.width
height: parent.height/2
anchors.top: parent.top
Loader {
id: pageLoader
objectName: "pageLoader"
anchors.fill: parent
anchors.centerIn: parent
signal textMsg(variant params)
onStatusChanged: console.log("QML: Loading status: ", status, " Item: ", item)
onLoaded: { console.log("QML Item: Loaded",item,status); }
}
}
states: [
State {
name: "page1"
PropertyChanges { target: pageLoader; source: "qrc:/page1.qml"}
}
,State {
name: "page2"
PropertyChanges { target: pageLoader; source: "qrc:/page2.qml"}
}
]
Timer {
// simulate signals from QObject
interval: 1000; running: true; repeat: true
onTriggered: pageLoader.textMsg({"msg2page1":"test","msg2page2":"test"})
}
Rectangle {
anchors.left: parent.left
anchors.bottom: parent.bottom
width: parent.width/2
height: parent.height/2
border {
color: "black"
width: 1
}
color: "yellow"
Text{
anchors.fill: parent
anchors.centerIn: parent
text: "Set Page 1"
}
MouseArea {
anchors.fill: parent
onClicked: {
root.state = "page1";
}
}
}
Rectangle {
anchors.right: parent.right
anchors.bottom: parent.bottom
width: parent.width/2
height: parent.height/2
border {
color: "black"
width: 1
}
color: "red"
Text{
anchors.fill: parent
anchors.centerIn: parent
text: "Set Page 2"
}
MouseArea {
anchors.fill: parent
onClicked: {
root.state = "page2";
}
}
}
}
页面1.qml
import QtQuick 1.1
Rectangle {
id: page1
objectName: "page1"
color: "yellow"
Component.onCompleted: {
parent.textMsg.connect(msgHandler);
}
Component.onDestruction: {
parent.textMsg.disconnect(msgHandler);
}
function msgHandler(params) {
page1text.text += " "+params.msg2page1;
}
Text {
id: page1text
anchors.fill: parent
wrapMode: Text.WordWrap
text: "page1"
}
}
页面2.qml
import QtQuick 1.1
Rectangle {
id: page2
objectName: "page2"
color: "red"
}
最佳答案
这在 Loader
中有很好的描述documenation .它写道:
Any signals emitted from the loaded item can be received using the Connections element.
还有一个例子,为了清楚起见,我复制在下面:
// Application.qml
import QtQuick 1.0
Item {
width: 100; height: 100
Loader {
id: myLoader
source: "MyItem.qml"
}
Connections {
target: myLoader.item
onMessage: console.log(msg)
}
}
// MyItem.qml
import QtQuick 1.0
Rectangle {
id: myItem
signal message(string msg)
width: 100; height: 100
MouseArea {
anchors.fill: parent
onClicked: myItem.message("clicked!")
}
}
显然,如果
item
被销毁,任何信号处理程序都将被忽略,直到再次重新创建目标。
关于qt - 如何在 Loader 的项目中正确连接信号?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/34207430/