qml性能优化-信号槽

目录信号槽性能隐患1对多问题点解决问题耗时操作分段处理多线程处理耗时操作信号槽性能隐患页面开发中信号槽连接是必不可少的如果我们不严谨的使用槽函数执行耗时太长就会产生页面卡顿掉帧长时间无响应等严重问题建议是在16ms以内而信号槽的连接方式是可以有1对1连接1对多连接都不建议执行时间过长1对多问题点qml开发中不同的页面使用的同一个信号进行绑定也就是我所说的1对多的情况触发信号触发了两次槽函数有两个连接那肯定是这样的但是不显示的页面槽函数也参与了计算计算量小的时候还能接受但是一旦计算量很大就会很耗时了页面就会表现为卡顿延迟掉帧长时间无响应View.qmlimportQtQuick2.12importQtQuick.Controls2.12Item{id:control property string text:Connections{target:MObject onCallSignal:{var dateTimeDate.now()var strcontrol.text dateTime.toString();console.log(str)label.textstr}}Label{id:label anchors.centerIn:parent}}main.qmlimportQtQuick2.12importQtQuick.Controls2.12importQtQuick.Layouts1.12importQtQuick.Window2.12Window{visible:truewidth:640height:480title:qsTr(Hello World)ColumnLayout{anchors.fill:parent Row{Button{text:qsTr(页面1)onClicked:{stackLayout.currentIndex0}}Button{text:qsTr(页面2)onClicked:{stackLayout.currentIndex1}}Button{text:qsTr(发送信号)onClicked:{MObject.callSignal();}}}StackLayout{id:stackLayout Layout.fillWidth:trueLayout.fillHeight:trueView{text:qsTr(页面1)}View{text:qsTr(页面2)}}}}解决问题如果是qwidget开发进入页面时候执行connect离开页面的时候执行disconnect进行解绑而qml开发就简单多了qml提供的连接信号槽组件Connections提供了enabledimportQtQuick2.12importQtQuick.Controls2.12Item{id:control property string text:Connections{target:MObject enabled:control.visible onCallSignal:{var dateTimeDate.now()var strcontrol.text dateTime.toString();console.log(str)label.textstr}}Label{id:label anchors.centerIn:parent}}耗时操作分段处理往有时候槽函数是很耗时的比如我们所谓的导入导出文件列表导出文件列表很长的时候就会很耗时了我们可以通过Timer进行分段处理importQtQuick2.0Item{id:worker propertyint_index:0propertyint_chunkSize:500// 每帧处理的数量按实测调整propertyboolrunning:falsepropertyinttotalCount:10000000Timer{id:timer interval:1000// 0ms 下一事件循环立即触发repeat:trueonTriggered:doChunk()}functionstart(){_index0runningtruetimer.start()}functiondoChunk(){var endMath.min(_index_chunkSize,totalCount)for(;_indexend;_index){//processOne(_index)console.log(_index)}if(_indextotalCount){timer.stop()runningfalsefinished()// 完成信号}else{var progress_index/totalCount}}signalfinished()signalprogressChanged(real progress)}多线程处理耗时操作我们可以使用QThread对耗时操作进行处理#includemobject.h#includeQDebug#includeQThreadMObject::MObject(QObject*parent):QObject(parent){// m_conn1 connect(this,SIGNAL(callSignal()),this,SLOT(sayHello()));// connect(this,SIGNAL(callSignal()),this,SLOT(sayHello()));// connect(this,SIGNAL(callSignal()),this,SLOT(sayHello()));QThread*workerThreadnewQThread;m_workernewWorker;m_worker-moveToThread(workerThread);connect(this,MObject::destroyed,workerThread,QThread::quit);connect(workerThread,QThread::finished,m_worker,Worker::deleteLater);connect(m_worker,Worker::destroyed,workerThread,QThread::deleteLater);connect(this,MObject::importFiles,m_worker,Worker::importFiles);workerThread-start();}