Pause application in QML when app is in background Symbian

问题

I want to know of any pure QML way to find out whether the application is in the background or not and then accordingly stop or play music. In meego the alternate way to do is through the PlatformWindow Element but it does not exist in Symbian QML. Help needed please

回答1:

Finally I got it working :) and i did it though Qt way... here are the steps

1) Create a class MyEventFilter

class myEventFilter : public QObject
{

bool eventFilter(QObject *obj, QEvent *event) {
    switch(event->type()) {
    case QEvent::WindowActivate:
        emit qmlvisiblechange(true);
        qDebug() << "Window activated";

        bis_foreground=true;
        return true;
    case QEvent::WindowDeactivate:
        emit qmlvisiblechange(false);
        qDebug() << "Window deactivated";

        bis_foreground=false;
        return true;
    default:
    return false;
    }
}


 void dosomething();

private:
   int something;
public:
   bool bis_foreground;
      Q_OBJECT
 public slots:
   Q_INVOKABLE QString checkvisibility() {
       if (bis_foreground==true) return "true";
       else return "false";
   }
signals:
    void qmlvisiblechange(bool is_foreground);

}; 

2) Then in main.cpp include this file include the class and add setContext propery like this

context->setContextProperty("myqmlobject", &ef);

3) in qml file call it like this:

 Item {
    id: name
    Connections
    {
        target:myqmlobject
        onQmlvisiblechange:
        {


            if(is_foreground)
            {
              //dont do anything...
            }
            else
            {


                playSound.stop()
            }
        }
    }
}

Enjoy :)

回答2:

Why do you need a pure QML way?

You can detect if an application has been sent to the background by installing an event filter. Check: http://www.developer.nokia.com/Community/Wiki/Detecting_when_a_Qt_application_has_been_switched_to_the_background_and_when_resumed

For a "pure" QML way, there is the Symbian QML element: http://doc.qt.nokia.com/qt-components-symbian/qml-symbian.html

It has a foreground property that indicates whether the app is in the foreground or in the background. You can try connecting to onForegroundChanged.

From the documentation, the Symbian element is not "creatable". It exists as a context property named symbian. So a sample usage would be:

import QtQuick 1.1
import com.nokia.symbian 1.1

    PageStackWindow {
        id: window
        initialPage: MainPage {tools: toolBarLayout}
        showStatusBar: true
        showToolBar: true

        function appForegroundChanged() {
             console.log("Foreground: " + symbian.foreground)
         }
        function appCurrentTimeChanged() {
             console.log("Current time: " + symbian.currentTime)
         }
        Component.onCompleted: {
            symbian.currentTimeChanged.connect(appCurrentTimeChanged)
            symbian.foregroundChanged.connect(appForegroundChanged)
        }

        ToolBarLayout {


      id: toolBarLayout
        ToolButton {
            flat: true
            iconSource: "toolbar-back"
            onClicked: window.pageStack.depth <= 1 ? Qt.quit() : window.pageStack.pop()
        }
    }
}

来源：https://stackoverflow.com/questions/10752489/pause-application-in-qml-when-app-is-in-background-symbian