///////////////////// main.qml -- call with qmlscene
import QtQuick 2.0

Rectangle
{
    id: main; width: 800; height: 480;
    color: "black";

    Rectangle {
        x: 100;
        y: 200;
        width: 200;
        height: 200;
        color: "red";

        MouseArea {
            enabled: true;
            anchors.fill: parent;
            onClicked: {
                if(blue_rect.opacity == 0) {
                    blue_rect.opacity = 1.0;
                }
                else {
                    blue_rect.opacity = 0.0;
                }
            }
        }
    }

    Rectangle {
        id: blue_rect;
        x: 400;
        y: 200;
        width: 200;
        height: 200;
        color: "blue";

        Behavior on opacity { FadeAnimation{} }
    }
}


////////////////////////////////// FadeAnimation.qml -- put in same folder as main.qml
import QtQuick 2.0

NumberAnimation { duration: 200; easing.type: Easing.InOutQuad; }