How to include child mouse hover events in the parent MouseArea using QML?

I want to implement the following scenario in QML.

Here is a sample/simplified delegate for ListView element:

Component {
    Item {
         id: container
         MouseArea {
         anchors.fill: parent
         hoverEnabled: true

         onClicked: {
             container.ListView.view.currentIndex = index
             container.forceActiveFocus();
         }
         onEntered: {
             actionList.state = "SHOW";
             myItem.state = "HOVER"
         }
         onExited: {
             actionList.state = "HIDE";
             myItem.state = "NORMAL"
         }
         Rectangle {
             id: myItem
             color: "gray"
             anchors.fill: parent
             Row {
                 id: actionList
                 spacing: 5; anchors.fill: parent
                 Image {
                     id: helpAction
                     source: ""    //Some image address
                     width: 16; height: 16; fillMode: Image.PreserveAspectFit
                     states: [
                         State {
                             name: "NORMAL"
                             PropertyChanges { target: helpAction; opacity: 0.7 }
                         },
                         State {
                             name: "HOVER"
                             PropertyChanges { target: helpAction; opacity: 1.0 }
                         }
                     ]
                     MouseArea {
                         hoverEnabled: true
                         anchors.fill: parent

                         onEntered: {
                             parent.state = "HOVER";
                         }
                         onExited: {
                             parent.state = "NORMAL";
                         }
                     }
                     states: [
                         State {
                             name: "SHOW"
                             PropertyChanges { target: actionList; visible: false }
                         },
                         State {
                             name: "HIDE"
                             PropertyChanges { target: actionList; visible: true }
                         }
                     ]
                 }

                 //Other action buttons...

                 states: [
                     // `NORMAL` and `HOVER` states definition here...
                 ]
             }
         }
    }
}

But I have a problem with MouseArea. Inner MouseArea (actionButton) does not work properly for entered event. When mouse enters on action button, outer MouseArea fires exited event.

Is there any mistake in my code? More generally, how can I implement such a scenario in QML?

Answers


I was faced by this same problem, and came across the answer in the QtQuick 5.0 documentation for MouseArea. The answer to this is actually quite simple.

If you want to include child mouse hover events in your parent MouseArea, make you child MouseArea a child of the parent MouseArea:

MouseArea {
    id: parent

    MouseArea {
        id: child
    }
}

Since I have a custom Widget type that would be used as the parent view, I ended up with the default property being the children of the MouseArea:

Item {
    default property alias children: mouseArea.data

    MouseArea {
        id: mouseArea
    }
}

make states for each state of the elements in the View then you can use things like if statements or case statements to change these properties In Other words, Try not to set your elements up to work on MouseArea but on properties And set the Elements properties to work on the set properties I hope that this helps if not here is example:

EDIT I added the color to be transparent. if there is no mouse what so ever. If I was using a Image I would use opacity then add a bunch of Behaviors also But this is a working

example

import QtQuick 2.0
Rectangle {
    width: 360
    height: 360
    property string state1:"OutMouse"
    property string state2: "OutMouse"
    property string state3: "OutMouse"
    property string state4: "OutMouse"
    Rectangle{
        id:blueRec
        width: parent.width
        height: parent.height / 6
        color: state1 === "InMouse" ? "blue" : "green"
        MouseArea{
            anchors.fill: blueRec
            hoverEnabled: true
            onEntered: state1 = "InMouse"
            onExited: {
                if (state1 === state2 || state3 || state4){
                    state1 = "InMouse"
                }
                if(state1 !== state2 || state3 || state4)
                {
                    state1 = "OutMouse"
                }
            }
        }
        Text {
            text: state1=== "InMouse"? qsTr("foo") :"bar"
            anchors.centerIn: blueRec
        }
        Row{
            width: parent.width
            height: parent.height / 4

            spacing: 2
            anchors{
                left: parent.left
                verticalCenter:  blueRec.verticalCenter
                leftMargin: blueRec.width / 12
            }
            Rectangle{
                id: rec1
                height: parent.height;
                width: height
                color: {
                    if  ( state3 === "InMouse")
                        return "gray"
                    if (state1 === "OutMouse")
                        return "transparent"
                    else
                        return "white"}
                MouseArea{
                    id: rec1M
                    anchors.fill: parent
                    hoverEnabled: true
                    onEntered:{
                        state1 = "InMouse"
                        state2 = "InMouse"
                    }
                    onExited: state2 = "OutMouse"
                }
            }

            Rectangle{
                id: rec2
                height: parent.height ;
                width: height
                color: {
                    if  (state3 === "InMouse")
                        return "gray"
                    if (state1 === "OutMouse")
                        return "transparent"
                    else
                        return "white"
                }
                MouseArea{
                    id: rec2M
                    anchors.fill: parent
                    hoverEnabled: true
                    onEntered:{
                        state1 = "InMouse"
                        state3 = "InMouse"
                    }
                    onExited: state3 = "OutMouse"
                }
            }

            Rectangle{
                id: rec3
                height: parent.height;
                width: height
                color:{
                    if  (state4 === "InMouse")
                        return "gray"
                    if (state1 === "OutMouse")
                        return "transparent"
                    else
                        return "white"
                }
                MouseArea{
                    id:  rec3M
                    anchors.fill: parent
                    hoverEnabled: true
                    onEntered:{
                        state4 = "InMouse"
                        state1 = "InMouse"
                    }
                    onExited: state4 = "OutMouse"
                }
            }
        }
    }
}

Iv'e tried a few things but it does not seem possible to hover over two MouseArea simultaneously. The preventStealing and propagateComposedEvents seem to only work when you have a click event. But from the inner MouseArea you can trigger the entered() signal of the other one. Something like this:

import QtQuick 2.1

Rectangle {
    width: 500
    height: 500

    Rectangle {
        width:300
        height: 300
        color: "red"

        MouseArea {
            id: big
            anchors.fill: parent
            hoverEnabled:true
            onEntered: {
                console.log("ENTERED BIG mousearea");
            }
            onExited: {
                console.log("EXITED BIG mousearea");
            }
        }

        Rectangle {
            anchors.centerIn: parent
            height: 100
            width: 100
            color: "green"

            MouseArea {
                anchors.fill: parent
                hoverEnabled:true
                onEntered: {
                    console.log("ENTERED small mousearea");
                    big.entered();
                }
                onExited: {
                    console.log("EXITED small mousearea");
                    big.exited();
                }
            }
        }
    }
}

The issue is that the exited() signal from the containing MouseArea will be called before calling the entered() back again. So you might need to "delay" the change of state in exited() just to make sure you really want to hide your action buttons. Another solution would be to save the current mouse position and hide the buttons ONLY if exited() is called with the mouse on one of its border.


Try this:

  • add a signal to the inner area that's emitted on mouse enter.
  • Connect the signal to the outer area.
  • The signal causes the outer area to enter the hovered state.

Mouse exit on both will still cancel hover state. As you move the mouse off the controls it should work correctly without any extra code


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