Qt QML ListView contentHeight行为

Question

导入QtQuick 1.1（对于>=Qt 4.7.4)

下面是一个独立的用例来演示我的问题：

import QtQuick 2.2

Rectangle {
    width: 800
    height: 800
    color: "black"

    property int pageNumber: 1
    property int totalPages: Math.ceil(animalListView.contentHeight/animalListView.height)

    Text {
        x: 2
        y: 90
        color: "Orange"
        text: "Expected height: " + (animalListView.count*70 + (50*10))
        font.pixelSize: 28
    }

    Text {
        x: 2
        y: 0
        color: "Orange"
        text: "Actual ContentHeight: " + animalListView.contentHeight
        font.pixelSize: 28
    }

    Text {
        x: 2
        y: 30
        color: "Orange"
        text: "Actual ChildrenRectHeight: " + animalListView.childrenRect.height
        font.pixelSize: 28
    }

    Text {
        x: 2
        y: 60
        color: "Orange"
        text: "Total model items (minus sections): " + animalListView.count
        font.pixelSize: 28
    }

    Rectangle {
        id: boundingRect
        width: 640
        height: 500
        x: 20
        y: 200
        radius: 10
        border.width: 1
        border.color: "green"
        color: "transparent"

        // The delegate for each section header
        Component {
            id: sectionHeaderDelegate
            Rectangle {
                width: parent.width
                height: 50 // this is the problem                
                color: "transparent"                

                Text {
                    anchors.left: parent.left
                    id: headerText
                    text: section
                    color: "red"
                }

                Rectangle {
                    anchors.fill: parent
                    border.color: "purple"                    
                    border.width: 1    
                    color: "transparent"
                }
            }
        }

        ListModel {
             id: animalsModel
             ListElement { name: "1Parrot"; size: "Small" }
             ListElement { name: "2Guinea pig"; size: "Small" }
             ListElement { name: "3Dog"; size: "Medium" }
             ListElement { name: "4Cat"; size: "Medium" }
             ListElement { name: "5Elephant"; size: "Medium" }
             ListElement { name: "6Parrot"; size: "Small" }
             ListElement { name: "7Guinea pig"; size: "Small" }
             ListElement { name: "8Dog"; size: "Medium" }
             ListElement { name: "9Cat"; size: "Medium" }
             ListElement { name: "10Elephant"; size: "Large" }
             ListElement { name: "11Parrot"; size: "Large" }
             ListElement { name: "12Guinea pig"; size: "Large" }
             ListElement { name: "13Dog"; size: "Large" }
             ListElement { name: "14Cat"; size: "Medium" }
             ListElement { name: "15Elephant"; size: "Large" }
             ListElement { name: "16Parrot"; size: "Small" }
             ListElement { name: "17Guinea pig"; size: "Small" }
             ListElement { name: "18Dog"; size: "Medium" }
             ListElement { name: "19Cat"; size: "Medium" }
             ListElement { name: "20Elephant"; size: "Large" }
        }

        ListView {
            id: animalListView
            anchors.fill: parent
            anchors.margins: 10
            clip: true
            interactive: true
            flickableDirection: Flickable.VerticalFlick
            boundsBehavior: Flickable.StopAtBounds
            model: animalsModel

            delegate: Item {
                width: parent.width
                height: 70
                    Text {
                        text: name
                        color: "green"
                    }

                    Rectangle {
                        anchors.fill: parent
                        border.color: "yellow"                    
                        border.width: 1    
                        color: "transparent"
                    }
                }

            section.property: "size"
            section.criteria: ViewSection.FullString
            section.delegate: sectionHeaderDelegate
        }
    }

    Rectangle {
        anchors.top: boundingRect.top
        anchors.left: boundingRect.right
        anchors.leftMargin: 20        
        width: 40
        height: 40
        color: "blue"

         MouseArea {
             anchors.fill: parent
             onClicked: {
                if (pageNumber > 1) {
                    animalListView.contentY -= animalListView.height;
                    animalListView.returnToBounds();
                    --pageNumber;
                }             
             }
         }

        enabled: (!animalListView.atYBeginning)
        visible: !(animalListView.atYBeginning && animalListView.atYEnd)

        Text {
            anchors.centerIn: parent
            font.family: "Wingdings 3"
            font.pixelSize: 40
            text: "Ç" // Up arrow
        }
    }

    Text {
        visible: totalPages > 1
        anchors.left: boundingRect.right
        anchors.verticalCenter: boundingRect.verticalCenter
        width: 100
        height: 20
        font.pixelSize: 18
        horizontalAlignment: Text.AlignHCenter
        color: "red"
        text: qsTr("%1 of %2").arg(pageNumber).arg(totalPages)
    }

    Rectangle {
        anchors.bottom: boundingRect.bottom
        anchors.left: boundingRect.right
        anchors.leftMargin: 20
        width: 40
        height: 40
        color: "orange"

         MouseArea {
             anchors.fill: parent
             onClicked: {
                if (pageNumber < totalPages) {
                    animalListView.contentY += animalListView.height;
                    ++pageNumber;
                }
             }
         }

        enabled: (!animalListView.atYEnd)
        visible: !(animalListView.atYBeginning && animalListView.atYEnd)

        Text {
            anchors.centerIn: parent
            font.family: "Wingdings 3"
            font.pixelSize: 40
            text: "È" // Down arrow
        }
    }

}

我正在使用ListView来显示动物模型的列表，按它们的大小分类。为了在视图中实现这种分类，我使用了上面代码中实现的ListView的Section.Property、Section.Critiria和Section.Delegate属性。

所以我的问题是，为什么QML ListView元素的contentHeight在且仅当我使用高度设置为非零值的节委托时才会动态更改？

另外，为了测试目的，我在ListView中保留了以下属性，ListView应该与向上/向下箭头一起使用：

          interactive: true
          flickableDirection: Flickable.VerticalFlick
          boundsBehavior: Flickable.StopAtBounds

Answer 1

我知道这是古老的，但无论如何我会在这里回答它，因为我正在寻找一个解决方案；

如果您的物品有固定的高度，您可以通过简单地通过公式设置值来动态设置容器的高度：

MyContainerWithListItems {
height: MyModel.items.length * height
}

如果你有可变高度的项目，这将更加困难；解决方案可能是让onChange事件触发一个函数，该函数在您的项目中爬行，并手动添加高度。