如何在 Python 和 QML 之间引用自定义角色索引

Question

我正在 python 中的 class 中实现 QAbstractListModel 以用于 QML。我在模型中定义了两个自定义角色。在模型中，我还实现了一个插槽函数 'get' 到来自指定索引和角色的 return 数据。当我将角色传回 'get' 函数时，我收到一个与我在模型中为角色定义的整数不同的整数。

我尝试将角色和索引从 QML 传回我的模型中定义的 'get' 函数。索引按预期工作，但角色 return 值与我在模型中定义的值不同。

gui.py

main()

def main():
    # create the application instance
    app = QApplication(sys.argv)
    # create a QML engine
    engine = PoaGUI()

    # instantiate Route class
    # route = Route()

    # add example routes for routemodel
    routelist = [
        {'stringinput' : 'Route 1', 'selected' : True},
        {'stringinput' : 'Route 2', 'selected' : False},
        {'stringinput' : 'Route 3', 'selected' : True},
        {'stringinput' : 'Route 4', 'selected' : False}
    ]

    # instantiate ListModel class
    routemodel = ListModel(routelist)

    # register the python type bindings to QML engine
    engine.rootContext().setContextProperty('RouteModel', routemodel)

    # load main QML file and start app engine
    engine.load('view.qml')

    if not engine.rootObjects():
        sys.exit(-1)

    sys.exit(app.exec_())

QAbstractListModel

class ListModel(QAbstractListModel):

    # create new user roles as class variables
    StringInput = Qt.UserRole + 0
    Selected = Qt.UserRole + 1
    # ADD USERROLE FOR SELECTED TO COMPLETE

    def __init__(self, datain=[], parent=None):
        super().__init__(parent)

        self._list = datain

    def rowCount(self, parent=QModelIndex()):

        return len(self._list)

    def data(self, index=QModelIndex, role=Qt.DisplayRole):

        #store QModelIndex passed to data
        row = index.row()

        if index.isValid() and role == self.StringInput:
            return self._list[row]['stringinput']
        if index.isValid() and role == self.Selected:
            return self._list[row]['selected']
        else:
            return None

    def roleNames(self):

        return {
            self.StringInput: b'stringinput',
            self.Selected: b'selected'
        }

    @Slot(int, int, result='QVariant')
    def get(self, row, role):
        # show difference between role supplied 
        # from QML vs definition in model
        print(role)
        print('Selected: ' + str(self.Selected))
        print('StringInput: ' + str(self.StringInput))
        if role == self.StringInput:
            print('stringinput')
            return self._list[row]['stringinput']
        elif role == self.Selected:
            print('selected')
            return self._list[row]['selected']
        else:
            return None


    @Slot(int, bool)
    def modSelected(self, row, selval):
        # set index of the row changes
        ix = self.index(row, 0)
        self._list[row]['selected'] = selval
        # communicate that changes were made
        self.dataChanged.emit(ix, ix, self.roleNames())

view.qml

ListView 实现

CustomComp.CustomList {
       id: routelist
       model: RouteModel
       keyNavigationWraps: true

       listwidth: 300
       listheight: 600
       delegate: CustomComp.SingleListDelegate {}

       Layout.alignment: Qt.AlignCenter
    }

ListView 的委托

import QtQuick 2.12
import QtQuick.Controls 2.12

Rectangle {
    id: singleItemList

    property int delegateIndex: index
    property bool altcolor: false
    property string altcolorcode: "#242526"
    property string highlightcolorcode: "#242526"

    width: parent.width; height: 20
    color: (singleItemList.altcolor) ? ((index % 2 == 0) ? altcolorcode:"#000000") : "#000000"
    border.color: "#ffcc00"

    Text {
        id: listText
        anchors.verticalCenter: parent.verticalCenter
        anchors.horizontalCenter: parent.horizontalCenter
        font.pixelSize: 14
        color: "#ffcc00"
        // delegate directly uses provided string
        text: stringinput
    }

    MouseArea {
        id: mousearea

        anchors.fill: parent
        onClicked: {
            singleItemList.ListView.view.currentIndex = index
            console.log(singleItemList.ListView.view.currentIndex)
            singleItemList.delegateSelect()
        }
    }

    function delegateSelect() {
        if (singleItemList.ListView.view.model.get(index, selected)) {
            singleItemList.color = "#000000"
            singleItemList.ListView.view.model.modSelected(index, false)
            // singleItemList.ListView.view.model.set(index, {"selected": false})
        }
        else {
            singleItemList.color = highlightcolorcode
            singleItemList.ListView.view.model.modSelected(index, true)
            // singleItemList.ListView.view.model.set(index, {"selected": true})
        }
        // console.log(singleItemList.ListView.view.model.get(index, selected))
    }
}

有两个自定义角色，当我将一个角色从 QML 传递回我的模型时，我收到 0 和 1 顺序的整数。我使用 Qt.UserRole 为我生成的模型定义我的角色编号在 Python。因此，我的模型中定义的那些角色的整数是 256 和 257。QML 似乎可以很好地处理模型，因为当我将模型提供给 ListView 并在委托中引用我的自定义角色之一以显示为文本时，列表会填充正如预期的那样。为什么我的两个自定义角色的整数在 Python 中与在 QML 中不同？既然如此，我如何才能成功 return 那些角色供我的模型中的另一个函数使用？

我的最终目标是在 QML ListView 中创建类似于 'get' 和 'set' 的函数，但这样做是为了我在 Python.[=15 中构建的模型=]

Answer 1

您有一个 XY problem，您的真正目标是从 QML 编辑模型值。因此，解决方案是实施 setData() 方法并使用 selected = foo_value 编辑数据，在您的特定情况下：selected != selected

TL；DR；

你对“selected”的概念有误解，QML中的“selected”是与Selected角色关联的模型的值，就是这个意思：

def roleNames(self):
    return {
        ListModel.StringInput: b"stringinput",
        ListModel.Selected: b"selected",
    }

即QML中选择的不是角色而是角色与索引关联的值，即相当于：

selected = model.data(index, ListModel.Selected)

因此你得到 1 和 0，它们分别是布尔值 true 和 false 的转换。

这样做是为了对角色进行抽象。

所以当你使用下面的时候你就明白了：

QML code               Python Code
foo_value = selected ~ foo_value = model.data(index, ListModel.Selected)

但是当你使用：

QML code               Python Code
selected = foo_value ~ model.setData(index, foo_value, ListModel.Selected)

解决方案

所以在你的情况下，解决方案是：

class ListModel(QAbstractListModel):

    StringInput = Qt.UserRole + 0
    Selected = Qt.UserRole + 1

    def __init__(self, datain=[], parent=None):
        super().__init__(parent)
        self._list = datain

    def rowCount(self, parent=QModelIndex()):
        return len(self._list)

    def data(self, index, role=Qt.DisplayRole):
        if not index.isValid():
            return QVariant()
        row = index.row()
        if 0 <= row < self.rowCount():
            if role == ListModel.StringInput:
                return self._list[row]["stringinput"]
            elif role == ListModel.Selected:
                return self._list[row]["selected"]
        return QVariant()

    def setData(self, index, value, role=Qt.EditRole):
        if not index.isValid():
            return False
        row = index.row()
        result = False
        if 0 <= row < self.rowCount():
            if role == ListModel.StringInput:
                self._list[row]["stringinput"] = value
                result = True
            elif role == ListModel.Selected:
                self._list[row]["selected"] = value
                result = True
        if result:
            self.dataChanged.emit(index, index, (role,))
        return result

    def roleNames(self):
        return {
            ListModel.StringInput: b"stringinput",
            ListModel.Selected: b"selected",
        }

SingleListDelegate.qml

import QtQuick 2.12
import QtQuick.Controls 2.12

Rectangle {
    id: singleItemList

    property int delegateIndex: index
    property color highlightcolor: "#242526"
    property color defaultcolor : "#000000"
    width: parent.width; height: 20
    color: selected ? highlightcolor : defaultcolor
    border.color: "#ffcc00"

    Text {
        id: listText
        anchors.verticalCenter: parent.verticalCenter
        anchors.horizontalCenter: parent.horizontalCenter
        font.pixelSize: 14
        color: "#ffcc00"
        text: stringinput
    }

    MouseArea {
        id: mousearea
        anchors.fill: parent
        onClicked: {
            singleItemList.ListView.view.currentIndex = index
            console.log(singleItemList.ListView.view.currentIndex)
            // invert the boolean
            selected = !selected
        }
    }
}

如何在 Python 和 QML 之间引用自定义角色索引

How to reference custom role indices between Python and QML

python

qml

python-3.x

pyside2

TL；DR；

解决方案