Qt for python with Qt Quick QML: TreeView Example

Question

I'm trying to get a QT Quick TreeView to display data from a QAbstractItemModel.

Here's my QAbstractItemModel class

from PySide2.QtCore import Qt, QAbstractItemModel, QModelIndex

class TreeItem(object):
    def __init__(self, data, parent=None):
        self.parentItem = parent
        self.itemData = data
        self.childItems = []

    def appendChild(self, item):
        self.childItems.append(item)

    def child(self, row):
        return self.childItems[row]

    def childCount(self):
        return len(self.childItems)

    def columnCount(self):
        return len(self.itemData)

    def data(self, column):
        try:
            return self.itemData[column]
        except IndexError:
            return None

    def parent(self):
        return self.parentItem

    def row(self):
        if self.parentItem:
            return self.parentItem.childItems.index(self)

        return 0


class TreeModel(QAbstractItemModel):
    def __init__(self, header, data, parent=None):
        super(TreeModel, self).__init__(parent)

        self.rootItem = TreeItem(header)
        self.setupModelData(data.split('\n'), self.rootItem)

    def columnCount(self, parent):
        if parent.isValid():
            return parent.internalPointer().columnCount()
        else:
            return self.rootItem.columnCount()

    def data(self, index, role):
        if not index.isValid():
            return None

        if role != Qt.DisplayRole:
            return None

        item = index.internalPointer()

        return item.data(index.column())

    def flags(self, index):
        if not index.isValid():
            return Qt.NoItemFlags

        return Qt.ItemIsEnabled | Qt.ItemIsSelectable

    def headerData(self, section, orientation, role):
        if orientation == Qt.Horizontal and role == Qt.DisplayRole:
            return self.rootItem.data(section)

        return None

    def index(self, row, column, parent):
        if not self.hasIndex(row, column, parent):
            return QModelIndex()

        if not parent.isValid():
            parentItem = self.rootItem
        else:
            parentItem = parent.internalPointer()

        childItem = parentItem.child(row)
        if childItem:
            return self.createIndex(row, column, childItem)
        else:
            return QModelIndex()

    def parent(self, index):
        if not index.isValid():
            return QModelIndex()

        childItem = index.internalPointer()
        parentItem = childItem.parent()

        if parentItem == self.rootItem:
            return QModelIndex()

        return self.createIndex(parentItem.row(), 0, parentItem)

    def rowCount(self, parent):
        if parent.column() > 0:
            return 0

        if not parent.isValid():
            parentItem = self.rootItem
        else:
            parentItem = parent.internalPointer()

        return parentItem.childCount()

    def setupModelData(self, lines, parent):
        parents = [parent]
        indentations = [0]

        number = 0

        while number < len(lines):
            position = 0
            while position < len(lines[number]):
                if lines[number][position] != ' ':
                    break
                position += 1

            lineData = lines[number][position:].strip()

            if lineData:
                # Read the column data from the rest of the line.
                columnData = [s for s in lineData.split('\t') if s]

                if position > indentations[-1]:
                    # The last child of the current parent is now the new
                    # parent unless the current parent has no children.

                    if parents[-1].childCount() > 0:
                        parents.append(parents[-1].child(parents[-1].childCount() - 1))
                        indentations.append(position)

                else:
                    while position < indentations[-1] and len(parents) > 0:
                        parents.pop()
                        indentations.pop()

                # Append a new item to the current parent's list of children.
                parents[-1].appendChild(TreeItem(columnData, parents[-1]))

            number += 1

This is the part which creates the QuickView():

self.view = QQuickView()
self.view.setResizeMode(QQuickView.SizeRootObjectToView)
data = 'some\tdata\there\nsome\tmore\tdata\nand\tsome\tmore'
self.can_signal_model = TreeModel(('One', 'Two', 'Three'), data)
self.view.rootContext().setContextProperty("modelCan", self.can_signal_model)
qml_file = os.path.join(os.path.dirname(__file__), "resources/view.qml")
self.view.setSource(QUrl.fromLocalFile(os.path.abspath(qml_file)))
if self.view.status() == QQuickView.Error:
    sys.exit(-1)
self.view.show()

And this is my qml file:

TreeView {
    id: treeView
    anchors.fill: parent
    anchors.margins: 6
    anchors.top: parent.top
    anchors.horizontalCenter: parent.horizontalCenter
    model: modelCan

    TableViewColumn {
        title: "One"
        resizable: true
    }

    TableViewColumn {
        title: "Two"
        resizable: true
    }

    TableViewColumn {
        title: "Three"
        resizable: true
    }
}

I can see that it's created the three rows of test data, but the actual data text isn't there.

image of treeview with rows without data

Answer 1

Most QML views do not support multiple column models, but each column is associated with a role, and that is the case of TreeView.

In this case, simply map the columns of the model to roles, as shown below:

from PySide2 import QtCore, QtGui, QtQuick


class TreeItem(object):
    def __init__(self, data=None, parent=None):
        self.parentItem = parent
        self.itemData = data or []
        self.childItems = []

    def appendChild(self, item):
        self.childItems.append(item)

    def child(self, row):
        return self.childItems[row]

    def childCount(self):
        return len(self.childItems)

    def columnCount(self):
        return len(self.itemData)

    def data(self, column):
        try:
            return self.itemData[column]
        except IndexError:
            return None

    def parent(self):
        return self.parentItem

    def row(self):
        if self.parentItem:
            return self.parentItem.childItems.index(self)
        return 0


class TreeModel(QtCore.QAbstractItemModel):
    def __init__(self, header, data, parent=None):
        super(TreeModel, self).__init__(parent)
        self.rootItem = TreeItem(header)
        self.setupModelData(data.split("\n"), self.rootItem)

    def columnCount(self, parent):
        if parent.isValid():
            return parent.internalPointer().columnCount()
        else:
            return self.rootItem.columnCount()

    def roleNames(self):
        d = dict()
        for i in range(self.rootItem.columnCount()):
            d[QtCore.Qt.UserRole + i] = self.rootItem.data(i).encode()
        return d

    def data(self, index, role):
        if not index.isValid():
            return None
        item = index.internalPointer()
        if role == QtCore.Qt.DisplayRole:
            return item.data(index.column())
        elif role >= QtCore.Qt.UserRole:
            return item.data(role - QtCore.Qt.UserRole)

    def flags(self, index):
        if not index.isValid():
            return QtCore.Qt.NoItemFlags
        return QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable

    def headerData(self, section, orientation, role):
        if orientation == Qt.Horizontal and role == Qt.DisplayRole:
            return self.rootItem.data(section)

    def index(self, row, column, parent):
        if not self.hasIndex(row, column, parent):
            return QtCore.QModelIndex()

        if not parent.isValid():
            parentItem = self.rootItem
        else:
            parentItem = parent.internalPointer()

        childItem = parentItem.child(row)
        if childItem:
            return self.createIndex(row, column, childItem)
        else:
            return QtCore.QModelIndex()

    def parent(self, index):
        if not index.isValid():
            return QtCore.QModelIndex()

        childItem = index.internalPointer()
        parentItem = childItem.parent()

        if parentItem == self.rootItem:
            return QtCore.QModelIndex()

        return self.createIndex(parentItem.row(), 0, parentItem)

    def rowCount(self, parent):
        if parent.column() > 0:
            return 0

        if not parent.isValid():
            parentItem = self.rootItem
        else:
            parentItem = parent.internalPointer()

        return parentItem.childCount()

    def setupModelData(self, lines, parent):
        parents = [parent]
        indentations = [0]

        number = 0

        while number < len(lines):
            position = 0
            while position < len(lines[number]):
                if lines[number][position] != " ":
                    break
                position += 1

            lineData = lines[number][position:].strip()

            if lineData:
                # Read the column data from the rest of the line.
                columnData = [s for s in lineData.split("\t") if s]

                if position > indentations[-1]:
                    # The last child of the current parent is now the new
                    # parent unless the current parent has no children.

                    if parents[-1].childCount() > 0:
                        parents.append(parents[-1].child(parents[-1].childCount() - 1))
                        indentations.append(position)

                else:
                    while position < indentations[-1] and len(parents) > 0:
                        parents.pop()
                        indentations.pop()

                # Append a new item to the current parent's list of children.
                parents[-1].appendChild(TreeItem(columnData, parents[-1]))

            number += 1


def main():
    import os
    import sys

    app = QtGui.QGuiApplication(sys.argv)
    view = QtQuick.QQuickView(resizeMode=QtQuick.QQuickView.SizeRootObjectToView)
    data = "some\tdata\there\nsome\tmore\tdata\nand\tsome\tmore"
    can_signal_model = TreeModel(("One", "Two", "Three"), data)
    view.rootContext().setContextProperty("modelCan", can_signal_model)
    qml_file = os.path.join(os.path.dirname(__file__), "resources/view.qml")
    view.setSource(QtCore.QUrl.fromLocalFile(os.path.abspath(qml_file)))
    if view.status() == QtQuick.QQuickView.Error:
        sys.exit(-1)
    view.show()
    view.resize(640, 480)
    sys.exit(app.exec_())


if __name__ == "__main__":
    main()

view.qml

// ...
TableViewColumn {
    title: "One"
    role: "One"
    resizable: true
}

TableViewColumn {
    title: "Two"
    role: "Two"
    resizable: true
}

TableViewColumn {
    title: "Three"
    role: "Three"
    resizable: true
}
// ...