Question

我开始学习Qt4模型/视图编程，我有初学者的问题。

我有一个简单的应用程序，它在QTableView中显示了sqlite表：

class Model(QtSql.QSqlTableModel):
    def __init__(self, parent=None):
        super(Model, self).__init__(parent)
        self.setEditStrategy(QtSql.QSqlTableModel.OnFieldChange)

        self.setTable("test")
        self.select()

class App(QtGui.QMainWindow):
    def __init__(self, model):
        QtGui.QMainWindow.__init__(self)

        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)

        self.ui.tableView.setModel(model)

if __name__ == "__main__":
    myDb = QtSql.QSqlDatabase.addDatabase("QSQLITE")
    myDb.setDatabaseName("test.db")

    if not myDb.open():
        print 'FIXME'

    model = Model()

    app = QtGui.QApplication(sys.argv)
    window = App(model)
    window.show()
    sys.exit(app.exec_())

这是数据库的样子：

sqlite> create table test (a INTEGER, b INTEGER, c STRING);
sqlite> insert into test VALUES(1, 2, "xxx");
sqlite> insert into test VALUES(6, 7, "yyy");

所以我得到了类似的东西：

+---+---+-----+
| a | b |  c  |
+---+---+-----+
| 1 | 2 | xxx |
+---+---+-----+
| 6 | 7 | yyy |
+---+---+-----+

是否可以修改Model以使QTableView像虚拟列一样？例如：

+---+---+-----+-----+
| a | b | sum |  c  |
+---+---+-----+-----+
| 1 | 2 |  3  | xxx |
+---+---+-----+-----+
| 6 | 7 | 13  | yyy |
+---+---+-----+-----+

或许我应该以其他方式做到这一点？

Answer 1

是的，你可以这样做。虽然@BrtH's answer是相关的，但模型很棘手，很容易丢失。所以我认为更好的例子会更好。

就个人而言，我使用的是从QAbstractProxyModel派生的代理模型。但是，在您的情况下，重新实现QSqlTableModel也是可行的。以下是您的目标实现。请注意，您必须了解Model/View methodology的基础知识，以便了解每种方法的作用。

class Model(QtSql.QSqlTableModel):
    def __init__(self, parent=None):
        super(Model, self).__init__(parent)
        self.setEditStrategy(QtSql.QSqlTableModel.OnFieldChange)

        self.setTable("test")
        self.select()


    def columnCount(self, parent=QtCore.QModelIndex()):
        # this is probably obvious
        # since we are adding a virtual column, we need one more column
        return super(Model, self).columnCount()+1


    def data(self, index, role=QtCore.Qt.DisplayRole):
        if role == QtCore.Qt.DisplayRole and index.column()==2:
            # 2nd column is our virtual column.
            # if we are there, we need to calculate and return the value
            # we take the first two columns, get the data, turn it to integer and sum them
            # [0] at the end is necessary because pyqt returns value and a bool
            # http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qvariant.html#toInt
            return sum(self.data(self.index(index.row(), i)).toInt()[0] for i in range(2))
        if index.column() > 2:
            # if we are past 2nd column, we need to shift it to left by one
            # to get the real value
            index = self.index(index.row(), index.column()-1)
        # get the value from base implementation
        return super(Model, self).data(index, role)


    def headerData(self, section, orientation, role=QtCore.Qt.DisplayRole):
        # this is similar to `data`
        if section==2 and orientation==QtCore.Qt.Horizontal and role==QtCore.Qt.DisplayRole:
            return 'Sum'
        if section > 2 and orientation==QtCore.Qt.Horizontal:
            section -= 1
        return super(Model, self).headerData(section, orientation, role)


    def flags(self, index):
        # since 2nd column is virtual, it doesn't make sense for it to be Editable
        # other columns can be Editable (default for QSqlTableModel)
        if index.column()==2:
            return QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsEnabled
        return QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsEditable


    def setData(self, index, data, role):
        # similar to data.
        # we need to be careful when setting data (after edit)
        # if column is after 2, it is actually the column before that
        if index.column() > 2:
            index = self.index(index.row(), index.column()-1)
        return super(Model, self).setData(index, data, role)

Answer 2

这当然是可能的。下面是我自己的一些代码示例，为您的数据进行了修改。

import sqlite3

conn = sqlite3.connect('test.db')


class MyTreeModel(QAbstractItemModel):
    def __init__(self, parent=None):
        super(MyTreeModel, self).__init__(parent)

        c = conn.cursor()
        c.execute("SELECT a, b, c FROM 'test'")
        self.items = c.fetchall()

        self.columns = ['a', 'b', 'sum', 'c']

    def columnCount(self, index):
        return len(self.columns)

    def rowCount(self, parent):
        return len(self.items)

    def data(self, index, role=Qt.DisplayRole):
        if index.isValid():
            col= index.column()
            spot = self.items[index.row()]
            if role == Qt.DisplayRole:
                if col == 0 or col == 1:
                    return self.items[index.row()][col]
                elif col == 2:
                    return self.items[index.row()][0] + self.items[index.row()][1]
                elif col == 3:
                    return self.items[index.row()][2]

    def headerData(self, section, orientation, role=Qt.DisplayRole):
        if orientation == Qt.Horizontal and role == Qt.DisplayRole:
            return self.columns[section]

    def index(self, row, col, index):
        if not index.isValid():
            return self.createIndex(row, col)
        else:
            return QModelIndex()

    def parent(self, child):
        return QModelIndex()

这是QTreeView的模型，但我认为您可以轻松地对其进行调整有关这些方法和模型的更多信息，请参阅http://srinikom.github.com/pyside-docs/PySide/QtCore/QAbstractItemModel.html。

Answer 3

你看过QSqlQueryModel了吗？它允许显示任何SQL查询的结果。您的示例代码：

class Model(QtSql.QSqlQueryModel):
    def __init__(self, parent=None):
        super(Model, self).__init__(parent)
        self.setQuery("SELECT a, b, a + b, c FROM test")
        self.setHeaderData(0, QtCore.Qt.Horizontal, "a")
        self.setHeaderData(1, QtCore.Qt.Horizontal, "b")
        self.setHeaderData(2, QtCore.Qt.Horizontal, "sum")
        self.setHeaderData(3, QtCore.Qt.Horizontal, "c")

但请记住：

默认情况下，模型是只读的。要使其成为读写，必须将其子类化并重新实现setData（）和flags（）。

QTableView中的虚拟列？

3 个答案: