QTableView 中的虚拟列? [英] Virtual column in QTableView?

问题描述

我开始学习 Qt4 模型/视图编程，我有初学者问题.

I'm started to learning Qt4 Model/View Programming and I have beginner question.

我有一个简单的应用程序，它在 QTableView 中显示 sqlite 表:

I have simple application which show sqlite table in QTableView:

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_())

这里是数据库的样子:

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信息:

So I'm getting something like:

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

是否可以修改 Model 以在 QTableView 中包含类似虚拟列的内容?例如类似:

Is it possible to modify Model to have in QTableView something like virtual column? For example something like:

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

或者我应该用其他方式来做吗?

Or maybe I should do it in some other way?

推荐答案

是的，您可以这样做.尽管 @BrtH 的答案 是相关的，但模型很棘手，而且很容易迷路.所以我认为更多的例子会更好.

Yes, you can do that. Although @BrtH's answer is relevant, models are tricky and it's easy to get lost. So I thought a more case in point example would be better.

就我个人而言，我会使用从 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.以下是您目标的实现.请注意，了解模型/视图方法 以便您了解每种方法的作用.

Personally, I'd use a proxy model derived from QAbstractProxyModel. But, in your case reimplementing QSqlTableModel is also feasible. Below is an implementation for your goal. Note that, it's essential for you to know basics of Model/View methodology so that you understand what each method does.

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)

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