setItemSelected在PyQt4上的QListWidget中

Question

I have this barebones code, I am trying to make it so some items (all even for this example) are preselected inside the QListWidget. Where am I going wrong?

from PyQt4 import QtGui, QtCore, Qt

import sys

class Main(QtGui.QWidget):
    def __init__(self, parent=None):    
        QtGui.QWidget.__init__(self,parent)

        grid = QtGui.QGridLayout()

        self.builtinpatternslist = QtGui.QListWidget()
        self.builtinpatternslist.setSelectionMode(QtGui.QAbstractItemView.MultiSelection)
        for i in range(5):
            self.builtinpatternslist.addItem(QtGui.QListWidgetItem(str(i)))
            if i % 2 == 0:
                self.builtinpatternslist.setItemSelected(QtGui.QListWidgetItem(str(i)),True)


        grid.addWidget(self.builtinpatternslist,0,0)

        self.setLayout(grid)


if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    gui = Main()
    gui.show()
    gui.raise_()
    sys.exit(app.exec_())

Answer 1

Each QtGui.QListWidgetItem(...) call creates a new item. What you are doing in that code is first creating an item, adding it to the list... And then, if it's in an odd position, creating a whole new item and selecting it without ever adding it to the list.

You need to make sure that you're only dealing with one item each time: save the result of a single QtGui.QListWidgetItem(...) call in a variable, and then operate on it:

    for i in range(5):
        item = QtGui.QListWidgetItem(str(i))
        self.builtinpatternslist.addItem(item)
        if i % 2 == 0:
            self.builtinpatternslist.setItemSelected(item, True)