当用户单击按钮后创建新字段时，如何分配绑定函数？

Question

我有一个表单，用户通过单击按钮创建产品属性的记录。单击后，四个组合框、一个标签和一个输入字段将加载到构成记录的表单上

第四个组合框上的下拉列表取决于前三个组合框中的条目。最终用户可能会在输入之前多次单击“添加”按钮。我如何确保当用户在单击“添加”按钮“N”次后返回第一条记录并更改第一条记录的组合框时，在第四个组合框中加载适当的值

这是我的

def addItemInEdit():
    global rowNum2
    global brandDropdownList2, typeDropdownList2, sizeDropdownList2, qtyTextList2, itemList2, 
     packedDateDropdownList2

####################### Loading label, dropdowns, and text fields

    itemList2.append(ttk.Label(frameEdit, text=str(rowNum2 + 1) + ". ").grid(row=rowNum2, column=0))
    brandDropdownList2.append(ttk.Combobox(frameEdit, state='readonly', values=listOfBrands, width=10))
    brandDropdownList2[-1].grid(row=rowNum2, column=1, pady=5, padx=5)
    brandDropdownList2[-1].current(0)

    typeDropdownList2.append(ttk.Combobox(frameEdit, state='readonly', values=listOftypes, width=5))
    typeDropdownList2[-1].grid(row=rowNum2, column=2)
    typeDropdownList2[-1].current(0)

    sizeDropdownList2.append(ttk.Combobox(frameEdit, state='readonly', values=listOfSizes, width=10))
    sizeDropdownList2[-1].grid(row=rowNum2, column=3, pady=5, padx=5)
    sizeDropdownList2[-1].current(0)

    packedDateDropdownList2.append(ttk.Combobox(frameEdit, state='disabled', width=7))
    packedDateDropdownList2[-1].grid(row=rowNum2, column=4, pady=5)

    qtyTextList2.append(ttk.Entry(frameEdit, width=7))
    qtyTextList2[-1].grid(row=rowNum2, column=5, padx=5)
    qtyTextList2[-1].insert(0, "Qty")


####################### Adding bind functions.

    for item in range(len(brandDropdownList2)):
        def getDates(event):
            listOfDates=[]

################################## Making sure the use has made actual selections
            if brandDropdownList2[len(brandDropdownList2)-1].get()!="Brand" and typeDropdownList2[len(brandDropdownList2)-1].get()!="Type" and sizeDropdownList2[len(brandDropdownList2)-1].get()!="Size":
                packedDateDropdownList2[len(brandDropdownList2) - 1].config(state='readonly')
                packedDateDropdownList[len(brandDropdownList) - 1].set('')
                getDatesQuery = "SELECT [PackedOn] FROM SalesData where [Brand]=? AND [Type] = ? AND [Size]=?"
                conForDates = pyodbc.connect(dbPath)
                curForDates = conForDates.cursor()
                dateListOutput = curForDates.execute(getDatesQuery,(brandDropdownList2[len(brandDropdownList2)-1].get(),typeDropdownList2[len(brandDropdownList2)-1].get(),sizeDropdownList2[len(brandDropdownList2)-1].get())).fetchall()

                for item in dateListOutput:
                    if item[0] not in listOfDates:
                        listOfDates.append(item[0])

                packedDateDropdownList2[len(brandDropdownList2)-1].config(values=listOfDates)
            else:
                packedDateDropdownList2[len(brandDropdownList2) - 1].set('')
                packedDateDropdownList2[len(brandDropdownList2) - 1].config(state='disabled')


        brandDropdownList2[len(brandDropdownList)-1].bind("<<ComboboxSelected>>",getDates)
        typeDropdownList2[len(brandDropdownList)-1].bind("<<ComboboxSelected>>",getDates)
        sizeDropdownList2[len(brandDropdownList)-1].bind("<<ComboboxSelected>>",getDates)

    rowNum2 = rowNum2 + 1

我知道绑定的“For”循环是错误的，但我觉得Python有一个我不知道的特性

Answer 1

1. getDates()函数总是从最后一行获取值 不正确的组合框
2. 您只需要将函数绑定到新添加的组合框
3. 最好将getDates()放在addItemInEdit()函数之外

以下是您的代码的修改版本：

def getDates(event):
    index = event.widget.row_id

    # get the dates from database
    # is SELECT DISTINCT supported???
    getDatesQuery = "SELECT [PackedOn] FROM SalesData where [Brand] = ? AND [Type] = ? AND [Size] = ?"
    conForDates = pyodbc.connect(dbPath)
    curForDates = conForDates.cursor()
    dateListOutput = curForDates.execute(getDatesQuery,(brandDropdownList2[index].get(), typeDropdownList2[index].get(), sizeDropdownList2[index].get())).fetchall()
    # should conForDates.close() be called???

    listOfDates = list(set(item[0] for item in dateListOutput))

    packedDateDropdownList2[index].config(state='readonly')
    packedDateDropdownList2[index].config(values=listOfDates)
    packedDateDropdownList2[index].set('')

def addItemInEdit():
    global rowNum2

    itemList2.append(ttk.Label(frameEdit, text=str(rowNum2 + 1) + ". ").grid(row=rowNum2, column=0))
    brandDropdownList2.append(ttk.Combobox(frameEdit, state='readonly', values=listOfBrands, width=10))
    brandDropdownList2[-1].grid(row=rowNum2, column=1, pady=5, padx=5)
    brandDropdownList2[-1].current(0)
    brandDropdownList2[-1].row_id = rowNum2 # save the current row number

    typeDropdownList2.append(ttk.Combobox(frameEdit, state='readonly', values=listOftypes, width=5))
    typeDropdownList2[-1].grid(row=rowNum2, column=2)
    typeDropdownList2[-1].current(0)
    typeDropdownList2[-1].row_id = rowNum2 # save the current row number

    sizeDropdownList2.append(ttk.Combobox(frameEdit, state='readonly', values=listOfSizes, width=10))
    sizeDropdownList2[-1].grid(row=rowNum2, column=3, pady=5, padx=5)
    sizeDropdownList2[-1].current(0)
    sizeDropdownList2[-1].row_id = rowNum2 # save the current row number

    packedDateDropdownList2.append(ttk.Combobox(frameEdit, state='disabled', width=7))
    packedDateDropdownList2[-1].grid(row=rowNum2, column=4, pady=5)
    packedDateDropdownList2[-1].row_id = rowNum2 # save the current row number

    qtyTextList2.append(ttk.Entry(frameEdit, width=7))
    qtyTextList2[-1].grid(row=rowNum2, column=5, padx=5)
    qtyTextList2[-1].insert(0, "Qty")
    qtyTextList2[-1].row_id = rowNum2 # save the current row number

    # bind the required callback to newly added comboboxes
    brandDropdownList2[-1].bind("<<ComboboxSelected>>", getDates)
    typeDropdownList2[-1].bind("<<ComboboxSelected>>", getDates)
    sizeDropdownList2[-1].bind("<<ComboboxSelected>>", getDates)

    rowNum2 += 1