本章介绍tkinter.ttk的Combobox控件。
2. 环境信息
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本系列运行平台：Windows10 64bit
Python 版本：3.7
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3. Combobox
Combobox为下拉列表控件，它可以包含一个或多个文本项(text item)，可以设置为单选或多选。使用方式为ttk.Combobox(root,option...)。
常用的参数列表如下：
|
参数 |
描述 |
|
master |
代表了父窗口 |
|
height |
设置显示高度、如果未设置此项，其大小以适应内容标签 |
|
width |
设置显示宽度，如果未设置此项，其大小以适应内容标签 |
|
state |
可读状态，如state= “readonly” |
|
textvariable |
设置textvariable属性 |
一些常用的函数：
|
函数 |
描述 |
|
get |
返回制定索引的项值，如listbox.get(1)；返回多个项值,返回元组，如listbox.get(0,2)；返回当前选中项的索引listbox.curselection() |
|
values |
设定下拉列表的内容。如 data = ["a","b","c"], cbx["values"] = data |
|
current(i) |
指定下拉列表生成时显示在列表值，i = index。如current(2)，显示列表中的第三个值 |
事件：
下拉列表没有command函数（方法)。
下拉列表的虚拟事件是 "<<ComboboxSelected>>"。
4. 实例
实例1
from tkinter import *
from tkinter import ttk
#Create an instance
win = Tk()
win.title("Learn Combobox")
#create a Label
lb1 = Label(win, text = "Below is a combobox 1", font = "tahoma 12 normal")
lb1.grid(column = 0, row = 0, padx = 8, pady = 4)
def show_select_1():
print("post_command: show_select")
print(value.get())
#Define tkinter data type
data = ["a","b","c"]
value = StringVar()
#Create a combobox, and tighter it to value
cbx_1 = ttk.Combobox(win, width = 12, height = 8, textvariable = value, postcommand = show_select_1)
cbx_1.grid(column = 0, row = 1)
#add data to combobox
cbx_1["values"] = data
#======================================================================================================
#create a Label
lb2 = Label(win, text = "Below is a combobox 2", font = "tahoma 12 normal")
lb2.grid(column = 0, row = 4, padx = 8, pady = 4)
def show_data_2(*args):
print("Event: ComboboxSelected")
print(cbx_2.get())
#Define tkinter data type
data2 = ["a2","b2","c2","d2","e2"]
#Create a combobox, and tighter it to value
cbx_2 = ttk.Combobox(win, width = 12, height = 8)
cbx_2.grid(column = 0, row = 5)
#set cbx_2 as readonly
cbx_2.configure(state = "readonly")
#add data to combobox
cbx_2["values"] = data2
#set the initial data [index =2] to shows up when win generated
cbx_2.current(2)
#bind a event
cbx_2.bind("<<ComboboxSelected>>", show_data_2)
win.mainloop()
