Python Chapter 9: 使用Tkinter进行GUI程序设计 Part 2

6.几何管理器

Tkinter中的几何管理器分为：网格管理器、包管理器与位置管理器（最好不要对同一容器中的小构件使用多种管理器）

①网格管理器：将各个空间分布在看不见的网格中

 1 # Program 9.7
 2 from tkinter import *
 3 
 4 class GridManagerDemo:
 5     window = Tk()
 6     window.title("Grid Manager Demo")
 7 
 8     message = Message(window, text = "This Message widget occupies three rows and two columns")
 9     message.grid(row = 1, column = 1, rowspan = 3, columnspan = 2)
10     Label(window, text = "First Name:").grid(row = 1, column = 3)
11     Entry(window).grid(row = 1, column = 4, padx = 5, pady = 5)
12     Label(window, text = "Last Name:").grid(row = 2, column = 3)
13     Entry(window).grid(row = 2, column = 4)
14     Button(window, text = "Get Name").grid(row = 3, column = 4, padx = 5, pady = 5, sticky = E)
15 
16     window.mainloop()
17 
18 GridManagerDemo()

9） rowspan与columnspan将message放置在多行多列中

11、14） padx与pady填充单元格在水平与竖直位置上的可选空间，sticky = E使Button设置在单元格东边，E亦可以是W、S、N、NW、NE等组合

② 包管理器：将小构件一次一个放在另一个顶部或者一个挨着一个放置

 1 # Program 9.8
 2 from tkinter import *
 3 
 4 class PackManagerDemo:
 5     def __init__(self):
 6         window = Tk()
 7         window.title("Pack Manager Demo 1")
 8 
 9         Label(window, text = "Blue", bg = "blue").pack()
10         Label(window, text = "Red", bg = "red").pack(fill = BOTH, expand = 1)
11         Label(window, text = "Green", bg = "green").pack(fill = BOTH)
12 
13         window.mainloop()
14 
15 PackManagerDemo()

10）fill参数选择X,Y或BOTH，代表小控件填充水平、竖直或两个方向上的空间

　　expand参数非零时，若父小构件比容纳所有打包小构件的所需空间都大，则将额外的空间分配给小构件

其运行结果如下（从上到下依次排布，有fill的会填充横纵向，有expand会被分配多余的空间）：

 1 # Program 9.9
 2 from tkinter import *
 3 
 4 class PackManagerDemoWithSide:
 5     window = Tk()
 6     window.title("Pack Manager Demo 2")
 7 
 8     Label(window, text = "Blue", bg = "blue").pack(side = LEFT)
 9     Label(window, text = "Red", bg = "red").pack(side = LEFT, fill = BOTH, expand = 1)
10     Label(window, text = "Green", bg = "green").pack(side = LEFT, fill = BOTH)
11 
12     window.mainloop()
13 
14 PackManagerDemoWithSide()

8-10） side = LEFT意味着靠左放，该选项可以是LEFT/RIGHT/TOP/BOTTOM

其运行结果如下（从左到右依次排布，有fill的会填充横纵向，有expand会被分配多余的空间）：

③ 位置管理器：将小构件放在绝对位置上

 1 # Program 9.10
 2 from tkinter import *
 3 
 4 class PlaceManagerDemo:
 5     def __init__(self):
 6         window = Tk()
 7         window.title("Place Manager Demo")
 8 
 9         Label(window, text = "Blue", bg = "blue").place(x = 20, y = 20)
10         Label(window, text = "Red", bg = "red").place(x = 50, y = 50)
11         Label(window, text = "Green", bg = "green").place(x = 80, y = 80)
12 
13         window.mainloop()
14 
15 PlaceManagerDemo()

9-11）小控件.place(x, y)用位置管理器将小控件放在一定的绝对位置上

其运行结果如下：

注意：位置管理器不能兼容所有计算机，受分辨率的影响而影响，应尽量避免使用位置管理器

7. 实例研究：贷款计算器

开发一个GUI程序的主要步骤：

1）绘制轮廓图来设计用户界面

2）处理按钮等引发的事件

 1 # Program 9.11
 2 from tkinter import *
 3 
 4 class LoanCalculator:
 5     def __init__(self):
 6         window = Tk()
 7         window.title("Loan Calculator")
 8 
 9         Label(window, text = "Annual Interest Rate").grid(row = 1, column = 1, sticky = W)
10         Label(window, text = "Number of Years").grid(row = 2, column = 1, sticky = W)
11         Label(window, text = "Loan Amount").grid(row = 3, column = 1, sticky = W)
12         Label(window, text = "Monthly Payment").grid(row = 4, column = 1, sticky = W)
13         Label(window, text = "Total Payment").grid(row = 5, column = 1, sticky = W)
14 
15         self.annualInterestRateVar = StringVar()
16         Entry(window, textvariable = self.annualInterestRateVar, justify = RIGHT).grid(row = 1, column = 2)
17         self.numberOfYearsVar = StringVar()
18         Entry(window, textvariable = self.numberOfYearsVar, justify = RIGHT).grid(row = 2, column = 2)
19         self.loanAmountVar = StringVar()
20         Entry(window, textvariable = self.loanAmountVar, justify = RIGHT).grid(row = 3, column = 2)
21 
22         self.monthlyPaymentVar = StringVar()
23         lblMonthlyPayment = Label(window, textvariable = self.monthlyPaymentVar).grid(row = 4, column = 2, sticky = E)
24         self.totalPaymentVar = StringVar()
25         lblTotalPayment = Label(window, textvariable = self.totalPaymentVar).grid(row = 5, column = 2, sticky = E)
26 
27         btComputePayment = Button(window, text = "Compute payment", command = self.computePayment).grid(row = 6, column = 2, sticky = E)
28 
29         window.mainloop()
30 
31     def computePayment(self):
32         monthlyPayment = self.getMonthlyPayment(float(self.loanAmountVar.get()), float(self.annualInterestRateVar.get()) / 1200, int(self.numberOfYearsVar.get()))
33         self.monthlyPaymentVar.set(format(monthlyPayment, "10.2f"))
34         totalPayment = float(self.monthlyPaymentVar.get()) * 12 * int(self.numberOfYearsVar.get())
35         self.totalPaymentVar.set(format(totalPayment, "10.2f"))
36 
37     def getMonthlyPayment(self, loanAmount, monthlyInterestRate, numberOfYears):
38         monthlyPayment = loanAmount * monthlyInterestRate / (1 - 1 / (1 + monthlyInterestRate) ** (numberOfYears * 12))
39         return monthlyPayment
40 
41 LoanCalculator()

33、35）可通过monthlyPaymentVar.set(...)的方式，更改与小构件绑定的变量值从而更改小构件的参数（如显示内容等）

16、23） Entry()与Label()皆使用textvariable的参数，不过Entry()中其指代用户输入的内容，Label()中指代标签显示的内容

many）很多行当中都用到了Label(...).grid(...)的连写方式，即小构件无需另外变量储存，除非需要更改小构件参数（当然与其绑定的参数更改可以如上上行进行，但背景颜色、字体等参数仍然需要通过调用原小控件变量的方式进行更改，这种情况下就需要thing = Label(...).grid(...）的方式）

程序的运行结果如下：

8. 显示图像

# 鉴于书上程序实例中的图片文件没有获取，这里仅概述创建图像对象与显示的语法

创建：

myimage = PhotoImage(file = "yourpath.gif")

此时创建了一个图片路径为"yourpath.gif"的图片对象myimage。

与Button、Checkbutton、Radiobutton的互动：

Button(frame, image = myimage)
Checkbutton(frame, image = myimage)
Radiobutton(frame, image = myimage)

此举将创建包含myimage对象中的图像的各种按钮

与Canvas的互动：

canvas = Canvas(frame1)
canvas.create_image(width, height, image = myimage)

此举将创建一个背景内容为myimage对象所含图片的画布，事实上一张画布可以显示多个图像

Python Chapter 9: 使用Tkinter进行GUI程序设计 Part 2

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