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Gui Gui programming (XIII) - event handling

2022-07-06 20:18:00 【Progress Xiaobai】

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Catalog

Preface

Mouse and keyboard events

event Object common properties

Test keyboard and mouse events

lambda Expression details

️ test lambda usage

Summary of various event binding methods

Binding of component objects

Binding of component classes

Summary of various event binding methods

Looking back

Preface

One individual GUI The whole application life cycle is in a message cycle (event loop) in . It waits for the event to happen , And deal with it accordingly .Tkinter Provides a mechanism for handling related events . Handling functions can be bound to various events of various controls .

widget.bind(event, handler)

If relevant events occur raw , handler The function will be triggered , Event object event Will pass to handler function .

Mouse and keyboard events

Code	explain
<Button-1> <ButtonPress-1> <1>	Press the left mouse button . 2 Right click ,3 Represents the middle key ;
<ButtonRelease-1>	Release the left mouse button
<B1-Motion>	Press and hold the left mouse button to move
<Double-Button-1>	Double left click
<Enter>	The mouse pointer enters a component area
<Leave>	The mouse pointer leaves a component area
<MouseWheel>	Scroll wheel ;
<KeyPress-a>	Press down a key ,a You can use another key instead of
<KeyRelease-a>	Release a key .
<KeyPress-A>	Press down A key （ uppercase A）
<Alt-KeyPress-a>	Press at the same time alt and a;alt You can use ctrl and shift replace
<Double-KeyPress-a>	Two quick clicks a
<Control-V>	CTRL and V The keys are pressed simultaneously ,V It can be changed to other key positions

event Object common properties

name	explain
char	Key characters , Valid only for keyboard events
keycode	Key code , Valid only for keyboard events
keysym	Key name , Only valid for keyboard events, such as pressing the spacebar ： Keyed char： Keyed keycode：32 Keyed keysym：space For example, press a key ： Keyed char：a Keyed keycode：65 Keyed keysym：a
num	Mouse button , Valid only for mouse events
type	The type of event triggered
widget	The component that caused the event
width,height	The size of the changed component , only Configure It works
x,y	Current mouse position , Relative to the parent container
x_root,y_root	Current mouse position , Relative to the whole screen

Test keyboard and mouse events

# coding=utf-8
#  Test keyboard and mouse events 

from tkinter import *

root = Tk();root.geometry("530x300")

c1 = Canvas(root,width=300,height=300,bg="pink")
c1.pack()


def mouseTest(event):
    print(" Left click position ( Relative to the parent container )：{0},{1}".format(event.x,event.y))
    print(" Left click position ( Relative to the screen )：{0},{1}".format(event.x_root,event.y_root))
    print(" Event bound components ：{0}".format(event.widget))

def testDrag(event):
    c1.create_oval(event.x,event.y,event.x+1,event.y+1)


def keyboardTest(event):
    print(" Keyed keycode:{0}, Keyed char:{1}, Keyed keysym:{2}"
          .format(event.keycode,event.char,event.keysym))

def press_a_test(event):
    print("press a")

def release_a_test(event):
    print("release a")


c1.bind("<Button-1>",mouseTest)
c1.bind("<B1-Motion>",testDrag)


root.bind("<KeyPress>",keyboardTest)
root.bind("<KeyPress-a>",press_a_test)          # Only for lowercase a, uppercase A No use 
root.bind("<KeyRelease-a>",release_a_test)

root.mainloop()

give the result as follows ：

Casually write numbers , events , Mouse events and keyboard events .

lambda Expression details

lambda The expression defines an anonymous function , Only suitable for simple input parameters , Simple calculation returns results , Not suitable for complex functions .lambda The defined anonymous function also has input 、 There's also output , Just no name . The syntax is as follows ：

lambda Parameter value list ： expression The parameter value list is the input . The structure of expression evaluation is output .

Write One individual most Jane single Of case example ： add3args = lambda x,y,z:x+y+z #print(add3args(10,20,30))

above lambda The expression is equivalent to the following function definition ：

def add3args(x,y,z):

return x+y+z

lambda The parameter value list of the expression can be as follows ：

lambda Format	explain
lambda x, y: x*y	The function input is x and y, The output is their product x*y
lambda:None	Function has no input parameters , The output is None
lambda:aaa(3,4)	Function has no input parameters , The output is aaa(3,4) The knot of fruit
lambda *args: sum(args)	The input is any number of parameters , The output is their sum
lambda **kwargs: 1	The input is any key value pair parameter , The output is

️ test lambda usage

from tkinter import *

root = Tk();root.geometry("270x50")


def mouseTest1():
    print("command The way , Simple case ： It does not involve obtaining event object , have access to ")


def mouseTest2(a,b):
    print("a={0},b={1}".format(a,b))


Button(root, text=" test command1",
       command=mouseTest1).pack(side="left")

Button(root, text=" test command2",
       command=lambda: mouseTest2(" Small ", " white ")).pack(side="left")

root.mainloop()

Select the event in the pop-up box .

Summary of various event binding methods

Binding of component objects

adopt command Attribute binding （ Suitable for simple without obtaining event object ）

Button(root,text=” Sign in ”,command=login)

adopt bind() Method binding （ Suitable for the need to obtain event object ）

c1 = Canvas(); c1.bind(“<Button-1>”,drawLine)

Binding of component classes

Call the object's bind_class function , Bind all components of this component class to events ：

w.bind_class(“Widget”,”event”,eventhanler)

Summary of various event binding methods

from tkinter import *

root = Tk();root.geometry("270x30")


def mouseTest1(event):
    print("bind() Methods the binding , Can get event object ")
    print(event.widget)


def mouseTest2(a, b):
    print("a={0},b={1}".format(a, b))
    print("command Methods the binding , You can't get it directly event object ")


def mouseTest3(event):
    print(" Right click on the event , Bound to all buttons ！！")
    print(event.widget)


b1 = Button(root, text=" test bind() binding ")
b1.pack(side="left")
# bind Bind events by 
b1.bind("<Button-1>", mouseTest1)

# command Property is directly bound to the event 
b2 = Button(root, text=" test command2",
       command=lambda: mouseTest2(" The small white ", " come on. "))
b2.pack(side="left")


#  To all Button Buttons are bound to right-click Events <Button-2>
b1.bind_class("Button", "<Button-2>", mouseTest3)

root.mainloop()