tkinter事件机制

一.tkinter.Event

tkinter的事件机制跟js是一样的，也是只有一个Event类，这个类包罗万象，集成了键盘事件，鼠标事件，包含各种参数。
不像java swing那种强类型事件，swing从Event派生出KeyEvent，MouseEvent等，层次分明，一切都是确定的。
这是两种哲学。
tkinter的事件机制也很好，简洁明了，知道一个就足够了。
tkinter.Event类包含以下属性

• 'char'键盘事件，按键的字符
• 'delta'鼠标滚动事件，鼠标滚动的距离
• 'height','width'仅用于Configure事件,即当控件形状发生变化之后的宽度和高度.相当于SizeChanged事件
• 'keycode'键盘事件，按键码
• 'keysym', 'keysym_num', 按键事件
• 'num'鼠标事件，鼠标按键码，1为左键，2为中建，3为右键
• 'serial',An integer serail number that is incremented every time the server processes a client request
  也就是serial相当于Event的ID
• 'state', A integer describing the state of all the modifier keys.用来表示修饰键的状态,即ctrl,shift,alt等修饰键的状态.
• 'time',事件发生的时间
• 'type', 事件的类型
• 'widget',事件的源头
• 'x', 'x_root', 'y', 'y_root'鼠标事件，鼠标的位置，x_root和y_root为绝对坐标系，x，y为相对坐标。

二.tkinter的bind函数

def bind(self, sequence=None, func=None, add=None)
函数包含三个可选参数,sequence描述事件类型,func描述回调函数,add感觉没卵用,就是确定即将绑定的事件会不会替代刚才绑定的事件(默认是不会,于是形成一个回调函数列表).
查看bind函数源代码，可以查看关于事件绑定函数如下doc string。
(1)一切事件都用字符串来表示,事件字符串格式为<MODIFIER-MODIFIER-TYPE-DETAIL>
(2)修饰符MODIFIER最多可以有两个,也可以有1个或者0个.修饰符MODIFIER取值必为以下之一:

• Control,Shift,Alt,Lock
• Meta, M
• Mod1, M1,Mod2, M2,Mod3, M3,Mod4, M4,Mod5, M5
• Button1,B1,Button2,B2,Button3,B3,Button4,B4,Button5,B5
• Double,Triple.

(3)TYPE是事件类型,是字符串中最重要的部分,可取值包括:

• Activate, Deactivate,
• Enter,Leave,FocusIn,FocusOut,
• Map, Unmap,
• ButtonPress,ButtonRelease, Button, Motion,MouseWheel,
• KeyRelease, KeyPress, Key
• Expose, Circulate, Property,Colormap, Gravity, Reparent,Visibility, Destroy,
• Configure

(4)详情DETAIL描述事件的具体内容,对于不同的事件类型,DETAIL的取值不一样.
DETAIL is the button number for ButtonPress,ButtonRelease
DETAIL is the Keysym for KeyPress and KeyRelease.
(5)举几个例子
<Control-Button-1> for pressing Control and mouse button 1.
<Alt-A> for pressing A and the Alt key (KeyPress can be omitted).
(6)An event pattern can also be a virtual event of the form <<AString>> where AString can be arbitrary. This event can be generated by event_generate.
(7)If events are concatenated they must appear shortly after each other.
(8)FUNC will be called if the event sequence occurs with an instance of Event as argument. If the return value of FUNC is "break" no further bound function is invoked.
(9)An additional boolean parameter ADD specifies whether FUNC will be called additionally to the other bound function or whether it will replace the previous function.
(10)Bind will return an identifier to allow deletion of the bound function with unbind without memory leak.
(11)If FUNC or SEQUENCE is omitted the bound function or list of bound events are returned.

三.事件举例

• <Button-1>
  这个事件表示一个鼠标按键被按下。Button 1表示左键，button 2表示中键，Button 3表示右键。当在一个组件上按下一个鼠标键的时候Tkinter会自动的'grab'鼠标指针，当这个鼠标按键一直被持续按下，接下来的鼠标事件（比如移动和释放事件）将会被发送到组件上，甚至鼠标已经被移到了当前组件的外面。鼠标指针的当前位置（相对于组件）会在event对象中以成员x 和 y 的形式传递给callback。
  你可以使用ButtonPress来替代Button，甚至不写：<Button-1><ButtonPress-1>和<1>是一样的意思。为了表达清晰，我更喜欢使用<Button-1>语句。
• <B1-Motion>
  The mouse is moved, with mouse button 1 being held down (use B2 for the middle button, B3 for the right button). The current position of the mouse pointer is provided in the x and y members of the event object passed to the callback.
  当Button 1被按下的时候移动鼠标（B2代表中键，B3代表右键），鼠标指针的当前位置将会以event对象的x y 成员的形式传递给callback。
• <ButtonRelease-1>
  Button 1 was released. The current position of the mouse pointer is provided in the x and y members of the event object passed to the callback.
  Button 1被释放。鼠标指针的当前位置将会以event对象的x y 成员的形式传递给callback。
• <Double-Button-1>
  Button 1 was double clicked. You can use Double or Triple as prefixes. Note that if you bind to both a single click () and a double click, both bindings will be called.
  Button 1被双击。可以使用Double 或者 Triple前缀。注意：如果你同时映射了一个单击和一个双击，两个映射都会被调用。
• <Enter>
  The mouse pointer entered the widget (this event doesn’t mean that the user pressed the Enter key!).
  鼠标指针进入组件范围（这个事件不是用户按下了Enter键的意思）。
• <Leave>
  The mouse pointer left the widget.
  鼠标指针离开组件范围。
• <FocusIn>
  Keyboard focus was moved to this widget, or to a child of this widget.
  键盘焦点切换到这个组件或者子组件。
• <FocusOut>
  Keyboard focus was moved from this widget to another widget.
  键盘焦点从一个组件切换到另外一个组件。
• <Return>
  The user pressed the Enter key. You can bind to virtually all keys on the keyboard. For an ordinary 102-key PC-style keyboard, the special keys are Cancel (the Break key), BackSpace, Tab, Return(the Enter key), Shift_L (any Shift key), Control_L (any Control key),Alt_L (any Alt key), Pause, Caps_Lock, Escape, Prior (Page Up), Next (Page Down), End, Home, Left, Up, Right, Down,Print, Insert, Delete, F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11,F12, Num_Lock, and Scroll_Lock.
  用户按下Enter键。你可以映射键盘上所有的按键。对于一个普通的102键键盘，特殊按键有Cancel (the Break key), BackSpace, Tab, Return(the Enter key), Shift_L (any Shift key), Control_L (any Control key),Alt_L (any Alt key), Pause, Caps_Lock, Escape, Prior (Page Up), Next (Page Down), End, Home, Left, Up, Right, Down,Print, Insert, Delete, F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11,F12, Num_Lock, and Scroll_Lock.
• <Key>
  The user pressed any key. The key is provided in the char member of the event object passed to the callback (this is an empty string for special keys).
  用户按下任何键。这个键会以event对象的char成员的形式传递给callback（对于特殊按键会是一个空字符串）
• a
  The user typed an “a”. Most printable characters can be used as is. The exceptions are space (<space>) and less than (<less>). Note that 1 is a keyboard binding, while <1> is a button binding.
  用户输入‘a’。所有的可打印字符都可以这样使用。空格和少于例外。 注意 ‘1’表示映射键盘上的数字1，而<1>是一个鼠标映射
• <Shift-Up>
  The user pressed the Up arrow, while holding the Shift key pressed. You can use prefixes like Alt, Shift, and Control.
  用户在按住Shift键的同时，按下Up箭头。你可以使用Alt + Shift + Control一样的各种组合。
• <Configure>
  The widget changed size (or location, on some platforms). The new size is provided in the width and height attributes of the event object passed to the callback.
  改变组件的形状（在某些平台上表示的是位置）。新形状以event对象中width 和 height属性的形式传递给callback。

四.事件绑定

tkinter的事件绑定分为四个层次:

• 本控件,the widget instance,use bind()
• the top-level window,use bind()
• the widget class,use bind_class()
• 本应用程序,the whole application,use bind_all()

事件回调顺序:按照上述顺序从上到下依次执行,每层只执行一个最恰当的事件处理函数.由此可知,最多形成一个长度为4的回调函数列表.当不想继续让其它回调函数处理这个事件时,只需要return 'break',即可停止事件回调函数列表.

# 事件级别间”传递"
from Tkinter import *
root = Tk()
# Key事件处理函数
def printEvent(event):
    print '<instance>',event.keycode
# Return事件处理函数
def printToplevel(event):
    print '<toplevel>',event.keycode
def printClass(event):
    print '<bind_class>',event.keycode
def printAppAll(event):
    print '<bind_all>',event.keycode
# 在instance级别与printEvent绑定
bt1 = Button(root,text = 'instance event')
bt1.bind('<Return>',printEvent)
# 在bt1的Toplevel级别与printToplevel绑定
bt1.winfo_toplevel().bind('<Return>',printToplevel)
# 在class级别绑定事件printClass
root.bind_class('Button','<Return>',printClass)
# 在application all级别绑定printAppAll
bt1.bind_all('<Return>',printAppAll)
# 将焦点定位到bt1上，回车一下，结果有4个打印输出。
bt1.focus_set()
bt1.grid()
root.mainloop()
# 输出结果：
# <instance> 13
# <bind_class> 13
# <toplevel> 13
# <bind_all> 13
# Return向高级别进行了“传递",调用顺序为instance/class/toplevel/all

bind_class的作用

# 使用bind_class将影响所有这个类的instance
from Tkinter import *
root = Tk()
def printClass(event):
    print '<bind_class>',event.keycode
# 改变button类的事件绑定
root.bind_class('Button','<Return>',printClass)
# 创建两个Button
bt1 = Button(root,text = 'a button')
bt2 = Button(root,text = 'another button')
bt1.focus_set()
bt1.grid()
bt2.grid()
root.mainloop()
# 回车，bt1打印结果
# TAB切换到bt2,回车同样打印出结果，即所有的Button对Return事件进行响应

五.protocols

from Tkinter import *  
import tkMessageBox  
  
def callback():  
    if tkMessageBox.askokcancel("Quit", "Do you really wish to quit?"):  
        root.destroy()  
  
root = Tk()  
root.protocol("WM_DELETE_WINDOW", callback)  
  
root.mainloop()  

六.按钮事件直接绑定command参数

b=tkinter.Button(window,text='haha', command=haha)
这样一点击按钮就会调用haha()函数