Wxpython 简明教程

wxPython - Event Handling

与按顺序执行的控制台模式应用程序不同，基于GUI的应用程序是事件驱动的。函数或方法根据用户的动作（如单击按钮、从集合中选择项目或单击鼠标等，称为事件）执行。

Unlike a console mode application, which is executed in a sequential manner, a GUI based application is event driven. Functions or methods are executed in response to user’s actions like clicking a button, selecting an item from collection or mouse click, etc., called events.

在应用程序运行时发生的事件相关的数据存储为从 wx.Event 派生的子类的对象。显示控件（例如按钮）是特定类型事件的源并生成与之关联的Event类对象。例如，单击按钮会发出wx.CommandEvent。此事件数据将调度给程序中的事件处理程序方法。wxPython具有许多预定义的事件绑定程序。一个 Event binder 将特定小部件（控件）、其关联的事件类型以及事件处理程序方法之间的关系封装起来。

Data pertaining to an event which takes place during the application’s runtime is stored as object of a subclass derived from wx.Event. A display control (such as Button) is the source of event of a particular type and produces an object of Event class associated to it. For instance, click of a button emits a wx.CommandEvent. This event data is dispatched to event handler method in the program. wxPython has many predefined event binders. An Event binder encapsulates relationship between a specific widget (control), its associated event type and the event handler method.

例如，要在按钮的单击事件上调用程序的 OnClick() method ，需要以下语句：

For example, to call OnClick() method of the program on a button’s click event, the following statement is required −

self.b1.Bind(EVT_BUTTON, OnClick)

Bind() method 由 wx.EvtHandler 类中的所有显示对象继承。此处 EVT_.BUTTON 是关联按钮点击事件至 OnClick() 方法的绑定器。

Bind() method is inherited by all display objects from wx.EvtHandler class. EVT_.BUTTON here is the binder, which associates button click event to OnClick() method.

Example

在以下示例中，MoveEvent 由拖动顶级窗口（本例中为一个 wx.Frame 对象）而引起，使用 wx.EVT_MOVE 绑定器连接至 OnMove() method 。此代码显示一个窗口。如果使用鼠标移动窗口，其瞬时坐标将显示在控制台上。

In the following example, the MoveEvent, caused by dragging the top level window – a wx.Frame object in this case – is connected to OnMove() method using wx.EVT_MOVE binder. The code displays a window. If it is moved using mouse, its instantaneous coordinates are displayed on the console.

import wx

class Example(wx.Frame):

   def __init__(self, *args, **kw):
      super(Example, self).__init__(*args, **kw)
      self.InitUI()

   def InitUI(self):
      self.Bind(wx.EVT_MOVE, self.OnMove)
      self.SetSize((250, 180))
      self.SetTitle('Move event')
      self.Centre()
      self.Show(True)

   def OnMove(self, e):
      x, y = e.GetPosition()
      print "current window position x = ",x," y= ",y

ex = wx.App()
Example(None)
ex.MainLoop()

上述代码生成以下输出 -

The above code produces the following output −

当前窗口位置 x = 562 y = 309

current window position x = 562 y = 309

当前窗口位置 x = 562 y = 309

current window position x = 562 y = 309

当前窗口位置 x = 326 y = 304

current window position x = 326 y = 304

当前窗口位置 x = 384 y = 240

current window position x = 384 y = 240

当前窗口位置 x = 173 y = 408

current window position x = 173 y = 408

当前窗口位置 x = 226 y = 30

current window position x = 226 y = 30

当前窗口位置 x = 481 y = 80

current window position x = 481 y = 80

从 wx.Event 继承的一些子类在下表中列出 −

Some of the subclasses inherited from wx.Event are listed in the following table −

WxPython 中的事件有两种类型：基本事件和命令事件。基本事件只存在于其源头的窗口中。大多数 wxWidget 会生成命令事件。一个 command event 可以传播到位于类层次结构中源窗口之上的窗口。

Events in wxPython are of two types. Basic events and Command events. A basic event stays local to the window in which it originates. Most of the wxWidgets generate command events. A command event can be propagated to window or windows, which are above the source window in class hierarchy.

Example

以下是事件传播的一个简单示例。完整代码如下：

Following is a simple example of event propagation. The complete code is −

import wx

class MyPanel(wx.Panel):

   def __init__(self, parent):
      super(MyPanel, self).__init__(parent)

      b = wx.Button(self, label = 'Btn', pos = (100,100))
      b.Bind(wx.EVT_BUTTON, self.btnclk)
      self.Bind(wx.EVT_BUTTON, self.OnButtonClicked)

   def OnButtonClicked(self, e):

      print 'Panel received click event. propagated to Frame class'
      e.Skip()

   def btnclk(self,e):
      print "Button received click event. propagated to Panel class"
      e.Skip()

class Example(wx.Frame):

   def __init__(self,parent):
      super(Example, self).__init__(parent)

      self.InitUI()

   def InitUI(self):

      mpnl = MyPanel(self)
      self.Bind(wx.EVT_BUTTON, self.OnButtonClicked)

      self.SetTitle('Event propagation demo')
      self.Centre()
      self.Show(True)

   def OnButtonClicked(self, e):

      print 'click event received by frame class'
      e.Skip()

ex = wx.App()
Example(None)
ex.MainLoop()

在以上代码中，有两个类。 MyPanel ，一个 wx.Panel 子类和 Example，一个 wx.Frame 子类，它是该程序的顶级窗口。一个按钮放置在面板中。

In the above code, there are two classes. MyPanel, a wx.Panel subclass and Example, a wx.Frame subclass which is the top level window for the program. A button is placed in the panel.

这个 Button 对象绑定到一个事件处理程序 btnclk()，它将事件传播到父类（在这个例子中是 MyPanel）。按钮单击会生成一个 CommandEvent ，它可以通过 Skip() 方法传播到它的父对象。

This Button object is bound to an event handler btnclk() which propagates it to parent class (MyPanel in this case). Button click generates a CommandEvent which can be propagated to its parent by Skip() method.

MyPanel 类对象也把接收到的事件绑定到另一个处理程序 OnButtonClicked()。该函数又依次把事件发送给它的父对象，也就是 Example 类。以上代码会产生以下输出 −

MyPanel class object also binds the received event to another handler OnButtonClicked(). This function in turn transmits to its parent, the Example class. The above code produces the following output −

Button received click event. Propagated to Panel class.
Panel received click event. Propagated to Frame class.
Click event received by frame class.