Update 事件和信号.md

事件和信号.md

@@ -137,12 +137,12 @@ def keyPressEvent(self, e):
     if e.key() == Qt.Key_Escape:
         self.close()
 ```
-If we click the Escape button, the application terminates.
+此时如果按下ESC键程序就会退出。
 
-Event sender
-
-Sometimes it is convenient to know which widget is the sender of a signal. For this, PyQt5 has the sender() method.
+## 事件发送
 
+有时候我们会想知道是哪个组件发出了一个信号，PyQt5里的`sender()`方法能搞定这件事。
+```
 #!/usr/bin/python3
 # -*- coding: utf-8 -*-
 
@@ -198,24 +198,29 @@ if __name__ == '__main__':
     app = QApplication(sys.argv)
     ex = Example()
     sys.exit(app.exec_())
-We have two buttons in our example. In the buttonClicked() method we determine which button we have clicked by calling the sender() method.
-
+```
+这个例子里有俩按钮，`buttonClicked()`方法决定了是哪个按钮能调用`sender()`方法。
+```
 btn1.clicked.connect(self.buttonClicked)            
 btn2.clicked.connect(self.buttonClicked)
-Both buttons are connected to the same slot.
-
+```
+两个按钮都和同一个slot绑定。
+```
 def buttonClicked(self):
   
     sender = self.sender()
     self.statusBar().showMessage(sender.text() + ' was pressed')
-We determine the signal source by calling the sender() method. In the statusbar of the application, we show the label of the button being pressed.
+```
+我们用调用`sender()`方法的方式决定了事件源。状态栏显示了被点击的按钮。
 
-Event sender
-Figure: Event sender
-Emitting signals
+程序展示：
 
-Objects created from a QObject can emit signals. In the following example we will see how we can emit custom signals.
+![event sender](./images/4-eventsender.png)
 
+## 信号发送
+
+`QObject`实例能发送事件信号。下面的例子是发送自定义的信号。
+```
 #!/usr/bin/python3
 # -*- coding: utf-8 -*-
 
@@ -268,18 +273,22 @@ if __name__ == '__main__':
     app = QApplication(sys.argv)
     ex = Example()
     sys.exit(app.exec_())
-We create a new signal called closeApp. This signal is emitted during a mouse press event. The signal is connected to the close() slot of the QMainWindow.
-
+```
+我们创建了一个叫closeApp的信号，这个信号会在鼠标按下的时候触发，事件与`QMainWindow`绑定。
+```
 class Communicate(QObject):
     
     closeApp = pyqtSignal()
-A signal is created with the pyqtSignal() as a class attribute of the external Communicate class.
-
+```
+`Communicate`类创建了一个`pyqtSignal()`属性的信号。
+```
 self.c = Communicate()
 self.c.closeApp.connect(self.close) 
-The custom closeApp signal is connected to the close() slot of the QMainWindow.
-
+```
+`closeApp`信号`QMainWindow`的`close()`方法绑定。
+```
 def mousePressEvent(self, event):
     
     self.c.closeApp.emit()
-When we click on the window with a mouse pointer, the closeApp signal is emitted. The application terminates.
+```
+当点击窗口的时候，closeApp信号发送，程序终止。