The constructor of the ViewSimple class registers the view with the model (the library) using the addListener method of the model, creates a JLabel object, stores it in the label instance variable of the ViewSimple class, initializes it to display the total number of books borrowed by all users of the library, and adds the label to the view (which is a frame). The update method of the ViewSimple class updates the text of the label as necessary so that the label always displays the current value of the total number of books borrowed by all users of the library. Since the ViewSimple does not have any button, it cannot perform any action, therefore the corresponding controller ControllerSimple does nothing. (We still want to have the ControllerSimple class so that our application follows the correct Model-View-Controller design pattern.) Fifth, create a GUI class with a main method. In this main method, create an anonymous class that implements the Runnable interface with a run method and use the javax.swing.SwingUtilities.invokeLater method to run that code on the event dispatch thread.
时间: 2023-11-28 15:50:05 浏览: 36
This GUI class should create an instance of the ModelSimple, an instance of the ViewSimple, and an instance of the ControllerSimple. Then, it should register the view with the model by calling the addListener method of the model and passing in the view as a parameter. Finally, it should set the size of the view and make it visible. Here's an example code:
```
public class LibraryGUI {
public static void main(String[] args) {
ModelSimple model = new ModelSimple();
ViewSimple view = new ViewSimple();
ControllerSimple controller = new ControllerSimple(model, view);
model.addListener(view);
JFrame frame = new JFrame("Library");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(view);
frame.pack();
frame.setVisible(true);
// run the code on the event dispatch thread
SwingUtilities.invokeLater(new Runnable() {
public void run() {
// update the view periodically
while (true) {
try {
Thread.sleep(1000); // wait for 1 second
} catch (InterruptedException e) {}
model.update(); // update the model
}
}
});
}
}
```
This code creates an infinite loop that periodically updates the model and the view. You can modify the frequency of the updates by changing the value of the sleep time. Note that this is just a simple example to demonstrate the basic structure of a Model-View-Controller application. In practice, you would typically use event listeners to trigger updates instead of polling the model periodically.