write java.The ViewHistory shows only a HistoryPanel object, nothing else. The update method of the ViewHistory class calls Swing’s repaint method (this forces Swing to redraw everything every time the model changes, which in turn forces Swing to automatically call the paintComponent method of the HistoryPanel to redraw the updated version of the history).
时间: 2023-12-10 16:41:43 浏览: 100
Sure, here's the Java code:
```java
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class ViewHistory {
private HistoryPanel historyPanel;
public ViewHistory() {
historyPanel = new HistoryPanel();
}
public JPanel getHistoryPanel() {
return historyPanel;
}
public void update() {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
historyPanel.repaint();
}
});
}
private class HistoryPanel extends JPanel {
// Implement paintComponent method to draw the history
}
}
```
In this code, `ViewHistory` is a class that represents the view for a history model. It has a single `JPanel` field called `historyPanel` that represents the panel where the history will be drawn. The `update` method is responsible for updating the view whenever the model changes. It does this by calling `repaint` on the `historyPanel`, which will cause Swing to call the `paintComponent` method of the `HistoryPanel` class to redraw the updated history.
Note that we use `SwingUtilities.invokeLater` to schedule the `repaint` call on the Event Dispatch Thread (EDT) to ensure that it is executed in a thread-safe manner. Also, the `HistoryPanel` class is declared as a private inner class of `ViewHistory` to encapsulate the view logic within the view class.
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