java - 如何在 Java Swing 中同步两个 View

Question

我正在尝试这样做:在我的 GUI 中，我有一个带有自定义模型的 JTable，在 GUI 的其他部分，我有一个面板，我在其中绘制了一些箭头。我想“同步这两个 View 。假设我的 JTable 中有 5 行，我将在箭头面板中绘制 5 个箭头。如果我修改行数，我必须具有相同的行数排。所以我正在尝试使用 Design Pattern Observer。

为简单起见，我尝试提供一个可在一个文件中计算的示例:我在第一个面板 (ButtonPanel) 中创建了 n 个按钮，并在第二个面板 (LabelButton) 中创建了 n 个标签。

问题是:如何用DP Observer同步标签个数

import java.awt.Color;
import java.awt.GridLayout;
import java.util.ArrayList;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.border.LineBorder;

interface Observer {
    public void update(Subject subject, int number);
}

interface Subject {
    public void addObserver(Observer observer);

    public void delObserver(Observer observer);

    public void notifyObservers();
}

class SynchronizeNumber implements Subject {
    private ArrayList<Observer> observers;

    private int numberSync;

    public SynchronizeNumber() {
        super();
        observers = new ArrayList<Observer>();

    }

    public SynchronizeNumber(int numberSync) {
        super();
        this.numberSync = numberSync;
        observers = new ArrayList<Observer>();

    }

    @Override
    public void addObserver(Observer observer) {
        observers.add(observer);

    }

    @Override
    public void delObserver(Observer observer) {
        observers.remove(observer);

    }

    @Override
    public void notifyObservers() {
        for (Observer o : observers) {
            o.update(this, this.numberSync);
        }
    }

    /**
     * @return the number
     */
    public int getNumberSync() {
        return numberSync;
    }

    /**
     * @param number
     *            the number to set
     */
    public void setNumberSync(int numberSync) {
        this.numberSync = numberSync;
        notifyObservers();
    }
}

class ButtonPanel extends JPanel implements Observer {

    private int numberButton;

    public ButtonPanel() {
        super();
    }

    public ButtonPanel(int numberButton) {
        this.numberButton = numberButton;
        for (int i = 1; i <= numberButton; i++)
            this.add(new JButton("" + i));
    }

    /**
     * @return the numberLabel
     */
    public int getNumberButton() {
        return numberButton;
    }

    /**
     * @param numberLabel
     *            the numberLabel to set
     */
    public void setNumberButton(int numberButton) {
        this.numberButton = numberButton;
    }

    @Override
    public void update(Subject subject, int number) {
        if (subject instanceof SynchronizeNumber) {
            SynchronizeNumber synchronizeNumber = (SynchronizeNumber) subject;
            numberButton = synchronizeNumber.getNumberSync();
            System.out.println("ButtonPanel, numberButton: " + numberButton);
        }
    }
}

class LabelPanel extends JPanel implements Observer {

    private int numberLabel;

    public LabelPanel() {
        super();
    }

    public LabelPanel(int numberLabel) {
        super();
        this.numberLabel = numberLabel;
        for (int i = 1; i <= numberLabel; i++)
            this.add(new JLabel("label numbe: " + i));
        this.setBorder(new LineBorder(Color.blue));
    }

    @Override
    public void update(Subject subject, int number) {
        if (subject instanceof SynchronizeNumber) {
            SynchronizeNumber synchronizeNumber = (SynchronizeNumber) subject;
            numberLabel = synchronizeNumber.getNumberSync();
            System.out.println("LabelPanel, numberLabel: " + numberLabel);
        }
    }

    /**
     * @return the numberLabel
     */
    public int getNumberLabel() {
        return numberLabel;
    }

    /**
     * @param numberLabel
     *            the numberLabel to set
     */
    public void setNumberLabel(int numberLabel) {
        this.numberLabel = numberLabel;
    }
}

public class Test {

    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setLayout(new GridLayout(2, 1));

        // create an subject synchronizeNumber
        SynchronizeNumber synchronizeNumber = new SynchronizeNumber();

        // set number to 1
        synchronizeNumber.setNumberSync(1);

        //create observers buttonPanel and labelPanel 
        ButtonPanel buttonPanel = new ButtonPanel(synchronizeNumber.getNumberSync());
        LabelPanel labelPanel = new LabelPanel(synchronizeNumber.getNumberSync());

        // add buttonPanel and labelPanel as observers
        synchronizeNumber.addObserver(buttonPanel);
        synchronizeNumber.addObserver(labelPanel);

        // make a change manually
        synchronizeNumber.setNumberSync(4);
        f.add(buttonPanel);
        f.add(labelPanel);
        f.setSize(400, 400);
        f.setLocationRelativeTo(null);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
    }

}

编辑:我使用自己的 DP Observer 而不是 API，因为不可能进行多次扩展

Answer 1

I use Observer pattern because I think it is the best solution.

Swing 是一种事件驱动的 API，在存在事件和订阅监听这些事件的监听器的意义上，它的行为非常像观察者模式。例如JButton组件发送 ActionEvent每次按下并通知订阅ActionListener是不是出事了。

同理，责任TableModel dispatch TableModelEvent每次更改数据(添加/删除行、更新单元格等)并通知订阅者TableModelListener在这样的事件中。

您可以使用这个事实来实现您的主要目标:

So let's say if we have 5 rows in my JTable, I will draw 5 arrows in the panel of arrows.

1. 创建一个JPanel，可以根据需要绘制许多箭头。参见 Performing Custom Painting教训。
2. 将 TableModelListener 附加到您的 TableModel，以便在插入/删除行时重新绘制您的 JPanel。

---

I have two classes and I want a minimun dependency between the two classes.

如果您遵循我的建议，您应该能够像这样创建一个独立且可重用的 JPanel:

class MyCustomPanel extends JPanel {

    private int numberOfArrows = 0;

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g); // never forget to call super.paintComponent(g)
        Graphics graphics = g.create();
        int y = 10;
        for(int i = 0; i < numberOfArrows; i++) {                
            graphics.drawLine(10, y, getWidth() - 10, y); // instead of lines just draw your arrows
            y += 10;
        }
        graphics.dispose();
    }

    /**
     * Public method to set the number of arrows that has to be drawn.
     * @param arrows 
     */
    public void setNumberOfArrows(int arrows) {
        numberOfArrows = arrows;
        repaint();
    }

    @Override
    public Dimension getPreferredSize() {
        return isPreferredSizeSet() 
             ? super.getPreferredSize() : new Dimension(200,200);
    }
}

通过这种方式，您的面板可以根据确定的方式独立地从外部获取箭头数量(它可以是表模型中的行数、列表中的元素数、固定值，任何你想要的)。