如何在Java Swing中同步兩個視圖

Question

我正在嘗試這樣做：在我的GUI中，我有一個帶有自定義模型的JTable，而在GUI的其他部分，我有一個面板，我繪制一些箭頭。 我想“同步這兩個視圖。所以讓我們說如果我的JTable中有5行，我將在箭頭面板中繪制5個箭頭。如果我對行數進行修改，我必須具有相同的數量因此我正在嘗試使用Design Pattern Observer。

為了簡化，我嘗試在一個文件中提供一個可計算的示例：我在第一個Panel（ButtonPanel）中創建了n個按鈕，並在第二個面板（LabelButton）中創建了n個標簽。

問題是：如何使用DP Observer同步標簽數量和標簽數量

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);
    }

}

編輯：我使用自己的DP Observer而不是API，因為無法進行多次擴展

Answer 1

我使用Observer模式因為我認為它是最好的解決方案。

Swing是一個事件驅動的API，其行為非常類似於觀察者模式，因為有訂閱的事件和監聽器可以監聽這些事件。 例如， JButton組件每次按下時都會調度一個ActionEvent，並通知訂閱的ActionListener發生了某些事情。

使用相同的原則， TableModel有責任在每次更改數據（添加/刪除行，更新單元格等）時調度TableModelEvent ，並在此類事件中通知訂閱的TableModelListener 。

您可以使用此事實來實現您的主要目標：

所以，假設我的JTable中有5行，我將在箭頭面板中繪制5個箭頭。

1. 創建一個JPanel ，可以根據需要繪制許多箭頭。 請參閱執行自定義繪畫課程。
2. 將TableModelListener附加到TableModel ，以便在插入/刪除行時重新繪制JPanel 。

---

我有兩個類，我想要兩個類之間的最小依賴。

如果您按照我的建議，您應該能夠創建一個獨立且可重復使用的JPanel如下所示：

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);
    }
}

通過這種方式，您的面板可以獨立地確定外部箭頭的數量（它可以是表模型中的行數，列表中的元素數，固定值，無論您想要的是什么）。

Answer 2

我已完全按照您的意願實現它：

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 = 0; i < numberButton; i++)
            this.add(createButton(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;
            int diff = numberButton + (number - numberButton);
            // if diff and numberButton are equal do nothing
            if (diff < numberButton) {
                for (int i = numberButton - 1; i >= diff; i--) {
                    this.remove(this.getComponent(i));
                }
            } else if (diff > numberButton) {
                for (int i = numberButton; i < diff; i++) {
                    this.add(createButton(i));
                }
            }
            numberButton = number;
            System.out.println("ButtonPanel, numberButton: " + numberButton);
        }
    }

    private JButton createButton(int i) {
        return new JButton("" + ++i);
    }
}

class LabelPanel extends JPanel implements Observer {

    private int numberLabel;

    public LabelPanel() {
        super();
    }

    public LabelPanel(int numberLabel) {
        super();
        this.numberLabel = numberLabel;
        for (int i = 0; i < numberLabel; i++)
            this.add(createLabel(i));
        this.setBorder(new LineBorder(Color.blue));
    }

    @Override
    public void update(Subject subject, int number) {
        if (subject instanceof SynchronizeNumber) {
            SynchronizeNumber synchronizeNumber = (SynchronizeNumber) subject;
            int diff = numberLabel + (number - numberLabel);
            // if diff and numberButton are equal do nothing
            if (diff < numberLabel) {
                for (int i = numberLabel - 1; i >= diff; i--) {
                    this.remove(this.getComponent(i));
                }
            } else if (diff > numberLabel) {
                for (int i = numberLabel; i < diff; i++) {
                    this.add(createLabel(i));
                }
            }
            numberLabel = number;
            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;
    }

    private JLabel createLabel(int i) {
        return new JLabel("label name:" + ++i);
    }
}

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);

        synchronizeNumber.setNumberSync(3);
        synchronizeNumber.setNumberSync(11);
        synchronizeNumber.setNumberSync(5);
        synchronizeNumber.setNumberSync(7);

        f.add(buttonPanel);
        f.add(labelPanel);
        f.setSize(400, 400);
        f.setLocationRelativeTo(null);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
    }

}