在绘制矩形和徒手之间切换

Question

我的 Java 绘图程序有一些问题。

我有一个JComboBox，我可以在其中选择绘制矩形或手绘。对象被添加到ArrayList。我希望能够在绘制矩形和徒手之间切换，然后回到绘制矩形，然后徒手……等等。

如果我按照代码现在的样子这样做，它首先会很好地绘制矩形，然后当我切换到徒手时，它会很好地绘制线条，但是当我切换回矩形时，它仍然会绘制线条（或者有时线条与奇怪的矩形）。我切换的越多，它就越奇怪。

谁能看到代码有什么问题，因为我看不到？

public abstract class Draw  {
    public int startX, startY, endX, endY, width, height, w, h;
    public String color = "Black";


    public Draw(int startX, int startY, int width, int height) {
        this.startX = startX;
        this.startY = startY;
        this.width = width;
        this.height = height;
    }

    public abstract void draw(Graphics2D g);       

    public int getX() {
        return startX;
    }

    public void setX(int startX) {
        this.startX = startX;
    }

    public int getY() {
        return startY;
    }

    public void setY(int startY) {
        this.startY = startY;
    }

    public int getWidth() {
        return width;
    }

    public void setWidth(int width) {
        this.width = width;
    }

    public int getHeight() {
        return height;
    }

    public void setHeight(int height) {
        this.height = height;
    }

    public void setColor(String color) {
        this.color = color;
    }
}



public class Rectangle extends Draw {

    public Rectangle(int x, int y, int width, int height) {
        super(x, y, width, height);
    }        

    @Override
    public void draw(Graphics2D g2) {
        g2.drawRect(getX(), getY(), getWidth(), getHeight());
    }  
}

public class FreeHand extends Draw {

     public FreeHand(int x, int y, int width, int height) {
        super(x, y, width, height);
    }

    @Override
    public void draw(Graphics2D g2) {            
        g2.drawLine(getX(), getY(), getWidth(), getHeight());
    }
}

public class PaintProgram extends JFrame implements ActionListener {

    public ArrayList<Draw> shapeList = new ArrayList<>();   
    int startX, startY, endX, endY, w, h;
    private JPanel topPanel;   
    private JPanel bottomPanel;
    private JPanel leftPanel;
    private JPanel rightPanel;
    private JComboBox comboBox;
    private final String[] boxOptions = new String[] {"Rectangle", "Freehand"};   
    Container cp = getContentPane();
    private int count = 0;


    public JavaApplication30(String title) {
        super(title);
        this.setLayout(new BorderLayout());
        this.setDefaultCloseOperation(DO_NOTHING_ON_CLOSE);
        this.setLocationRelativeTo(null);        
        this.setSize(840, 500);     
        this.initComponents();
        this.setVisible(true);            
    }


    private void initComponents() {

        cp.setBackground(Color.WHITE);

        comboBox = new JComboBox(boxOptions);
        topPanel = new JPanel();     
        bottomPanel = new JPanel(new GridLayout(1,2));  
        rightPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
        leftPanel = new JPanel(new FlowLayout(FlowLayout.LEFT));

        comboBox.setSelectedIndex(0);          
        comboBox.addActionListener(this); 

        topPanel.setPreferredSize(new Dimension(0,40));        
        bottomPanel.setPreferredSize(new Dimension(0,30));                       
        bottomPanel.setBackground(Color.LIGHT_GRAY);        

        topPanel.add(comboBox);
        bottomPanel.add(leftPanel);        
        bottomPanel.add(rightPanel);

        this.add(topPanel, BorderLayout.PAGE_START);          
        this.add(bottomPanel, BorderLayout.PAGE_END);                  
    }


    @Override
    public void paint(Graphics g) {
        if(count == 0) {
            cp.repaint();
        }
        Graphics2D g2 = (Graphics2D) g;

        for (Draw d : shapeList) {
            d.draw(g2);
        }        

        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        g2.setStroke(new BasicStroke(1));

        if (startX != 0 && startY != 0 && endX != 0 && endY != 0) {

            int width = Math.abs(startX - endX);
            int height = Math.abs(startY - endY);

            int minX = Math.min(startX, endX);
            int minY = Math.min(startY, endY);               

            Rectangle r = new Rectangle(minX, minY, width, height);

            g2.setPaint(Color.WHITE);
            g2.fillRect(r.getX(), r.getY(), r.getWidth(), r.getHeight()); 
            r.setColor(pickedColor);

            r.draw(g2);
        }
    }


    @Override
    public void actionPerformed(ActionEvent e) {

        count++;

        if (e.getSource().equals(comboBox)) {    

            JComboBox cb = (JComboBox)e.getSource();

            if (cb.getSelectedItem().equals("Rectangle")) {

                this.addMouseListener(new MouseAdapter() {    

                    @Override
                    public void mousePressed(MouseEvent e) {                   
                        startX = e.getX();     
                        startY = e.getY(); 

                        endX = startX;  
                        endY = startY;  
                        repaint(); 
                    }

                    @Override
                    public void mouseReleased(MouseEvent e) {
                        endX = e.getX();
                        endY = e.getY();

                        int width = Math.abs(startX - endX);
                        int height = Math.abs(startY - endY);

                        int minX = Math.min(startX, endX);
                        int minY = Math.min(startY, endY);               

                        Rectangle r =  new Rectangle(minX, minY, width, height);
                        shapeList.add(r);
                        r.setColor(pickedColor);

                        startX = 0;
                        startY = 0;
                        endX = 0;
                        endY = 0;
                        repaint();
                    }
                });    

                this.addMouseMotionListener(new MouseMotionAdapter() {
                    @Override
                    public void mouseDragged(MouseEvent e) {
                        endX = e.getX();
                        endY = e.getY();
                        repaint();
                    }
                });
            }            


            else if (cb.getSelectedItem().equals("Freehand")) {

                this.addMouseListener(new MouseAdapter() {                   
                    @Override
                    public void mousePressed(MouseEvent e) {                   
                        startX = e.getX();
                        startY = e.getY();                       
                        addCoordinate(startX, startY);
                    }
                });

                this.addMouseMotionListener(new MouseMotionAdapter() {
                    @Override
                    public void mouseDragged(MouseEvent e) {                
                        Graphics g = getGraphics();    
                        Graphics2D g2 = (Graphics2D) g;         

                        FreeHand fh =  new FreeHand(startX, startY, e.getX(), e.getY());
                        shapeList.add(fh);
                        fh.setColor(pickedColor);
                        fh.draw(g2);                    
                        startX = e.getX();
                        startY = e.getY();                         
                    }
                });    
            }
        }
    }                 

    public static void main(String args[]) {
        new PaintProgram("Paint");
    }
}

Answer 1

您添加了 MouseListeners 但没有删除它们。每次您在组合框中选择某些内容时，都会添加一个新的侦听器。因此，当您绘制某些东西时，每个侦听器都会被应用，并且会发生奇怪的事情。

您应该在添加新的之前删除以前的 MouseListener。您可能必须在实例变量中记住它。

或者，您可以在开始时添加所有侦听器，但检查侦听器内部组合框的值。如果该值与侦听器的用途不符，则不应执行任何操作。

编辑：这是删除所有侦听器的方法

    for (MouseListener listener : this.getMouseListeners()) {
        this.removeMouseListener(listener);
    }
    for (MouseMotionListener listener : this.getMouseMotionListeners()) {
        this.removeMouseMotionListener(listener);
    }

在 actionPerformed() 方法中添加新的侦听器之前放入此代码

Answer 2

如前所述here 和here，不要在ActionListener 中添加MouseListeners，而是创建一个MosueListener，并根据当前选择的项目确定您要执行的操作。

基本上，每次调用actionPerformed 时，您都会不断添加一个新的MouseListener...它们正在累积...

解决方案是使用单个 MouseListener 和某种工厂...

从定义工厂接口开始...

public interface DrawFactory {

    public Draw createDrawing(int x, int y, int width, int height, Color color);
    public void addPoint(Draw draw, int x, int y);

}

为您要绘制的每种形状创建工厂的实现...

public class RectangleFactory implements DrawFactory {

    @Override
    public Draw createDrawing(int x, int y, int width, int height, Color color) {
        return new Rectangle(x, y, width, height);
    }

    @Override
    public void addPoint(Draw draw, int x, int y) {
        // Does nothing...
    }

    @Override
    public boolean isMutable() {
        return false;
    }

    @Override
    public String getName() {
        return "Rectangle";
    }

    @Override
    public String toString() {
        return getName();
    }

}

public class FreeHandFactory implements DrawFactory {

    @Override
    public Draw createDrawing(int x, int y, int width, int height, Color color) {
        return new FreeHand(x, y, width, height);
    }

    @Override
    public void addPoint(Draw draw, int x, int y) {
        if (draw instanceof FreeHand) {
            FreeHand fh = (FreeHand)draw;
            //fh.addPoint(x, y);
        }
    }

    @Override
    public boolean isMutable() {
        return true;
    }

    @Override
    public String getName() {
        return "Free Hand";
    }

    @Override
    public String toString() {
        return getName();
    }

}

接下来，创建一个从 JPanel 扩展的自定义组件，该组件将充当主绘图表面，这将负责监视 MouseLstener 并绘制 Draw 实例，正如 here 所提到的那样

public class DrawSurface extends JPanel {

    private DrawFactory factory;
    private Draw currentDraw;
    private List<Draw> shapeList = new ArrayList<>();
    private Color drawColor;

    public DrawSurface() {
        shapeList = new ArrayList<>(25);
        MouseAdapter ma = new MouseAdapter() {

            private Point pressPoint;

            @Override
            public void mousePressed(MouseEvent e) {
                pressPoint = e.getPoint();
            }

            @Override
            public void mouseReleased(MouseEvent e) {
                DrawFactory factory = getDrawFactory();
                if (factory != null) {
                    Point p = e.getPoint();
                    if (factory.isMutable() && currentDraw != null) {
                        factory.addPoint(currentDraw, p.x, p.y);
                    } else {
                        int x = Math.min(p.x, pressPoint.x);
                        int y = Math.min(p.y, pressPoint.y);

                        int width = Math.abs(p.x - pressPoint.x);
                        int height = Math.abs(p.y - pressPoint.y);

                        Draw draw = factory.createDrawing(x, y, width, height, getDrawColor());
                        shapeList.add(draw);
                        if (factory.isMutable()) {
                            currentDraw = draw;
                        }
                    }
                }
            }
        };
    }

    public DrawFactory getDrawFactory() {
        return factory;
    }

    public void setDrawFactory(DrawFactory factory) {
        this.factory = factory;
        currentDraw = null;
    }

    public Color getDrawColor() {
        return drawColor;
    }

    public void setDrawColor(Color drawColor) {
        this.drawColor = drawColor;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g.create();
        for (Draw draw : shapeList) {
            draw.draw(g2d);
        }
        g2d.dispose();
    }

    public Dimension getPreferredSize() {
        return new Dimension(200, 200);
    }

}

接下来，将您的boxOptions 从String 更改为DrawFactory，这将更容易确定您应该使用哪个工厂。不要忘记添加对DrawSurface的引用

private final DrawFactory[] boxOptions = new DrawFactory[]{new RectangleFactory(), new FreeHandFactory()};
private DrawSurface drawSurface;

在您的initComponents 中创建DrawSurface 的新实例并将其添加到您的框架中...

private void initComponents() {
    //...    
    drawSurface = new DrawSurface();
    this.add(drawSurface);
}

更改您的 actionPerformed 方法，使其看起来更像...

@Override
public void actionPerformed(ActionEvent e) {
    count++;
    drawSurface.setDrawFactory((DrawFactory)comboBox.getSelectedItem());
}

由于示例代码不完整，不确定如何确定当前颜色，但基本上，您希望类似地设置DrawSurface 的drawColor。

摆脱PaintProgram 中的paint 方法，因为您不应该覆盖顶级容器的paint 方法，建议您至少不要这样做一次，如果不是两次的话。

这一切的重点很简单，当你想添加一个新的“绘图形状”时，你为它创建一个Draw 和DrawFactory 并将工厂添加到组合框中......工作完成...... .