java - 绘制形状时，形状属性未在类之间正确传递 - Java Swing

Question

我对 java 相当陌生(编码大约 8 个月)，在 JPanel 上绘制形状时遇到一些问题。我已经可以通过单击并拖动鼠标来绘制形状。我遇到的问题是:

• 当我尝试将颜色传递给正在绘制形状的类时，颜色不会更新并保持默认颜色(黑色)。

• 当我尝试更改形状的 pointSize(使用 setStroke 方法)时，我正确绘制的第一个形状会更新 pointSize，但我绘制的下一个形状具有默认的 pointSize。 (看起来好像每次绘制新形状时 pointSize 都会重置)

长话短说；我认为实例化新对象的方式以及将值传递给其他类的方式有问题。我一直在从其他人的问题中寻找答案，但我就是不知道出了什么问题。

这是我的代码:

我的 inputHandler 类:

        package colors;

    import java.awt.Color;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.awt.event.MouseEvent;
    import java.util.Random;

    import javax.swing.JLabel;
    import javax.swing.event.ChangeEvent;
    import javax.swing.event.ChangeListener;
    import javax.swing.event.MouseInputListener;


    public class InputHandler implements ActionListener, MouseInputListener, ChangeListener
    {
        private DrawPanel dp;
        public int pos = 0;
        public String mode = "";
        public String shapeColor = "";
        private double startx;
        private double starty;  

        ButtonPanel bp;
        myRectangle rectangle = new myRectangle();
        myLine line = new myLine();
        myEllipse ellipse = new myEllipse();

        JLabel label;



        public InputHandler(DrawPanel dpanel, ButtonPanel bpanel) 
        {
            this.dp = dpanel;
            this.bp = bpanel;
            dp.addMouseListener(this);
            dp.addMouseMotionListener(this);
        }   


        public void actionPerformed (ActionEvent e) 
        {   

            switch (buttonPressed(e)) //handles the pressed button
            {

                case "Paint":
                    mode = "paint";
                    myRectangle.paint = true;
                    myEllipse.paint = true;
                    break;      

                case "Add Line":
                    mode = "place line";            
                    break;

                case "Add Ellipse":
                    mode = "place ellipse";         
                    break;

                case "Add Rectangle":
                    mode = "place rectangle";           
                    break;  

                case "Delete":              
                    for(int i = dp.shapesList.size()-1; i>=0; i--)
                    {
                        dp.shapesList.remove(i);                    
                    }
                    System.out.println("Canvas cleared.");
                    dp.repaint();
                    break;

                case "Image":
                    mode  = "image";            
                    dp.repaint();
                    break;

                case "Text":
                    mode  = "text";         
                    dp.repaint();
                    break;



                    //colors
                case "red":
                    shapeColor = "red";
                    rectangle.setColor(Color.red);  
                    ellipse.setColor(Color.red);                
                    line.setColor(Color.red);
                    System.out.println("red");
                    break;

                case "blue":
                    shapeColor = "blue";            
                    rectangle.color = Color.blue;
                    ellipse.color = Color.blue;         
                    line.color = Color.blue;
                    System.out.println("blue");
                    break;

                case "green":
                    shapeColor = "green";
                    rectangle.color = Color.green;          
                    ellipse.color = Color.green;                
                    line.color = Color.green;
                    System.out.println("green");
                    break;

                case "yellow":
                    shapeColor = "yellow";          
                    rectangle.color = Color.yellow;
                    ellipse.color = Color.yellow;           
                    line.color = Color.yellow;
                    System.out.println("yellow");
                    break;

                case "black":
                    shapeColor = "black";
                    rectangle.color = Color.black;          
                    ellipse.color = Color.black;                
                    line.color = Color.black;
                    System.out.println("black");
                    break;

                case "purple":
                    shapeColor = "purple";          
                    rectangle.color = Color.magenta;
                    ellipse.color = Color.magenta;          
                    line.color = Color.magenta;         
                    System.out.println("magenta");
                    break;

                default:
                    break;
            }
        }



        public String buttonPressed (ActionEvent e)
        {
            String buttonPressed = e.getActionCommand();        
            return buttonPressed;
        }




        @Override
        public void mouseClicked(MouseEvent me) 
        {       


            if(mode.equals("paint"))
            {   
                double x = me.getX();
                double y = me.getY();


                for(int i = 0; i<dp.shapesList.size(); i++)
                {
                    if(dp.shapesList.get(i).contains(x, y))
                    {

                    }
                }
            }

            if(mode.equals("text"))
            {
                System.out.println("test");
                double x = me.getX();
                double y = me.getY();

            }
        }







        @Override
        public void mouseEntered(MouseEvent me) 
        {


        }

        @Override
        public void mouseExited(MouseEvent me) 
        {
            // TODO Auto-generated method stub

        }

        @Override
        public void mousePressed(MouseEvent me) 
        {
            double x = me.getX();
            double y = me.getY();
            startx = me.getX();
            starty = me.getY();

            if(mode.equals("place line"))
            {   
                 line = new myLine(startx,starty,x,y);
                dp.shapesList.add(line);
                dp.repaint();
            }

            if(mode.equals("place rectangle"))
            {       
                 rectangle = new myRectangle(startx,starty,x,y);
                dp.shapesList.add(rectangle);
                dp.repaint();
            }

            if(mode.equals("place ellipse"))
            {   
                 ellipse = new myEllipse(startx,starty,x,y);
                dp.shapesList.add(ellipse);
                dp.repaint();
            }



        }

        @Override
        public void mouseReleased(MouseEvent me) 
        {
            startx = 0;
            starty = 0;

        }

        @Override
        public void mouseDragged(MouseEvent me) 
        {
            double x = me.getX();
            double y = me.getY();


                if(mode.equals("place line"))
                {   
                     line = new myLine(startx,starty,x,y);
                    dp.shapesList.remove(dp.shapesList.size()-1);
                    dp.shapesList.add(line);
                    dp.repaint();               
                }

                if(mode.equals("place rectangle"))
                {   
                     rectangle = new myRectangle(startx,starty,x,y);
                    dp.shapesList.remove(dp.shapesList.size()-1);
                    dp.shapesList.add(rectangle);
                    dp.repaint();               

                }

                if(mode.equals("place ellipse"))
                {   
                     ellipse = new myEllipse(startx,starty,x,y);
                    dp.shapesList.remove(dp.shapesList.size()-1);
                    dp.shapesList.add(ellipse);
                    dp.repaint();

                }


        }

        @Override
        public void mouseMoved(MouseEvent me) 
        {

        }


        @Override
        public void stateChanged(ChangeEvent ce) 
        {

            if(ce.getSource() == bp.pointSize)
            {
                rectangle.setStroke(bp.pointSize.getValue());
                ellipse.setStroke(bp.pointSize.getValue());
                line.setStroke(bp.pointSize.getValue());
            }
        }


    }

myRectangle 类(绘制矩形的类):` 包装颜色；

        import java.awt.BasicStroke;
        import java.awt.Color;
        import java.awt.Graphics2D;
        import java.awt.geom.Rectangle2D;

        public class myRectangle implements Drawable {

            private double x1, y1, x2, y2;
            DrawPanel dp;
            public Color color;
            public static boolean paint;
            public  int pointSize;

            public myRectangle() {

            }

            public myRectangle(double x1, double y1, double x2, double y2) {
                this.x1 = x1;
                this.y1 = y1;
                this.x2 = x2;
                this.y2 = y2;       
            }

            @Override
            public void draw(Graphics2D g) {         
                 double x = getStartX();
                 double y = getStartY();
                 double width = getWidth();
                 double height = getHeight();
                 Rectangle2D r = new Rectangle2D.Double(x, y, width, height);           
                 g.setColor(color);      
                 g.draw(r);          
                 g.setStroke(new BasicStroke(pointSize));
                 if(paint)
                 {
                     g.fillRect((int)x, (int)y, (int)width, (int)height);            
                 }

                 System.out.println("rectangle called");
            }





            public boolean contains(double x, double y) {
                return x >= getStartX() && x <= getEndX() && y >= getStartY() && y <= getEndY();
            }

            public double getWidth() {
                return Math.abs(x1 - x2);
            }

            public double getHeight() {
                return Math.abs(y1 - y2);
            }

            public double getStartX() {
                return Math.min(x1, x2);
            }

            public double getStartY() {
                return Math.min(y1, y2);
            }

            public double getEndX() {
                return Math.max(x1, x2);
            }

            public double getEndY() {
                return Math.max(y1, y2);
            }

            public String getShape()
            {
                return "Rectangle";
            }

            public void setStroke(int stroke)
            {
                pointSize = stroke;
            }


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

我的DrawPanel类(在JPanel上绘制形状的类):`包颜色；

        import java.awt.Graphics;
        import java.awt.Graphics2D;
        import java.util.ArrayList;

        import javax.swing.JPanel;

        @SuppressWarnings("serial")
        public class DrawPanel extends JPanel 
        {
            public ArrayList<Drawable> shapesList = new ArrayList<Drawable>();
            public static int pointSize;



            public DrawPanel()
            {
                super();
            }



            @Override
            public void paintComponent(Graphics g)
            {
                super.paintComponent(g);            

                // Cast the graphics object to type Graphics2D
                Graphics2D g2d = (Graphics2D) g;    
                // Loop through the shapesList and draw every shape
                for(Drawable s : shapesList)
                {   
                    s.draw(g2d);        
                }

            }







        }`

最后，这是一张图像，可以让您对我的程序有一个基本的了解:image of my program

我知道这是很多代码，但我已经在这些问题上苦苦挣扎了一段时间，我只是无法弄清楚出了什么问题，所以我最终决定发表一篇文章。

预先感谢您的帮助。

-米克

Answer 1

Long story short; I think there is something wrong with the way I instantiate new objects and how I pass values to other classes

是的，您在创建形状对象时并未设置它们的所有参数。

rectangle.setColor(Color.red);  
ellipse.setColor(Color.red);                
line.setColor(Color.red);

当您单击颜色按钮时，您可以在上面设置现有对象的颜色。

rectangle = new myRectangle(startx,starty,x,y);
dp.shapesList.add(rectangle);

但是随后您创建了一个新对象并将该对象添加到列表中，但您从未设置颜色。

创建对象时需要设置所有参数。

“红色”按钮应该只在类中设置一个变量，以便在创建形状对象时使用下一个颜色。

查看Custom Painting有关在绘制矩形时设置颜色的工作示例。

此外，您通常会在将形状添加到 shapeList 后调用 repaint()，而不是使用“Paint”按钮。不需要“paint”变量。只要调用draw()方法就可以绘制形状。