Java Mousepress()绘制图像

Question

我创建它是为了当鼠标按下鼠标的x和y坐标时绘制一条鱼。但是我似乎并没有调用drawfish方法。我找不到它不工作的原因。如果有任何帮助，我将不胜感激。

  /*FishTank*/
  import java.awt.Graphics;
  import javax.swing.JComponent;
  import javax.swing.JFrame;
  import java.awt.event.*;
  import javax.swing.*;
  import java.awt.*;
  import java.awt.geom.*;
  /*FishTank class-contains a frame and the WinstonCanvas.*/
  public class FishTank{

    public static void main ( String[] args ){
      javax.swing.SwingUtilities.invokeLater(new Runnable(){
  public void run(){
          JFrame window = new JFrame();
          window.setTitle("Fish Tank");
          window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          window.setBounds(30, 30, 700, 430);
          window.getContentPane().add(new FishTankCanvas());
          window.setVisible(true);
        }
      });
    }
  }
  /*FishTankCanvas is a component that allows drawing shapes.*/
  class FishTankCanvas extends JComponent {
    static Graphics2D g;
    int x = 11;
    Timer myTimer;
    public FishTankCanvas(){
      myTimer = new Timer (2, new ActionListener(){
        public void actionPerformed (ActionEvent evt){
          repaint();
        }
      });
      myTimer.start();
    }

    public void paint(Graphics graphics) {
      g = (Graphics2D)graphics;
      //makes the background white
      Color backgroundColor = new Color(89, 216, 255);//light blue
      g.setColor(backgroundColor);
      g.fillRect(0,0,this.getWidth(),this.getHeight());

      //  drawfish (Graphics graphics, int bodyX, int bodyY, int            bodyLength,int bodyHeight, int tailwidth, int eyesize,int tailcolor, int bodycolor)

      // Mouselistener and mouseadapter  
      this.addMouseListener (new MouseAdapter() {
        public void mousePressed(MouseEvent e) {  
          //call drawfish method
          drawfish(FishTankCanvas.g,e.getX(), e.getY(),118,74,1,((int)            (Math.random()*(4 - 0))));
          repaint();
        }
      });

      // x coordinate plus 1 of fish (animate)
      x= x + 1; 
    }
    // drawfish method
    public void drawfish(Graphics graphics, int bodyX, int bodyY, int       bodyLength,int bodyHeight,int tailcolor, int bodycolor ){

      Graphics2D g = (Graphics2D)graphics;
      bodyX +=x;
      //colours
      Color[] colours= new Color[5];
      colours[0] =  new Color(0, 0, 0);//black
      colours[1] = new Color(162, 0, 255);//purple
      colours[2] = Color.red;//red
      colours[3] = new Color(255,255,0);// yellow
      colours[4] = new Color(60,179,113);//green

      //draw fish
      // body
      g.setColor(colours[bodycolor]);
      g.fillOval(bodyX, bodyY, bodyLength, bodyHeight);
      // tail
      g.setColor(colours[tailcolor]);
      int tailWidth = bodyLength/4;
      int tailHeight = bodyHeight/2;
      int[] tailPointx = new int[3];
      int[] tailPointy = new int[3];
      tailPointx[0]=bodyX;
      tailPointy[0]=bodyY+bodyHeight/2;
      tailPointx[1]=bodyX-tailWidth;
      tailPointy[1]=bodyY+bodyHeight/2-tailHeight;
      tailPointx[2]=bodyX-tailWidth;
      tailPointy[2]=bodyY+tailHeight+tailHeight;
      g.fillPolygon(tailPointx, tailPointy, 3);
      // eye
      g.setColor(colours[0]);
      g.fillOval(bodyX+3*bodyLength/4, bodyY+bodyHeight/2-bodyHeight/5,          bodyHeight/5, bodyHeight/5);      
    }
  }      

Answer 1

那么，

方法似乎没有被调用。

好的，这很容易验证。您所需要做的就是将调试代码添加到方法中，以确定这是否为真。然后，您可以告诉我们这是否是问题所在，而不是猜测。

其他问题：

1. 不要将MouseListener添加到绘制方法中的组件。侦听器应该被添加到你的类的构造函数中。
2. 不要重写paint()。自定义绘制是通过重写paintComponent()方法来完成的。别忘了调用super.paintComponent(...).
3. Extend JPanel而不是JComponent。然后，您可以只使用setBackground()方法来绘制背景。

然而，真正的问题是，当你点击鼠标时，鱼可能会被画出来，但随后计时器会重新绘制，这将在2毫秒后清除面板，所以你永远看不到鱼。把定时器扔掉。不需要计时器来绘制一条鱼。

假设你想绘制多条鱼，你需要跟踪你点击的每一个地方，然后绘制所有的鱼。有两种方法可以做到这一点：

1. 保存你想要绘制鱼的点的ArrayList，然后在你的绘制方法中迭代这个列表
2. 当鼠标点击时在BufferedImage上绘制鱼，然后只绘制图像。

有关这两种方法的工作示例，请参阅Custom Painting Approaches。