Java Mousepress() 绘制图像

Question

我创建这个是为了当在鼠标的 x 和 y 坐标处按下鼠标时画一条鱼。但我似乎没有调用drawfish 方法。我找不到它不起作用的原因。我将非常感谢任何帮助。

  /*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

i seems then that the drawfish method is not being called.

这很容易验证。您所需要做的就是向该方法添加调试代码以确定这是否属实。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. 不要在绘画方法中将 MouseListener 添加到组件。应将监听器添加到类的构造函数中。

2. 不要重写paint()。自定义绘制是通过重写 paintComponent() 方法来完成的。并且不要忘记调用 super.paintComponent(...)。

3. 扩展 JPanel 而不是 JComponent。然后你就可以使用setBackground()方法来绘制背景。

然而，真正的问题是，当您单击鼠标时，鱼可能会被绘制出来，但是计时器会进行重新绘制，这将在 2 毫秒后清除面板，因此您永远不会真正看到鱼。摆脱计时器。计时器不需要画鱼。

假设您想绘制多条鱼，您需要跟踪您单击的每个位置，然后绘制所有鱼。执行此操作的两种方法是:

1. 保留要绘制鱼的点的 ArrayList，然后在绘制方法中迭代此列表
2. 当鼠标点击发生时，在 BufferedImage 上绘制鱼，然后绘制图像。

参见Custom Painting Approaches了解这两种方法的工作示例。