java - 如何使用 drawLine() 获得一条随机方向拍摄的线？

Question

我正在做一个有趣的作业，它包括一艘小船，它随着 mouseMoved() 移动并向随机方向发射激光束。我想为激光使用 drawLine(mouse_x, mouse_y, ?, ?) 但我无法定义 x2 和 y2 的坐标。激光必须穿过屏幕。

这就是我目前所拥有的。 page.drawLine(mouse_x-15, mouse_y-5,300,300);当然不希望激光一直射在拐角处(300,300)

import java.applet.*;
import java.awt.*;
import java.awt.event.*;


public class SpaceShip extends Applet
   implements MouseListener, MouseMotionListener {

   private int applet_width = 300; //width of applet
   private int applet_height =300; //height of applet
   private int mouse_x, mouse_y;  // the mouse coordinates
   private int shots = 0; //count of shots
   private boolean buttonPressed = false;


   //init()
   public void init() {
      setSize(applet_width, applet_height); //set size of applet
      setBackground( Color.black ); //set color of background

      mouse_x = applet_width/2; //initiate mouse in the middle of the applet
      mouse_y = applet_height/2;

      addMouseListener( this ); //adding mouse listener
      addMouseMotionListener( this ); // adding motion listener
   }


  // Drawing of the spaceship and laser beam
   public void paint( Graphics page ) {

          page.setColor(colorRand()); // random color laser beam
          page.drawLine(mouse_x-15, mouse_y-5,300,300);

          page.setColor( Color.YELLOW );//yellow spaceship
          page.fillOval( mouse_x-30, mouse_y-15, 60, 30 );


       }

   public void mouseEntered( MouseEvent e ) {

   }
   public void mouseExited( MouseEvent e ) {

   }
   public void mouseClicked( MouseEvent e ) {
      shots++;
      showStatus("Number of shots: " + shots);

   }
   public void mousePressed( MouseEvent e ) { 
      buttonPressed = true;  
      repaint();

   }
   public void mouseReleased( MouseEvent e ) {
      buttonPressed = false;
      setBackground( Color.black );
      repaint();

   }
   public void mouseMoved( MouseEvent e ) { 
      mouse_x = e.getX();
      mouse_y = e.getY();
      repaint();

   }
   public void mouseDragged( MouseEvent e ) {

   }

   //method generating a random color RGB
   public Color colorRand(){

       int r = (int)(Math.random()*256);
       int g = (int)(Math.random()*256);
       int b = (int)(Math.random()*256);

        Color randomColor = new Color(r,g,b);
        return randomColor;
   }


}

提前谢谢你，我已经坚持了很长一段时间了。

滴滴

Answer 1

类似于Snicolas给出的答案:

int x2;
int y2;

//get direction for x cooord
int direction = (int) (Math.random() * 2);

if(direction == 0)
    x2 = (int) (300 + Math.random() * applet_width);
else
    x2 = ((int) (300 + Math.random() * applet_width)) * -1;


//get direction for the y coord
direction = (int) (Math.random() * 2);

if(direction == 0)
    y2 = (int) (300 + Math.random() * applet_width);
else
    y2 = ((int) (300 + Math.random() * applet_width)) * -1;


//draw the line
page.drawLine(mouse_x-15, mouse_y-5,x2,y2);

这将创建一条线到一个随机点，该点经过屏幕边缘