java - 用矩形模拟物体的直线运动

Question

我对 Java 比较陌生，一直在尝试模拟物体(比如汽车)在直线路径上的运动。 我希望我的对象在输出中逐步移动，而不是只出现在该行的最后一点。

我使用了 2 个类:Veh.java - 车辆对象和 SimuFrame.java - 来创建模拟环境。

我引用了一些在线教程的想法:http://www.newthinktank.com/2012/07/java-video-tutorial-52/ (这模拟了小行星游戏。但是我希望我的物体沿直线移动而不是沿随机方向移动)

请帮助我了解我错在哪里以及下一步该怎么做..

非常感谢。

这是我的代码:

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


public class Veh extends Rectangle{

    int uLeftX, uLeftY; //upper LH Position for Rectangle
    static int height = 20;
    static int width = 20;
    int[] pathCoords=new int[1000]; 

    int startPosY;  // start position of the objet - anywhere on the left bounday of the frame.
    int goalPosY; // end position of the objet - anywhere on the right boundary of the frame.

//Constructor to Create a new Veh
    public Veh(int startPosY,int goalPosY){ 

    //Create a new rectangle vehicle from super class constructor
    super(0, startPosY, height, width);  

    this.startPosY=startPosY;

    this.goalPosY=goalPosY;

    this.pathCoords = Pathmove();

    }


    //Calculating the 1000 points on the line joining (0,startPosY) and  (goalPosY,999)
        int[] Pathmove(){

//Slope calculation
    float s=(float)(this.goalPosY-this.startPosY)/999;

    pathCoords[0]=this.startPosY;
        System.out.println("First xy pair is: 0," +this.pathCoords[0]);
    for(int m=1; m<1000; m++){
    pathCoords[m]= (int)(m*s)-(int)((m-1)*s)+ pathCoords[m-1];
    }
        return pathCoords;
    }

    //Function to move the Reactangular object along the line using the Y coordinate   values from Pathmove()

    void move(){
    int[] a = (int[])this.pathCoords.clone();
    for (int c=0; c<a.length;c++){
    this.setLocation(c,a[c]);
    }
    } 



} 

---

这是创建模拟环境的代码。

import javax.swing.*;
import java.awt.*;
import java.util.*;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class SimuFrame extends JFrame{

public static int frameWidth=1000;
public static int frameHeight=1000;

public static void main(String[] args){

new SimuFrame();
}

public SimuFrame(){
this.setSize(frameWidth,frameHeight);
this.setTitle("Path Planning Results");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

SimuObject SO=new SimuObject();
this.add(SO);
// Used to execute code after a given delay
// The attribute is corePoolSize - the number of threads to keep in 
// the pool, even if they are idle
ScheduledThreadPoolExecutor executor= new ScheduledThreadPoolExecutor(5);

executor.scheduleAtFixedRate(new RepaintTheFrame(this), 0L, 20L,    TimeUnit.MILLISECONDS); 

this.setVisible(true);

}

}

// Class implements the runnable interface
// By creating this thread I want to continually redraw the screen
// while other code continues to execute

class RepaintTheFrame implements Runnable{

SimuFrame theFrame;

public RepaintTheFrame(SimuFrame theFrame){
}

@Override
public void run() {

    theFrame.repaint();
    }

}

class SimuObject extends JComponent{

//Holds every Veh created

public ArrayList<Veh> vehs=new ArrayList<Veh>();

public SimuObject(){

    int startPosY = (int)(Math.random()*999);
    int goalPosY = (int)(Math.random()*999);
    vehs.add(new Veh(startPosY,goalPosY));

}

public void paint(Graphics g){

    // Allows me to make many settings changes in regards to graphics
    Graphics2D graphicSettings = (Graphics2D)g;
    // Draw a background that is as big as the Simu board
    graphicSettings.setColor(Color.WHITE);
    graphicSettings.fillRect(0, 0, getWidth(), getHeight());
    // Set rendering rules
    graphicSettings.setRenderingHint( RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    // Set the drawing color to red
    graphicSettings.setPaint( Color.RED);
    // Cycle through all of the Rock objects
    for(Veh veh : vehs){
        // Move the vehicle
        veh.move();
        graphicSettings.draw(veh);

    }
}

Answer 1

你的代码中有很多问题:

• 您在 RepaintTheFrame.run() 中有一个(被吞噬的)NullPointerException (NPE)，这会导致 ScheduledThreadPoolExecutor.scheduleAtFixedRate() 只运行一次，根据 scheduleAtFixedRate()'s javadoc .

• 您正在 JComponent.paint() 中移动汽车。

  在任何图形框架中，框架都会自动调用重绘，通常是在操作系统事件上，例如移动窗口，将鼠标移到窗口上等。

  您的paint() 方法应该只绘制。它不应修改您的领域模型。

• 您的 move() 方法总是以车辆结束。那可能不是你的意图。您可能希望您的 move() 方法仅增加汽车的位置。