试图为Jframe上的线/圆的ArrayList设置动画（形成一个汽车），但我似乎无法抹去绘制的旧线

Question

从图像中可以看出，我需要删除旧行，但我不确定如何。被困在这几天了。我很确定问题是我正在移动线条和圆圈错误（分别使用setLine，setFrame），因为我用矩形替换了汽车并使用了translate（）并且它工作正常。下面是一些复制它的最小代码。非常感谢您的帮助。 （第1部分是组件，第2部分是汽车类，主程序只是设置Jframe和第1部分组件。）

import java.awt.*;
import javax.swing.JComponent;
import java.util.*;
import javax.swing.JFrame;
import java.awt.event.*;
import javax.swing.Timer;
public class VehicleComponent extends JComponent
{
   //Car class which is an arraylist of line segments and a couple circles
 Car car;
 // The constructor initializes the car to the location 300, 300 on a Jframe
     public VehicleComponent()
  {
     car = new Car(300, 300);
      drive();
  }

//to be painted on a jframe
public void paintComponent(Graphics g)
{
    Graphics2D g2 = (Graphics2D) g;
        car.draw(g2);


}

//this function will be called in timer triggered actionListener. will move the car forward by certain pixels per given seconds
public void drive()
{
        car.move();
        repaint();

}
}        

public class Car extends Vehicle
{

ArrayList<Line2D.Double> detailLines;
ArrayList<Ellipse2D.Double> tires;
private int height;
private int length;
private int velocity;


public Car(int xStartingPosition, int yStartingPosition)
{
    super(xStartingPosition, yStartingPosition);
    detailLines = new ArrayList<Line2D.Double>();
    tires = new ArrayList<Ellipse2D.Double>();
    setVelocity();
    height = 5;
    length = 14;


}
/** draws the car */
public void draw(Graphics2D g2){
    BasicStroke tireStroke = new BasicStroke(3);
    BasicStroke vehicleStroke = new BasicStroke(2);
    initializeLines();
    initializeTires();

    g2.setStroke(vehicleStroke);
    for (Line2D.Double e : detailLines){
                g2.draw(e);
    }
    g2.setStroke(tireStroke);
    for (Ellipse2D.Double e: tires){
        g2.draw(e);
    }
}



private void initializeLines()
{
    detailLines.add(new Line2D.Double((getX()-10), (getY()+10), (getX()+50), (getY()+10)));//hood
    detailLines.add(new Line2D.Double((getX() + 60), getY(), (getX()+50), (getY()+10)));//hoodtwo
    detailLines.add(new Line2D.Double((getX()+50), (getY()+10), (getX()+70), (getY()+30)));//Passengerwindshield
    detailLines.add(new Line2D.Double((getX()+70), (getY()+30), (getX() + 80), (getY() + 20)));//hood three
    detailLines.add(new Line2D.Double((getX() + 70), (getY() + 30), (getX()+100), (getY()+30)));//front
    detailLines.add(new Line2D.Double((getX()+100), (getY()+30), (getX()+100), (getY()+40)));//front two
    detailLines.add(new Line2D.Double((getX()+100), (getY()+30), (getX() + 110), (getY() + 20)));//sideLine horizontal
    detailLines.add(new Line2D.Double((getX() + 60), (getY()+20), (getX()-20), (getY() + 20)));//windowsperator
    detailLines.add(new Line2D.Double((getX()+30), (getY()+10), (getX() +30), (getY() +20)));//striketrhough
    detailLines.add(new Line2D.Double((getX()), (getY()), (getX() +60), (getY())));//roof
    detailLines.add(new Line2D.Double((getX()+60), (getY()), (getX() +80), (getY() +20)));//border top
    detailLines.add(new Line2D.Double((getX()+80), (getY()+20), (getX() +110), (getY() +20)));//border 3
    detailLines.add(new Line2D.Double((getX()+110), (getY()+20), (getX() +110), (getY() +30)));//border4
    detailLines.add(new Line2D.Double((getX()+110), (getY()+30), (getX() +100), (getY() +40)));//border5
    detailLines.add(new Line2D.Double((getX()+100), (getY()+40), (getX() - 30), (getY() +40)));//border6
    detailLines.add(new Line2D.Double((getX()-30), (getY()+40), (getX() - 30), (getY() +30)));//border7
    detailLines.add(new Line2D.Double((getX()-30), (getY()+30), (getX()), (getY())));//border8

}
private void initializeTires()
{
    tires.add(new Ellipse2D.Double((getX()-10), getY()+30, 20, 20));
    tires.add(new Ellipse2D.Double((getX()+65), getY()+30, 20, 20));
}

public void move()
{

    for(Line2D.Double e : detailLines){
        e.setLine((e.getX1()+velocity), (e.getY1()), (e.getX2()+velocity), (e.getY2()));

    }
    for(Ellipse2D.Double e : tires)
    {
        e.setFrame((e.getX()+velocity), (e.getY()), e.getWidth(), e.getHeight());
    }

}

Answer 1

原因是您需要在每次绘制时通过调用clearRect来清除绘图表面：

g2.clearRect(0, 0, getWidth(), getHeight() );

尽管Line2D对象在调用draw之间仍然存在，但他们实际上并未将自己从缓冲区中拉出来 - 他们会在下次想要绘制它们时简单记住它们的状态。

Answer 2

public void paintComponent(Graphics g)
{
    // Very important, paint the component BG etc.
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g;
    // ...

Answer 3

在绘制下一帧之前，使用g2.fillRect（）擦除面板的内容。

Answer 4

这是JComponent的常见行为。在您的情况下，以下应该有效：

Graphics.clearRect(0,0, getWidth(),getHeight());