重复矩形而不是移动动画

Question

这是我的代码!

package softwarea1;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author Leo
 */
//534
public class Simulation extends JPanel implements ActionListener
{
    DataModels dm;
    Timer tm = new Timer(20, this);
    private int velX = 2;
    private int a = 0; 

    public void create()
    {

        Simulation sm = new Simulation(dm);
        JFrame simulation = new JFrame();
        simulation.setTitle("Traffic light and Car park Siumulation");
        simulation.setSize(600,600);
        simulation.setResizable(false);
        simulation.setVisible(true);
        simulation.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        simulation.add(sm);
    }
    public void paintComponent(Graphics g)
    {



        // Moving Rectangle
        g.setColor(Color.RED);
        g.fillRect(a ,300, 1 ,30);
        tm.start();
    }
    @Override
    public void actionPerformed(ActionEvent e) {
        a += velX;
        repaint();
    }


}

主要类别:

 public class StartProj {
        public static void main(String[] args) {
            DataModels dm = new DataModels();
            Simulation sm = new Simulation(dm);
            sm.create();

        }
    }

我尝试动画帧中的矩形,但它重复多个矩形.怎么了？帮我？我有更多的课,但他们没有必要.非常感谢你

Answer 1

你的paintComponent(...)方法需要在第一行调用super的方法:

public void paintComponent(Graphics g)
{
    super.paintComponent(g); // **** add this
    // Moving Rectangle
    g.setColor(Color.RED);
    g.fillRect(a ,300, 1 ,30);
    // tm.start(); // **** get rid of this.
}

这很重要,因为super方法重新绘制了组件的背景,这是擦除旧矩形所必需的.

此外,你在这个方法中有程序逻辑,你从内部启动一个Swing Timer,这是永远不应该做的事情.而是找到一个更好的更可控的地方来启动你的Timer.