java - 重新绘制/刷新 JFrame

Question

我有一辆使用图形 g 用各种对象制成的“汽车”，我想在按下按钮时移动它。就这样，我没有问题，但我的路径有问题。当汽车移动时，旧位置不会被清除。

汽车代码(按下按钮时移动):

    static void gPostavi2(Graphics g){
    Graphics2D g2d = (Graphics2D) g;

    for(int x=500; x>89; x--){
        //risanje
        g2d.setColor(Color.blue);
        g2d.fillRect(x+10, 351, 118, 23);
        g2d.fillRect(x+12, 321, 30, 40);
        g2d.fillRect(x+45, 330, 83, 20);
        g2d.setColor(Color.black);      
        g2d.fillOval(x+19, 362, 20, 20);
        g2d.fillOval(x+90, 362, 20, 20);
        g2d.drawString("2t", x+70, 344);
        try {

            Thread.sleep(5);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }       
}

这个类中只有用于移动物体的方法，该类扩展了另一个具有非移动对象、按钮、标签...和paintComponent方法的类。

每次 for 语句运行时，如何清除旧位置？

编辑:这里还有一些代码。在主类中我只有这段代码:

    public static void main(String[] args) {
    staticnaGrafika.dodajGumbe();
}

在 staticnaGrafika 中，我有大量代码，但这是 PaintComponent 的开始:

public class staticnaGrafika extends JPanel{

staticnaGrafika(){
        setBorder(BorderFactory.createLineBorder(Color.black));
    }
    public Dimension getPreferredSize(){
        return new Dimension(1100, 740);
    }

public void paintComponent(Graphics g){
    super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.RED);

        //opticno stikalo 
        //preveri, ce ga plosca prekriva pri max. dvigu
        g2d.setColor(Color.black);
        g2d.fillOval(21, 148, 33, 33);
        g2d.setColor(Color.yellow);
        g2d.fillOval(22, 149, 31, 31);
        g2d.setColor(Color.black);      
        g2d.fillRect(13, 159, 11, 1); //el. prikljucnice
        g2d.fillRect(13, 166, 10, 1);
        g2d.drawOval(7, 157, 5, 5);
        g2d.drawOval(7, 164, 5, 5);

        //naslon; spodnji omejevalec hoda bata
        g2d.setColor(Color.black);
        g2d.fillRect(5, 350, 13, 43);
        g2d.fillRect(5, 380, 63, 13);
        g2d.fillRect(262, 350, 408, 13);
        g2d.fillRect(262, 350, 13, 43);
        g2d.fillRect(212, 380, 63, 13);

这里只是绘画。下面我有另一个方法，它添加按钮、actionListeners:

    public static void dodajGumbe() {
    final JFrame f = new JFrame();

    //dvig, stop, spust
    JButton dvig = new JButton("DVIGNI");
    dvig.setBackground(Color.WHITE);
    dvig.setFocusPainted(false);
    dvig.setBounds(850,15,120,30);

    JButton stop = new JButton("STOP");
    stop.setBackground(Color.WHITE);
    stop.setFocusPainted(false);
    stop.setBounds(850,50,120,30);

    JButton spust = new JButton("SPUSTI");
    spust.setBackground(Color.WHITE);
    spust.setFocusPainted(false);
    spust.setBounds(850,85,120,30);

    //komande bremen
    JButton postavi2 = new JButton("nalozi breme");
    postavi2.setBackground(Color.WHITE);
    postavi2.setFocusPainted(false);
    postavi2.setBounds(760,240,120,30);

    JButton odvzemi2 = new JButton("razlozi breme");
    odvzemi2.setBackground(Color.WHITE);
    odvzemi2.setFocusPainted(false);
    odvzemi2.setBounds(760,275,120,30);

    JButton postavi5 = new JButton("nalozi breme");
    postavi5.setBackground(Color.WHITE);
    postavi5.setFocusPainted(false);
    postavi5.setBounds(760,330,120,30);

    JButton odvzemi5 = new JButton("razlozi breme");
    odvzemi5.setBackground(Color.WHITE);
    odvzemi5.setFocusPainted(false);
    odvzemi5.setBounds(760,365,120,30);

    Container gumbi = f.getContentPane();

    spust.addActionListener(new ActionListener(){ 
        public void actionPerformed(ActionEvent arg0) {
        dinamicnaGrafika.gSpusti(f.getGraphics());
    }});

    dvig.addActionListener(new ActionListener(){ 
        public void actionPerformed(ActionEvent arg0) {
            dinamicnaGrafika.gDvigni(f.getGraphics());
    }});

    stop.addActionListener(new ActionListener(){ 
        public void actionPerformed(ActionEvent arg0) {
            dinamicnaGrafika.gStop(f.getGraphics());
    }});

    postavi2.addActionListener(new ActionListener(){ 
        public void actionPerformed(ActionEvent arg0) {
            dinamicnaGrafika.gPostavi2(f.getGraphics());
    }});

    odvzemi2.addActionListener(new ActionListener(){ 
        public void actionPerformed(ActionEvent arg0) {
            dinamicnaGrafika.gOdvzemi2(f.getGraphics());
    }});

    postavi5.addActionListener(new ActionListener(){ 
        public void actionPerformed(ActionEvent arg0) {
            dinamicnaGrafika.gPostavi5(f.getGraphics());
    }});

    odvzemi5.addActionListener(new ActionListener(){ 
        public void actionPerformed(ActionEvent arg0) {
            dinamicnaGrafika.gOdvzemi5(f.getGraphics());
    }});

    gumbi.add(dvig);
    gumbi.add(stop);
    gumbi.add(spust);
    gumbi.add(postavi2);
    gumbi.add(odvzemi2);
    gumbi.add(postavi5);
    gumbi.add(odvzemi5);

    f.getContentPane();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.add(new staticnaGrafika());
    f.pack();
    f.setVisible(true);
}

Answer 1

您可能忘记打电话

super.paintComponent(g);

在您的paintComponent()方法中

@Override
protected void paintComponent(Graphics g){
    super.paintComponent(g);  //Clear screen before redraw
    //Your codes for painting..
}