Question

PaintComponent doest绘制数字。什么都没发生，干净的Jframe出现了。 我认为列表或我称之为方法的方式有问题 List在类中，带有Paint Component

public class Paint extends JPanel implements ActionListener {
     List<Figures> figuresList = new ArrayList<Figures>();
     Timer t = new Timer(5, this);

public void paintComponent(Graphics g) {

    super.paintComponent(g);
    for (Figures figure : figuresList) {
        figure.drawItself(g, figure.getLocationX(), figure.getLocationY());
    }
    t.start();
}

@Override
public void actionPerformed(ActionEvent e) {

    {
        for (Figures figure : figuresList) {
            if (figure.getLocationX() < 0 || figure.getLocationX() > 540) {
                figure.setVelocityX(-figure.getVelocityX());
            }
            if (figure.getLocationY() < 0 || figure.getLocationX() > 220) {
                figure.setVelocityY(-figure.getVelocityY());
            }
            figure.setLocationX(figure.getLocationX()
                    + figure.getVelocityX());
            figure.setLocationY(figure.getLocationY()
                    + figure.getVelocityY());
        }
    }
    repaint();

}

并绘制自己：

public class Circle implements Figures {    
    public int locationX = 12;
    public int locationY = 12;
    public int velocityX =1;
    public int velocityY =1;


    public void drawItself(Graphics g, int locationX, int locationY){
        this.locationX = locationX;
        this.locationY = locationY;
        g.drawOval(locationX, locationY, 40, 40);  
        g.fillOval(locationX, locationY, 40, 40);
    }

主：

public static void main(String[] args) {

    Circle c = new Circle();
    Quadrat q = new Quadrat();
    Paint p = new Paint();
    p.figuresList.add(c);
    p.figuresList.add(q);
    GUI.Configuration();


    }

GUI

public class GUI {


    public static void Configuration(){
        JFrame frame = new JFrame("Figures Animation");
        frame.setSize(600,300);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new Paint();
        frame.getContentPane().add(BorderLayout.CENTER, panel);
    }

Answer 1

您可以在此处创建并添加一个Paint实例：

public class GUI {
    public static void Configuration(){
        JFrame frame = new JFrame("Figures Animation");
        frame.setSize(600,300);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new Paint(); // *** new Paint is here, but nothing is added
        frame.getContentPane().add(BorderLayout.CENTER, panel);
    }

但是没有添加任何用途。所有重要的东西都被添加到一个完全不同的Paint JPanel中，一个永远不会显示的：

public static void main(String[] args) {
    Circle c = new Circle();
    Quadrat q = new Quadrat();
    Paint p = new Paint();  // **** ANOTHER new Paint is here, and it gets goodies
    p.figuresList.add(c);
    p.figuresList.add(q);

    // but is never added to a JFrame and is never displayed.

    GUI.Configuration();
}

不要这样做。创建一个 Paint JPanel，仅添加一个，向其添加重要组件，然后仅将其添加到JFrame。最重要的是，在提交代码之前，不要只输入代码，思考和规划您的程序，而且您不会看到这样的错误。

另外，不要在paintComponent中启动Timer，也不要在那里创建Circle。您可以在paintComponent中绘制Circle实例，但创建它并在Paint构造函数中启动Timer。

PaintComponent中的Object.drawItself不起作用

1 个答案: