缓冲策略 IllegalStateException

Question

我知道以前有人问过这个问题，但我仍然无法让它工作。

public class GUI extends JFrame implements Runnable{

    public static JPanel contentPane;
    public static Graphics2D graphics;
    public static BufferStrategy bufferStrategy;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    GUI frame = new GUI();
                    frame.setVisible(true);
                    frame.setResizable(false);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public GUI() {
        setResizable(false);
        setTitle("Tower Defense Game");
        setIgnoreRepaint(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 450, 300);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(0, 0));
        setContentPane(contentPane);


    }

    @Override
    public void run() {

        createBufferStrategy(2);
        bufferStrategy = getBufferStrategy();
        graphics = (Graphics2D) bufferStrategy.getDrawGraphics();

        for(int infiniteVar = 0; infiniteVar == -1; infiniteVar++){

            graphics.setBackground(Color.WHITE);
            graphics.drawLine(100, 100, (int) (Math.random() * ((200-50) + 1) + 50), (int) (Math.random() * ((200-50) + 1) + 50));

            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            infiniteVar = 0;
        }
    }
}
public class Initialize {

public static void main(String[] args){

    GUI.main(args);

    GUI objGUI = new GUI();
    Thread threadGUI = new Thread(objGUI);
    threadGUI.start();
}
}

我得到Exception in thread "Thread-2" java.lang.IllegalStateException: Component must have a valid peer on the line，在那里我尝试制​​定缓冲策略。我想我应该先制作框架，但我确实在制作制作缓冲区策略的线程之前调用它。

Answer 1

基本上，您的问题从这里开始......

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                GUI frame = new GUI();
                frame.setVisible(true);
                frame.setResizable(false);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

在这里被激怒了......

public class Initialize {

    public static void main(String[] args) {

        GUI.main(args);

        GUI objGUI = new GUI();
        Thread threadGUI = new Thread(objGUI);
        threadGUI.start();
    }
}

基本上，发生了什么，GUI.main 方法正在创建 GUI 的一个新实例，它会显示在屏幕上，然后您创建另一个 GUI 实例...

GUI objGUI = new GUI();
Thread threadGUI = new Thread(objGUI);
threadGUI.start();

您尝试使用它来创建BufferStrategy，但此实例在屏幕上不可见（可显示，或附加到本机对等方），因此您的问题...

相反，摆脱GUI 中的main 方法，它并没有真正为您带来任何好处，并将其逻辑应用到Initialize 中

GUI frame = new GUI();
// Better idea to do this before you make the frame visible
// as it can change the frame borders and cause some issues
frame.setResizable(false); 
frame.setVisible(true);

Thread thread = new Thread(frame);
thread.start();

您还可以在 run 方法中添加一个检查，以等待 JFrame 变为可显示...

@Override
public void run() {

    while (!isDisplayable()) {
        try {
            Thread.sleep(100);
        } catch (InterruptedException ex) {
        }
    }
    //...

您还应该阅读BufferStrategy 上的 JavaDocs 以更好地了解如何管理它们...