如何将JPanel添加到JFrame

Question

I am a beginner in java and I have this objective to be done:

This is my partial code:

public class Trial extends JFrame {

public static final int WIDTH = 800;
public static final int HEIGHT = 600;
public static final int SCALE = 3;

private BufferedImage backBuffer;

public KeyboardInput input;
private Stage stage;
public static Trial Trial;
public static String message = "";
private Object Object;
private Message MessageBox;

public void init() {
    this.Trial = this;
    input = new KeyboardInput();
    this.addWindowListener(new WinListener());
    this.setSize(WIDTH, HEIGHT);
    this.setLocationRelativeTo(null);
    this.setResizable(false);
    this.setUndecorated(false);
    this.setVisible(true);
    this.addKeyListener(input);
    client = new TrialClient(SERVER_IP, this);
    MessageBox = new Message(username);
    backBuffer = new BufferedImage(WIDTH * SCALE, HEIGHT * SCALE, BufferedImage.TYPE_INT_RGB);
}

public Stage getStage() {
    return stage;
}

public class WinListener extends WindowAdapter {

    @Override
    public void windowClosing(WindowEvent e) {
        disconnect();
        System.exit(0);
    }

}


private Font font = new Font("Munro Small", Font.PLAIN, 96);
private Font font2 = new Font("Munro Small", Font.PLAIN, 50);
private Font fontError = new Font("Munro Small", Font.PLAIN, 25);
private int op = 0;


public void updateMenu() {
    if (input.up.isPressed()) {
        input.up.toggle(false);
    } else if (input.down.isPressed()) {
        input.down.toggle(false);
    } else if (input.enter.isPressed() && op == 0) {
    } else if (input.enter.isPressed() && op == 1) {
        System.exit(0);
    }
}


public void drawMenu() {
    Graphics g = getGraphics();
    Graphics bbg = backBuffer.getGraphics();
    bbg.setFont(font);
    bbg.setColor(Color.white);

    bbg.drawString("Sample", 189, 180);
    bbg.setFont(font2);
    if (op == 0) {
        bbg.setColor(Color.red);
        bbg.drawString("Start", 327, 378);
    }

    g.drawImage(backBuffer, 0, 0, this);
}

public void draw() {
    Graphics g = getGraphics();
    Graphics bbg = backBuffer.getGraphics();
    bbg.setColor(Color.black);
    bbg.fillRect(0, 0, WIDTH, HEIGHT);
    stage.drawStage(bbg, this);
    for (Object t : stage.getPlayers()) {
        t.draw(bbg, SCALE, this);
    }
    g.drawImage(backBuffer, 0, 0, this);
}


public void drawLogin() {
    Graphics g = getGraphics();
    Graphics bbg = backBuffer.getGraphics();
    bbg.setColor(Color.black);
    bbg.fillRect(0, 0, 800, 600);
    bbg.setColor(Color.red);
    bbg.setFont(fontError);
    bbg.drawString(message, 100, 100);
    bbg.setFont(font2);
    bbg.setColor(Color.white);
    bbg.drawString("Username", 284, 254);
    bbg.setColor(Color.red);
    bbg.drawString(username, 284, 304);
    g.drawImage(backBuffer, 0, 0, this);
}



public class StringWait extends Thread {

    public void run() {
        while (true) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException ex) {
            }
        }
    }
}

public void start() {
    init();
    while (true) {
       ...
    }
}

public static void main(String[] args) {
    Trial g = new Trial();
    g.start();
}

}

how will I declare the Jpanel in JFrame? Or there is a way to create a Jpanel in different window after the JFrame was created? I am doing this in netbeans.

Answer 1

I think the problem is that the line

backBuffer = new BufferedImage(WIDTH * SCALE, HEIGHT * SCALE, BufferedImage.TYPE_INT_RGB);

please modify it, so that it will not occupy the whole area.

Answer 2

Just declare a variable JPanel and add it to the Frame.

JPanel panel = new JPanel();
this.setContentPane(panel);

Answer 3

Declare variable outside init methode Create jpanel, add component to the panel create jscrollpane with panel as view set jscrollpane as contentpane of your frame see exemple below

public class Game extends JFrame {

public Game() throws HeadlessException {
    setSize(100, 100);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setLocationRelativeTo(null);
    setResizable(false);
    setVisible(true);
}

private javax.swing.JButton jButton1;
private javax.swing.JPanel jPanel1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTextArea jTextArea1;
private javax.swing.JTextField jTextField1;

void init() {

    jButton1 = new JButton("jButton1");

    jTextArea1 = new JTextArea("jTextArea1");
    jTextField1 = new JTextField("jTextField1");
    JPanel panel2 = new JPanel();
    panel2.setLayout(new FlowLayout());
    panel2.add(jTextField1);
    panel2.add(jButton1);
    jPanel1 = new JPanel();
    jPanel1.setLayout(new BoxLayout(jPanel1, BoxLayout.Y_AXIS));
    jPanel1.add(jTextArea1);
    jPanel1.add(panel2);
    jScrollPane1 = new JScrollPane(jPanel1);
    setContentPane(jScrollPane1);
    System.out.println("init");
    revalidate();
}

public static void main(String[] args) throws InterruptedException {
    Game g = new Game();
    //wait just to find the effect of revalidate
    Thread.sleep(1000);

    g.init();
}

}

Answer 4

You need to add

JPanel panel = new JPanel();

and other declarations inside the init(), then make sure that BufferedImage function don't overlaps on it