为什么我的渲染方法不会显示任何内容？

Question

I'm making a game for my APCS class in Java. It uses Algebra and Math, but that's not the problem:

I have a State class instead of a State Enum because for some reason, Enum doesn't work.

public class State {
    private int option;
    public int getState(){
        return option;
    }
    public void setState(int option){
        this.option=option;
    }
}

Now, I'm 90% sure this isn't the problem because when I set the state to the actual game state number, It runs fine, except it doesn't display the background.

My Menu class looks like this:

    public Rectangle playButton= new Rectangle(GameMain.WIDTH/2 +120,200,117,49);
    public Rectangle helpButton= new Rectangle(GameMain.WIDTH/2 +120,300,117,49);
    public Rectangle quitButton= new Rectangle(GameMain.WIDTH/2 +120,400,117,49);

    ImageLoader loader = new ImageLoader();

    GameMain game;

    public BufferedImage bgrd, play,help, quit;

    public void init(){
        try {
            bgrd = loader.loadImage("res/imgs/bgrd.png");
            play = loader.loadImage("res/imgs/play.png");
            help = loader.loadImage("res/imgs/help.png");
            quit = loader.loadImage("res/imgs/exit.png");
        } catch (IOException e) {
            e.printStackTrace();
        }

    }



    public void render(Graphics g){
        Graphics2D g2d = (Graphics2D) g;

        g.drawImage(bgrd,0,0, null);
        g.drawImage(play,game.WIDTH/2 +120,200,null);
        g.drawImage(help,game.WIDTH/2 +120,300,null);
        g.drawImage(quit,game.WIDTH/2 +120,400,null);

    }

You can test it out yourself, but all images are in the correct directory and the res folder has been added to the build path.

The ImageLoader class just includes a method loadImage which returns a BufferedImage.

In my GameMain class, this is my render method which should display the images:

private void render(){
        BufferStrategy bStrat = this.getBufferStrategy();
        if(bStrat==null){
            createBufferStrategy(3);
            return;
        }
        Graphics g = bStrat.getDrawGraphics();
        if(state.getState()==1){
            menu.render(g);
        }
        if(state.getState()==2){

        }
        if(state.getState()>2 && state.getState()<11){

            Font font=new Font("Verdana",Font.BOLD,20);

            g.setFont(font);

            g.drawImage(bgrd,0,0,this);

            g.drawString(gameName, 300, 100);
            g.drawImage(wizard,x,y-75,this);
            g.drawImage(hdkn,x,y,this);

            g.dispose();
            bStrat.show();
        }
        if(state.getState()==11){

        }

    }

And here is my init method which (when I'm done) will initialize everything:

public void init(){
        state=new State();
        state.setState(1);
        loader = new ImageLoader();
        menu=new Menu();
        menu.init();

        try{
            bgrd=loader.loadImage("res/imgs/bgrd.png");
            wizard=loader.loadImage("res/sprites/wiz.png");
            hdkn=loader.loadImage("res/sprites/hdkn.png");
        }catch(IOException e){
            e.printStackTrace();
        }

    }

This is the result when I set the state to the Menu state(1): Menu State Game

And this is the result when the State is set to the Game state (Numbers 3-10): Game State Game

EDIT: Someone wanted to see my main method, I guess...

game=new GameMain();

        game.setPreferredSize(new Dimension(WIDTH,HEIGHT));
        game.setMaximumSize(new Dimension(WIDTH,HEIGHT));
        game.setMinimumSize(new Dimension(WIDTH,HEIGHT));



        JFrame frame = new JFrame("Math Game");
        frame.add(game);

        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

        game.start();

EDIT: Found out why it didn't work. I didn't include a bStrat.show() after my call to the render method in my GameMain render method.

EDIT 2: I looked back at my code and if anyone wants to use it, you should also put g.dispose() before it, so that it frees up resource allocation or something

Answer 1

Maybe your Graphic object g cannot be painted immediately. Try using

g.paintImmediately(0,0, /*your graphic width here*/, /*your graphic height here */)

after you asked for the picture to get drawn. This will force a UI refresh of your graphics, without letting your system choose when to refresh it, for this time only.

Have a look here: https://docs.oracle.com/javase/7/docs/api/javax/swing/JComponent.html#paintImmediately(int,%20int,%20int,%20int)