Java LWJGL blinking states

Question

I have a problem, that when i hit the Return key, in the state INTRO (as default) it have to switch to GAME state. It does, but when it does, it blinks between INTRO and GAME State. The Text blinks, and the bar at the bottom blinks.

I'd try to print out the current state, and it seems that its not changing between those two states, but when i run the application, my INTRO state, and GAME state, is both there, and is blinking.

public Renderer() {
    try {
        Display.setDisplayMode(new DisplayMode(screenWidth, screenHeight));
        Display.setTitle(gameTitle);
        Display.create();
    } catch (LWJGLException e) {
        e.printStackTrace();
        System.exit(0);
    }

    GL11.glMatrixMode(GL11.GL_PROJECTION);
    GL11.glLoadIdentity();
    GL11.glOrtho(0, 640, 0, 480, 1, -1);
    GL11.glMatrixMode(GL11.GL_MODELVIEW);

    lastFrame = getTime();


    while (!Display.isCloseRequested()) {
        //long delta = (long) getDelta();

        System.out.println(state);

        while (Keyboard.next()) {
            if(Keyboard.isKeyDown(Keyboard.KEY_RETURN)) {
                if(state == State.INTRO) {
                    clearCanvas();
                    state = State.GAME;
                }
            }
            if(Keyboard.isKeyDown(Keyboard.KEY_BACK)) {
                if(state == State.GAME) {
                    clearCanvas();
                    state = State.INTRO;
                }
            }
        }

        switch (state) {
        case INTRO:
            GL11.glColor3f(1.0f, 1.0f, 1.0f);
            TextDraw.drawString("PRESS 'RETURN' TO START GAME, and then hit CTRL z", Display.getWidth() / 2 - 160, Display.getHeight() / 2);
            TextDraw.drawString("CONTROLS:", Display.getWidth() / 2 - 30, Display.getHeight() / 2 - 50);
            TextDraw.drawString("1 key is Paint Red", Display.getWidth() / 2 - 70, Display.getHeight() / 2 - 70);
            TextDraw.drawString("2 key is Paint Green", Display.getWidth() / 2 - 70, Display.getHeight() / 2 - 85);
            TextDraw.drawString("3 key is Paint Blue", Display.getWidth() / 2 - 70, Display.getHeight() / 2 - 100);
            TextDraw.drawString("CTRL Z is Clear canvas", Display.getWidth() / 2 - 70, Display.getHeight() / 2 - 115);
            TextDraw.drawString("Escape to Close Program", Display.getWidth() / 2 - 70, Display.getHeight() / 2 - 130);
            break;
        case GAME:
            keyBindings();
            int MouseX = Mouse.getX();
            int MouseY = Mouse.getY();
            paint(MouseX, MouseY);
            break;
        }

        Display.update();
        Display.sync(250);
    }

    //Closed
    System.out.println("Program Closed");
    Display.destroy();
    System.exit(0);

}

Answer 1

Try replacing these parts:

while (Keyboard.next()) {
        if(Keyboard.isKeyDown(Keyboard.KEY_RETURN)) {
            if(state == State.INTRO) {
                clearCanvas();
                state = State.GAME;
            }
        }
        if(Keyboard.isKeyDown(Keyboard.KEY_BACK)) {
            if(state == State.GAME) {
                clearCanvas();
                state = State.INTRO;
            }
        }
    }

with this:

if (Keyboard.isKeyDown(Keyboard.KEY_RETURN)){
    clearCanvas(); //Don't check for the state which is going to be true most likely, just adds confusion to coding
    state = State.GAME;
}

if (Keyboard.isKeyDown(Keyboard.KEY_BACK)){
    clearCanvas();
    state = State.INTRO;
}

If you're worried about speed if the keys aren't pressed, don't worry. The difference is really small, and most likely not noticeable.

Also, you're not clearing the screen! Without that, all sorts of remnants can be left on there! Use this method to clear in the main loop:

while (!Display.isCloseRequested()){
    GL11.glClear(GL_COLOR_BUFFER_BIT);
    //Rest of your code here
}