LibGDX游戏暂停状态：动画闪烁/错误

Question

Im trying to implement a pause option for my following game. By pressing the back button my game should go to the updatePause() method. But instead it renders the latest 2-3 frames repeatedly. Making it look like it's "flickering".

By trying to prevent this I've added (in the comments) non-continously rendering which prevented the flickering. But then Im facing the problem that pressing the back-button more than once will render another frame. (one of those flickering frames). This is my code structure in short:

public class GameScreen implements Screen {
    private static final int GAME_RUNNING = 0;
    private static final int GAME_PAUSED = 1;
    private static final int GAME_OVER = 2;
    private static final int GAME_LEVEL_END = 3;
    private int gameState;

    private GdxGame game;

    //create()
    public GameScreen(final GdxGame game) {
        //create all the stuff
    }

    @Override
    public void render(float deltaTime) {
        switch (gameState) {
            case GAME_RUNNING:
                updateRunning(deltaTime);
                break;
            case GAME_PAUSED:
                updatePause(deltaTime);
                break;
            case GAME_OVER:
                updateGameOver();
                break;
        }
    }

    public void updateRunning(float deltaTime) {
        //draw section
        if (gameState == GAME_RUNNING) {
            game.batch.begin();
            //Draw some stuff
            game.batch.end();

            //move section
            handleInput();
        }
    }

    public void updatePause(float deltaTime) {
        //Gdx.graphics.setContinuousRendering(false);
        //resume
        if (Gdx.input.isTouched()) {
            gameState = GAME_RUNNING;
            //Gdx.graphics.setContinuousRendering(true);
            return;
        }
    }

    private void handleInput() {
        //catch back button
        Gdx.input.setCatchBackKey(true);
        if (Gdx.input.isKeyJustPressed(Input.Keys.BACK)) {
            gameState = GAME_PAUSED;
            return;
        }
    }
}

Any tips to prevent the flickering?

Answer 1

The render() method is supposed to draw something to the screen. If it doesn't, then the contents of the back buffer will be undefined (so may contain a previous frame) and you get this flicker.

Disabling continuous rendering sounds like a good approach. Alternatively, continue drawing even if the game is paused.

Answer 2

As Thomas points out in his answer. It should be drawing every frame.

I haven't see you draw anything on screen yet, so backbuffer might just contain junk information. One way to solve this is to always clear the screen at the top of render() . This means when you switch immediately to another game state, it will make sure that screen is clear and no flickering result as you experienced.

public void render(float deltaTime) {
    // clear screen
    Gdx.gl.glClearColor(0f, 0f, 0f, 1.0f);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
    ...
}

Answer 3

屏幕上的所有对象还是仅使用动画的对象都会出现闪烁现象？

Answer 4

As Thomas said: continue drawing is a way to fix it. So I drew the latest frame and disabled continous rendering after that. The result is having no bug at all and giving the CPU a rest.