java libgdx游戏屏幕不会显示

Question

//这是我的脚本，我把游戏称为Overscreen。当我的精灵与另一个精灵重叠时，我希望它设置为这个屏幕

if (grumpface.whiteballoon.getBoundingRectangle().overlaps(spriterect)) {
            System.out.println("hey");
            ((Game) Gdx.app.getApplicationListener()).setScreen(new GameOverScreen());
        };

下面是我正在设置屏幕的课程。它给了我一个绘制舞台的错误，这让我觉得show（）方法并不是在创建舞台

class GameOverScreen implements Screen{

    private Stage stage;

    // Called automatically once for init objects
    @Override
    public void show() { 

        Stage stage = new Stage();
        float delta = Gdx.graphics.getDeltaTime();
        stage.setDebugAll(true); // Set outlines for Stage elements for easy debug

        BitmapFont white = new BitmapFont(Gdx.files.internal("hazey.fnt"), false);
        LabelStyle headingStyle = new LabelStyle(white, Color.WHITE);
        Label gameoverstring = new Label("game ovaaaa!", headingStyle);
        gameoverstring.setPosition(100, 100);
        stage.addActor(gameoverstring);

    }

    // Called every frame so try to put no object creation in it
    @Override
    public void render(float delta) { 
        Gdx.gl.glClearColor(0, 0, 0, 1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

        stage.act();
        stage.draw();
    } 

这里是每当发生重叠时的堆栈跟踪错误

Exception in thread "LWJGL Application" java.lang.NullPointerException
    at com.mygdx.game.GameOverScreen.render(GameOverScreen.java:72)
    at com.badlogic.gdx.Game.render(Game.java:46)
    at com.mygdx.game.MyGdxGame.render(MyGdxGame.java:139)
    at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:214)
    at com.badlogic.gdx.backends.lwjgl.LwjglApplicationrun(LwjglApplication.java:120)

Answer 1

您正在show（）方法中创建一个名为stage的局部变量，而名为stage的全局变量尚未初始化，这就是为什么您会得到一个名为null pointer exception的异常。在show（）方法中初始化全局阶段，而不是创建新的局部变量

public void show()
{
 stage= new Stage();
}

如果您混淆了局部变量和全局变量，请查看以下链接：

http://www.amitranjanji.com/2012/05/differentiate-between-global-local.html