Question

我开始尝试创建一个TestGame。目前有一个NPE，并在谷歌上花了几个小时，并尝试我能想到的一切，我似乎无法理解我正在忽视或遗忘。我把所有东西放在一个班级里，一切都很完美。虽然我想创建一个GUI，我可以在MainMenu和PlayScreen之间切换。我的MainMenu类工作正常，但是当我按下我整洁的小“播放”按钮进入PlayScreen类时，我得到了这些错误：

Exception in thread "LWJGL Application" java.lang.NullPointerException
at com.me.game.PlayScreen.render(PlayScreen.java:90)
at com.badlogic.gdx.Game.render(Game.java:46)
at com.me.game.TestGame.render(TestGame.java:27)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:214)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:120)

播放屏错误：

batch.draw(player.getCurrentFrame(), player.getPosition().x , player.getPosition().y);

游戏错误：

if (screen != null) screen.render(Gdx.graphics.getDeltaTime());

TestGame错误：

super.render();

TestMenu类（游戏类）

public class TestGame extends Game {

Game game;

@Override
public void create() {
    game = this;
    setScreen(new MainMenu(game));

public void render() {
    super.render();
}

MainMenu 类

public class MainMenu implements Screen{

SpriteBatch batch;
Game game;
Stage stage;

public MainMenu(Game game){
    this.game = game;

public void render(float delta) {
    Gdx.gl.glClearColor(1, 1, 1, 1);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

    stage.act();  

    batch.begin();
    stage.draw();
    batch.end();

}

 public boolean touchDown(InputEvent event, float x, float y, int pointer, int button) {
                     game.setScreen(new PlayScreen(game));
                     stage.clear();
                      return true;

播放屏幕

public class PlayScreen implements Screen {

SpriteBatch batch;
Player player;
Game game; 
Texture playerTexture;

       public PlayScreen(Game game){
        this.game = game;

    }

 public void render(float delta) {

        Gdx.gl.glClearColor(1, 1, 1, 1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

        batch.begin();

        batch.draw(player.getCurrentFrame(), player.getPosition().x , player.getPosition().y);

        }

        player.update();

        batch.end();

 }

public void show() {                        
        batch = new SpriteBatch();

玩家类

public class Player {
Texture playerTexture ;
Vector2 position;
String textureLoc;

 public Player(Vector2 position, String textureLoc){
            this.position = position;                
            movement = "";

            playerTexture = new Texture(Gdx.files.internal("Character.png"));

public String getTextureLoc() {
        return textureLoc;
    }

    public void setTextureLoc(String textureLoc) {
        this.textureLoc = textureLoc;
    }

最有帮助的是Libgdx Screen NullPointerException when referencing another class，其中问题似乎也是我没有在show方法中初始化PlayerScreen类中的播放器。虽然当我填充player = new Player（position，textureLoc）时;在show方法下

public void show() {                        
        batch = new SpriteBatch();
        player = new Player(position, textureLoc);

我收到其他错误

at com.me.game.Player.<init>(Player.java:50)
at com.me.game.PlayScreen.show(PlayScreen.java:90)
at com.badlogic.gdx.Game.setScreen(Game.java:61)
at com.me.game.MainMenu$1.touchDown(MainMenu.java:90)

指向：

bounds = new Rectangle(position.x, position.y, currentFrame.getRegionWidth(), currentFrame.getRegionHeight());

player = new Player(position, textureLoc);

game.setScreen(new PlayScreen(game));

虽然我认为它与未正确初始化的播放器有关？无论如何由于某种原因我似乎无法解决这个问题。任何想法都将不胜感激。

Answer 1

问题就在这里

player = new Player(position, textureLoc);

position和textureLoc是占位符，您创建的这些参数如下

Vector2 position, String textureLoc

这意味着您需要创建一个新的Vector2并将其放置在position和String之间并将其放置在textureLoc所在的位置。

请尝试使用以下代码，这样您的播放器就会大致位于屏幕中间。

player = new Player(new Vector2(Gdx.graphics.getWidth()/2,Gdx.graphics.getHeight()/2), "I am not sure why you put this parameter here");

切换屏幕时，Libgdx屏幕NullPointerException

1 个答案: