Question

我正在使用Slick2D for Java制作游戏，但当我尝试显示一个Image（Slick2D类型）时，它给了我这个错误：

java.lang.NullPointerException
at org.newdawn.slick.Graphics.drawImage(Graphics.java:1384)
at org.newdawn.slick.Graphics.drawImage(Graphics.java:1433)
at luke_r.games.java.broadway.states.M.render(M.java:21)
at org.newdawn.slick.state.StateBasedGame.render(StateBasedGame.java:199)
at org.newdawn.slick.GameContainer.updateAndRender(GameContainer.java:688)
at org.newdawn.slick.AppGameContainer.gameLoop(AppGameContainer.java:411)
at org.newdawn.slick.AppGameContainer.start(AppGameContainer.java:321)
at luke_r.games.java.broadway.C.main(C.java:21)

这是M类（不包括导入和类声明，不需要它们）：

@Override
public void init(GameContainer gc, StateBasedGame sbg) throws SlickException
{
    PL.x = 100;
    PL.y = 100;
}
@Override
public void render(GameContainer gc, StateBasedGame sbg, Graphics g) throws SlickException
{
    g.drawImage(I.title, 0, 0); //Line 21, the error
    PL.render(g);
}
@Override
public void update(GameContainer gc, StateBasedGame sbg, int delta) throws SlickException
{}
@Override
public int getID()
{
    return 0;
}

Answer 1

问题是I.title == null。将其设置为正确的值。

Answer 2

在init函数中将图像的url设置为I.title，我的意思是=＆gt; I.title =新图片（＆＃34; -your URL - ＆＃34;）; Slick2D以这种形式工作：首先，他在方法init中初始化所有参数，然后直到发生改变当前状态的所有参数＃34;他＆＃34; render =＆gt; update =＆gt; render =＆gt; update =＆gt; render =＆gt;更新...您可以使用SetTargetFrameRate方法设置SetUpClass中的更新量。

Slick2D NullPointerException

2 个答案: