LibGDX異常：線程「LWJGL Application」中的異常java.lang.NullPointerException

我的代碼用於完美工作，但現在當我啓動應用程序時，出現空白屏幕並出現錯誤。LibGDX異常：線程「LWJGL Application」中的異常java.lang.NullPointerException

「異常在線程「LWJGL應用程序」在com.mygdx.game.Bunny.render（Bunny.java:70）顯示java.lang.NullPointerException 在com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop （LwjglApplication.java:215）在com.badlogic.gdx.backends.lwjgl.LwjglApplication $ 1.run（LwjglApplication.java:120）」

這表明到線70：

batch.draw(paddle, paddleRect.x, paddleRect.y);

我的全代碼是：

package com.mygdx.game; 

import java.util.Iterator; 

import com.badlogic.gdx.ApplicationAdapter; 
import com.badlogic.gdx.Gdx; 
import com.badlogic.gdx.Input; 
import com.badlogic.gdx.graphics.GL20; 
import com.badlogic.gdx.graphics.OrthographicCamera; 
import com.badlogic.gdx.graphics.Texture; 
import com.badlogic.gdx.graphics.g2d.SpriteBatch; 
import com.badlogic.gdx.math.Rectangle; 
import com.badlogic.gdx.utils.Array; 

public class Bunny extends ApplicationAdapter { 
    SpriteBatch batch; 
    Texture paddle; 
    Texture blockImg; 
    Rectangle paddleRect; 

    float speed = 300.0f; 

    private OrthographicCamera camera; 

    private Array<Rectangle> blocks; 

    private void spawnBlock(int x, int y){ 
     Rectangle block = new Rectangle(); 
     block.x = x*90; 
     block.y = 400-(y*30); 
     block.width = 30; 
     block.height = 10; 
     blocks.add(block); 
    } 

    @Override 
    public void create() { 
     Rectangle paddleRect = new Rectangle(); 

     paddleRect.x = 0; 
     paddleRect.y = 0; 
     paddleRect.width = 60; 
     paddleRect.height = 20; 

     batch = new SpriteBatch(); 
     paddle = new Texture("paddle.png"); 
     blockImg = new Texture("block.png"); 

     camera = new OrthographicCamera(); 
     camera.setToOrtho(false, 400, 400); 

     blocks = new Array<Rectangle>(); 

     for(int x = 0; x < 5; x++){ 
      for(int y = 0; y < 4; y++){ 
       spawnBlock(x, y); 
      } 
     } 

    } 

    @Override 
    public void render() { 
     Gdx.gl.glClearColor(0.5f, 0, 0, 1); 
     Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); 
     camera.update(); 

     batch.setProjectionMatrix(camera.combined); 
     batch.begin(); 
     batch.draw(paddle, paddleRect.x, paddleRect.y); 
     for(Rectangle block: blocks){ 
      batch.draw(blockImg, block.x, block.y); 
     } 
     batch.end(); 

     if(Gdx.input.isKeyPressed(Input.Keys.RIGHT)) 
      paddleRect.x += speed * Gdx.graphics.getDeltaTime(); 
     else if(Gdx.input.isKeyPressed(Input.Keys.LEFT)) 
      paddleRect.x -= speed * Gdx.graphics.getDeltaTime(); 
     if(Gdx.input.isKeyPressed(Input.Keys.UP)) 
      paddleRect.y += speed * Gdx.graphics.getDeltaTime(); 

     if(paddleRect.x < 0f) 
      paddleRect.x = 0f; 
     if(paddleRect.x > 340f) 
      paddleRect.x = 340f; 

     Iterator<Rectangle> iter = blocks.iterator(); 
     while(iter.hasNext()){ 
      Rectangle block = iter.next(); 
      if(block.overlaps(paddleRect)) 
       iter.remove(); 
     } 
    } 
}

來源

2015-09-15 George Jennison

可能重複[？什麼是空指針異常，以及如何修復它（http://stackoverflow.com/questions/218384/what-is-a-空指針異常和如何-DO-I-FIX-IT） – lukelazarovic

在create要分配新Rectangle到類領域paddleRect而是創建一個名爲paddleRect的方法變量，類字段保留null。

嘗試：的

public void create() { 
     paddleRect = new Rectangle(); 

     paddleRect.x = 0; 
     paddleRect.y = 0; 
     ...

來源

2015-09-15 09:15:56 Sebastian

LibGDX異常：線程「LWJGL Application」中的異常java.lang.NullPointerException

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