我正在尝试在 android 中使用 andengine.And 制作简单的河内塔游戏，我遇到了异常

Question

package com.example.testnew;

import org.andengine.opengl.texture.ITexture;
import org.andengine.opengl.texture.bitmap.BitmapTexture;
import org.andengine.opengl.texture.region.ITextureRegion;
import org.andengine.opengl.texture.region.TextureRegionFactory;
import org.andengine.util.adt.io.in.IInputStreamOpener;
import org.andengine.util.debug.Debug;

import java.io.IOException;
import java.io.InputStream;

import org.andengine.engine.camera.Camera;
import org.andengine.engine.options.EngineOptions;
import org.andengine.engine.options.ScreenOrientation;
import org.andengine.engine.options.resolutionpolicy.RatioResolutionPolicy;
import org.andengine.entity.scene.Scene;
import org.andengine.entity.sprite.Sprite;
import org.andengine.ui.activity.SimpleBaseGameActivity;


import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends SimpleBaseGameActivity {

    private static int CAMERA_WIDTH = 800;
    private static int CAMERA_HEIGHT = 480;

    private ITextureRegion mBackgroundTextureRegion, mTowerTextureRegion,      mRing1, mRing2, mRing3;

    ITexture backgroundTexture,ring1,ring2,ring3,towerTexture;



    @Override
public EngineOptions onCreateEngineOptions() {

     final Camera camera = new Camera(0, 0, CAMERA_WIDTH, CAMERA_HEIGHT);

             return new EngineOptions(true, ScreenOrientation.LANDSCAPE_FIXED, 
     new RatioResolutionPolicy(CAMERA_WIDTH, CAMERA_HEIGHT), camera);

}


@Override
protected void onCreateResources() throws IOException {

 try{

      ITexture backgroundTexture = new BitmapTexture(this.getTextureManager(), new IInputStreamOpener() 
      {

         @Override
         public InputStream  open() throws IOException  
         {
            //AssetManager Class:-getAsset();
            //Provides access to an application's raw asset files 
             // for the way most applications will want to retrieve their   resource data.
            return getAssets().open("gfx/background.png");
          }
       });
ITexture towerTexture = new BitmapTexture(this.getTextureManager(), new  IInputStreamOpener() 
        {
            @Override
            public InputStream  open() throws IOException  {
             return getAssets().open("gfx/tower.png");
             }
        });

        ITexture ring1 = new BitmapTexture(this.getTextureManager(), new IInputStreamOpener()
        {
             @Override
             public InputStream  open() throws IOException  {
                 return getAssets().open("gfx/ring1.png");
                }
        });

        ITexture ring2 = new BitmapTexture(this.getTextureManager(), new IInputStreamOpener()
        {
              @Override
              public InputStream  open() throws IOException  {
              return getAssets().open("gfx/ring2.png");
               }
        });

        ITexture ring3 = new BitmapTexture(this.getTextureManager(), new IInputStreamOpener() 
        {
             @Override
             public InputStream  open() throws IOException  {
             return getAssets().open("gfx/ring3.png");
              }
        });

            backgroundTexture.load();
            towerTexture.load();
            ring1.load();
            ring2.load();
            ring3.load();    
  } catch (IOException  e) {
            Debug.e(e);
    }       

this.mBackgroundTextureRegion =   TextureRegionFactory.extractFromTexture(backgroundTexture);
this.mTowerTextureRegion = TextureRegionFactory.extractFromTexture(towerTexture);
this.mRing1 = TextureRegionFactory.extractFromTexture(ring1);
this.mRing2 = TextureRegionFactory.extractFromTexture(ring2);

mBackgroundTextureRegion.setTextureSize(1600, 1000);
}

@Override
protected Scene onCreateScene() {

    final Scene scene = new Scene();

    Sprite backgroundSprite = new Sprite(0, 0,  this.mBackgroundTextureRegion, getVertexBufferObjectManager());
    scene.attachChild(backgroundSprite);

    return scene;   

}

}

我的异常：

07-03 13:04:23.904: E/AndEngine(7060): MainActivity.onCreateGame failed. @(Thread: 'GLThread 216')
07-03 13:04:23.904: E/AndEngine(7060): java.lang.NullPointerException
07-03 13:04:23.904: E/AndEngine(7060):  at org.andengine.opengl.texture.region.TextureRegionFactory.extractFromTexture(TextureRegionFactory.java:50)
07-03 13:04:23.904: E/AndEngine(7060):  at org.andengine.opengl.texture.region.TextureRegionFactory.extractFromTexture(TextureRegionFactory.java:42)
07-03 13:04:23.904: E/AndEngine(7060):  at com.example.testnew.MainActivity.onCreateResources(MainActivity.java:144)
07-03 13:04:23.904: E/AndEngine(7060):  at org.andengine.ui.activity.SimpleBaseGameActivity.onCreateResources(SimpleBaseGameActivity.java:43)
07-03 13:04:23.904: E/AndEngine(7060):  at org.andengine.ui.activity.BaseGameActivity.onCreateGame(BaseGameActivity.java:183)
07-03 13:04:23.904: E/AndEngine(7060):  at org.andengine.ui.activity.BaseGameActivity.onSurfaceCreated(BaseGameActivity.java:112)
07-03 13:04:23.904: E/AndEngine(7060):  at org.andengine.opengl.view.EngineRenderer.onSurfaceCreated(EngineRenderer.java:80)
07-03 13:04:23.904: E/AndEngine(7060):  at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1494)
07-03 13:04:23.904: E/AndEngine(7060):  at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1240)

Answer 1

您的问题可能是您捕获并记录了任何异常，然后继续您的 onCreateResources 方法，这意味着您的一些变量（backgroundTexture、towerTexture、ring1 或 ring2 - 以第 43 行中的那个为准）保持未初始化状态，导致 NullPointerException.

而不是 Debug.e(e)，重新将异常作为初学者的 RuntimeException 抛出，这样您的代码将编译，并且您的代码将因问题的真正原因而崩溃 - 直到您修复它:

} catch (IOException e) {
  throw new RuntimeException(e);
}

一般来说，捕获并记录异常然后继续运行是非常糟糕的做法，因为您在不一致的状态下继续运行程序。我总是首先将异常重新抛出为未经检查的异常 (RuntimeException)，直到我的代码正常工作，然后我才弄清楚我想如何处理特定的异常。

我正在尝试在 android 中使用 andengine.And 制作简单的河内塔游戏，我遇到了异常

I am trying to make simple game Tower of Hanoi in android with andengine.And i am getting below Exception

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