我得到java.lang.ExceptionInInitializerError启动一个libgdx游戏

Question

我想在Android Studio（0.8.14）中使用libgdx开发一个简单的2D游戏，但在这一点上（只是一个飞溅和一个空的菜单）我得到一个错误，这个logcat的输出，当我启动的应用程序（我测试的设备，索尼的Xperia Z1）：

12-02 18:01:52.146 24248-24248/com.ak.thesoccerball.android D/dalvikvm﹕ Late-enabling CheckJNI 
12-02 18:01:52.196 24248-24248/com.ak.thesoccerball.android W/ActivityThread﹕ Application com.ak.thesoccerball.android can be debugged on port 8100... 
12-02 18:01:52.246 24248-24248/com.ak.thesoccerball.android D/dalvikvm﹕ Trying to load lib /data/app-lib/com.ak.thesoccerball.android-1/libgdx.so 0x447c06f0 
12-02 18:01:52.246 24248-24248/com.ak.thesoccerball.android D/dalvikvm﹕ Added shared lib /data/app-lib/com.ak.thesoccerball.android-1/libgdx.so 0x447c06f0 
12-02 18:01:52.246 24248-24248/com.ak.thesoccerball.android D/dalvikvm﹕ No JNI_OnLoad found in /data/app-lib/com.ak.thesoccerball.android-1/libgdx.so 0x447c06f0, skipping init 
12-02 18:01:52.246 24248-24248/com.ak.thesoccerball.android W/dalvikvm﹕ Exception Ljava/lang/NullPointerException; thrown while initializing Lcom/ak/thesoccerball/AKGame; 
12-02 18:01:52.246 24248-24248/com.ak.thesoccerball.android D/AndroidRuntime﹕ Shutting down VM 
12-02 18:01:52.246 24248-24248/com.ak.thesoccerball.android W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41618d88) 
12-02 18:01:52.256 24248-24248/com.ak.thesoccerball.android E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    Process: com.ak.thesoccerball.android, PID: 24248 
    java.lang.ExceptionInInitializerError 
      at com.ak.thesoccerball.android.AndroidLauncher.onCreate(AndroidLauncher.java:17) 
      at android.app.Activity.performCreate(Activity.java:5231) 
      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2201) 
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2286) 
      at android.app.ActivityThread.access$800(ActivityThread.java:144) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1246) 
      at android.os.Handler.dispatchMessage(Handler.java:102) 
      at android.os.Looper.loop(Looper.java:212) 
      at android.app.ActivityThread.main(ActivityThread.java:5135) 
      at java.lang.reflect.Method.invokeNative(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:515) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:877) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693) 
      at dalvik.system.NativeStart.main(Native Method) 
    Caused by: java.lang.NullPointerException 
      at com.ak.thesoccerball.AKGame.<clinit>(AKGame.java:9) 
            at com.ak.thesoccerball.android.AndroidLauncher.onCreate(AndroidLauncher.java:17) 
            at android.app.Activity.performCreate(Activity.java:5231) 
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2201) 
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2286) 
            at android.app.ActivityThread.access$800(ActivityThread.java:144) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1246) 
            at android.os.Handler.dispatchMessage(Handler.java:102) 
            at android.os.Looper.loop(Looper.java:212) 
            at android.app.ActivityThread.main(ActivityThread.java:5135) 
            at java.lang.reflect.Method.invokeNative(Native Method) 
            at java.lang.reflect.Method.invoke(Method.java:515) 
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:877) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693) 
            at dalvik.system.NativeStart.main(Native Method) 

涉及的类如下： - AndroidLauncher.java

package com.ak.thesoccerball.android; 

import android.os.Bundle; 

import com.badlogic.gdx.backends.android.AndroidApplication; 
import com.badlogic.gdx.backends.android.AndroidApplicationConfiguration; 

import com.ak.thesoccerball.AKGame; 

public class AndroidLauncher extends AndroidApplication { 
    @Override 
    protected void onCreate (Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     AndroidApplicationConfiguration config = new AndroidApplicationConfiguration(); 
     config.useAccelerometer = false; 
     config.useCompass = false; 
     initialize(new AKGame(), config); 
    } 
} 

AKGame.java

package com.ak.thesoccerball; 

import com.badlogic.gdx.Game; 
import com.badlogic.gdx.Gdx; 
import com.badlogic.gdx.graphics.g2d.SpriteBatch; 

public class AKGame extends Game { 

    public static final int WIDTH = Gdx.graphics.getWidth(); 
    public static final int HEIGHT = Gdx.graphics.getHeight(); 

    public SpriteBatch batch; 

    @Override 
    public void create() { 
     batch = new SpriteBatch(); 
     setScreen(new SplashScreen(this)); 
    } 

    public void render() { 
     super.render(); //important! 
    } 

    public void dispose() { 
     batch.dispose(); 
    } 


} 

而这里的AndroidManifest.xml中：

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="com.ak.thesoccerball.android" 
    android:versionCode="1" 
    android:versionName="1.0" > 

    <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="21" /> 

    <uses-feature android:glEsVersion="0x00020000" android:required="true" /> 

    <application 
     android:allowBackup="true" 
     android:icon="@drawable/ic_launcher" 
     android:label="@string/app_name" 
     android:theme="@style/GdxTheme" > 
     <activity 
      android:name="com.ak.thesoccerball.android.AndroidLauncher" 
      android:label="@string/app_name" 
      android:screenOrientation="portrait" 
      android:configChanges="keyboard|keyboardHidden|orientation|screenSize"> 
      <intent-filter> 
       <action android:name="android.intent.action.MAIN" /> 
       <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
     </activity> 
    </application> 

</manifest> 

我错过这么难？

Answer 1

移动验证码：

public static final int WIDTH = Gdx.graphics.getWidth(); 
public static final int HEIGHT = Gdx.graphics.getHeight(); 

到create()方法，例如：

@Override 
public void create() { 
    WIDTH = Gdx.graphics.getWidth(); 
    HEIGHT = Gdx.graphics.getHeight(); 
    //.. 
} 

的事情是，之前的创建方法被调用的Gdx仍然是空，不能尚未使用。