我试图在Android Studio（0.8.14）中使用libgdx开发一个简单的2D游戏，但此时（只是一个闪烁和一个空菜单）我得到一个错误，这个LogCat输出，当我启动应用程序时（我在设备上测试，索尼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)
所涉及的课程如下： - 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();
}
}
这里是AndroidManifest.xml：
<?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>
我怎么这么难过？
答案 0 :(得分：3)
移动此代码：
public static final int WIDTH = Gdx.graphics.getWidth();
public static final int HEIGHT = Gdx.graphics.getHeight();
进入create()方法，例如：
@Override
public void create() {
WIDTH = Gdx.graphics.getWidth();
HEIGHT = Gdx.graphics.getHeight();
//..
}
问题是之前调用create方法时Gdx仍然为空且无法使用。