wallpaperManager

Question

调试软件中发现，在程序中加入下面一句话就会报错
paperservice.javaWallpaperManager wallpaperManager=WallpaperManager.getInstance(this);
是在service中加的这一句，编译不会错，就运行到这里的时候就出错~求解

Answer 1

输出什么log阿？
WallpaperManager wallpaperManager=WallpaperManager.getInstance(this);
传入的this不清楚可以是service吗，一般都是activity的吧~

Answer 2

08-09 01:45:18.171: ERROR/AndroidRuntime(1240): FATAL EXCEPTION: main
08-09 01:45:18.171: ERROR/AndroidRuntime(1240): java.lang.RuntimeException: Unable to instantiate service com.walter2006.PaperService: java.lang.NullPointerException
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at android.app.ActivityThread.handleCreateService(ActivityThread.java:2943)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at android.app.ActivityThread.access$3300(ActivityThread.java:125)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2087)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at android.os.Looper.loop(Looper.java:123)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at android.app.ActivityThread.main(ActivityThread.java:4627)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at java.lang.reflect.Method.invokeNative(Native Method)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at java.lang.reflect.Method.invoke(Method.java:521)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at dalvik.system.NativeStart.main(Native Method)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240): Caused by: java.lang.NullPointerException
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at android.content.ContextWrapper.getSystemService(ContextWrapper.java:363)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at android.app.WallpaperManager.getInstance(WallpaperManager.java:335)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at com.walter2006.PaperService.<init>(PaperService.java:15)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at java.lang.Class.newInstanceImpl(Native Method)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at java.lang.Class.newInstance(Class.java:1429)
08-09 01:45:18.171: ERROR/AndroidRuntime(1240):     at android.app.ActivityThread.handleCreateService(ActivityThread.java:2940)
是不是只能在Activity中用wallpaperManager？但是我不想用wallpaperservice，没有办法么？