安卓判断APP是运行在前台还是后台

做项目的时候，遇到问题需要判断app是否运行在后台，问了一下度娘，顺利解决了问题，再次深表感谢并将答案记录在此。

1. public static boolean isBackground(Context context) {  
2.         ActivityManager activityManager = (ActivityManager) context  
3.                 .getSystemService(Context.ACTIVITY_SERVICE);  
4.         List<RunningAppProcessInfo> appProcesses = activityManager  
5.                 .getRunningAppProcesses();  
6.         for (RunningAppProcessInfo appProcess : appProcesses) {  
7.             if (appProcess.processName.equals(context.getPackageName())) {  
8.                 /* 
9.                 BACKGROUND=400 EMPTY=500 FOREGROUND=100 
10.                 GONE=1000 PERCEPTIBLE=130 SERVICE=300 ISIBLE=200 
11.                  */  
12.                 Log.i(context.getPackageName(), "此appimportace ="  
13.                         + appProcess.importance  
14.                         + ",context.getClass().getName()="  
15.                         + context.getClass().getName());  
16.                 if (appProcess.importance != RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {  
17.                     Log.i(context.getPackageName(), "处于后台"  
18.                             + appProcess.processName);  
19.                     return true;  
20.                 } else {  
21.                     Log.i(context.getPackageName(), "处于前台"  
22.                             + appProcess.processName);  
23.                     return false;  
24.                 }  
25.             }  
26.         }  
27.         return false;  
28.     }