这里给大家介绍两种方法，直接上代码：

第一种：

public static boolean isApplicationBroughtToBackground(final Context context) {
 ActivityManager am = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
 List<RunningTaskInfo> tasks = am.getRunningTasks(1);
 if (!tasks.isEmpty()) {
  ComponentName topActivity = tasks.get(0).topActivity;
  if (!topActivity.getPackageName().equals(context.getPackageName())) {
   return true;
  }
 }
 return false;
}

权限配置

< uses-permission Android:name=”android.permission.GET_TASKS” />

第二种

后台分为：service后台和activity后台，这里认为不是前台的都认为后台。
•service运行在后台，appProcess.importance = IMPORTANCE_SERVICE，
•没有service运行的后台

public static boolean isBackground(Context context) {
 
 
  ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
  List<ActivityManager.RunningAppProcessInfo> appProcesses = activityManager.getRunningAppProcesses();
  for (ActivityManager.RunningAppProcessInfo appProcess : appProcesses) {
   if (appProcess.processName.equals(context.getPackageName())) {
    if (appProcess.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
     System.out.print(String.format("Foreground App:", appProcess.processName));
     return false;
    }else{
     System.out.print("Background App:"+appProcess.processName);
     return true;
    }
   }
  }
  return false;
 }

希望可以帮助大家
如果哪里有什么不对或者不足的地方，还望读者多多提意见或建议
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