Android判断Activity是否在前台运行

public boolean isActivityRunning(Context mContext, String activityClassName) {
ActivityManager activityManager = (ActivityManager) mContext
.getSystemService(Context.ACTIVITY_SERVICE);
List<RunningTaskInfo> info = activityManager.getRunningTasks(1);
if (info != null && info.size() > 0) {
ComponentName component = info.get(0).topActivity;
String string = component.getShortClassName();
if (activityClassName.equals(component.getShortClassName())) {
return true;
}
}
return false;
}