好吧，我终于找到了解决方案...

Okay, I finnaly found solution ... here for curious

因此，如果您遇到相同的问题，则必须将函数loadRankOfLeaderBoard放在函数"onConnected"上，当您在Google Play服务上连接设备时会调用该函数.

So if you have the same problem, you have to put the function loadRankOfLeaderBoard on the function "onConnected" which will be call when you connect your device at google play service.