消息推送時問題：
You've implemented -[<UIApplicationDelegate> application:didReceiveRemoteNotification:fetchCompletionHandler:], but you still need to add "remote-notification" to the list of your supported UIBackgroundModes in your Info.plist. 意思是說：
你已經實現了——(< UIApplicationDelegate >應用程序:didReceiveRemoteNotification:fetchCompletionHandler:],但你仍然需要添加“remote-notification”你的支持UIBackgroundModes Info.plist列表。
解決辦法：PORJECT --> Capabilities --> Background Modes --> Background fetch & Remote notifications -->選中爲on 狀態