Android向PCL传递数据未收到MessagingCenter消息

Question

我正在尝试将数据从MainActivity发送回PCL视图。当我发送一条没有数据的消息时，它会接收它。但是，当我试图用它传递回一个字符串时，代码永远也达不到。

在MainActivity中：

if(data != null)
            {

                MessagingCenter.Send<object, string>(this, data, "MapIntentReceived");
                MessagingCenter.Send<object>(this, "MapIntentReceived");

            }

在PCL中：

            MessagingCenter.Subscribe<object, string>(this, "MapIntentReceived",
                async (sender, roomString) =>
                {   //his code is not reached
                    await SearchForRooms(roomString);
                });

            MessagingCenter.Subscribe<object>(this, "MapIntentReceived",
                async (sender) =>
                {   //this code is reached
                    await SearchForRooms("blah");
                });

谢谢你的帮助。

Answer 1

若要发送带有参数的消息，请在send方法调用中包括Type泛型参数和参数的值。

MessagingCenter.Send<MainPage, string> (this, "MapIntentReceived", data);

若要在消息中传递参数，请在订阅泛型参数和操作签名中指定参数类型。

MessagingCenter.Subscribe<MainPage, string> (this, "MapIntentReceived", (sender, arg) => {
    await SearchForRooms(arg);
});

对于取消订阅

MessagingCenter.Unsubscribe<MainPage, string> (this, "MapIntentReceived");