第三次更新：

Question

我正在使用具有蓝牙功能的Xamarin.Forms构建应用程序。连接到设备后，我有ObsevableCollection收集可用的服务。然后我想选择我正在寻找的服务。

使用Monkey.Robotics插件，并基于示例HeartRate Monitor应用。目前，有一个

this.services = new ObservableCollection<IService> ();
listView.ItemsSource = services;

// when device is connected
adapter.DeviceConnected += (s, e) => {
    device = e.Device; 

    // when services are discovered
    device.ServicesDiscovered += (object se, EventArgs ea) => {

        if (services.Count == 0)  //if it's only just started
            Device.BeginInvokeOnMainThread(() => {
                foreach (var service in device.Services) {
                    services.Add(service); //add all new services found to ObservableCollection
                }
            });
    };

    // start looking for services
    device.DiscoverServices ();

};

因此，当前代码检索所有服务并将它们放入ObservableCollection，然后填充列表视图。我想搜索结果以寻找我想要的服务，而不是填充列表并等待用户输入。即

await Task.Delay (5000); // wait 5 seconds for the scan to complete
IService ChosenService = null;

try {
        foreach(var data in services)
        {
            if (data!=null && data.ID!=null && data.ID.ToString() == 0x180D.ToString()){ ChosenService = data; break; }

        }
    }
    catch {

            Debug.WriteLine ("Exception");
    } 
    Debug.WriteLineIf(ChosenService == null, "Not Chosen");

第三次更新：

我已经添加了如上所示的try，catch块，并添加了检查以确保我们不使用空引用。所有这些都可以编译，应用程序在任何时候都不会崩溃！但是，该过程以ChosenService = null结束？所以这段代码不起作用。任何想法为什么不呢？服务扫描似乎正常，因为在调试窗口中，我得到以下反馈：

2015-09-26 22:09:38.329 Gas_SenseiOS[1431:605554] Device.Discovered Service: <CBService: 0x12832e7e0, isPrimary = YES, UUID = Heart Rate>
2015-09-26 22:09:38.333 Gas_SenseiOS[1431:605554] Device.Discovered Service: <CBService: 0x12831c950, isPrimary = YES, UUID = Device Information>
2015-09-26 22:09:38.349 Gas_SenseiOS[1431:605554] Device.Discovered Service: <CBService: 0x12832e7e0, isPrimary = YES, UUID = Heart Rate>
2015-09-26 22:09:38.350 Gas_SenseiOS[1431:605554] Device.Discovered Service: <CBService: 0x12831c950, isPrimary = YES, UUID = Device Information>
2015-09-26 22:09:38.352 Gas_SenseiOS[1431:605554] Device.Discovered Service: <CBService: 0x12832e7e0, isPrimary = YES, UUID = Heart Rate>
2015-09-26 22:09:38.352 Gas_SenseiOS[1431:605554] Device.Discovered Service: <CBService: 0x12831c950, isPrimary = YES, UUID = Device Information>

Answer 1

从臀部拍摄我怀疑您的服务中的数据元素为null或具有空ID。尝试

if (data!=null && data.ID!=null && data.ID.ToString() == 0x180D.ToString()){ ChosenService = data; break; }

Answer 2

使用上面的所有评论，以及对BLE规范和插件编写方式的一些研究，解决方案是：

            IService ChosenService = null;
            try {
                foreach(var data in services)
                {
                    if (data!=null && data.Name == "Heart Rate"){ ChosenService = data; }


                }
            }
            catch {

                Debug.WriteLine ("Exception");
            }

如何在C＃中搜索集合ID

第三次更新：

2 个答案: