Question

我正在开发基于Xamarin框架的C＃跨平台移动应用程序。以下代码使用setExactAndAllowWhileIdle插件，该插件定义adapter类型。此代码编译，但运行时，我得到以下NullReference错误消息，即使在程序的顶部定义了public partial class HomePage : ContentPage { // Class Definitions ObservableCollection<IDevice> devices; IAdapter adapter; public HomePage(IAdapter adapter) { InitializeComponent(); this.adapter = adapter; this.devices = new ObservableCollection<IDevice>(); Debug.WriteLine ("Before Button Clicked"); NewDeviceButton.Clicked += async (sender, e) => { adapter.StartScanningForDevices (0x133D.UuidFromPartial ()); //Scan for a specific device await Task.Delay (2000); // wait 2 seconds for the scan to complete adapter.StopScanningForDevices (); }; adapter.DeviceDiscovered += (object sender, DeviceDiscoveredEventArgs e) => { Xamarin.Forms.Device.BeginInvokeOnMainThread(() => { devices.Add (e.Device); }); }; } }。我错过了什么？

adapter.DeviceDiscovered

System.NullReferenceException：未将对象引用设置为对象的实例在/Projects/my_App/My_App/Views/HomePage.xaml.cs:72的My_App.HomePage..ctor（IAdapter适配器）[0x00081]中

注意：第72行是app.cs行。

这是HomePage我的public class App : Application { static IAdapter Adapter; public App () { MainPage = new HomePage (Adapter); } public static void SetAdapter (IAdapter adapter) { Adapter = adapter; } }来自：

<ul id="featuresOptions" class="options" style="display: block;">
    <li><label><input type="checkbox" name="Apartment" value="6"> Apartment</label></li>
    <li><label><input type="checkbox" name="House" value="7"> House</label></li>
    <li><label><input type="checkbox" name="Lot" value="8"> Lot</label></li>
    <li><button class="button" id="featuresButton">Filter</button></li>
</ul>

$(document).on('click', "#featuresButton", function() {
    var formData = [];
    $("#featuresOptions li input").each(function(e) {
        if($(this).is(":checked")) {
            formData.push($(this).val());
        }
    });
});

NullReferenceException与定义的自定义类型？

0 个答案: