Question

我正在尝试使用Xamarin.Forms框架构建跨平台应用程序。我一直在努力向我的应用程序显示一个虚拟的Restful API，但是当我启动以下页面时，应用程序会一直崩溃。请你帮助我好吗？如果我能弄清楚这一点，这对我来说将是一大步。谢谢！

这是我的观点页面：的 ApiPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="MyApp.Views.ApiPage">
    <StackLayout>
        <StackLayout Orientation="Horizontal">

        </StackLayout>
        <ListView x:Name="postsListView">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <TextCell Text="{Binding Title}" />
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </StackLayout>
</ContentPage>

这是背后的代码：的 ApiPage.xaml.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace MyApp.Views
{
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public class Post
    {
        public int Id { get; set; }
        public string Title { get; set; }
        public string Body { get; set; }
    }

    public partial class ApiPage : ContentPage
    {
        private const string Url = "https://jsonplaceholder.typicode.com/posts";
        private HttpClient _client = new HttpClient();
        private ObservableCollection<Post> _posts;
        public ApiPage()
        {
            InitializeComponent();
        }

        protected override async void OnAppearing()
        {
            var content = await _client.GetStringAsync(Url);
            var posts = JsonConvert.DeserializeObject<List<Post>>(content);
            _posts = new ObservableCollection<Post>(posts);
            postsListView.ItemsSource = _posts;

            base.OnAppearing();
        }

        void OnAdd(object sender, System.EventArgs e)
        {
        }

        void OnUpdate(object sender, System.EventArgs e)
        {
        }

        void OnDelete(object sender, System.EventArgs e)
        {
        }
    }
}

这是控制台输出，但没有说明任何内容：

11-04 18:12:09.430 D/Mono    ( 4185): Probing 'java_interop_jnienv_call_boolean_method'.
11-04 18:12:09.431 D/Mono    ( 4185): Found as 'java_interop_jnienv_call_boolean_method'.
11-04 18:12:09.521 W/art     ( 4185): JNI RegisterNativeMethods: attempt to register 0 native methods for md5b60ffeb829f638581ab2bb9b1a7f4f3f.CellRenderer_RendererHolder
11-04 18:12:12.450 D/Mono    ( 4185): Assembly Ref addref MyApp[0x9e1a6480] -> Newtonsoft.Json[0xb030b7c0]: 2
11-04 18:12:12.576 D/Mono    ( 4185): Assembly Ref addref Mono.Security[0xad5563a0] -> System[0x9e1a78c0]: 14
An unhandled exception occured.

Answer 1

似乎这是Ssl页面证书和Android操作系统之间的问题，您可以通过执行后续步骤来解决此问题

请确保您在项目中有关于System.Net.Http的引用， 1）双击＆＃34;参考文献＆＃34; Android应用项目下的文件夹 2）检查您是否已选择＆＃34; System.Net.Http＆＃34;选择＆＃34;全部＆＃34;标签

步骤2：验证您是否正在使用Native Http Handler和Native SSL / TLS impl。 1）双击Xamarin Android项目打开项目设置 2）在＆＃34;构建/ Android构建 - ＆gt;一般＆＃34;部分验证您是否具有正确的本机选项为＆＃34; HttpClient impl＆＃34; ＆安培; ＆＃34; SSL / TLS impl＆＃34;如下

Xamarin.Forms：尝试实现Restful API，但应用程序不断崩溃

1 个答案: