Xamarin.Form未处理的异常Java.lang.NumberformatException：无效的int：

Question

我是Xamarin的新手。我想了解Sqlite并在我的项目上实现。昨天我没有收到任何错误，它已经工作了。今天我继续我的项目。但是当我开始编译时，出现异常处理错误消息。我不知道是什么错误我做。希望你们能帮我解决这个问题。

MainActivity.cs

using System;

using Android.App;
using Android.Content.PM;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using System.IO;

namespace TravellerApp.Droid
{
    [Activity(Label = "TravellerApp", Icon = "@drawable/icon", Theme = "@style/MainTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        protected override void OnCreate(Bundle bundle)
        {
            TabLayoutResource = Resource.Layout.Tabbar;
            ToolbarResource = Resource.Layout.Toolbar;

            base.OnCreate(bundle);

            global::Xamarin.Forms.Forms.Init(this, bundle);

            //initialize Forms map
            Xamarin.FormsMaps.Init(this, bundle);


            string fileName = "travel_db.sqlite";
            string folderPath = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
            string fullPath = Path.Combine(folderPath, fileName);

            LoadApplication(new App(fullPath));
        }
    }
}

App.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Xamarin.Forms;

namespace TravellerApp
{
    public partial class App : Application
    {
        public static string DatabaseLocation = string.Empty;

        public App ()
        {
            InitializeComponent();

            MainPage = new NavigationPage(new MainPage());

        }

        public App(String databaseLocation)
        {
            InitializeComponent();

            //MainPage = new TravelRecordApp.MainPage();
            MainPage = new NavigationPage(new MainPage());

            DatabaseLocation = databaseLocation;
        }

        protected override void OnStart ()
        {
            // Handle when your app starts
        }

        protected override void OnSleep ()
        {
            // Handle when your app sleeps
        }

        protected override void OnResume ()
        {
            // Handle when your app resumes
        }
    }
}