Android sqlite查询不返回

Question

应用程序应该采取一种成分，并搜索数据库，并返回像卡路里等东西。我只是从Assets打开文件并复制它，打开副本并创建一个表格（据推测，我对它们运行了try catch（exception），它表示它们已经成功）。但我尝试运行一个查询，它给出了一个错误“不能将nutr_grabber.mainactivity.usdProto转换为int”。 如果我尝试使用query.Energ_Kcal，它不会给出任何错误，但完全不会返回任何结果。 任何想法？

using System; 
using Android.Views; 
using Android.Content; 
using Android.Runtime; 
using Android.App; 
using Android.Widget; 
using Android.OS; 
using Android.Content.Res; 
using System.IO; 
using SQLite; 
using System.Linq; 
using Android.Database.Sqlite; 

namespace nutr_grabber 
{ 

    [Activity(Label = "nutr_grabber", MainLauncher = true, Icon = "@drawable/icon")] 
    public class MainActivity : Activity 
    { 
     string str1; 

     // Android needs a databse to be copied from assets to a useable location 
     public void copyDataBase() 
     { 
      var dbPath = System.IO.Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), "UsdDataProto.db"); 

      if (!System.IO.File.Exists(dbPath)) 
      { 
       var dbAssetStream = Assets.Open("UsdDataProto.db"); 
       var dbFileStream = new FileStream(dbPath, FileMode.OpenOrCreate); 
       var buffer = new byte[1024]; 

       int b = buffer.Length; 
       int length; 

       while ((length = dbAssetStream.Read(buffer, 0, b)) > 0) 
       { 
        dbFileStream.Write(buffer, 0, length); 
       } 

       dbFileStream.Flush(); 
       dbFileStream.Close(); 
       dbAssetStream.Close(); 
      } 
     } 

     protected override void OnCreate(Bundle bundle) 
     { 
      base.OnCreate(bundle); 

      // makes the database 
      try 
      { 
       copyDataBase(); 
       new AlertDialog.Builder(this) 
        .SetMessage("Database created ...") 
        .Show(); 
      } 
      catch(Exception e) 
      { 

       new AlertDialog.Builder(this) 
        .SetMessage("Database not created ...") 
        .Show();     

      } 


      // Set our view from the "main" layout resource 

      SetContentView(Resource.Layout.Main); 


      //set widgets 
      TextView message = FindViewById<TextView>(Resource.Id.message); 
      EditText ingred = FindViewById<EditText>(Resource.Id.enterHere); 
      Button search = FindViewById<Button>(Resource.Id.search); 

      //open sqlite connection, create table 
      var Path = System.IO.Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), "UsdDataProto.db"); 
      var db = new SQLiteConnection(Path); 
      db.CreateTable<usdProto>(); 


      search.Click += (object sender, EventArgs e) => 
      { 
       str1 = ingred.Text; 

       var query = db.Query<usdProto>("SELECT * FROM usdProto WHERE Shrt_Desc = ?", str1); 

       foreach (var item in query) 
       { 
        new AlertDialog.Builder(this) 
         .SetMessage(item.Energ_Kcal) 
         .Show(); 
       } 
      }; 

     } 

     //---------------------------------------------------------------------------- 

     public class usdProto 
     { 
      [PrimaryKey] 
      public int NDB_No { get; set; } 
      public string Shrt_Desc { get; set; } 
      public int Energ_Kcal { get; set; } 
      public int Protein_g { get; set; } 
      public int Lipid_Tot_g { get; set; } 
      public int Ash_g { get; set; } 
      public int Carbohydrt_g { get; set; } 
      public int Fiber_TD_g { get; set; } 
      public int Sugar_Tot_g { get; set; } 
      public int Calcium_mg { get; set; } 
      public int Iron_mg { get; set; } 
      public int Magnesium_mg { get; set; } 
      public int Phosphorus_mg { get; set; } 
      public int Potassium_mg { get; set; } 
      public int Sodium_mg { get; set; } 
      public int Zinc_mg { get; set; } 
      public int Copper_mg { get; set; } 
      public int Manganese_mg { get; set; } 
      public int Selenium_ug { get; set; } 
      public int Vit_C_mg { get; set; } 
      public int Thiamin_mg { get; set; } 
      public int Riboflavin_mg { get; set; } 
      public int Niacin_mg { get; set; } 
      public int Panto_Acid_mg { get; set; } 
      public int Vit_B6_mg { get; set; } 
      public int Folate_Tot_ug { get; set; } 
      public int Folic_Acid_ug { get; set; } 
      public int Food_Folate_ug { get; set; } 
      public int Folate_DFE_ug { get; set; } 
      public int Choline_Tot_mg { get; set; } 
      public int Vit_B12_ug { get; set; } 
      public int Vit_A_IU { get; set; } 
      public int Vit_A_RAE { get; set; } 
      public int Retinol_ug { get; set; } 
      public int Alpha_Carot_ug { get; set; } 
      public int Beta_Carot_ug { get; set; } 
      public int Beta_Crypt_ug { get; set; } 
      public int Lycopene_ug { get; set; } 
      public int Lut_Zea_ug { get; set; } 
      public int Vit_E_mg { get; set; } 
      public int Vit_D_ug { get; set; } 
      public int Vit_D_IU { get; set; } 
      public int Vit_K_ug { get; set; } 
      public int FA_Sat_g { get; set; } 
      public int FA_Mono_g { get; set; } 
      public int FA_Poly_g { get; set; } 
      public int Cholestrl_mg { get; set; } 
      public int Gm_unit { get; set; } 
      public int num { get; set; } 
      public int unit { get; set; } 
     } 
    } 
} 

肯定有一个在资产文件中的数据： enter image description here

Answer 1

有事情不对您的代码数量巨大。这些都是亮点：

1. 在您的资产文件夹中的文件不是一个SQLite数据库

2. 表名在DB（一旦你修复＃1）是“USDADataProto”，而不是“usdProto” 。您正在查询不存在的表格。

3. 你映射类应该使用正确的表名，“USDADataProto”

4. 你的数据在全部大写，所以你需要考虑的是查询

这样的时候：

var query = db.Query<USDADataProto>("SELECT * FROM USDADataProto where Shrt_Desc = ?",str1.ToUpper()); 

foreach (var item in query) 
{ 
    new AlertDialog.Builder(this) 
    .SetMessage(item.Shrt_Desc) 
    .Show(); 
}