Xamarin.Forms
Lavorare con database locali
Ricerca…
Utilizzo di SQLite.NET in un progetto condiviso
SQLite.NET è una libreria open source che consente di aggiungere il supporto dei database locali utilizzando SQLite versione 3 in un progetto Xamarin.Forms .
I passaggi seguenti mostrano come includere questo componente in un progetto condiviso Xamarin.Forms :
Scarica l'ultima versione della classe SQLite.cs e aggiungila al Progetto condiviso.
Ogni tabella che verrà inclusa nel database deve essere modellata come classe nel Progetto condiviso. Una tabella viene definita aggiungendo almeno due attributi nella classe:
Table(per la classe) ePrimaryKey(per una proprietà).
Per questo esempio, una nuova classe denominata Song viene aggiunta al progetto condiviso, definita come segue:
using System;
using SQLite;
namespace SongsApp
{
[Table("Song")]
public class Song
{
[PrimaryKey]
public string ID { get; set; }
public string SongName { get; set; }
public string SingerName { get; set; }
}
}
- Successivamente, aggiungi una nuova classe chiamata
Database, che eredita dalla classeSQLiteConnection(inclusa in SQLite.cs). In questa nuova classe, viene definito il codice per l'accesso al database, la creazione di tabelle e le operazioni CRUD per ogni tabella. Il codice di esempio è mostrato di seguito:
using System;
using System.Linq;
using System.Collections.Generic;
using SQLite;
namespace SongsApp
{
public class BaseDatos : SQLiteConnection
{
public BaseDatos(string path) : base(path)
{
Initialize();
}
void Initialize()
{
CreateTable<Song>();
}
public List<Song> GetSongs()
{
return Table<Song>().ToList();
}
public Song GetSong(string id)
{
return Table<Song>().Where(t => t.ID == id).First();
}
public bool AddSong(Song song)
{
Insert(song);
}
public bool UpdateSong(Song song)
{
Update(song);
}
public void DeleteSong(Song song)
{
Delete(song);
}
}
}
- Come si può vedere nel passaggio precedente, il costruttore della nostra classe
Databaseinclude un parametropath, che rappresenta la posizione del file che archivia il file di database SQLite. Un oggettoDatabasestatico può essere dichiarato inApp.csIlpathè specifico per la piattaforma:
public class App : Application
{
public static Database DB;
public App ()
{
string dbFile = "SongsDB.db3";
#if __ANDROID__
string docPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
var dbPath = System.IO.Path.Combine(docPath, dbFile);
#else
#if __IOS__
string docPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
string libPath = System.IO.Path.Combine(docPath, "..", "Library");
var dbPath = System.IO.Path.Combine(libPath, dbFile);
#else
var dbPath = System.IO.Path.Combine(ApplicationData.Current.LocalFolder.Path, dbFile);
#endif
#endif
DB = new Database(dbPath);
// The root page of your application
MainPage = new SongsPage();
}
}
- Ora chiama semplicemente l'oggetto
DBtramite la classeAppogni volta che devi eseguire un'operazione CRUD alla tabellaSongs. Ad esempio, per inserire una nuovaSongdopo che l'utente ha fatto clic su un pulsante, è possibile utilizzare il seguente codice:
void AddNewSongButton_Click(object sender, EventArgs a)
{
Song s = new Song();
s.ID = Guid.NewGuid().ToString();
s.SongName = songNameEntry.Text;
s.SingerName = singerNameEntry.Text;
App.DB.AddSong(song);
}
Lavorare con database locali utilizzando xamarin.forms in visual studio 2015
Esempio SQlite Passo dopo passo Spiegazione
I passaggi seguenti mostrano come includere questo componente in un progetto condiviso Xamarin.Form: aggiungere pacchetti in (pcl, Andriod, Windows, Ios) Aggiungi riferimenti Fare clic su Gestisci pacchetti Nuget -> fare clic su Sfoglia per installare SQLite.Net.Core- PCL , SQLite Net Extensions dopo aver completato l'installazione, controllalo una volta nei riferimenti quindi
Per aggiungere Class Employee.cs sotto il codice
using SQLite.Net.Attributes; namespace DatabaseEmployeeCreation.SqlLite { public class Employee { [PrimaryKey,AutoIncrement] public int Eid { get; set; } public string Ename { get; set; } public string Address { get; set; } public string phonenumber { get; set; } public string email { get; set; } } }Per aggiungere un'interfaccia ISQLite
using SQLite.Net;
//using SQLite.Net;
namespace DatabaseEmployeeCreation.SqlLite.ViewModel
{
public interface ISQLite
{
SQLiteConnection GetConnection();
}
}
- È possibile creare una classe per le logiche del database e seguire i seguenti metodi.
utilizzando SQLite.Net; using System.Collections.Generic; using System.Linq; usando Xamarin.Forms; namespace DatabaseEmployeeCreation.SqlLite.ViewModel {public class DatabaseLogic {static object locker = new object (); Database SQLiteConnection;
public DatabaseLogic()
{
database = DependencyService.Get<ISQLite>().GetConnection();
// create the tables
database.CreateTable<Employee>();
}
public IEnumerable<Employee> GetItems()
{
lock (locker)
{
return (from i in database.Table<Employee>() select i).ToList();
}
}
public IEnumerable<Employee> GetItemsNotDone()
{
lock (locker)
{
return database.Query<Employee>("SELECT * FROM [Employee]");
}
}
public Employee GetItem(int id)
{
lock (locker)
{
return database.Table<Employee>().FirstOrDefault(x => x.Eid == id);
}
}
public int SaveItem(Employee item)
{
lock (locker)
{
if (item.Eid != 0)
{
database.Update(item);
return item.Eid;
}
else
{
return database.Insert(item);
}
}
}
public int DeleteItem(int Eid)
{
lock (locker)
{
return database.Delete<Employee>(Eid);
}
}
}
}
- creare un xaml.forms EmployeeRegistration.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="DatabaseEmployeeCreation.SqlLite.EmployeeRegistration"
Title="{Binding Name}" >
<StackLayout VerticalOptions="StartAndExpand" Padding="20">
<Label Text="Ename" />
<Entry x:Name="nameEntry" Text="{Binding Ename}"/>
<Label Text="Address" />
<Editor x:Name="AddressEntry" Text="{Binding Address}"/>
<Label Text="phonenumber" />
<Entry x:Name="phonenumberEntry" Text="{Binding phonenumber}"/>
<Label Text="email" />
<Entry x:Name="emailEntry" Text="{Binding email}"/>
<Button Text="Add" Clicked="addClicked"/>
<!-- <Button Text="Delete" Clicked="deleteClicked"/>-->
<Button Text="Details" Clicked="DetailsClicked"/>
<!-- <Button Text="Edit" Clicked="speakClicked"/>-->
</StackLayout>
</ContentPage>
EmployeeRegistration.cs
using DatabaseEmployeeCreation.SqlLite.ViewModel;
using DatabaseEmployeeCreation.SqlLite.Views;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
namespace DatabaseEmployeeCreation.SqlLite
{
public partial class EmployeeRegistration : ContentPage
{
private int empid;
private Employee obj;
public EmployeeRegistration()
{
InitializeComponent();
}
public EmployeeRegistration(Employee obj)
{
this.obj = obj;
var eid = obj.Eid;
Navigation.PushModalAsync(new EmployeeRegistration());
var Address = obj.Address;
var email = obj.email;
var Ename = obj.Ename;
var phonenumber = obj.phonenumber;
AddressEntry. = Address;
emailEntry.Text = email;
nameEntry.Text = Ename;
//AddressEntry.Text = obj.Address;
//emailEntry.Text = obj.email;
//nameEntry.Text = obj.Ename;
//phonenumberEntry.Text = obj.phonenumber;
Employee empupdate = new Employee(); //updateing Values
empupdate.Address = AddressEntry.Text;
empupdate.Ename = nameEntry.Text;
empupdate.email = emailEntry.Text;
empupdate.Eid = obj.Eid;
App.Database.SaveItem(empupdate);
Navigation.PushModalAsync(new EmployeeRegistration());
}
public EmployeeRegistration(int empid)
{
this.empid = empid;
Employee lst = App.Database.GetItem(empid);
//var Address = lst.Address;
//var email = lst.email;
//var Ename = lst.Ename;
//var phonenumber = lst.phonenumber;
//AddressEntry.Text = Address;
//emailEntry.Text = email;
//nameEntry.Text = Ename;
//phonenumberEntry.Text = phonenumber;
// to retriva values based on id to
AddressEntry.Text = lst.Address;
emailEntry.Text = lst.email;
nameEntry.Text = lst.Ename;
phonenumberEntry.Text = lst.phonenumber;
Employee empupdate = new Employee(); //updateing Values
empupdate.Address = AddressEntry.Text;
empupdate.email = emailEntry.Text;
App.Database.SaveItem(empupdate);
Navigation.PushModalAsync(new EmployeeRegistration());
}
void addClicked(object sender, EventArgs e)
{
//var createEmp = (Employee)BindingContext;
Employee emp = new Employee();
emp.Address = AddressEntry.Text;
emp.email = emailEntry.Text;
emp.Ename = nameEntry.Text;
emp.phonenumber = phonenumberEntry.Text;
App.Database.SaveItem(emp);
this.Navigation.PushAsync(new EmployeeDetails());
}
//void deleteClicked(object sender, EventArgs e)
//{
// var emp = (Employee)BindingContext;
// App.Database.DeleteItem(emp.Eid);
// this.Navigation.PopAsync();
//}
void DetailsClicked(object sender, EventArgs e)
{
var empcancel = (Employee)BindingContext;
this.Navigation.PushAsync(new EmployeeDetails());
}
// void speakClicked(object sender, EventArgs e)
// {
// var empspek = (Employee)BindingContext;
// //DependencyService.Get<ITextSpeak>().Speak(empspek.Address + " " + empspek.Ename);
// }
}
}
per visualizzare EmployeeDetails sotto il codice sottostante
using DatabaseEmployeeCreation; using DatabaseEmployeeCreation.SqlLite; using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using Xamarin.Forms; namespace DatabaseEmployeeCreation.SqlLite.Views { public partial class EmployeeDetails : ContentPage { ListView lv = new ListView(); IEnumerable<Employee> lst; public EmployeeDetails() { InitializeComponent(); displayemployee(); } private void displayemployee() { Button btn = new Button() { Text = "Details", BackgroundColor = Color.Blue, }; btn.Clicked += Btn_Clicked; //IEnumerable<Employee> lst = App.Database.GetItems(); //IEnumerable<Employee> lst1 = App.Database.GetItemsNotDone(); //IEnumerable<Employee> lst2 = App.Database.GetItemsNotDone(); Content = new StackLayout() { Children = { btn }, }; } private void Btn_Clicked(object sender, EventArgs e) { lst = App.Database.GetItems(); lv.ItemsSource = lst; lv.HasUnevenRows = true; lv.ItemTemplate = new DataTemplate(typeof(OptionsViewCell)); Content = new StackLayout() { Children = { lv }, }; } }
public class OptionsViewCell : ViewCell
{
int empid;
Button btnEdit;
public OptionsViewCell()
{
}
protected override void OnBindingContextChanged()
{
base.OnBindingContextChanged();
if (this.BindingContext == null)
return;
dynamic obj = BindingContext;
empid = Convert.ToInt32(obj.Eid);
var lblname = new Label
{
BackgroundColor = Color.Lime,
Text = obj.Ename,
};
var lblAddress = new Label
{
BackgroundColor = Color.Yellow,
Text = obj.Address,
};
var lblphonenumber = new Label
{
BackgroundColor = Color.Pink,
Text = obj.phonenumber,
};
var lblemail = new Label
{
BackgroundColor = Color.Purple,
Text = obj.email,
};
var lbleid = new Label
{
BackgroundColor = Color.Silver,
Text = (empid).ToString(),
};
//var lblname = new Label
//{
// BackgroundColor = Color.Lime,
// // HorizontalOptions = LayoutOptions.Start
//};
//lblname.SetBinding(Label.TextProperty, "Ename");
//var lblAddress = new Label
//{
// BackgroundColor = Color.Yellow,
// //HorizontalOptions = LayoutOptions.Center,
//};
//lblAddress.SetBinding(Label.TextProperty, "Address");
//var lblphonenumber = new Label
//{
// BackgroundColor = Color.Pink,
// //HorizontalOptions = LayoutOptions.CenterAndExpand,
//};
//lblphonenumber.SetBinding(Label.TextProperty, "phonenumber");
//var lblemail = new Label
//{
// BackgroundColor = Color.Purple,
// // HorizontalOptions = LayoutOptions.CenterAndExpand
//};
//lblemail.SetBinding(Label.TextProperty, "email");
//var lbleid = new Label
//{
// BackgroundColor = Color.Silver,
// // HorizontalOptions = LayoutOptions.CenterAndExpand
//};
//lbleid.SetBinding(Label.TextProperty, "Eid");
Button btnDelete = new Button
{
BackgroundColor = Color.Gray,
Text = "Delete",
//WidthRequest = 15,
//HeightRequest = 20,
TextColor = Color.Red,
HorizontalOptions = LayoutOptions.EndAndExpand,
};
btnDelete.Clicked += BtnDelete_Clicked;
//btnDelete.PropertyChanged += BtnDelete_PropertyChanged;
btnEdit = new Button
{
BackgroundColor = Color.Gray,
Text = "Edit",
TextColor = Color.Green,
};
// lbleid.SetBinding(Label.TextProperty, "Eid");
btnEdit.Clicked += BtnEdit_Clicked1; ;
//btnEdit.Clicked += async (s, e) =>{
// await App.Current.MainPage.Navigation.PushModalAsync(new EmployeeRegistration());
//};
View = new StackLayout()
{
Orientation = StackOrientation.Horizontal,
BackgroundColor = Color.White,
Children = { lbleid, lblname, lblAddress, lblemail, lblphonenumber, btnDelete, btnEdit },
};
//View = new StackLayout()
//{ HorizontalOptions = LayoutOptions.Center, WidthRequest = 10, BackgroundColor = Color.Yellow, Children = { lblAddress } };
//View = new StackLayout()
//{ HorizontalOptions = LayoutOptions.End, WidthRequest = 30, BackgroundColor = Color.Yellow, Children = { lblemail } };
//View = new StackLayout()
//{ HorizontalOptions = LayoutOptions.End, BackgroundColor = Color.Green, Children = { lblphonenumber } };
//string Empid =c.eid ;
}
private async void BtnEdit_Clicked1(object sender, EventArgs e)
{
Employee obj= App.Database.GetItem(empid);
if (empid > 0)
{
await App.Current.MainPage.Navigation.PushModalAsync(new EmployeeRegistration(obj));
}
else {
await App.Current.MainPage.Navigation.PushModalAsync(new EmployeeRegistration(empid));
}
}
private void BtnDelete_Clicked(object sender, EventArgs e)
{
// var eid = Convert.ToInt32(empid);
// var item = (Xamarin.Forms.Button)sender;
int eid = empid;
App.Database.DeleteItem(eid);
}
//private void BtnDelete_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
//{
// var ename= e.PropertyName;
//}
}
//private void BtnDelete_Clicked(object sender, EventArgs e)
//{
// var eid = 8;
// var item = (Xamarin.Forms.Button)sender;
// App.Database.DeleteItem(eid);
//}
}
- Per implementare il metodo nel metodo Android e ios GetConnection ()
using System;
using Xamarin.Forms;
using System.IO;
using DatabaseEmployeeCreation.Droid;
using DatabaseEmployeeCreation.SqlLite.ViewModel;
using SQLite;
using SQLite.Net;
[assembly: Dependency(typeof(SQLiteEmployee_Andriod))]
namespace DatabaseEmployeeCreation.Droid
{
public class SQLiteEmployee_Andriod : ISQLite
{
public SQLiteEmployee_Andriod()
{
}
#region ISQLite implementation
public SQLiteConnection GetConnection()
{
//var sqliteFilename = "EmployeeSQLite.db3";
//string documentsPath = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal); // Documents folder
//var path = Path.Combine(documentsPath, sqliteFilename);
//// This is where we copy in the prepopulated database
//Console.WriteLine(path);
//if (!File.Exists(path))
//{
// var s = Forms.Context.Resources.OpenRawResource(Resource.Raw.EmployeeSQLite); // RESOURCE NAME ###
// // create a write stream
// FileStream writeStream = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write);
// // write to the stream
// ReadWriteStream(s, writeStream);
//}
//var conn = new SQLiteConnection(path);
//// Return the database connection
//return conn;
var filename = "DatabaseEmployeeCreationSQLite.db3";
var documentspath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
var path = Path.Combine(documentspath, filename);
var platform = new SQLite.Net.Platform.XamarinAndroid.SQLitePlatformAndroid();
var connection = new SQLite.Net.SQLiteConnection(platform, path);
return connection;
}
//public SQLiteConnection GetConnection()
//{
// var filename = "EmployeeSQLite.db3";
// var documentspath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
// var path = Path.Combine(documentspath, filename);
// var platform = new SQLite.Net.Platform.XamarinAndroid.SQLitePlatformAndroid();
// var connection = new SQLite.Net.SQLiteConnection(platform, path);
// return connection;
//}
#endregion
/// <summary>
/// helper method to get the database out of /raw/ and into the user filesystem
/// </summary>
void ReadWriteStream(Stream readStream, Stream writeStream)
{
int Length = 256;
Byte[] buffer = new Byte[Length];
int bytesRead = readStream.Read(buffer, 0, Length);
// write the required bytes
while (bytesRead > 0)
{
writeStream.Write(buffer, 0, bytesRead);
bytesRead = readStream.Read(buffer, 0, Length);
}
readStream.Close();
writeStream.Close();
}
}
}
Spero che questo esempio sopra sia un modo molto semplice che ho spiegato
Modified text is an extract of the original Stack Overflow Documentation
Autorizzato sotto CC BY-SA 3.0
Non affiliato con Stack Overflow