Xamarin.Forms
Mit lokalen Datenbanken arbeiten
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Verwenden von SQLite.NET in einem freigegebenen Projekt
SQLite.NET ist eine Open Source-Bibliothek, die es ermöglicht, mithilfe von SQLite Version 3 Unterstützung für lokale Datenbanken in einem Xamarin.Forms Projekt hinzuzufügen.
Die folgenden Schritte zeigen, wie diese Komponente in ein Xamarin.Forms Shared Project Xamarin.Forms :
Laden Sie die neueste Version der SQLite.cs- Klasse herunter und fügen Sie sie dem freigegebenen Projekt hinzu.
Jede Tabelle, die in die Datenbank aufgenommen werden soll, muss im Shared Project als Klasse modelliert werden. Eine Tabelle wird durch Hinzufügen von mindestens zwei Attributen in der Klasse definiert:
Table(für die Klasse) undPrimaryKey(für eine Eigenschaft).
In diesem Beispiel wird dem Shared Project eine neue Klasse namens Song hinzugefügt, die wie folgt definiert ist:
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; }
}
}
-
SQLiteConnectionals Nächstes eine neue Klasse mit dem NamenDatabase, die von derSQLiteConnectionKlasse (in SQLite.cs enthalten) erbt. In dieser neuen Klasse wird der Code für den Datenbankzugriff, die Tabellenerstellung und CRUD-Operationen für jede Tabelle definiert. Beispielcode wird unten gezeigt:
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);
}
}
}
- Wie Sie im vorherigen Schritt, der Konstruktor unserer sehen konnten
Database- Klasse enthält einenpathder repräsentiert den Ort der Datei , die speichert die SQLite - Datenbank - Datei. Ein statischesDatabasekann inApp.csdeklariertApp.cs. Derpathist plattformspezifisch:
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();
}
}
- Rufen Sie das
DBObjekt jetzt einfach über dieAppKlasse auf, wenn Sie eine CRUD-Operation für dieSongsTabelle ausführen müssen. Um beispielsweise einen neuenSongeinzufügen, nachdem der Benutzer auf eine Schaltfläche geklickt hat, können Sie den folgenden Code verwenden:
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);
}
Arbeiten mit lokalen Datenbanken mit xamarin.forms in Visual Studio 2015
SQlite-Beispiel Schritt für Schritt Erklärung
Die folgenden Schritte zeigen, wie Sie diese Komponente in ein Xamarin.Forms Shared Project einbinden: Hinzufügen von Paketen in (pcl, Andriod, Windows, Ios) Hinzufügen von Referenzen Klicken Sie auf Nuget-Pakete verwalten -> klicken Sie auf Durchsuchen, um SQLite.Net.Core- zu installieren PCL , SQLite Net Extensions nach Abschluss der Installation überprüfen Sie es einmal in den Referenzen
Um die Klasse Employee.cs unter dem Code hinzuzufügen
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; } } }Eine Schnittstelle hinzufügen ISQLite
using SQLite.Net;
//using SQLite.Net;
namespace DatabaseEmployeeCreation.SqlLite.ViewModel
{
public interface ISQLite
{
SQLiteConnection GetConnection();
}
}
- Erstellen Sie eine Klasse für Datenbanklogiken und Methoden unter dem folgenden Code.
mit SQLite.Net; using System.Collections.Generic; using System.Linq; mit Xamarin.Forms; Namespace DatabaseEmployeeCreation.SqlLite.ViewModel {öffentliche Klasse DatabaseLogic {statisches Objekt locker = new object (); SQLiteConnection-Datenbank;
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);
}
}
}
}
- Erstellen Sie eine 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);
// }
}
}
um EmployeeDetails hinter dem Code anzuzeigen
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);
//}
}
- So implementieren Sie eine Methode in Android und der ios GetConnection () -Methode
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();
}
}
}
Ich hoffe, dass dieses Beispiel sehr einfach ist
Modified text is an extract of the original Stack Overflow Documentation
Lizenziert unter CC BY-SA 3.0
Nicht angeschlossen an Stack Overflow
