XamarinSQLite教程在Xamarin.Android项目中使用数据库
在Xamarin.Android项目中使用预设数据库的具体操作步骤如下:
(1)创建一个Xamarin.Android项目,如AndroidSQLiteDemo。
(2)在AndroidSQLiteDemo项目的Resources文件夹下创建一个Raw文件夹。
(3)将上一节中创建的Documents.db数据库拖动到Raw文件夹中。
(4)打开MainActivity.cs文件,将Documents.db数据库的内容复制到/data/data/[your packageName/files/ MyDocuments.db中,代码如下:
using System; using Android.App; using Android.Content; using Android.Runtime; using Android.Views; using Android.Widget; using Android.OS; using Android.Support.V7.App; using System.IO; using System.Text; namespace AndroidSQLiteDemo { [Activity(Label = "@string/app_name", MainLauncher = true, LaunchMode = Android.Content.PM.LaunchMode.SingleTop, Icon = "@drawable/icon")] public class MainActivity : AppCompatActivity { protected override void OnCreate(Bundle bundle) { base.OnCreate(bundle); SetContentView(Resource.Layout.main); var toolbar = FindViewById<Android.Support.V7.Widget.Toolbar>(Resource.Id.toolbar); if (toolbar != null) { SetSupportActionBar(toolbar); SupportActionBar.SetDisplayHomeAsUpEnabled(false); SupportActionBar.SetHomeButtonEnabled(false); } // Get our button from the layout resource, // and attach an event to it var clickButton = FindViewById<Button>(Resource.Id.my_button); clickButton.Click += (sender, args) => { var sqliteFilename = "MyDocuments.db"; string documentsPath = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal); // Documents folder var path = Path.Combine(documentsPath, sqliteFilename); Console.WriteLine("数据库文件的目录:{0}",path); if (!File.Exists(path)) { var s = Resources.OpenRawResource(Resource.Raw.Documents); //创建写入列 FileStream writeStream = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write); ReadWriteStream(s, writeStream); } }; } void ReadWriteStream(Stream readStream, Stream writeStream) { int Length = 256; Byte[] buffer = new Byte[Length]; int bytesRead = readStream.Read(buffer, 0, Length); // 写入所需字节 while (bytesRead > 0) { writeStream.Write(buffer, 0, bytesRead); bytesRead = readStream.Read(buffer, 0, Length); } readStream.Close(); writeStream.Close(); } } }
运行程序后,初始状态如图1.31所示。
轻拍HELLO WORLD,CLICK ME!按钮后,会在输出窗口输出以下的内容:
数据库文件的目录:/data/user/0/com.company.AndroidSQLiteDemo/files/MyDocuments.db
此时Documents.db数据库中的内容就会复制到MyDocuments.db文件中。