Android利用Intent实现记事本功能（NotePad）

本文实例为大家分享了Intent如何实现一个简单的记事本功能的演示过程，供大家参考，具体内容如下

1、运行截图

单击右上角【…】会弹出【添加】菜单项，长按某条记录会弹出快捷菜单【删除】项。

2、主要设计步骤

（1）添加引用

鼠标右击【引用】à【添加引用】，在弹出的窗口中勾选“System.Data”和“System.Data.SQlite”，如下图所示：

注意：不需要通过NuGet添加SQLite程序包，只需要按这种方式添加即可。

（2）添加图片

到Android SDK API 23的Samples的NotePad例子下找到app_notes.png，将其添加到该项目中，并将其换名为ch12_app_notes.png。

（3）添加ch1205_NoteEditor.axml文件

（4）添加ch1205_Main.axml文件

（5）添加ch1205Note.cs文件

using System;
namespace MyDemos.SrcDemos
{
  class ch1205Note : Java.Lang.Object
  {
    public long Id { get; set; }
    public string Body { get; set; }
    public DateTime ModifiedTime { get; set; }

    public ch1205Note()
    {
      Id = -1L;
      Body = string.Empty;
    }

    public ch1205Note(long id, string body, DateTime modified)
    {
      Id = id;
      Body = body;
      ModifiedTime = modified;
    }

    public override string ToString()
    {
      return ModifiedTime.ToString();
    }
  }
} 

（6）添加ch1205LinedEditText.cs文件

using Android.Content;
using Android.Runtime;
using Android.Widget;
using Android.Graphics;
using Android.Util;

namespace MyDemos.SrcDemos
{
  [Register("MyDemos.SrcDemos.ch1205LinedEditText")]
  class ch1205LinedEditText : EditText
  {
    private Rect rect;
    private Paint paint;

    // 为了LayoutInflater需要提供此构造函数
    public ch1205LinedEditText(Context context, IAttributeSet attrs)
      : base(context, attrs)
    {
      rect = new Rect();
      paint = new Paint();
      paint.SetStyle(Android.Graphics.Paint.Style.Stroke);
      paint.Color = Color.LightGray;
    }

    protected override void onDraw(Canvas canvas)
    {
      int count = LineCount;
      for (int i = 0; i < count; i++)
      {
 int baseline = GetLineBounds(i, rect);
 canvas.DrawLine(rect.Left, baseline + 1, rect.Right, baseline + 1, paint);
      }
      base.onDraw(canvas);
    }
  }
}

（7）添加ch1205NoteRepository.cs文件

using System;
using System.Collections.Generic;
using Mono.Data.Sqlite;

namespace MyDemos.SrcDemos
{
  class ch1205NoteRepository
  {
    private static string db_file = "notes.db3";

    private static SqliteConnection GetConnection()
    {
      var dbPath = System.IO.Path.Combine(
 System.Environment.GetFolderPath(
   System.Environment.SpecialFolder.Personal), db_file);
      bool exists = System.IO.File.Exists(dbPath);
      if (!exists) SqliteConnection.CreateFile(dbPath);
      var conn = new SqliteConnection("Data Source=" + dbPath);
      if (!exists) CreateDatabase(conn);
      return conn;
    }

    private static void CreateDatabase(SqliteConnection connection)
    {
      var sql = "CREATE TABLE ITEMS (Id INTEGER PRIMARY KEY AUTOINCREMENT, Body ntext, Modified datetime);";
      connection.Open();
      using (var cmd = connection.CreateCommand())
      {
 cmd.CommandText = sql;
 cmd.ExecuteNonQuery();
      }

      // Create a sample note to get the user started
      sql = "INSERT INTO ITEMS (Body, Modified) VALUES (@Body, @Modified);";
      using (var cmd = connection.CreateCommand())
      {
 cmd.CommandText = sql;
 cmd.Parameters.AddWithValue("@Body", "今天有个约会");
 cmd.Parameters.AddWithValue("@Modified", DateTime.Now);
 cmd.ExecuteNonQuery();
      }
      connection.Close();
    }

    public static IEnumerable GetAllNotes()
    {
      var sql = "SELECt * FROM ITEMS;";
      using (var conn = GetConnection())
      {
 conn.Open();
 using (var cmd = conn.CreateCommand())
 {
   cmd.CommandText = sql;
   using (var reader = cmd.ExecuteReader())
   {
     while (reader.Read())
     {
yield return new ch1205Note(
  reader.GetInt32(0),
  reader.GetString(1),
  reader.GetDateTime(2));
     }
   }
 }
      }
    }

    public static ch1205Note GetNote(long id)
    {
      var sql = "SELECt * FROM ITEMS WHERe Id = id;";
      using (var conn = GetConnection())
      {
 conn.Open();
 using (var cmd = conn.CreateCommand())
 {
   cmd.CommandText = sql;
   using (var reader = cmd.ExecuteReader())
   {
     if (reader.Read())
return new ch1205Note(reader.GetInt32(0), reader.GetString(1), reader.GetDateTime(2));
     else
return null;
   }
 }
      }
    }

    public static void DeleteNote(ch1205Note note)
    {
      var sql = string.Format("DELETE FROM ITEMS WHERe Id = {0};", note.Id);
      using (var conn = GetConnection())
      {
 conn.Open();
 using (var cmd = conn.CreateCommand())
 {
   cmd.CommandText = sql;
   cmd.ExecuteNonQuery();
 }
      }
    }

    public static void SaveNote(ch1205Note note)
    {
      using (var conn = GetConnection())
      {
 conn.Open();
 using (var cmd = conn.CreateCommand())
 {
   if (note.Id < 0)
   {
     // Do an insert
     cmd.CommandText = "INSERT INTO ITEMS (Body, Modified) VALUES (@Body, @Modified); SELECT last_insert_rowid();";
     cmd.Parameters.AddWithValue("@Body", note.Body);
     cmd.Parameters.AddWithValue("@Modified", DateTime.Now);
     note.Id = (long)cmd.ExecuteScalar();
   }
   else
   {
     // Do an update
     cmd.CommandText = "UPDATE ITEMS SET Body = @Body, Modified = @Modified WHERe Id = @Id";
     cmd.Parameters.AddWithValue("@Id", note.Id);
     cmd.Parameters.AddWithValue("@Body", note.Body);
     cmd.Parameters.AddWithValue("@Modified", DateTime.Now);
     cmd.ExecuteNonQuery();
   }
 }
      }
    }
  }
} 

（8）添加ch1205NoteAdapter.cs文件

using Android.App;
using Android.Content;
using Android.Widget;

namespace MyDemos.SrcDemos
{
  class ch1205NoteAdapter : ArrayAdapter
  {
    private Activity activity;

    public ch1205NoteAdapter(Activity activity, Context context, int textViewResourceId, ch1205Note[] objects)
      : base(context, textViewResourceId, objects)
    {
      this.activity = activity;
    }

    public override Android.Views.View GetView(int position, Android.Views.View convertView, Android.Views.ViewGroup parent)
    {
      //Get our object for this position
      var item = (ch1205Note)GetItem(position);

      // 如果convertView不为null则重用它，否则从当前布局中填充（inflate）它。
      // 由于这种方式不是每次都填充一个新的view，因此可提高性能。
      var view = (convertView ?? activity.LayoutInflater.Inflate(
 Resource.Layout.ch1205_Main, parent, false)) as LinearLayout;

      view.FindViewById(Resource.Id.body).Text = Left(item.Body.Replace("n", " "), 25);
      view.FindViewById(Resource.Id.modified).Text = item.ModifiedTime.ToString();

      return view;
    }

    private string Left(string text, int length)
    {
      if (text.Length <= length) return text;

      return text.Substring(0, length);
    }
  }
} 

（9）添加ch1205NoteEditorActivity.cs文件

using Android.App;
using Android.Content;
using Android.OS;
using Android.Widget;
using Android.Content.PM;

namespace MyDemos.SrcDemos
{
  [Activity(Label = "ch1205NoteEditorActivity", 
  ScreenOrientation = ScreenOrientation.Sensor,
  ConfigurationChanges = ConfigChanges.KeyboardHidden | ConfigChanges.Orientation)]
  public class ch1205NoteEditorActivity : Activity
  {
    private ch1205Note note;
    private EditText text_view;

    protected override void onCreate(Bundle savedInstanceState)
    {
      base.onCreate(savedInstanceState);
      SetContentView(Resource.Layout.ch1205_NoteEditor);

      text_view = FindViewById(Resource.Id.note);
      var note_id = Intent.GetLongExtra("note_id", -1L);
      if (note_id < 0) note = new ch1205Note();
      else note = ch1205NoteRepository.GetNote(note_id);
    }

    protected override void onResume()
    {
      base.onResume();
      text_view.SetTextKeepState(note.Body);
    }

    protected override void onPause()
    {
      base.onPause();
      // 如果是新建的记事本且没有内容，不保存直接返回。
      if (IsFinishing && note.Id == -1 && text_view.Text.Length == 0)
 return;
      // 保存记事本
      note.Body = text_view.Text;
      ch1205NoteRepository.SaveNote(note);
    }
  }
}

（10）添加ch1205NotePadMain.cs文件

using System.Linq;
using Android.App;
using Android.Content;
using Android.OS;
using Android.Views;
using Android.Widget;

namespace MyDemos.SrcDemos
{
  [Activity(Label = "ch1205NotePadMain")]
  public class ch1205NotePadMain : ListActivity
  {
    // 菜单项
    public const int MenuItemDelete = Menu.First;
    public const int MenuItemInsert = Menu.First + 1;

    protected override void onCreate(Bundle savedInstanceState)
    {
      base.onCreate(savedInstanceState);
      SetDefaultKeyMode(DefaultKey.Shortcut);
      ListView.SetonCreateContextMenuListener(this);
      PopulateList();
    }

    public void PopulateList()
    {
      // 获取存放到列表中的所有记事本项
      var notes = ch1205NoteRepository.GetAllNotes();
      var adapter = new ch1205NoteAdapter(this, this, Resource.Layout.ch1205_Main, notes.ToArray());
      ListAdapter = adapter;
    }

    public override bool onCreateOptionsMenu(IMenu menu)
    {
      base.onCreateOptionsMenu(menu);
      menu.Add(0, MenuItemInsert, 0, "添加")
 .SetShortcut('3', 'a')
 .SetIcon(Android.Resource.Drawable.IcMenuAdd);
      return true;
    }

    public override bool onOptionsItemSelected(IMenuItem item)
    {
      switch (item.ItemId)
      {
 case MenuItemInsert: // 通过intent添加新项
   var intent = new Intent(this, typeof(ch1205NoteEditorActivity));
   intent.PutExtra("note_id", -1L);
   StartActivityForResult(intent, 0);
   return true;
      }
      return base.onOptionsItemSelected(item);
    }

    public override void onCreateContextMenu(IContextMenu menu, View view, IContextMenuContextMenuInfo menuInfo)
    {
      var info = (AdapterView.AdapterContextMenuInfo)menuInfo;
      var note = (ch1205Note)ListAdapter.GetItem(info.Position);
      menu.Add(0, MenuItemDelete, 0, "删除");
    }

    public override bool onContextItemSelected(IMenuItem item)
    {
      var info = (AdapterView.AdapterContextMenuInfo)item.MenuInfo;
      var note = (ch1205Note)ListAdapter.GetItem(info.Position);
      switch (item.ItemId)
      {
 case MenuItemDelete: // 删除该记事本项
   ch1205NoteRepository.DeleteNote(note);
   PopulateList();
   return true;
      }
      return false;
    }

    protected override void onListItemClick(ListView l, View v, int position, long id)
    {
      var selected = (ch1205Note)ListAdapter.GetItem(position);
      // 执行activity，查看/编辑当前选中的项
      var intent = new Intent(this, typeof(ch1205NoteEditorActivity));
      intent.PutExtra("note_id", selected.Id);
      StartActivityForResult(intent, 0);
    }

    protected override void onActivityResult(int requestCode, Result resultCode, Intent data)
    {
      base.onActivityResult(requestCode, resultCode, data);
      // 当列表项发生变化时，这里仅关心如何刷新它，并没有处理选定的项
      PopulateList();
    }
  }
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持考高分网。