正文
【Android】12.6 利用Intent实现记事本功能（NotePad）
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分类：C#、Android、VS2015；
创建日期：2016-02-23
一、简介
这个例子演示如何实现一个简单的记事本功能。
该例子提前使用了后面章节将要介绍的SQLLite数据库。
二、示例—ch1205NotePadDemo
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
<?xml version="1.0" encoding="utf-8"?>
<view xmlns:android="http://schemas.android.com/apk/res/android"
class="MyDemos.SrcDemos.ch1205LinedEditText"
android:id="@+id/note"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="5dip"
android:scrollbars="vertical"
android:fadingEdge="vertical"
android:gravity="top"
android:textSize="22sp"
android:capitalize="sentences" />
（4）添加ch1205_Main.axml文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:background="#ffffff"
android:padding="10px">
<ImageView
android:id="@+id/icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ch12_app_notes" />
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:paddingTop="6px">
<TextView
android:id="@+id/body"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/modified"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
</LinearLayout>
（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<ch1205Note> 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<TextView>(Resource.Id.body).Text = Left(item.Body.Replace("\n", " "), 25);
view.FindViewById<TextView>(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<EditText>(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();
}
}
}
OK，这一章就讲到这了。
