【Android】12.6 利用Intent实现记事本功能（NotePad）

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。

巴特西

【Android】12.6 利用Intent实现记事本功能（NotePad）

一、简介

二、示例—ch1205NotePadDemo

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