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

<?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();
    }
  }
}

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。