数据库的操作，需用到数据库类SQLiteDatabase，重写管理员类SQLiteOpenHelper，用Cursor查询数据

一、操作数据库的辅助类，包含打开、关闭、增删改查方法

//自定义的数据库的接口，其中包含SQLiteHelper

public class NotesDbAdapter

{

//创建数据库所需语句及相关字符串

private static final String DATABASE_NAME = "note.db";

private static final int DATABASE_VERSION = 1;

private static final String DATABASE_TABLE = "note";

private static final String DATABASE_CREATE =

"create table note("

+"_id INTEGER PRIMARY KEY,"

+"note TEXT,"

+"date TEXT,"

+"created INTEGER,"

+"modified INTEGER"

+");";

//数据库对象

private SQLiteDatabase db;

//定义数据库管理员类

private static class DatabaseHelper extends

SQLiteOpenHelper

{

public DatabaseHelper(Context context) {

super(context, DATABASE_NAME, null, DATABASE_VERSION);

// TODO Auto-generated constructor stub

}

@Override

public void onCreate(SQLiteDatabase db) {

// TODO Auto-generated method stub

db.execSQL(DATABASE_CREATE);

}

@Override

public void onUpgrade(SQLiteDatabase db, int oldVersion, int

newVersion) {

// TODO Auto-generated method stub

db.execSQL("DROP TABLE IF EXISTS "+DATABASE_TABLE);

onCreate(db);

}

}

//抽象界面

private Context mCtx =

null;

//数据库管理员对象

private DatabaseHelper dbHelper ;

//数据库各列名称

public static final String KEY_ROWID = "_id";

public static final String KEY_NOTE = "note";

public static final String KEY_DATE = "date";

public static final String KEY_CREATED = "created";

public NotesDbAdapter(Context ctx) {

this.mCtx = ctx;

}

//打开数据库

public NotesDbAdapter open () throws SQLException {

dbHelper = new DatabaseHelper(mCtx);

db = dbHelper.getWritableDatabase();

return this;

}

//关闭数据库

public void close() {

dbHelper.close();

}

//查询所有项目，返回一个Cursor

public Cursor getall()

{

return db.query(DATABASE_TABLE,

new String[] {KEY_ROWID, KEY_NOTE, KEY_DATE,

KEY_CREATED},

null, null, null, null, null);

}

// 新增一项

public long create(String Note,String mDate) {

Date now = new Date();

ContentValues args = new ContentValues();

args.put(KEY_NOTE, Note);

args.put(KEY_DATE, mDate);

args.put(KEY_CREATED, now.getTime());

return db.insert(DATABASE_TABLE, null, args);

}

//删除一项

public boolean delete(long rowId) {

return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null)

> 0;

}

//查询一项

public Cursor get(long rowId) throws SQLException

{

Cursor mCursor = db.query(true,

DATABASE_TABLE,

new String[] {KEY_ROWID, KEY_NOTE, KEY_DATE,

KEY_CREATED},

KEY_ROWID + "=" + rowId,

null, null, null, null, null);

if (mCursor != null) {

mCursor.moveToFirst();

}

return mCursor;

}

//修改一项

public boolean update(long rowId, String note,String

date)

{

ContentValues args = new ContentValues();

args.put(KEY_NOTE, note);

args.put(KEY_DATE, date);

return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId,

null) > 0;

}

}

二、在主类中通过写好的辅助类操作数据库

private NotesDbAdapter mDbHelper;

private Cursor mNotesCursor;

//用自定义的数据库接口提供的方法打开数据库

mDbHelper = new NotesDbAdapter(this);

mDbHelper.open();

//获取cursor,当需要表中数据时再通过cursor访问

mNotesCursor = mDbHelper.getall();

startManagingCursor(mNotesCursor);

//实例化各list存储数据库各列内容

aryListNoteContent=new

ArrayList();

aryListNoteDate=new

ArrayList();

aryListNoteID=new

ArrayList();

linkListNoteIcon=new

LinkedList();

//先用Cursor获取内容，装入ArrayList,最后关闭cursor

try

{

if(mNotesCursor.moveToFirst())

{

do

{

//获取数据库rowID，以便操作数据库

String noteId=mNotesCursor.getString(0);

String noteContent=mNotesCursor.getString(1);

String noteDate=mNotesCursor.getString(2);

aryListNoteID.add(noteId);

aryListNoteContent.add(noteContent);

aryListNoteDate.add(noteDate);

linkListNoteIcon.add(getApplicationContext().getResources().getDrawable(R.drawable.icon));

}while(mNotesCursor.moveToNext());

}

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}finally

{

mNotesCursor.close();

}

//删除一项

String RowId=aryListNoteID.get(info.position);

mDbHelper.delete(Long.parseLong(RowId));

//新增一项

mDbHelper.create(String,String);

//查询一项

//若该行id不为空，返回该行cursor，根据cursor读取内容，读取完毕关闭cursor

if (mRowId != null) {

Cursor cursor = mDbHelper.get(mRowId);

startManagingCursor(cursor);

try

{

mEditText.setText(cursor.getString(

cursor.getColumnIndexOrThrow(NotesDbAdapter.KEY_NOTE)

));

} catch (IllegalArgumentExceptione) {

// TODO Auto-generated catch block

e.printStackTrace();

}finally

{

cursor.close();

}

}

//修改一项

mDbHelper.update(mRowId, String,String);