学习笔记 SQLite数据库应用

</pre>菜鸟可以进来看看一起学习，当然，大神看了如果能给出指导，那最好不过了。<p></p><p>一直以来对sqlite都只是简单的了解，没有做过什么系统的东西，正好最近有时间，就做了一个比较系统的demo练练手<img alt="大笑" src="http://static.blog.csdn.net/xheditor/xheditor_emot/default/laugh.gif" /></p><p>代码在我的资源</p><p>有答题。收藏。错题集等功能</p><p>可以实现简单做题，收藏题，答完自动显示解析，答错自动添加到错题集等。</p><p>下面是基本框架</p><p><img src="http://img.blog.csdn.net/20150902160339039?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQv/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" alt="" /></p><p>对于SQLite所必需的：第一件事就是建立一个数据库文件，然后建表。</p><p>这里有很重要的一个类：SQLiteOpenHelper，此类不可为抽象类，不可实例化只能继承并重写其方法。</p><p></p><pre name="code" class="java">//建库，例子如下：public class MyDBHelper extends SQLiteOpenHelper {	public MyDBHelper(Context context) {		//dbname数据库名称，factory这里传null，version版本号		super(context,dbname,factory,version);	}}

SQLiteOpenHelper有两个方法：getReadableDatabase()和getWritableDatabase()，当他们两个其中任何一个被调用时，创建数据库。创建完之后会调用SQLiteOpenHelper的onCreate(SQLiteDatabase db)方法，在其中建立数据表：

//例如：private static final String CREATE_TABLE = "CREATE TABLE [" + TABLE_NAME + "]("								+ "[_id] INTEGER PRIMARY KEY,"								+ "[titleContent] VERCHAR,"								+ "[rightAnswer] VERCHAR,"								+ "[analisys] VERCHAR,"								+ "[A_answer] VERCHAR,"								+ "[B_answer] VERCHAR,"								+ "[C_answer] VERCHAR,"								+ "[D_answer] VERCHAR);";

<span style="white-space:pre">	</span>//使用事务来管理建表，想要了解事务的功能可参看如下网址内容

<span style="white-space:pre">	<a target=_blank href="http://blog.csdn.net/w250shini11/article/details/8676556">点击打开链接</a></span>	@Override	public void onCreate(SQLiteDatabase db) {		db.beginTransaction();		try {			db.execSQL(CREATE_TABLE);			db.execSQL(CREATE_ERRORTABLE);			db.setTransactionSuccessful();		} catch (Exception e) {			e.printStackTrace();		} finally {			db.endTransaction();		}	}

还有数据库版本的更新，说实话这一块我也比较模糊。。。希望有大神指点

@Override	public void onUpgrade(SQLiteDatabase db, int arg1, int arg2) {		String sql = "DROP TABLE IF EXISTS " + TABLE_NAME; 		db.execSQL(sql); 		onCreate(db);			}

这样，一个数据库就基本成型，剩下的就是增删改查的应用了直接上代码吧下面是一个数据库建库建表，以及简单操作的工具类：

package com.example.zx_demo.utils;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DBUtils extends SQLiteOpenHelper {		private static SQLiteDatabase db;		/**数据库操作工具实体**/	private static DBUtils instance;		/**数据库名称**/	private static final String DB_NAME = "savequestion.db";		/**数据收藏表名称**/	private static final String TABLE_NAME = "TABLE_S***EQUESTION";		/**创建收藏表**/	private static final String CREATE_TABLE = "CREATE TABLE [" + TABLE_NAME + "]("								+ "[_id] INTEGER PRIMARY KEY,"								+ "[titleContent] VERCHAR,"								+ "[rightAnswer] VERCHAR,"								+ "[analisys] VERCHAR,"								+ "[A_answer] VERCHAR,"								+ "[B_answer] VERCHAR,"								+ "[C_answer] VERCHAR,"								+ "[D_answer] VERCHAR);";		/**数据表名称 错题**/	public static final String TABLE_ERRORNAME = "TABLE_ERRORQUESTION";		/**创建错题表**/	private static final String CREATE_ERRORTABLE = "CREATE TABLE [" + TABLE_ERRORNAME + "]("								+ "[_id] INTEGER PRIMARY KEY,"								+ "[titleContent] VERCHAR,"								+ "[rightAnswer] VERCHAR,"								+ "[analisys] VERCHAR,"								+ "[A_answer] VERCHAR,"								+ "[B_answer] VERCHAR,"								+ "[C_answer] VERCHAR,"								+ "[D_answer] VERCHAR);";		private DBUtils(Context context) {		super(context, DB_NAME, null, 1);	}	

<span style="white-space:pre">	</span>//懒汉单例模式	public static synchronized DBUtils getInstance(Context context) {		if(instance == null) {			instance = new DBUtils(context);			db = instance.getWritableDatabase();		}		return instance;	}	@Override	public void onCreate(SQLiteDatabase db) {		db.beginTransaction();		try {			db.execSQL(CREATE_TABLE);			db.execSQL(CREATE_ERRORTABLE);			db.setTransactionSuccessful();		} catch (Exception e) {			e.printStackTrace();		} finally {			db.endTransaction();		}	}	@Override	public void onUpgrade(SQLiteDatabase db, int arg1, int arg2) {		String sql = "DROP TABLE IF EXISTS " + TABLE_NAME; 		db.execSQL(sql); 		onCreate(db);			}		/**	 * 对数据库插入数据	 * @param table            要插入数据的表名	 * @param nullColumnHack   null	 * @param values		       要插入的值	 * @return				       最近插入行的id,出错则返回-1	 */	public long insertData(String table, String nullColumnHack, ContentValues values) {		/**the row ID of the newly inserted row, or -1 if an error occurred			返回最近插入行的id,如果出错则返回-1**/		long result = -1;		synchronized (this) {			if(!db.isOpen()) {				db = instance.getWritableDatabase();			}			db.beginTransaction();			try {				result = db.insert(table, nullColumnHack, values);				db.setTransactionSuccessful();			} catch (Exception e) {				e.printStackTrace();			} finally {				db.endTransaction();			}		}		return result;	}	public void deleteData(String table, String whereClause, String[] whereArgs) {		synchronized (this) {			if(!db.isOpen()) {				db = instance.getReadableDatabase();			}			db.beginTransaction();			try {				db.delete(table, whereClause, whereArgs);				db.setTransactionSuccessful();			} catch (Exception e) {				e.printStackTrace();			} finally {				db.endTransaction();			}		}	}	public int updateData(String table, ContentValues values, String whereClause, String[] whereArgs) {				return 0;	}	public Cursor queryData(String table, String selection, String[] selectionArgs, String orderBy) {		Cursor c = null;		synchronized (this) {			if(!db.isOpen()) {				db = instance.getReadableDatabase();			}			db.beginTransaction();			try {				c = db.query(table, null, selection, selectionArgs, null, null, null);				db.setTransactionSuccessful();			} catch (Exception e) {				e.printStackTrace();			} finally {				db.endTransaction();			}					}		return c;	}}