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Android SQlite数据库常规操作

1.Sqlite简介

       Sqlite是一款轻型的数据库,它包含在一个相对小的C库中,它的设计目标是嵌入式的,由于它占用资源非常少,可能只需要几百K的内存就可以了,并且支持Windows/Linux/Unix等等主流的操作系统,同时可以和很多种程序语言相结合,比如:C#/Java/php等,所以在嵌入式设备中特别受欢迎,这一点也正好符合android的开发要求,所以在Android开发中经常要用到该数据库。

2. 运用Sqlite,一般要有一个SQLiteOpenHelper来辅助创建数据库,连接数据库。

eg:

public class DatabaseHelper extends SQLiteOpenHelper  {
	public static final String DBNAME = "cbg_download.db";
	public static final int VERSION = 1;
	
	
//    public DatabaseHelper(Context context) {
//		//必须通过super调用父类当中的构造函数 
//		super(context,DBNAME,null,VERSION);	
//	}
    //创建多项数据库连接
    public DatabaseHelper(Context context,String name){ 
        this(context,name,VERSION); 
    } 
    public DatabaseHelper(Context context,String name,int version){ 
        this(context, name,null,version); 
    } 
    //在SQLiteOepnHelper的子类当中,必须有该构造函数 
    public DatabaseHelper(Context context, String name, CursorFactory factory, int version) { 
        //必须通过super调用父类当中的构造函数 
        super(context, name, factory, version); 
    } 
    
    
	@Override
	public void onCreate(SQLiteDatabase db) {
		//存在数据库则不会调用。进行初始操作
		db.execSQL("CREATE TABLE IF NOT EXISTS priaseTable(id integer primary key autoincrement,clickId varchar(100),clickType varchar(100),clickCount INTEGER)");
	}
	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		// TODO Auto-generated method stub
		db.execSQL("DROP TABLE IF EXISTS filedownlog");
		onCreate(db);
	}

}
 注意:

 (1)DatabaseHelper 继承SQLiteOpenHelper。必须实现3点,

构造函数:用于初始化数据库,创建数据库

public void onCreate(SQLiteDatabase db) :用于创建表。在调getReadableDatabase或getWritableDatabase时,会判断指定的数据库是否存在,不存在则调SQLiteDatabase.create创建, onCreate只在数据库第一次创建时才执行

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion):用于数据库更新操作

3.//单例模式  Dao 类,做一个对数据表进行操作的类

eg:

package cdv.cq.mobilestation.Activity.praise;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.widget.Toast;

//单例模式
public class Dao {
	private static Dao dao = null;
	private Context context;

	private Dao(Context contex) {
		this.context = contex;
	}

	public static Dao getInstance(Context context) {
		if (dao == null) {
			dao = new Dao(context);
		}
		return dao;
	}

	// 连接数据库
	public SQLiteDatabase getConnection() {
		SQLiteDatabase sqLiteDatabase = null;
		try {
			sqLiteDatabase = new DatabaseHelper(context, DatabaseHelper.DBNAME)
					.getReadableDatabase();
		} catch (Exception e) {
			e.printStackTrace();
		}

		return sqLiteDatabase;
	}
	
	public void createTable(SQLiteDatabase sqLiteDatabase){
		sqLiteDatabase.execSQL("CREATE TABLE IF NOT EXISTS priaseTable(id integer primary key autoincrement,clickId varchar(100),clickType varchar(100),clickCount INTEGER)");
	}

	public synchronized int isHasInfors(String clickId, String clickType) {
		SQLiteDatabase database = getConnection();
		int id = -1;
		Cursor cursor = null;
		try {
			cursor = database.query("priaseTable", null,
					"clickId=? AND clickType=?", new String[] { clickId,
							clickType }, null, null, null);
			if (cursor.moveToFirst()) {
				id = cursor.getInt(0);
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (null != database) {
				database.close();
			}
			if (null != cursor) {
				cursor.close();
			}
		}
		return id;
	}

	//增
	public synchronized void insert(String clickId, String clickType,
			int count) {
		SQLiteDatabase database = getConnection();
		// int id = dao.isHasInfors(clickId,clickType);
		// if(id == 0){
		// ContentValues cv = new ContentValues();
		// cv.put("clickId", clickId);
		// cv.put("clickType", clickType);
		// cv.put("clickCount", 1);
		// database.insert("priaseTable", null, cv);
		// String sql =
		// "insert into priaseTable(clickId,clickType,clickCount) values(?,?,?)";
		// Object[] info ={clickId,clickType,"1"};
		// database.execSQL(sql,info);
		// }
		// else{
		// //更改数据操作
		//
		// }
		try {
			String sql = "insert into priaseTable(clickId,clickType,clickCount) values(?,?,?)";
			Object[] info = { clickId, clickType, count};
			database.execSQL(sql, info);
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (null != database) {
				database.close();
			}
		}

	}

	// 改
	public synchronized void update(int Id, boolean isAdd) {
		SQLiteDatabase database = getConnection();
		int count = 0;
		try{
			
			Cursor curor = database.rawQuery("select * from priaseTable where id =?",new String[]{String.valueOf(Id)});
			if(curor.moveToFirst())
				 count = curor.getInt(3);
			if(isAdd){
				String sql = "update priaseTable set clickCount=? where id = ?";
				Object[] info = {++count,Id};
				database.execSQL(sql,info);
				//这是在新的线程打开的,Toast只能在主线程修改UI界面
				//Toast.makeText(context, "点赞加1成功",2*1000).show();
			}
			else{
				String sql = "update priaseTable set clickCount=? where id = ?";
				Object[] info = {--count,Id};
				database.execSQL(sql,info);
				//Toast.makeText(context, "点赞减1成功",2*1000).show();
			}
		}catch(Exception e){
			e.printStackTrace();
		}finally{
			if (null != database) {
				database.close();
			}
		}
	}
	
	//查 点赞数
	public synchronized int queryPraise(String id){
		SQLiteDatabase database = getConnection();
		int count = 0;
		try{
			Cursor curor = database.rawQuery("select from priaseTable where id =?", new String[]{id});
			while(curor.moveToFirst())
				 count = curor.getInt(4);
		}catch(Exception e){
			e.printStackTrace();
		}finally{
			if (null != database) {
				database.close();
			}
		}
		return count;
		
	}

}
注意:

(1)sqlite 数据库中的表 列号是从0开始的,
eg:Cursor curor = database.rawQuery("select * from priaseTable where id =?",new String[]{String.valueOf(Id)});
while(curor.moveToFirst())
count = curor.getInt(3); //一共4列

(2)做成一个DAO类单例模式可以很好的对数据库中的表进行操作

(3)增删改查功能跟SQLserver语句一样的但是要注意:不必记太多的android自带的方法

增删改::database.execSQL(sql, info); 直接对数据库进行操作

查询用:  database.query(sql, infoquery()方法可以直接返回一个游标进行相关操作

Android SQlite数据库常规操作