android数据库操作

大部分代码转自 http://blog.youkuaiyun.com/barryhappy/article/details/7240390

DBUtil类，继承自SQLiteOpenHelper，用以实现各种操作功能：

package barry.android.db;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DBUtil extends SQLiteOpenHelper {

	private final static String DATABASE_NAME = "db2004";
	private final static int DATABASE_VERSION = 1;
	private static final String TABLE_NAME ="students";
	private static final String FILED_1 = "name";
	private static final String FILED_2 = "password";

	public DBUtil(Context context){
		super(context, DATABASE_NAME,null,DATABASE_VERSION);
		System.out.println("new DBUtil");
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		String sql = "CREATE TABLE "+TABLE_NAME+" ( "+FILED_1 +" TEXT, "+ FILED_2 +" TEXT );";
		db.execSQL(sql);
		System.out.println("oncreate创建表");
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
		System.out.println("onUpgrade删除表");
		this.onCreate(db);
	}
	
	/**
	 * 查询表中所有的数据
	 * @return
	 */
	public Cursor select(){
		return this.getReadableDatabase()
			.query(TABLE_NAME, null, null, null, null, null, null);		
	}

	/**
	 * 插入一条数据到表中
	 * @param name 字段一的值
	 * @param password 字段二的值
	 */
	public void insert(String name ,String password){
		ContentValues cv = new ContentValues();
		cv.put(FILED_1, name);
		cv.put(FILED_2, password);		
		this.getWritableDatabase().insert(TABLE_NAME, null, cv);
		this.getWritableDatabase().close();//关闭数据库对象 
	}	
	
	/**
	 * 删除表中的若干条数据
	 * @param name 一个包含所有要删除数据的"name"字段的数组
	 */
	public void delete(String[] name){
		String where = FILED_1+" = ?";
		String[] whereValues = name; 
		this.getWritableDatabase().delete(TABLE_NAME, where, whereValues);
		this.getWritableDatabase().close();
	}
	
	/**
	 * 更新表中的数据(修改字段二"password")
	 * @param name 要更新的数据"name"字段值
	 * @param newPassword 新的"password"字段
	 */
	public void update(String name,String newPassword){		
		ContentValues cv = new ContentValues();
		cv.put(FILED_2, newPassword);		
		String where =FILED_1+" = ?";
		String[] whereValues= {name};		
		this.getWritableDatabase().update(TABLE_NAME, cv, where, whereValues);
		this.getWritableDatabase().close();
	}	
	
	/**
	 * 清空表中的数据
	 */
	public void clean (){
		this.getWritableDatabase().execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
		System.out.println("clean删除表");
		this.onCreate(this.getWritableDatabase());
		this.getWritableDatabase().close();
	}
}

操作方法

package barry.android.db;

import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;

public class Demo04_helperActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        
        DBUtil dbUtil = new DBUtil(this);
        dbUtil.insert("周杰伦", "jaychou");
        dbUtil.insert("韩寒", "twocolds");
        dbUtil.insert("郭德纲", "yunhejiuxiao");        
        
        System.out.println("***********************************全部数据息");
        printData(dbUtil);        
        
        dbUtil.delete(new String[]{"周杰伦"});
        
        System.out.println("***********************************删除'周杰伦'之后数据");
        printData(dbUtil); 
        
        dbUtil.update("郭德纲", "longtengsihai");;
        System.out.println("***********************************修改‘郭德纲’的密码为'longtengsihai'");
        printData(dbUtil); 
        
        dbUtil.clean();
        
    }

	private void printData(DBUtil dbUtil) {
		Cursor cursor = dbUtil.select();        
		if(cursor.moveToFirst()){
			System.out.println("当前表中的数据条数："+cursor.getCount());
			do{
				System.out.println(cursor.getString(0)+cursor.getString(1));				
			}while(cursor.moveToNext());
		}
		cursor.close();
	}
}

一般来说 我都喜欢把数据库弄成单例的

	private static DBUtil instance;

	private DBUtil (Context context) {
		super(context, dbName, null, DATABASE_VERSION);
	}

	public static DBUtil getInstance(Context context) {
		if (instance == null) {
			instance = new DBUtil (context);
		}
		return instance;
	}