day03:数据库操作

• 封装的InfoDao类（数据的封装，增删改查）

    public boolean add(Context context,InfoBean bean){
        //由于每个方法都需要创建数据库，提取出来 
        //MysqliteOpenHelper mysqliteOpenHelper = new MysqliteOpenHelper(context);
        SQLiteDatabase db = mysqliteOpenHelper.getReadableDatabase();
        //table:表名   nullColumnHack  values：数据一行的值
        
        ContentValues values = new ContentValues();//用map封装的对象，用来存放值
        values.put("name", bean.name);
        values.put("phone", bean.phone);
        long insert_result = db.insert("info", null, values);

        db.close();
        
        if(insert_result !=-1){
            return true;
        }else{
            return false;
        }
    }
    
    public int del(String name){
        
        SQLiteDatabase db = mysqliteOpenHelper.getReadableDatabase();
        //db.delete(table, whereClause, whereArgs)
        int result_del = db.delete("info","name=?",new String[]{name});
        db.close();
        return result_del;
    }
    public int update(InfoBean bean){
        SQLiteDatabase db = mysqliteOpenHelper.getReadableDatabase();
        //db.update(table, values, whereClause, whereArgs)
        
        ContentValues values = new ContentValues();//用map封装的对象，用来存放值
        values.put("phone", bean.phone);//只更新phone
        
        
        int result_update = db.update("info", values, "name=?",new String[]{bean.name} );
        db.close();
        return result_update;
    }
    
/*  public void query(String name){
        SQLiteDatabase db = mysqliteOpenHelper.getReadableDatabase();
        //execSQL没有返回值，不适合做查询操作
        //sql:sql语句   selectionArgs占位符的值
        Cursor cursor = db.rawQuery("select * from info where name=?",new String[]{name} );
        //解析cursor的数据
        if(cursor !=null && cursor.getCount()>0){//是否存在数据
            while(cursor.moveToNext()){
                int _id = cursor.getInt(0);
                String name_str = cursor.getString(1);
                String phone = cursor.getString(2);
                System.out.println("_id:"+_id+";name:"+name_str+";phone:"+phone);
            }
        }
    }*/
    public void query(String name){
        SQLiteDatabase db = mysqliteOpenHelper.getReadableDatabase();
        /*
         * table:         columns:查询的列名，为null查询所有列   selection：查询条件
         * selectionArgs  查询条件参数    groupBy：按什么分组   having 分组的条件        orderBy：按什么排序
         *  */
        Cursor cursor = db.query("info", new String[]{"_id","name","phone"}, "name=?", 
                new String[]{name}, null, null, null);
        if(cursor !=null && cursor.getCount()>0){//是否存在数据
            while(cursor.moveToNext()){
                int _id = cursor.getInt(0);
                String name_str = cursor.getString(1);
                String phone = cursor.getString(2);
                System.out.println("_id:"+_id+";name:"+name_str+";phone:"+phone);
            }
        }
    }

• 在MysqliteOpenHelper类的onCreate函数中创建info.db
• 在MainActivity中实现相应操作

public void onClick(View v) {
        InfoDao infoDao = new InfoDao(mContext);
        switch (v.getId()) {
        case R.id.bt_add:
            InfoBean bean = new InfoBean ();
            bean.name="Kavin";
            bean.phone="100";
            boolean result = infoDao.add(mContext, bean);
            if(result){
                Toast.makeText(mContext, "添加成功", Toast.LENGTH_SHORT).show();
            }else {
                Toast.makeText(mContext, "添加成功", Toast.LENGTH_SHORT).show();
            }
            
            break;
        case R.id.bt_del:
            int result_del = infoDao.del("Kavin");
            Toast.makeText(mContext, "成功删除"+result_del+"条信息", Toast.LENGTH_SHORT).show();
            break;
        case R.id.bt_update:
            InfoBean bean2 = new InfoBean ();
            bean2.name="Kavin";
            bean2.phone="100000000";
            int result_update = infoDao.update(bean2);
            Toast.makeText(mContext, "成功更新"+result_update+"条信息", Toast.LENGTH_SHORT).show();
            break;
        case R.id.bt_query:
            infoDao.query("Kavin");
            infoDao.query("Aris");
            
            break;
        }