大二寒假作业之Android

今日学习了Android操作SQLite数据库，对数据库实现了增删改查与创建。

首先创建一个类继承SQLDBHelper实现对数据库的创建

 public void onCreate(SQLiteDatabase db) {
        String sql="create table person(id integer primary key autoincrement,name varchar,age varchar)";
        db.execSQL(sql);
        db.execSQL("insert into person(name,age) values('李明','1')");
        db.execSQL("insert into person(name,age) values('王五','19')");
        db.execSQL("insert into person(name,age) values('大大','17')");
        db.execSQL("insert into person(name,age) values('恋恋','12')");
        Toast.makeText(context,"数据库已创建",Toast.LENGTH_LONG).show();
    }

在activity层中分别写增删改查的代码：

 public void createDB(View view)
    {
        MyDBHelper mydbh=new MyDBHelper(this,"mydb.db",1);
        SQLiteDatabase sqldb=mydbh.getReadableDatabase();
    }
    public void insertDB(View view)
    {
        MyDBHelper mydbh=new MyDBHelper(this,"mydb.db",1);
        SQLiteDatabase sqldb=mydbh.getReadableDatabase();
        ContentValues contentvalues=new ContentValues();
        contentvalues.put("name","小小");
        contentvalues.put("age","15");
        long flag=sqldb.insert("person",null,contentvalues);
        sqldb.close();
        Toast.makeText(this,"已加入"+flag+"条数据",Toast.LENGTH_LONG).show();
    }
    public void updateData(View view)
    {
        MyDBHelper mydbh=new MyDBHelper(this,"mydb.db",1);
        SQLiteDatabase sqldb=mydbh.getReadableDatabase();
        ContentValues contentvalues=new ContentValues();
        contentvalues.put("name","明明");
        contentvalues.put("age","12");
        int flag=sqldb.update("person",contentvalues,"name=?",new String[]{"李明"});
        Toast.makeText(this,"已有"+flag+"条数据修改",Toast.LENGTH_LONG).show();
    }
    public void deleteDate(View view)
    {
        MyDBHelper mydbh=new MyDBHelper(this,"mydb.db",1);
        SQLiteDatabase sqldb=mydbh.getReadableDatabase();
        int flag=sqldb.delete("person","id=1",null);
        Toast.makeText(this,"已有"+flag+"条数据删除",Toast.LENGTH_LONG).show();
    }
    public void queryData(View view)
    {
        MyDBHelper mydbh=new MyDBHelper(this,"mydb.db",1);
        SQLiteDatabase sqldb=mydbh.getReadableDatabase();
        Cursor cursor=sqldb.rawQuery("select * from person",null);
        if(cursor.moveToFirst())
        {
            do{
                String name=cursor.getString(cursor.getColumnIndex("name"));
                String age=cursor.getString(cursor.getColumnIndex("age"));
                Log.v("TAG",name+":"+age);
            }while(cursor.moveToNext());
        }
    }