SQLiteOpenHelper学习

0.视频：http://www.imooc.com/video/3384

1.SQLiteOpenHelper笔记：

2.SQLiteOpenHelper.java代码：

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class DBOpenHelper extends SQLiteOpenHelper {

    public DBOpenHelper(Context context, String name) {
        super(context, name,null, 1);
        // TODO Auto-generated constructor stub
    }
    public DBOpenHelper(Context context, String name, CursorFactory factory,
            int version) {
        super(context, name, factory, version);
        // TODO Auto-generated constructor stub
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub
       //首次创建数据库时调用 一般有建库建表的操作
        db.execSQL("create table if not exists stutb(_id integer primary key autoincrement,name text not null,sex text not null,age integer not null)");
        db.execSQL("insert into stutb(name,sex,age)values('张三','女',18)");
    }

    @Override//当数据库的版本发生变化的时候 会自动执行
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

    }

}

3.MainActivity.java:

import com.example.sqlitedemo03.DBOpenHelper;
import com.example.sqlitedemo03.MainActivity;

import android.os.Bundle;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import android.view.Menu;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        DBOpenHelper helper =    new DBOpenHelper(MainActivity.this, "stu.db");
//        helper.getReadableDatabase();//获取一个只读的数据库 只能查询 不能写入 不能更新
        SQLiteDatabase db = helper.getWritableDatabase();
//        db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy)
        Cursor c = db.rawQuery("select * from stutb", null);
        if (c!=null) {
            String [] cols = c.getColumnNames();
            while (c.moveToNext()) {
                for (String ColumnName : cols) {
                    Log.i("info", ColumnName+":"+c.getString(c.getColumnIndex(ColumnName)));
                }
            }
            c.close();
        }
        db.close();
    }
}

4.运行结果：

5.小记：构造方法重载的使用。