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。