安卓开发之嵌入式数据库sqlite的操作方法

package com.web.redrain;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DBHelper extends SQLiteOpenHelper {
 public DBHelper(Context context) {
  super(context, "user.db", null, 1); //创建user.db数据库
 }
 @Override
 public void onCreate(SQLiteDatabase db) {
  db.execSQL("CREATE table IF NOT EXISTS user"
    + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, id TEXT, name TEXT, img TEXT, isOnline TEXT)");//创建user表
 }
 @Override
 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
  db.execSQL("ALTER TABLE user ADD COLUMN other TEXT");
 }
}

DBHelper helper = new DBHelper(getBaseContext());
     SQLiteDatabase db = helper.getWritableDatabase();
     
     
     db.execSQL("delete from user where 1=1");
  
      db.execSQL("insert into user (id,name,img,isOnline) values('我是个人','见人在此','我会乱说','我是神，oh,my god!!!!')");
      
      Cursor c = db.rawQuery("select * from user", null);
      while (c.moveToNext()) {
       
       alert(c.getString(c.getColumnIndex("id")));
       alert(c.getString(c.getColumnIndex("name")));
       alert(c.getString(c.getColumnIndex("img")));
       alert(c.getString(c.getColumnIndex("isOnline")));
      }

 public void alert(String txt){
   Toast.makeText(MainActivity.this,txt, 1).show();
  }