SQLiteOpenHelper的使用

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

public class NoteDBHelper extends SQLiteOpenHelper {

    private static final String DATABASE_NAME = "notedatabase.db";
    private static final String TABLE_NAME = "NOTETABLE";
    private static final String UID = "_id";
    private static final String NAME = "Name";
    private static final int DATABASE_VERSION = 1;//upgrade时需要改版本号
    private static final String CREATE_TABLE = "CREATE TABLE "+TABLE_NAME
            +"("+UID+" INTEGER PRIMARY KEY AUTOINCREMENT, "+NAME+" VARCHAR(255))";
    private static final String DROP_TABLE = "DROP TABLE IF EXISTS"+TABLE_NAME;
    private Context context;  

    NoteDBHelper(Context context){

        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.context=context;
        Message.message(context, "constructor called");
    }

    public void onCreate(SQLiteDatabase db){

        try {
            db.execSQL(CREATE_TABLE);
            Message.message(context, "onCreate called");
        }catch (SQLException e){

            Message.message(context, ""+e);
        }

    }

    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){

        try {
            db.execSQL(DROP_TABLE);
            onCreate(db);
            Message.message(context, "onUpgrade called");
        }catch (SQLException e){

            Message.message(context, "" + e);
        }

    }
}

在Activity中：

NoteDBHelper noteDBHelper;

@Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_activity_demo);

        noteDBHelper = new NoteDBHelper(this);//have not yet accessed the database
        SQLiteDatabase sqLiteDatabase = noteDBHelper.getWritableDatabase();//this time noteDBhelper call onCreate()
        Log.e(TAG, "start onCreate()~~~~~");
    }

这样在第一次运行app的时候一个叫notedatabase.db的数据库文件将会在android设备的/data/data/com.practice.apple.activitydemo/目录下生成，可以拷到电脑上进行操作。

（/data/data正常情况下是没有读写权限的，可以机器先root然后把这个目录的权限改成可读写，比如RE）