为什么使用SQLiteOpenHelper了SQLiteDatabase？

问题描述

在我的活动我有例如：

  SQLiteDatabase DB = openOrCreateDatabase（preferences.DB_NAME，Context.MODE_PRIVATE，NULL）;
db.execSQL（CREATE TABLE IF NOT EXISTS数据（ID INTEGER PRIMARY KEY，价值VARCHAR））;
光标dbResult = db.rawQuery（从数据中选择值，NULL）;
//做光标sometning
dbResult.close（）;
db.close（）;
 

什么是使用的 SQLiteOpenHelper 喜欢

的好处

  DatabaseHelper帮手=新DatabaseHelper（本）;
SQLiteDatabase DB = helper.getWriteableDatabase（）;
SQLiteDatabase db_2 = helper.getReadableDatabase（）;
光标dbResult = db_2.rawQuery（从数据中选择值，NULL）;
//做光标sometning
dbResult.close（）;
helper.close（）;
 

本身类

 公共类DatabaseHelper扩展SQLiteOpenHelper {
    公共DatabaseHelper（上下文的背景下）{
        超（背景下，preferences.DB_NAME，空，preferences.DB_VERSION）;
    }

    @覆盖
    公共无效的onCreate（SQLiteDatabase DB）{
        查询字符串=CREATE TABLE IF NOT EXISTS数据（ID INTEGER PRIMARY KEY，价值VARCHAR）;
        db.execSQL（查询）;
        db.close（）;
    }

    @覆盖
    公共无效onUpgrade（SQLiteDatabase分贝，INT oldVersion，诠释静态网页）{
    }
}
 

解决方案

SQLiteDatabase

SQLiteOpenHelper

我会说这么多，升级您的应用程序时附带SQLiteOpenHelper的onUpgrade进来非常方便。它主要用于创建和升级/版本管理。 SQLiteDatabase主要是为CRUD操作（你可以创建它，但是这就是SQLiteOpenHelper是）。

In my activity I have for example

SQLiteDatabase db = openOrCreateDatabase(Preferences.DB_NAME, Context.MODE_PRIVATE, null);
db.execSQL("CREATE TABLE IF NOT EXISTS data (id INTEGER PRIMARY KEY, value VARCHAR)");
Cursor dbResult = db.rawQuery("SELECT value FROM data", null);
// do sometning with cursors
dbResult.close();
db.close();

What's the benefit of using SQLiteOpenHelper like

DatabaseHelper helper = new DatabaseHelper(this);
SQLiteDatabase db = helper.getWriteableDatabase();
SQLiteDatabase db_2 = helper.getReadableDatabase();
Cursor dbResult = db_2.rawQuery("SELECT value FROM data", null);
// do sometning with cursors
dbResult.close();
helper.close();

Class itself

public class DatabaseHelper extends SQLiteOpenHelper {
    public DatabaseHelper(Context context) {
        super(context, Preferences.DB_NAME, null, Preferences.DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String query = "CREATE TABLE IF NOT EXISTS data (id INTEGER PRIMARY KEY, value VARCHAR)";
        db.execSQL(query);
        db.close();
    }

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

解决方案

SQLiteDatabase

SQLiteOpenHelper

I will say this much, the onUpgrade that comes with SQLiteOpenHelper comes in REALLY handy when upgrading your application. It's mainly for creation and upgrading / version management. SQLiteDatabase is mainly for CRUD operations (you can create with it but that is what SQLiteOpenHelper is for).

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