Question

我使用此示例创建了一个我在全新安装时复制的数据库

http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/

我现在遇到的问题是我现在已对数据库进行了一些更新，并且我已经对构建中的主文件进行了此更新，因此用户始终在新安装时获得最新版本

我有一个不同的类来处理所有db调用查询语句。

我已设置此行

private static final int DATABASE_VERSION = 5;

现在在全新安装时，数据库被正确复制，但当查询类再次调用databasehelper时，调用onupgrade（）方法并尝试更新到最新版本，并且应用程序崩溃，因为它正在尝试升级无法完成

我的理解是，以下设置了全新安装的数据库版本，或者这是错误的。如果是，如何为新安装设置数据库版本

public DatabaseHelper(Context context) {
        super(context, DB_NAME, null, DATABASE_VERSION);
        this.context = context;
    }

这里的completness是onupgrade（）

的示例

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

        dbUpgrade = new DatabaseUpgrades(context);

        Log.d(DEBUG_TAG, "Calling onupgrade db");
        Log.d(DEBUG_TAG + " : " + DatabaseHelper.class.getName(),
                "Upgrading database from version " + oldVersion + " to "
                    + newVersion);

        if (oldVersion == 1) {
            Log.d(DEBUG_TAG, "Updating to Version 2");
            dbUpgrade.upgradeDB2(db);
            oldVersion++;
        }
}

在新安装时询问新数据库设置的版本，如果不是版本5，如何覆盖它

由于

Answer 1

这是正确的：

public DatabaseHelper(Context context) {
        super(context, DB_NAME, null, DATABASE_VERSION);
        /* ... */
}

我在getWritableDatabase()下面放了源代码，如你所见，它不会调用onUpgrade()，除非db文件中的版本不等于你在构造函数中传递的当前新版本（{{ 1}}行）。因此，您的数据库文件不会被覆盖，或者新数据库中的版本号错误。请检查一下。

version != mNewVersion

修改
您可以使用以下查询检查新数据库文件中的版本：

/** * Create and/or open a database that will be used for reading and writing. * Once opened successfully, the database is cached, so you can call this * method every time you need to write to the database. Make sure to call * {@link #close} when you no longer need it. * * <p>Errors such as bad permissions or a full disk may cause this operation * to fail, but future attempts may succeed if the problem is fixed.</p> * * @throws SQLiteException if the database cannot be opened for writing * @return a read/write database object valid until {@link #close} is called */ public synchronized SQLiteDatabase getWritableDatabase() { if (mDatabase != null && mDatabase.isOpen() && !mDatabase.isReadOnly()) { return mDatabase; // The database is already open for business } if (mIsInitializing) { throw new IllegalStateException("getWritableDatabase called recursively"); } // If we have a read-only database open, someone could be using it // (though they shouldn't), which would cause a lock to be held on // the file, and our attempts to open the database read-write would // fail waiting for the file lock. To prevent that, we acquire the // lock on the read-only database, which shuts out other users. boolean success = false; SQLiteDatabase db = null; if (mDatabase != null) mDatabase.lock(); try { mIsInitializing = true; if (mName == null) { db = SQLiteDatabase.create(null); } else { db = mContext.openOrCreateDatabase(mName, 0, mFactory); } int version = db.getVersion(); if (version != mNewVersion) { db.beginTransaction(); try { if (version == 0) { onCreate(db); } else { onUpgrade(db, version, mNewVersion); } db.setVersion(mNewVersion); db.setTransactionSuccessful(); } finally { db.endTransaction(); } } onOpen(db); success = true; return db; } finally { mIsInitializing = false; if (success) { if (mDatabase != null) { try { mDatabase.close(); } catch (Exception e) { } mDatabase.unlock(); } mDatabase = db; } else { if (mDatabase != null) mDatabase.unlock(); if (db != null) db.close(); } } }

在您的情况下应该返回PRAGMA user_version;。

Answer 2

它有一个叫做的方法 onUpgrade（SQLiteDatabase db，int oldVersion，int newVersion）{ 在这里执行升级的东西。。。 }

如果您使用的是SQLiteOpenHelper类，则只能覆盖此方法。

Answer 3

只需创建一个

@Override
    public void onCreate(SQLiteDatabase db) {
        onUpgrade(db, 0, DATABASE_VERSION);

SQLITE - 设置新数据库的版本

3 个答案: