android - 为什么 SQLiteOpenHelper 会导致 IllegalArgumentException 数据库打不开？

Question

首先，这里所有类似的帖子都没有帮助。

在 AsyncTask 中，我检查应用程序启动是否是第一次启动，这意味着我检查是否有数据库。我想通过从表中查询来做到这一点。这是正在执行的内容:

@Override
public List<Entity> loadAll(Entity markerEntity)
{
    Log.i(TAG, "trying to load all entities of type " + markerEntity.getTable());

    List<Entity> results = new LinkedList<Entity>();

    SQLiteDatabase db = defaultSQLiteOpenHelper.getWritableDatabase();

    Cursor cursor = db.query(markerEntity.getTable(), markerEntity.getAllColumns(), null, null, null, null, null);    
    cursor.moveToFirst();

    while (!cursor.isAfterLast())
    {
        Entity result = markerEntity.createNewInstance(cursor);
        results.add(result);

        cursor.moveToNext();
    }

    db.close();

    return results;
}

IllegalArgumentException: database not open 的崩溃发生在这一行。

SQLiteDatabase db = defaultSQLiteOpenHelper.getWritableDatabase();

它恰好发生在方法上(见下文)createAllTables。

documentation说:

Create and/or open a database that will be used for reading and writing. The first time this is called, the database will be opened and onCreate(SQLiteDatabase), onUpgrade(SQLiteDatabase, int, int) and/or onOpen(SQLiteDatabase) will be called.

在我看来，它应该执行我的 DefaultSQLiteOpenhelper 并创建所有数据库表，但它并没有这样做:

public class DefaultSQLiteOpenHelper extends SQLiteOpenHelper implements ISQLiteOpenHelper
{
    private static final String TAG = DefaultSQLiteOpenHelper.class.getSimpleName();

    private static final String DATABASE_NAME = "MY_DATABASE";
    private static final int DATABASE_VERSION = 1;

    @Inject
    public DefaultSQLiteOpenHelper(Context context)
    {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    //is called by the framework if the database doesn't exist
    @Override
    public void onCreate(SQLiteDatabase db)
    {
        Log.i(TAG, "no database found. Generating new database...");

        createAllTables(db);    
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
    {
         Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion);
//       db.execSQL("DROP TABLE IF EXISTS " + TABLE_COMMENTS); ///TODO when upgrade
//       onCreate(db);
    }

    //The order must not be changed because sqlite doesn't allow
    //table modification. That means one cannot add constraints afterwards
    //which results in creating tables in a specific order
    private final void createAllTables(SQLiteDatabase db)
    {
        db.beginTransaction();

        //create lookups at first
        db.execSQL(TableFactory.createUsage());
        db.execSQL(TableFactory.createLanguage());

        db.execSQL(TableFactory.createAccount());
        db.execSQL(TableFactory.createPreferences());
        db.execSQL(TableFactory.createLanguageUsageRel());
        db.execSQL(TableFactory.createPantry());
        db.execSQL(TableFactory.createProduct());

        //populate lookups
        db.execSQL(DataFactory.populateUsage());
        db.execSQL(DataFactory.populateLanguage());

        db.setTransactionSuccessful();
        db.endTransaction();
        db.close();
    }
}

问题是，为什么不打开数据库呢？文档说它必须。我不接受任何肮脏的解决方法作为解决方案，例如手动打开数据库或其他方式。我的代码到底出了什么问题？我不敢相信这是 Android 中的错误。

这是堆栈跟踪:

05-27 17:25:50.370: I/DefaultSQLiteOpenHelper(719): no database found. Generating new database... 05-27 17:25:50.400: W/dalvikvm(719): threadid=10: thread exiting with uncaught exception (group=0x40015560) 05-27 17:25:50.400: E/AndroidRuntime(719): FATAL EXCEPTION: AsyncTask

1 05-27 17:25:50.400: E/AndroidRuntime(719): java.lang.RuntimeException: An error occured while executing

doInBackground() 05-27 17:25:50.400: E/AndroidRuntime(719): at android.os.AsyncTask$3.done(AsyncTask.java:200) 05-27 17:25:50.400: E/AndroidRuntime(719): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274) 05-27 17:25:50.400: E/AndroidRuntime(719): at java.util.concurrent.FutureTask.setException(FutureTask.java:125) 05-27 17:25:50.400: E/AndroidRuntime(719): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308) 05-27 17:25:50.400: E/AndroidRuntime(719): at java.util.concurrent.FutureTask.run(FutureTask.java:138) 05-27 17:25:50.400: E/AndroidRuntime(719): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088) 05-27 17:25:50.400: E/AndroidRuntime(719): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581) 05-27 17:25:50.400: E/AndroidRuntime(719): at java.lang.Thread.run(Thread.java:1019) 05-27 17:25:50.400: E/AndroidRuntime(719): Caused by: java.lang.IllegalStateException: database not open 05-27 17:25:50.400: E/AndroidRuntime(719): at android.database.sqlite.SQLiteDatabase.endTransaction(SQLiteDatabase.java:555) 05-27 17:25:50.400: E/AndroidRuntime(719): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:137) 05-27 17:25:50.400: E/AndroidRuntime(719): at com.mydomain.android.base.persistence.PersistenceManager.loadAll(PersistenceManager.java:58) 05-27 17:25:50.400: E/AndroidRuntime(719): at com.mydomain.android.base.main.StartupTask.isFirstStartAfterInstallation(StartupTask.java:107) 05-27 17:25:50.400: E/AndroidRuntime(719): at com.mydomain.android.base.main.StartupTask.doInBackground(StartupTask.java:52) 05-27 17:25:50.400: E/AndroidRuntime(719): at com.mydomain.android.base.main.StartupTask.doInBackground(StartupTask.java:18) 05-27 17:25:50.400: E/AndroidRuntime(719): at android.os.AsyncTask$2.call(AsyncTask.java:185) 05-27 17:25:50.400: E/AndroidRuntime(719): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306) 05-27 17:25:50.400: E/AndroidRuntime(719): ... 4 more

Answer 1

首先，您将在 createAllTables() 中关闭数据库。切勿通过 SQLiteOpenHelper 的 onCreate() 或 onUpgrade() 关闭数据库。

其次，createAllTables() 中不需要您的事务逻辑，因为 onCreate() 是在事务中执行的。这很好，因为您的交易逻辑无论如何都没有正确实现。

为了澄清后面的评论，正确的交易方式是:

try {
    db.beginTransaction();

    // SQL

    db.setTransactionSuccessful();
}
// optional catch block
finally {
    db.endTransaction();
}

如果出现 SQL 异常，您需要调用 endTransaction() —— 您的实现会跳过这个。