java - Android Studio SQLite 错误 : Couldn't read row 0, 来自 CursorWindow 的第 3 列

Question

这里是 Android Studio 新手。我正在使用 Databasehelper 文件将书籍添加到我的 HashMap 中。我的 Databasehelper 位于模型文件夹中。我相信我的代码看起来不错，但是下面发布了以下错误:

E/AndroidRuntime: FATAL EXCEPTION: main
                                                                              Process: edu.monash.libraryofalexandria, PID: 2828
                                                                              java.lang.RuntimeException: Unable to start activity ComponentInfo{edu.monash.libraryofalexandria/edu.monash.libraryofalexandria.MainActivity}: java.lang.IllegalStateException: Couldn't read row 0, col 3 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.
                                                                                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
                                                                                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
                                                                                  at android.app.ActivityThread.-wrap11(Unknown Source:0)
                                                                                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
                                                                                  at android.os.Handler.dispatchMessage(Handler.java:106)
                                                                                  at android.os.Looper.loop(Looper.java:164)
                                                                                  at android.app.ActivityThread.main(ActivityThread.java:6494)
                                                                                  at java.lang.reflect.Method.invoke(Native Method)
                                                                                  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
                                                                                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
                                                                               Caused by: java.lang.IllegalStateException: Couldn't read row 0, col 3 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.
                                                                                  at android.database.CursorWindow.nativeGetString(Native Method)
                                                                                  at android.database.CursorWindow.getString(CursorWindow.java:438)
                                                                                  at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:51)
                                                                                  at edu.monash.libraryofalexandria.models.DatabaseHelper.getAllBooks(DatabaseHelper.java:56)
                                                                                  at edu.monash.libraryofalexandria.MainActivity.onCreate(MainActivity.java:41)
                                                                                  at android.app.Activity.performCreate(Activity.java:7009)
                                                                                  at android.app.Activity.performCreate(Activity.java:7000)
                                                                                  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
                                                                                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
                                                                                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
                                                                                  at android.app.ActivityThread.-wrap11(Unknown Source:0) 
                                                                                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
                                                                                  at android.os.Handler.dispatchMessage(Handler.java:106) 
                                                                                  at android.os.Looper.loop(Looper.java:164) 
                                                                                  at android.app.ActivityThread.main(ActivityThread.java:6494) 
                                                                                  at java.lang.reflect.Method.invoke(Native Method) 
                                                                                  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
                                                                                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 

这是我的 DatabaseHelper 类

public class DatabaseHelper extends SQLiteOpenHelper {

    public static final String DATABASE_NAME = "PersonDB";
    public static final int DATABASE_VERSION = 1;
    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        sqLiteDatabase.execSQL(Book.CREATE_STATEMENT);
    }
    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
        sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + Book.TABLE_NAME);
        onCreate(sqLiteDatabase);
    }
    public void addBook(Book book) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(Book.COLUMN_NAME, book.getName());
        values.put(Book.COLUMN_AUTHOR, book.getAuthor());
        values.put(Book.COLUMN_GENRE, book.getGenre());
        values.put(Book.COLUMN_ISBN, book.getISBN());
        values.put(Book.COLUMN_PUBLISHER, book.getPublisher());
        values.put(Book.COLUMN_DATE, book.getDate());
        values.put(Book.COLUMN_EDITION, book.getEdition());
        values.put(Book.COLUMN_DESCRIPTION, book.getDescription());
        db.insert(Book.TABLE_NAME, null, values);
        db.close();
    }
    public HashMap<Long, Book> getAllBooks() {
        HashMap<Long, Book> books = new LinkedHashMap<>();
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery("SELECT * FROM " + Book.TABLE_NAME, null);
        // Add each book to hashmap (Each row has 1 book)
        while (cursor.moveToNext()) {
            Book book = new Book(cursor.getLong(0),
                    cursor.getString(1),
                    cursor.getString(2),
                    cursor.getString(3),
                    cursor.getString(4),
                    cursor.getString(5),
                    cursor.getString(6),
                    cursor.getString(7),
                    cursor.getString(8));
            books.put(book.getId(), book);
        }
        cursor.close();
        db.close();
        if(books.size() == 0) {
            Log.d("myTag", "This is my message");

            // If there are no people in the db then add some default books
            createDefaultBook();
            books = getAllBooks();
        }
        return books;
    }

    public void removeBook(Book book)
    {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(Book.TABLE_NAME,
                Book.COLUMN_ID + " = ?",
                new String[] {String.valueOf(book.getId())});
    }

    private void createDefaultBook()
    {
        addBook(new Book(0, "The Green House", "William", "Romance", "26756898", "Harper", "29/2/1993", "1", "There are no men like me there is only me."));

    }
}

为什么会出现这个错误？我该如何修复它？
谢谢您，
亲切的问候

Answer 1

我找到了问题的解决方案!
最初我有一个旧版本的程序，仅支持 2 列我的新版本还有 6 列，当我运行新版本时，我收到了问题中描述的错误。我通过卸载应用程序并再次运行有效的代码来修复它。