Question

使用SQLite DATABASE时出现此错误。

07-16 17:45:13.106: E/AndroidRuntime(7703): Caused by: 
android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0

我正在使用SQLite数据库将书籍对象存储在其中。

public class MySQLiteHelper extends SQLiteOpenHelper {

    // Database Version
    private static final int DATABASE_VERSION = 1;
    // Database Name
    private static final String DATABASE_NAME = "BookDB";

    public MySQLiteHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION); 
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // SQL statement to create book table
        String CREATE_BOOK_TABLE = "CREATE TABLE books ( " +
                "id INTEGER PRIMARY KEY AUTOINCREMENT, " +
                "title TEXT, "+
                "author TEXT )";

        // create books table
        db.execSQL(CREATE_BOOK_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Drop older books table if existed
        db.execSQL("DROP TABLE IF EXISTS books");

        // create fresh books table
        this.onCreate(db);
    }
    //---------------------------------------------------------------------

    /**
     * CRUD operations (create "add", read "get", update, delete) book + get all books + delete all books
     */

    // Books table name
    private static final String TABLE_BOOKS = "books";

    // Books Table Columns names
    private static final String KEY_ID = "id";
    private static final String KEY_TITLE = "title";
    private static final String KEY_AUTHOR = "author";

    private static final String[] COLUMNS = {KEY_ID,KEY_TITLE,KEY_AUTHOR};

    public void addBook(Book book){
        Log.d("addBook", book.toString());
        // 1. get reference to writable DB
        SQLiteDatabase db = this.getWritableDatabase();

        // 2. create ContentValues to add key "column"/value
        ContentValues values = new ContentValues();
        values.put(KEY_TITLE, book.getTitle()); // get title
        values.put(KEY_AUTHOR, book.getAuthor()); // get author

        // 3. insert
        db.insert(TABLE_BOOKS, // table
                null, //nullColumnHack
                values); // key/value -> keys = column names/ values = column values

        // 4. close
        db.close();
    }

    public Book getBook(int id){

        // 1. get reference to readable DB
        SQLiteDatabase db = this.getReadableDatabase();

        // 2. build query
        Cursor cursor =
                db.query(TABLE_BOOKS, // a. table
                COLUMNS, // b. column names
                " id = ?", // c. selections
                new String[] { String.valueOf(id) }, // d. selections args
                null, // e. group by
                null, // f. having
                null, // g. order by
                null); // h. limit

        // 3. if we got results get the first one
        if (cursor != null)
            cursor.moveToFirst();

        // 4. build book object
        Book book = new Book();
        book.setId(Integer.parseInt(cursor.getString(0)));
        book.setTitle(cursor.getString(1));
        book.setAuthor(cursor.getString(2));

        Log.d("getBook("+id+")", book.toString());

        // 5. return book
        return book;
    }

    // Get All Books
    public List<Book> getAllBooks() {
        List<Book> books = new LinkedList<Book>();

        // 1. build the query
        String query = "SELECT  * FROM " + TABLE_BOOKS;

        // 2. get reference to writable DB
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(query, null);

        // 3. go over each row, build book and add it to list
        Book book = null;
        if (cursor.moveToFirst()) {
            do {
                book = new Book();
                book.setId(Integer.parseInt(cursor.getString(0)));
                book.setTitle(cursor.getString(1));
                book.setAuthor(cursor.getString(2));

                // Add book to books
                books.add(book);
            } while (cursor.moveToNext());
        }

        Log.d("getAllBooks()", books.toString());

        // return books
        return books;
    }

     // Updating single book
    public int updateBook(Book book) {

        // 1. get reference to writable DB
        SQLiteDatabase db = this.getWritableDatabase();

        // 2. create ContentValues to add key "column"/value
        ContentValues values = new ContentValues();
        values.put("title", book.getTitle()); // get title
        values.put("author", book.getAuthor()); // get author

        // 3. updating row
        int i = db.update(TABLE_BOOKS, //table
                values, // column/value
                KEY_ID+" = ?", // selections
                new String[] { String.valueOf(book.getId()) }); //selection args

        // 4. close
        db.close();

        return i;

    }

    // Deleting single book
    public void deleteBook(Book book) {

        // 1. get reference to writable DB
        SQLiteDatabase db = this.getWritableDatabase();

        // 2. delete
        db.delete(TABLE_BOOKS,
                KEY_ID+" = ?",
                new String[] { String.valueOf(book.getId()) });

        // 3. close
        db.close();

        Log.d("deleteBook", book.toString());

    }
}

Answer 1

您必须检查Cursor是否有任何行。像这样：

// 3. if we got results get the first one
    if (cursor.moveToFirst()){
       // do the work
}

如果cursor不为空，则

cursor.moveToFirst()返回true，否则返回false。

您试图在Cursor空的时候阅读，Exception。

编辑：它位于getBook(0)，而是调用getBook(1)，第一个自动递增的id值为1，而不是0.并更改Cursor检查表达式。

Answer 2

尝试使用

if(v != null && v.moveToFirst()) {
//your code
}

IT WORKED 4 ME

Answer 3

JUst尝试下面的单个条件的代码你必须首先检查光标是否为null然后移动到开始位置后不要忘记在工作完成后关闭它

Cursor cursor = db.query(...);if (cursor != null) {
if (cursor.moveToFirst()) {
    //do your stuff
}
cursor.close();

}

现在，如果您想要检查多个列，只需将替换条件，如果 感谢

Android.database.CursorIndexOutOfBoundsException：请求索引0，大小为0-s

3 个答案: