java - ORMLite Android-从单个表中获取 17 列中的 1 列

Question

我有一个表“公司”，其中包含 3 列 [ name、id 、address ]。但我只想获取“名称”列值。我就是这样做的

Dao<Company, String> dao = getDBHelper().getCompanyDao();

QueryBuilder<Company, String> queryBuilder = dao.queryBuilder();
queryBuilder.orderBy(Company.USERNAME_FIELD_NAME, true);
**queryBuilder.selectColumns("name");**
PreparedQuery<Company> preparedQuery = queryBuilder.prepare();
CloseableIterator<Company> iterator = dao.iterator(preparedQuery);
 AndroidDatabaseResults results = (AndroidDatabaseResults) iterator.getRawResults();
Cursor cursor = results.getRawCursor();

但是当我添加“queryBuilder.selectColumns("name") ”时，应用程序崩溃了。请帮助我。我想要光标，因为我使用光标适配器来填充数据。

崩溃日志在这里:

java.lang.NullPointerException
    at com.j256.ormlite.stmt.QueryBuilder.appendFieldColumnName(QueryBuilder.java:593)
    at com.j256.ormlite.stmt.QueryBuilder.appendColumns(QueryBuilder.java:585)
    at com.j256.ormlite.stmt.QueryBuilder.appendStatementStart(QueryBuilder.java:405)
    at com.j256.ormlite.stmt.StatementBuilder.appendStatementString(StatementBuilder.java:122)
    at com.j256.ormlite.stmt.StatementBuilder.buildStatementString(StatementBuilder.java:106)
    at com.j256.ormlite.stmt.StatementBuilder.prepareStatement(StatementBuilder.java:74)
    at com.j256.ormlite.stmt.QueryBuilder.prepare(QueryBuilder.java:98)

Answer 1

But application is crashing when I add "queryBuilder.selectColumns("name")

哇。这是一个非常微妙且长期存在的错误。每当您尝试从没有 ID 字段的实体中选择列时，就会发生这种情况。我添加了此错误报告:

https://sourceforge.net/p/ormlite/bugs/162/

此问题已在 trunk 中修复，并将在 4.49 中修复。这是签到。

https://github.com/j256/ormlite-core/commit/ee95883040a3618a1d455b44f6bfd6935a8d4ec7