与null比较,不在java中工作

Question

我一直试图null在条件下进行比较,但它不起作用,总是在Else中.以下是代码,

String authEmail = cursor.getString(cursor.getColumnIndexOrThrow("AUTHOR_EMAIL"));
Log.i(gtag, "author email => " + authEmail);
    if (authEmail == null ) {
        Log.i(gtag, "in author check - IF NULL");
     } else {
            Log.i(gtag, "in author check - ELSE ");                 
     }

这cursor是查询SQLite数据库的结果,AUTHOR_EMAIL是列的名称.Logcat将作者电子邮件显示为null,但仍然在ELSE中.以下是Logcat:

06-24 15:30:55.307: I/GCA-Abs-Con(1282): author email => foo@bar.de
06-24 15:30:55.307: I/GCA-Abs-Con(1282): in author check - ELSE 
06-24 15:30:55.357: I/GCA-Abs-Con(1282): author email => null
06-24 15:30:55.357: I/GCA-Abs-Con(1282): in author check - ELSE 

的logcat的显示第3行authorEmail是null但仍进去else.

我试过authEmail.equals(null)了,但那也行不通.

我应该如何修改if条件以完美地检查null？
提前致谢.

Answer 1

要检查数据库字段是否具有SQL NULL值,请使用游标的isNull方法:

int index = cursor.getColumnIndexOrThrow("AUTHOR_EMAIL");
if (cursor.isNull(index)) {
    ...
} else {
    String authEmail = cursor.getString(index);
    ...
}