Time for action – creating warning and error messages

In free-form text fields, it's sometimes possible to enter a value that isn't valid. For example, when asking for an e-mail address, it might be necessary to validate it against some kind of regular expression such as .+@.+ to provide a simple check.

1. To test the default validation, run the target Eclipse instance and go to the Clock preference page. Type some text in the numeric field. A warning message, Value must be an integer, will be displayed:

   

2. To add validation, create a new field called offset that allows values between -14 and +12 (by default, IntegerFieldEditor validates against the 0..MAX_INT range). Add the following to the createFieldEditors method:

   IntegerFieldEditor offset = new IntegerFieldEditor("offset","Current offset from GMT", getFieldEditorParent());offset.setValidRange(-14, +12);addField(offset);

3. Run the target Eclipse instance, go to the Clock preference page, and type in an invalid value:

   

What just happened?

Each field...