Lists and Forms - Beginning J2ME: From Novice to Professional - page 78

Figure 6-7. A form with a single TextField and a Back command

TextFields can limit input. The following constants are defined:

• ANY allows any type of input.

• NUMERIC restricts the input to numbers.

• DECIMAL allows numbers with fractional parts.

• PHONENUMBER requires a telephone number.

• EMAILADDR input must be an e-mail address.

• URL input must be a URL.

These input constraints might look familiar; they're the same ones used by TextBox , which
we covered in the previous chapter. As with TextBox , the flags PASSWORD , SENSITIVE , UNEDITABLE ,
NON_PREDICTIVE , INITIAL_CAPS_WORD , and INITIAL_CAPS_SENTENCE can be combined with
constraints using the OR operator.
To create a TextField , you need to supply the label, text value, maximum length, and input
constraints.

public TextField(String label, String text, int maxSize, int constraints)

For an initially empty TextField , pass null for the text parameter.
As with TextBox , the TextField class includes a setInitialInputMode() method for suggesting
to the implementation an appropriate input mode.

ImageItem
Forms can also contain images, which are represented by instances of ImageItem . ImageItem s
have several pieces of associated data:

•A label may be displayed with the image.

• The layout determines the placement of the image.

• Alternate text is displayed if the image cannot be shown.