ZK Developer's Guide

alert('Hello '+username.value);
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Chapter 1
It was mentioned before that the page contains one hidden button (Say Hello). This
button has the buttonToSayHello id. The idea behind this is that the button is only
shown if there is some input in the textbox with the username id. After the input of
some content (at least one character that is not a white space character) the output
looks like the following screenshot.
One way to define this "event listener" is to define the onChanging attribute for the
textbox username. The implementation of the event is done in Java.
Each main element should have an id attribute. With the id of an
element it's easy to access such an element. In the example, we set the
button visible with buttonToSayHello.setVisible(true).
If we click on the Say Hello button a window with a message is opened (see the
following screenshot).
To show this messagebox the onClick attribute of the button is defined as
alert("Hello "+username.value). We used the globally defined
method alert to show the message. The parameter for the method is a text string.
We first have a constant Hello text, and then the value of the username (username.
value) textbox.
Always in development, it's important to remember that a ZUL file is just
an XML file. Also if we want to use Java in that file, we have to keep in
mind that some characters could conflict with XML. Therefore, we have
to use the XML entities for special characters. In the example, we used
" for ' and & for the & sign.