I've been working on a prototype but it's a big job and I've got "real"
work to do. I've implemented an annotation and an annotation processor
that creates a property change dispatcher for an annotated property
through bytecode enhancement of a setter. It doesn't use reflection and
it supports binding to any property, whether there's a listener defined
for it or not. I haven't gotten any farther than that and don't know when
I'll resume work.
Cheers,
Michael
On Mon, 5 Jul 2010, Greg Brown wrote:
Another question that seems to come up fairly often is - "does Pivot
support dynamic data binding like Flex?" Historically, the answer we
have given is, "no, Pivot's data binding support is based on a
load/store model that maps well to client/server applications such as
REST clients."
However, there are cases where Flex-like data binding can be useful.
Given the recent updates to BXMLSerializer, I think it may now be
relatively straightforward to implement. It may also be a good way to
support dynamically updatable styles, since style values are simply page
variables, just like everything else. Consider the following example:
<Label text="$text">
<styles color="$styles.color"/>
</Label>
When loaded, the text property of the label will be set to the value of
the "text" variable, and the color style will be set to the value of the
"styles.color" variable. It may be possible to (fairly easily) extend
the syntax of BXML such that something like the following would cause
the text property and color style to automatically reflect changes to
the source variable:
<Label text="${text}">
<styles color="${styles.color}"/>
</Label>
Basically, this syntax (or something like it) would be a cue to the
serializer to register a change listener on the given variable and
propagate any changes to the bound property.
I haven't prototyped it, so I'm not sure what hidden gotchas we might
run into, but I think it could work. The primary trick will be in
determining the type of the parent object and registering an appropriate
listener. For example, if "styles" in the above example is a Map, we
would register a MapListener on the "styles" object to be notified of
changes to the "color" variable. If it is a bean, we'd need to use
something like the BeanMonitor class used in the Component Explorer
demo. That means we'd probably want to move that class to
org.apache.pivot.beans (which might be worth doing anyways).
Let me know what you think. If there is sufficient interest, I may try
to get it working.
G
