Question

I have a custom field I have created that loads images from a url. What I would like to do is have the field take up no space and then when the image is loaded resize itself to the size of the image. I have almost everything done but I can’t work out a way to get the layout to be re done after the image is loaded. It works if I specify the size of the image beforehand. Calling invalidateLayout on the parent will not work as the screen is visible, but just calling invalidate does nothing. What steps to I have to go through to make a field resize?

It would also be preferable if I could call the method on the custom view rather than the parent but this is not essential.

This is for blackberry 4.5.0.

Answer 1

First of all, you will have to invalidate the parent manager, because it does need the new size of your custom field in order to redraw correctly the whole manager. (If there is other fields in the manager after your custom one, or even a scroll).

In the top of my head, here’s two solutions you can try to implement :

• When your custom field is done downloading the image, call the parent manager to invalidate all fields in it (you will have to hold a reference to the parent manager in your custom field)

— or —

• create the custom field object, without adding it to the manager. Start downloading you image, when it is done, call a parent specific method that will add the custom field to the manager (you will still have to hold a reference to the parent manager in your custom field) (You can use insert if you want to add it between two field already present on the manager). Like that you will not have to resize the field, but only add it to the manager when it is ready to be shown.

Answer to your comment :

Then you should use the synchronized scope :

synchronized(UiApplication.getUiApplication().getEventLock())) {  
    // UI Code here  
}  

Basically in this scope, you should only use an invalidate, do your size change somewhere else, before this call.