I haven't sorted out in my mind the best approach for a few of the details,
in particular making it reusable, but this works. Consider it more of a
"proof of concept".
You'd need to create red.png in the war directory, or could try out a data
url (which per my tests works with this).
For a bundle with more images, the asynchronicity gets to be a bigger
issue, since you'd need to have something like a "master" callback once all
of the individual image callbacks have completed. Also, there's no
facility for sprites, although I think it could be implemented.
public class DynamicResourcesDemo implements EntryPoint {
private DynamicMenuBarResources resources;
private MenuBar bar;
public void onModuleLoad() {
MenuBar.Resources defaultResources =
GWT.create(MenuBar.Resources.class);
MyImageResource imgres = new
MyImageResource(defaultResources.menuBarSubMenuIcon());
resources = new DynamicMenuBarResources(imgres);
imgres.load("red.png", new Callback<Void, Throwable>() {
@Override
public void onSuccess(Void result) {
showUi();
}
@Override
public void onFailure(Throwable reason) {
Window.alert("Error");
}
});
}
private void showUi() {
MenuBar fileMenu = new MenuBar(true);
fileMenu.addItem("Open", new Scheduler.ScheduledCommand() {
@Override
public void execute() {
Window.alert("Open File");
}
});
fileMenu.addItem("Exit", new Scheduler.ScheduledCommand() {
@Override
public void execute() {
Window.alert("So long!");
}
});
MenuBar actionsMenu = new MenuBar(true, resources);
actionsMenu.addItem("File", fileMenu);
bar = new MenuBar();
bar.addItem("Actions", actionsMenu);
RootPanel.get().add(bar);
}
}
//-------------------------------------------------------------
public class DynamicMenuBarResources implements Resources {
private static Resources base = GWT.create(Resources.class);
private ImageResource menuBarSubmenuIconResource;
public DynamicMenuBarResources() {
}
public DynamicMenuBarResources(ImageResource
menuBarSubmenuIconResource) {
this.menuBarSubmenuIconResource = menuBarSubmenuIconResource;
}
@Override
@ImageOptions(flipRtl = true)
public ImageResource menuBarSubMenuIcon() {
if (menuBarSubmenuIconResource != null) {
return menuBarSubmenuIconResource;
} else {
return base.menuBarSubMenuIcon();
}
}
}
//----------------------------------------------------
public class MyImageResource implements ImageResource {
private Image image;
private ImageResource defaultResource;
private boolean imageValid = false;
public MyImageResource(ImageResource defaultResource) {
image = new Image();
this.defaultResource = defaultResource;
}
public void load(String url, final Callback<Void, Throwable> callback) {
image.setUrl(url);
final Panel pnl = new SimplePanel();
pnl.add(image);
Style pnlStyle = pnl.getElement().getStyle();
pnlStyle.setVisibility(Visibility.HIDDEN);
pnlStyle.setPosition(Position.ABSOLUTE);
image.addLoadHandler(new LoadHandler() {
@Override
public void onLoad(LoadEvent event) {
RootPanel.get().remove(pnl);
imageValid = true;
if (callback != null) callback.onSuccess(null);
}
});
image.addErrorHandler(new ErrorHandler() {
@Override
public void onError(ErrorEvent event) {
RootPanel.get().remove(pnl);
// this lets the resource fall back to the default
if (callback != null) callback.onSuccess(null);
// this would instead invoke the error handling for the
callback
//if (callback != null) callback.onFailure(new
Exception("Image Resource Load Error"));
}
});
RootPanel.get().add(pnl);
}
@Override
public String getName() {
return imageValid ? "" : defaultResource.getName(); // ???
}
@Override
public int getHeight() {
return imageValid ? image.getHeight() : defaultResource.getHeight();
}
@Override
public int getLeft() {
return imageValid ? 0 : defaultResource.getLeft();
}
@Override
public SafeUri getSafeUri() {
return imageValid ? UriUtils.fromSafeConstant(image.getUrl()) :
defaultResource.getSafeUri();
}
@Override
public int getTop() {
return imageValid ? 0 : defaultResource.getTop();
}
@Override
@Deprecated
public String getURL() {
return imageValid ? image.getUrl() : defaultResource.getURL();
}
@Override
public int getWidth() {
return imageValid ? image.getWidth() : defaultResource.getWidth();
}
@Override
public boolean isAnimated() {
return imageValid ? false : defaultResource.isAnimated(); // ???
}
}
On Saturday, August 17, 2013 12:30:11 PM UTC-4, df wrote:
>
> Could you give some code?
> Thanks
>
> W dniu czwartek, 15 sierpnia 2013 01:05:30 UTC+2 użytkownik Steve C
> napisał:
>>
>> Thanks for asking that question - it led me to a solution to a problem
>> that I've had, which is "skinning" an app using different versions of
>> resources loaded asynchronously from the war directory as opposed to coded
>> into a ClientBundle.
>>
>> I created a client bundle extending SimplePager.Resources, with sources
>> that reference dummy placeholder images in my source tree, then created a
>> separate class implementing that interface. In the constructor I populate
>> it from the GWT.created bundle (since some of the resources aren't dynamic,
>> and I can just delegate through to them) but then load my dynamic images
>> into Image widgets. Those, in turn, are each given to an implementation of
>> ImageResource that holds an Image widget, and obtains the width, height,
>> url, etc. from it (wasn't sure what the heck to do with getName, or how to
>> implement isAnimated). Those are the return values from the associated
>> methods in my resource object. And then I give that to the pager
>> constructor.
>>
>> The asychronicity turned out to be a bear, since I'm using a LoadHandler
>> for each image to know when the size values will be available, and that
>> won't do anything unless I actually add the Image to the document, so I had
>> to create a hidden div to put them into. I haven't yet tested if that's
>> necessary with a data: url. And a lot of layout tasks had to be pushed off
>> into a callback.
>>
>> The concept works, but I suspect that unless I make all versions of a
>> particular image the same size, I can't use any CssResource tricks based on
>> the image. That's probably not a big deal - since the variations generally
>> would all be the same size. Also, I don't think that there's any existing
>> Resource class in the API with CSS resources that depend on the images, so
>> it would only be an issue with custom resource classes.
>>
>> On Wednesday, August 14, 2013 3:42:34 AM UTC-4, df wrote:
>>>
>>> Hello. Is There any way to create ImageResource dynamically? For example
>>> : I get images from WebService in base64 format and I don't have
>>> opportunity to have all images on the server at compile time. Can i cast
>>> Images to ImageResource? Or is there any other solution?
>>> Thanks for help.
>>>
>>
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