问题
My question is really simple and shot. but hope I can have a clear answer. We can create GWT Image in many ways.
Image image = new Image ( (ImageResource)imageRes);
Image image = new Image ( (ImageResource)imageRes.getSafeUri() );
Image image = new Image ();
image.setUrl((ImageResource)imageRes.getSafeUri().asString() );
My question is: what are the difference among these 3 ways to create a new image using ImageResouce. Which one is best or faster for first-time loading?
Thanks
回答1:
First, you should not use the last two.
An ImageResource
technically represents a region within a "sprited" image: it has a URL to the sprite and the coordinates of the region on that image. In many browsers, and for most images, the URL will actually be a data:
URL and the region will represent the whole image. This can be controlled on a per-image basis using @ImageOptions(preventInlining=true)
or globally with a set-property
on your gwt.xml
. In other words, your code shouldn't rely on it, and should always treat an ImageResource
as a region within a sprited image.
FYI, the cases where a sprited image is actually used by default are for IE6/7 which does not support data:
URLs, and for images that are too large to fit within a data:
URL (all browsers).
This is however exactly what you're doing in the last two cases: use only the URL of the ImageResource
, as if it weren't (potentially) a sprited image.
来源:https://stackoverflow.com/questions/11674279/gwt-create-image-using-imageresource