GWT's CellTable loading bar won't display while refreshing contents

I do the following:

1. Create the CellTable (loading bar displays)
2. Put data in it (loading bar disappears, data appears)

I now want to:

1. Clear data and show the loading bar
2. Put more 开发者_运维百科data in it (loading bar disappears, data appears)

Has anyone done this? I've tried a few methods but they seem like hacks and haven't worked.

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In GWT trunk there is a revision r9687 just for your case, which sadly wasn't included in latest GWT-2.2 release:

Log message

Adding a LoadingStateEvent to CellList and CellTable so users can receive an event when the data is loaded. Now, LoadingState is a first class citizen (an interface so users can define their own loading state). Both CellList and CellTable now support setting a custom loading indicator Widget and a custom Widget to display when the table is empty.