How to display a progress icon when clicking "Show more" on a CellTree? - gwt

Question

I'm using the CellTree for the very first time and slowly getting a hang of it.
Right now I'm struggling how to display a progress icon (just like when opening a tree node) beside the "Show more" text when clicking on it.
Any ideas?
I guess it is a common problem that users are clicking on "Shore more" multiple times if they do not get any visual feedback - which leads to multiple server calls and a bunch of duplicated nodes (in my case).

Answer 1

Any time you send a call off to the server, you know that you are making the call. Likewise, you will get a call back into your code, whether it succeeded or failed.
For the sake of this example, I'm assuming you are using something like GWT-RPC (since the question doesn't specify):
// field to track if we're loading
private boolean isLoading = false
//...
// inside a method which needs to load data:
if (isLoading) {
return;//don't attempt to load again
}
isLoading = true;
//just before we start the call, show the loading indicator
loadingIndicator.flash();//or whatever you'd like to make it do
//then start the request
service.getMyData(param1, param2, new AsyncCallback<MyData> () {
public void onSuccess(MyData response) {
//loading was successful, so stop the loading marker
isLoading = false;
loadingIndicator.success();
//do something with the data
//...
}
public void onFailure(Throwable ex) {
//loading stopped, but it was an error, tell the user
isLoading = false;
loadingIndicator.error();
}
});