GWT DataGrid setLoadingIndicator has no effect

Question

I'm trying to use the feature of GWT DataGrid to show an animated gif when data is loading from a RPC call to the server.

I didn't find any resource whatsoever anywehere. The support for this is really poor.

I inizialize my DataGrid using:

myDataGrid.setLoadingIndicator(new Image(/*my ImageResource object*/);

and during the flow of the program I use:

myDataGrid.fireEvent(new LoadingStateChangeEvent(LoadingState.LOADING));

when I want to put the DataGrid in the 'LOADING' state, i.e. just before making an RPC call, and then:

myDataGrid.fireEvent(new LoadingStateChangeEvent(LoadingState.LOADED));

just after the grid has been populated with data.

This doesn't work. I do not see any change in the DataGrid, I can't see the animated gif, it just remains unchanged during the process. Is there something I'm doing wrong?

Please help.

Answer 1

If you call updateRowCount(0, false), the loading image will be displayed.

Answer 2

I have several DataGrids in my application and I use the code-snippet below for all of them. You have to clear the data first, so that there are zero records in the grid, and then set the row-count to a number greater than zero. Please note that the loading indicator is only animated while data is received via RPC. As soon as the grid is rendered (which may also take a while) the animation freezes.

    // Only required if you are using a pager
    int pageSize = pager.getPageSize();

    // This will trigger the onRangeChanged-event and call
    // the data provider
    dataGrid.setVisibleRangeAndClearData(new Range(0, 1), true);
    // Together with the row above, this will show the loading-indicator
    // in the data grid
    dataGrid.setRowCount(1);

    // Usually, the data is loaded when the data grid is initialized.
    // In my application, the user has to enter some input first and
    // then (re-)load the data via a button.
    // If you want your data grid to be filled when it is intialized,
    // simply remove the if-block
    if (dataProvider.getDataDisplays().size() == 0) {
        dataProvider.addDataDisplay(dataGrid);
    }

    // This will re-set the paging (only required if you are using a pager)
    dataGrid.setPageSize(pageSize);