Undo Reorder of Columns in af:table

A question on OTN about how to undo a reorder of columns in an af:table can be undone. In this blog I show how to undo such a reorder to show the columns of an af:table in their natural order.
The natural order is defined when you create the table. You can move the attributes in the create dialog or delete attributes you don’t want to see in the UI from the table.

In the image above we see the dialog after we drop a VO as table onto a page. To change is order of the columns in the table you can use the arrows on the right (in the red rectangle). Once you save the table you can reorder the columns in the property editor of the af:table.

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The order of the columns you see in the dialog or the property editor is what is called default order of the columns. This default order can be different than the order of the attributes in the query the VO is based on.
The page we drop the af:table on is very simple. It is build from a quick layout and has a header for the page title and a panelCollection which holds the table.

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We can reorder the columns in the UI by dragging a column and dropping it at a different location.

The question now is how to undo this manual reorder without refreshing the browser window.

To understand how this is implemented, we need to look how the the reorder is done in the first place. A table is build from one or more columns. Each of the columns describes the data to be shown in the column, the header to show and the display index which is the order of the columns shown in the UI. If the display index is less then zero (e.g. -1) the default order is used. Any other positive number is used to show the columns in ascending order of these display index.
To undo any reorder of the columns is an af:table we simply have to get to each column and set it’s display index to -1.

public class UndoColumnReorderBean {
    private static ADFLogger _logger = ADFLogger.createADFLogger(UndoColumnReorderBean.class);
    private RichTable table;

    public UndoColumnReorderBean() {
    }

    public void undoColunmReorder(ActionEvent actionEvent) {
        _logger.info("Undo reorder...");
        // get the tables child components
        List<UIComponent> children = this.table.getChildren();
        for (UIComponent comp : children) {
            // check if the child is a column
            if (comp instanceof RichColumn) {
                RichColumn col = (RichColumn) comp;
                // if hte display index is greater 0 set it to -1
                if (col.getDisplayIndex() >= 0) {
                    _logger.info("...unset column "+col);
                    col.setDisplayIndex(-1);
                }
            }
        }
        _logger.info("... done!");
    }

    public void setTable(RichTable table) {
        this.table = table;
    }

    public RichTable getTable() {
        return table;
    }
}

The bean above has a method undoColumnReorder which is an action event Listener triggered by clicking the ‘Undo Column Reorder’ button. This method uses the af:table component which is bound to the bean as property. It iterates over the child components of the table, checking if the child is a RichColumn (or af:column in the UI) and if yes sets its display index to -1;
To show the change in the UI, we have to ppr the table by adding the button as partial Trigger to the table

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After clicking the button in the ui the table again looks like

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so the default order of the columns is shown again.

You can download the application from GitHub BlogUndoColumnReorder. The sample is build using JDev 12.2.1.2 but you can do the same with any other JDev version 11g or 12c you use. It uses the HR DB schema.

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