Class ProgressBarTreeTableCell<S>

public ProgressBarTreeTableCell()

Creates a default ProgressBarTreeTableCell instance

public static <S> Callback<TreeTableColumn<S,Double>,TreeTableCell<S,Double>> forTreeTableColumn()

Provides a ProgressBar that allows easy visualisation of a Number value as it proceeds from 0.0 to 1.0. If the value is -1, the progress bar will appear indeterminate.

public void updateItem(Double item, boolean empty)

The updateItem method should not be called by developers, but it is the best method for developers to override to allow for them to customise the visuals of the cell. To clarify, developers should never call this method in their code (they should leave it up to the UI control, such as the ListView control) to call this method. However, the purpose of having the updateItem method is so that developers, when specifying custom cell factories (again, like the ListView cell factory), the updateItem method can be overridden to allow for complete customisation of the cell.

It is very important that subclasses of Cell override the updateItem method properly, as failure to do so will lead to issues such as blank cells or cells with unexpected content appearing within them. Here is an example of how to properly override the updateItem method:

 protected void updateItem(T item, boolean empty) {
     super.updateItem(item, empty);

     if (empty || item == null) {
         setText(null);
         setGraphic(null);
     } else {
         setText(item.toString());
     }
 }
 

Note in this code sample two important points:

1. We call the super.updateItem(T, boolean) method. If this is not done, the item and empty properties are not correctly set, and you are likely to end up with graphical issues.
2. We test for the empty condition, and if true, we set the text and graphic properties to null. If we do not do this, it is almost guaranteed that end users will see graphical artifacts in cells unexpectedly.