Ronon Ronon - 2 days ago 4
CSS Question

Javafx tableview changelistener changes to often

I want to color the rows in my table depending on the the state. After a search I found this Formatting Rows in a JavaFX TableView Using CSS Pseudo Classes.

I tried to implement it for my purpose. It also works, but if I scroll the color will change back to the default one.

What am i doing wrong?

@FXML
private void initialize(){

PseudoClass online = PseudoClass.getPseudoClass("online");
PseudoClass offline = PseudoClass.getPseudoClass("offline");
PseudoClass unknown = PseudoClass.getPseudoClass("unknown");

//Set a rowFactory for the table view.
overviewTable.setRowFactory(tableView -> {
TableRow<State> row = new TableRow<>();
ChangeListener<String> changeListener = (obs, oldValue, newValue) -> {
System.out.println("1: " + obs + " : " + oldValue + " : " + newValue);
row.pseudoClassStateChanged(online, newValue.equals("online"));
row.pseudoClassStateChanged(offline, newValue.equals("offline"));
row.pseudoClassStateChanged(unknown, newValue.equals("unknown"));
};

row.itemProperty().addListener((obs, oldValue, newValue) -> {
System.out.println("2: " + obs + " : " + oldValue + " : " + newValue);
if (oldValue != null) {
oldValue.stateProperty().removeListener(changeListener);
}
if (newValue != null) {
newValue.stateProperty().addListener(changeListener);
row.pseudoClassStateChanged(online, newValue.equals("online"));
row.pseudoClassStateChanged(offline, newValue.equals("offline"));
row.pseudoClassStateChanged(unknown, newValue.equals("unknown"));
} else {
row.pseudoClassStateChanged(online, false);
row.pseudoClassStateChanged(offline, false);
row.pseudoClassStateChanged(unknown, false);
}
});
return row;
});
}


CSS:

.table-row-cell:unknown{
-fx-background-color: blue;
}

.table-row-cell:online{
-fx-background-color: #2EAB15;
}

.table-row-cell:offline{
-fx-background-color: #BB0000;
}

.table-row-cell .text{
-fx-fill: white;
}

Answer

The issue is right here in the listener to the item property:

if (newValue != null) {
    newValue.stateProperty().addListener(changeListener);
    row.pseudoClassStateChanged(online, newValue.equals("online"));
    row.pseudoClassStateChanged(offline, newValue.equals("offline"));
    row.pseudoClassStateChanged(unknown, newValue.equals("unknown"));

Here newValue is a object of type State. It's unlikely that equals is overridden in a way that returns true, if a String is passed (and I'd advise never implementing equals in such a way).

You should instead pass the new value to the listener to trigger an update as if the value of the state property had changed:

if (newValue != null) {
    newValue.stateProperty().addListener(changeListener);
    changeListener.changed(null, null, newValue.getState());

or alternatively compare to the state property (which violates the DRY principle though):

if (newValue != null) {
    newValue.stateProperty().addListener(changeListener);
    row.pseudoClassStateChanged(online, newValue.getState().equals("online"));
    row.pseudoClassStateChanged(offline, newValue.getState().equals("offline"));
    row.pseudoClassStateChanged(unknown, newValue.getState().equals("unknown"));

I assume here that the State class contains a getState() method returning the content of the state property. If this is not the case all calls to that method need to be replaced with stateProperty().getValue().

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