How to prevent firing ActionEvent when ComboBox value property is changed programmatically? - javafx

Question

I'm working with ComboBox control and I want to do something easy with it. I want ComboBox to fire an ActionEvent when its value is changed during mouse click on the ComboBox dropdown list (This is automatically done). In the opposite side, I want ComboBox Not to fire ActionEvent when its value is changed programmatically (e.g. when using comboBox.getSelectionModel().selectFirst()).
Here is a simple code to demonstrate the problem:
#Override
public void start(Stage primaryStage) {
VBox vBox = new VBox();
ComboBox<String> comboBox = new ComboBox<>();
comboBox.setItems(FXCollections.observableArrayList("John", "Josh", "Mosh"));
comboBox.setOnAction(event -> {
System.out.println("Action");
});
Task<Void> task = new Task<Void>() {
#Override
protected Void call() throws Exception {
return null;
}
};
task.setOnSucceeded(e -> comboBox.getSelectionModel().select("John"));
new Thread(task).start();
vBox.getChildren().addAll(comboBox);
vBox.setPrefWidth(200);
vBox.setPrefHeight(200);
vBox.setAlignment(Pos.CENTER);
Scene scene = new Scene(vBox);
Stage stage = new Stage();
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
launch(args);
}
As you can see, ComboBox has a setOnAction method which should be invoked only when ComboBox value is changed by a mouse click on the dropdown list. Also, there is a Task that does some operations. (Those operations are omitted for code simplicity reasons). After the Task is completed successfully, the ComboBox's value changes and setOnAction method is invoked too, while the value should be changed without invoking setOnAction method. I don't know how to achieve this. Any useful suggestions or tips are greatly appreciated.

Answer 1

I have successfully used Slaw's approach to suppress event firing across multiple controls at once -
set up a boolean field
private boolean programmedAction = false;
in the programmatic method updating the control, set the flag first to suppress actions
private void someMethod(){
programmedAction = true;
// manipulate controls
programmedAction = false;
}
in the control related events, check the boolean before firing
private void someControlsAction(ActionEvent actionEvent) {
if (programmedAction) return;
// do regular action stuff
}