CODEWITHSUNDEEP
javafxtabsclickeventhandler
Pete
Pete

Reputation: 1561

Javafx EventHandler kicks in when I click a tab... and again when I click another tab

In my Javafx app, I have a number of tabs in a tab pane. I needed the contents of a tab's display to update when the user clicked on the tab, so I found the below code and used it in the tab's controller:

    tabB.setOnSelectionChanged(new EventHandler<Event>() {
        @Override
        public void handle(Event t) {
            refreshTabBData();
        }
    });

That worked great until I realized the above actually creates two events: the first is when you click on the tab; the second event is when you click on a different tab. I need the refresh to happen only when the target tab is clicked the first time.

Here's my code, reduced to a toy example. First, the "launcher" class:

package tabsAndListeners;

import java.io.IOException;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;

public class GoGoGo extends Application {

    public void start(Stage primaryStage) {
        FXMLLoader loader = new FXMLLoader();
        loader.setLocation(getClass().getResource("TabScreen.fxml"));

        AnchorPane root;
        try {
            root = (AnchorPane) loader.load();
            TabScreenController tsc = loader.getController();
            tsc.start(primaryStage);
            Scene scene = new Scene(root);
            primaryStage.setScene(scene);
            primaryStage.show();
        } catch (IOException e) {
                e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        launch(args);
    }
}

Nothing fancy there. Here's TabScreenController.java:

package tabsAndListeners;

import javafx.event.Event;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.scene.control.Tab;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;

public class TabScreenController {

    @FXML   AnchorPane  anchorPaneRoot;
    @FXML   Tab         tabA, tabB, tabC;

    Stage stage;
    int counter = 0;

    public void start(Stage stage){
        this.stage = stage;

        tabB.setOnSelectionChanged(new EventHandler<Event>() {
            @Override
                public void handle(Event t) {
                    // refreshTabBData();
                    System.out.println("tabB.setOnSelectionChanged() :: counter is now: "+counter);
                    counter++;
            }
        });
    }
}

And finally the FXML, "TabScreen.fxml":

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Tab?>
<?import javafx.scene.control.TabPane?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane fx:id="anchorPaneRoot" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.111" xmlns:fx="http://javafx.com/fxml/1" fx:controller="tabsAndListeners.TabScreenController">
   <children>
      <TabPane layoutX="10.0" layoutY="70.0" prefHeight="324.0" prefWidth="576.0" tabClosingPolicy="UNAVAILABLE">
        <tabs>
          <Tab fx:id="tabA" text="Tab A">
            <content>
              <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
            </content>
          </Tab>
          <Tab fx:id="tabB" text="Tab B">
            <content>
              <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
            </content>
          </Tab>
            <Tab fx:id="tabC" text="Tab C">
              <content>
                <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
              </content>
            </Tab>
        </tabs>
      </TabPane>
   </children>
</AnchorPane>

So when I run this, and then click TabA, TabB, TabC, TabC, TabB, TabA, TabC. Here's the output:

tabB.setOnSelectionChanged() :: counter is now: 0     // I clicked on TabB
tabB.setOnSelectionChanged() :: counter is now: 1     // I clicked on TabC
tabB.setOnSelectionChanged() :: counter is now: 2     // I clicked on TabB
tabB.setOnSelectionChanged() :: counter is now: 3     // I clicked on TabA

You see the problem. The refreshTabBData() code is called when I click TabB... which I want... but then it is called again when I click another tab, any other tab. I don't want that second event. I want the refresh() code to be called only when TabB is clicked, and that's it.

I've been researching EventHandlers all afternoon, but everything I find it either supergeneralized or superspecific and not relevent to my situation. Can anyone offer any advice on where I am going wrong?

Many thanks!

Upvotes: 1

Views: 1583

Answers (1)

James_D
James_D

Reputation: 209330

Just add an if statement in the handler:

tabB.setOnSelectionChanged(new EventHandler<Event>() {
    @Override
    public void handle(Event t) {
        if (tabB.isSelected()) {
            // refreshTabBData();
            System.out.println("tabB.setOnSelectionChanged() :: counter is now: "+counter);
            counter++;
        }
    }
});

Upvotes: 4

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