JAVAFX - Label field not updating on action event handler

Question

I'm a newbie to JAVAFX. I have a login form in JavaFx application. It has a Label field defined in fxml file, whose text value is set after authentication with different messages. Please see code below.

CODE

if(userid>0){ 
    //the below setText call doesn't work and update the UI
    actiontarget.setText("Modems are initializing. It may take longer time... ");
    bootstrap =new Bootstrap();
    new Thread(){
        public void run(){
            bootstrap.run();
        }
    }.start();  
    while(!bootstrap.isSet()){
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        // the below call also doesn't work
        actiontarget.setText("Modems are getting initialized. Please wait for sometime..");
    }
    serialModemList=bootstrap.getSerialModemList();
    getPanelList(serialModemList);

}else{
    // this one method call works fine. not sure why?
    actiontarget.setText("Invalid Terminal and Password ");
}

The call actiontarget.setText(..) doesn't work when the user is valid. but, it works if the user enters invalid credentials. Please let me know what's wrong with the code.

FXML

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

<?import java.net.*?>
<?import javafx.geometry.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.text.*?>
<?import javafx.scene.image.*?>

<BorderPane maxHeight="-Infinity" maxWidth="-Infinity"
    minHeight="-Infinity" minWidth="-Infinity" prefHeight="469.0"
    prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.40" xmlns:fx="http://javafx.com/fxml/1">
    <center>

        <GridPane fx:id="gridpane" xmlns:fx="http://javafx.com/fxml"
            alignment="center" hgap="10" vgap="10">

            <Text text="Welcome" GridPane.columnIndex="0" GridPane.rowIndex="0"
                GridPane.columnSpan="2" />

            <Label text="Terminal" GridPane.columnIndex="0"
                GridPane.rowIndex="1">
                <font>
                    <Font size="15.0" />
                </font>
            </Label>

            <TextField fx:id="txtuser" GridPane.columnIndex="1"
                GridPane.rowIndex="1" />

            <Label text="Password" GridPane.columnIndex="0"
                GridPane.rowIndex="2">
                <font>
                    <Font size="15.0" />
                </font>
            </Label>
            <PasswordField fx:id="txtaun" GridPane.columnIndex="1"
                GridPane.rowIndex="2" />
            <HBox spacing="10" alignment="bottom_right"
                GridPane.columnIndex="1" GridPane.rowIndex="4">
                <Button fx:id="loginbtn" onAction="#handleLoginAction" text="LOGIN" />
            </HBox>
            <Label fx:id="message" GridPane.columnIndex="1"
                GridPane.rowIndex="6" />
            <Label fx:id="actiontarget" GridPane.columnIndex="1"
                GridPane.rowIndex="7" />
        </GridPane>
    </center>
    <top>
        <Label id="Header" minWidth="400.0" prefHeight="81.0" prefWidth="174.0"
            text="Sim Manager" BorderPane.alignment="CENTER">
            <font>
                <Font size="50.0" />
            </font>
        </Label>
    </top>
    <bottom>
        <Label prefHeight="69.0" prefWidth="126.0" text="Powered by CIAR"
            textFill="#20209e" BorderPane.alignment="bottom_right" />
    </bottom> 
</BorderPane>

Please let me know if any information is needed.

Answer 1

I believe your problem is in using Thread.sleep you are halting the UI thread, which makes it impossible for it to update the display.

Try using Task ( https://docs.oracle.com/javafx/2/threads/jfxpub-threads.htm ) and set the text in the onSucceeded and onFailed .