Java dynamically add items to a listview

Question

Hey guys I have this small problem. I'm a newbie to Java and I just want to figure out "how to add another item at the end of the list view below in my code". This should happen dynamically while the program is running. I just wanna click that appropriate space at the bottom of the listview and just add an item. Could someone please help me on this concern. thanks!

Note: Run the application and everything will appear there. I just want to add functionalities to these buttons. When I click "Add" button, i should be able to add more items.

package layoutsizingaligning;

import java.util.Scanner;
import javafx.application.Application;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.geometry.Orientation;
import javafx.scene.control.Control;
import javafx.scene.Scene;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ListView;
import javafx.scene.control.PasswordField;
import javafx.scene.control.Tab;
import javafx.scene.control.TabPane;
import javafx.scene.control.TextField;
import javafx.scene.layout.*;
import javafx.stage.Stage;

/**
 * Sample application that shows how the sized of controls can be managed.
 * Sample is for demonstration purposes only, most controls are inactive.
 */
public class LayoutSizingAligning extends Application {

    // Define buttons here for access by multiple methods
    private Button btnApply = new Button("Apply");
    private Button btnContinue = new Button("Continue");
    private Button btnExit = new Button("Exit");

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Application.launch(LayoutSizingAligning.class, args);

    }

    //@Override
    public void start(Stage primaryStage) {

        // Make Exit button bigger by using larger font for label
        //btnExit.setStyle("-fx-font-size: 12pt;");

        // Use tab pane with one tab for sizing UI and one tab for alignment UI
        TabPane tabs = new TabPane();
        Tab tabSize = new Tab();
        tabSize.setText("Sizing");
        tabSize.setContent(sizingSample());

        Tab tabAlign = new Tab();
        tabAlign.setText("Alignment");
        tabAlign.setContent(alignmentSample());

        tabs.getTabs().addAll(tabSize, tabAlign);

        Scene scene = new Scene(tabs, 300, 400); // Manage scene size
        primaryStage.setTitle("Sizing and Aligning");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

/*
 * Creates the UI for the sizing sample, which demonstrates ways to manage
 * the size of controls when you don't want the default sizes.
 */
    private Pane sizingSample() {

        BorderPane border = new BorderPane();
        border.setPadding(new Insets(20, 0, 20, 20));

        ListView<String> lvList = new ListView<String>(); 
        ObservableList<String> items = FXCollections.observableArrayList (
                 "Hot dog", "Hamburger", "French fries", 
                 "Carrot sticks", "Chicken salad");
//        Scanner scan = new Scanner(System.in);
//        String s = scan.next();
//        items.add(s);
        lvList.setItems(items);
        lvList.setMaxHeight(Control.USE_PREF_SIZE);
        lvList.setPrefWidth(150.0);

        border.setLeft(lvList);    
        border.setRight(createButtonColumn());  
        border.setBottom(createButtonRow());  // Uses a tile pane for sizing
//        border.setBottom(createButtonBox());  // Uses an HBox, no sizing 

        return border;
    }

/*
 * Creates the UI for the alignment sample, which demonstrates ways to manage
 * the alignment of controls when you don't want the default alignment.
 */
    private Pane alignmentSample() {

        GridPane grid = new GridPane();
        grid.setAlignment(Pos.CENTER);  // Override default
        grid.setHgap(10);
        grid.setVgap(12);

        // Use column constraints to set properties for columns in the grid
        ColumnConstraints column1 = new ColumnConstraints();
        column1.setHalignment(HPos.RIGHT);  // Override default
        grid.getColumnConstraints().add(column1); 

        ColumnConstraints column2 = new ColumnConstraints();
        column2.setHalignment(HPos.LEFT);  // Override default
        grid.getColumnConstraints().add(column2); 

        HBox hbButtons = new HBox();
        hbButtons.setSpacing(10.0);
        hbButtons.setAlignment(Pos.CENTER);  // Aligns HBox and controls in HBox


        Button btnSubmit = new Button("Submit");
        Button btnClear = new Button("Clear");
        Button btnExit2 = new Button("Exit");
        //btnSubmit.setStyle("-fx-font-size: 15pt;");

        Label lblName = new Label("User name:");
        TextField tfName = new TextField();
        Label lblPwd = new Label("Password:");
        PasswordField pfPwd = new PasswordField();

        hbButtons.getChildren().addAll(btnSubmit, btnClear, btnExit2);
        grid.add(lblName, 0, 0);
        grid.add(tfName, 1, 0);
        grid.add(lblPwd, 0, 1);
        grid.add(pfPwd, 1, 1);
        grid.add(hbButtons, 0, 2, 2, 1);

        /* Uncomment the following statements to bottom-align the buttons */        
//        hbButtons.setAlignment(Pos.BOTTOM_CENTER);
//        GridPane innergrid = new GridPane();
//        innergrid.setAlignment(Pos.CENTER);
//        innergrid.add(hbButtons, 0, 0);
//        grid.add(innergrid, 0, 2, 2, 1);

        return grid;
    }

/*
 * Creates a column of buttons and makes them all the same width as the
 * largest button.
 */
    private VBox createButtonColumn() { 

        Button btnAdd = new Button("Add");
        Button btnDelete = new Button("Delete");
        Button btnMoveUp = new Button("Move Up");
        Button btnMoveDown = new Button("Move Down");

        // Comment out the following statements to see the default button sizes
        btnAdd.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
        btnDelete.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
        btnMoveUp.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
        btnMoveDown.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
        btnMoveDown.setMinWidth(Control.USE_PREF_SIZE);

        btnAdd.setOnAction(new EventHandler<ActionEvent>() {

            //@Override
            public void handle(ActionEvent event) {
                Scanner scan = new Scanner(System.in);
                String s = scan.next();

            }
        });

        VBox vbButtons = new VBox();
        vbButtons.setSpacing(10);
        vbButtons.setPadding(new Insets(0, 20, 10, 20)); 

        vbButtons.getChildren().addAll(
                btnAdd, btnDelete, btnMoveUp, btnMoveDown);

        return vbButtons;
    }

/*
 * Creates a row of buttons and makes them all the same size.
 */
    private TilePane createButtonRow() {

        // Let buttons grow, otherwise they will be different sizes based
        // on the length of the label
        btnApply.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
        btnContinue.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
        btnExit.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
        btnExit.setOnAction(new EventHandler<ActionEvent>() {

            //@Override
            public void handle(ActionEvent event) {
                System.exit(0);
            }
        });
        TilePane tileButtons = new TilePane(Orientation.HORIZONTAL);
        tileButtons.setPadding(new Insets(20, 10, 20, 0));
        tileButtons.setHgap(10.0);
        tileButtons.setVgap(8.0); // In case window is reduced and buttons 
                                  // require another row
        tileButtons.getChildren().addAll(btnApply, btnContinue, btnExit);

        return tileButtons;
    }

/*
 * Creates a row of buttons with the default sizes.
 */
    private HBox createButtonBox() { 

        HBox hbButtons = new HBox();
        hbButtons.setSpacing(10);
        hbButtons.setPadding(new Insets(20, 10, 20, 0)); 
        hbButtons.getChildren().addAll(btnApply, btnContinue, btnExit);

        return hbButtons;
    }
}

Solution

First of all, you need to put your ListView in an accessible place, so that you can find the reference again later. Thus, do not declare it as a local variable, but as a field.

Then, to add an item, you simply do:

listview.getItems().add("some new element");

Comments

[wr93_]

Yeah I figured it out! Declaring the listview outside the method was the solution to some extent.

[mtj]

@Wagee_CDR If the answer is correct, accepting it would not hurt and motivate the community members to keep trying to be helpful.