Java動態添加項目到列表視圖

Question

嘿傢伙我有這個小問題。我是Java的新手，我只想弄清楚「如何在我的代碼下面的列表視圖的末尾添加另一個項目」。這應該在程序運行時動態發生。我只想單擊列表視圖底部的適當空間，然後添加一個項目。有人可以幫助我解決這個問題。謝謝！

注意：運行應用程序，所有內容都會顯示在那裏。我只是想爲這些按鈕添加功能。當我點擊「添加」按鈕時，我應該可以添加更多項目。

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; 
    } 
} 

Answer 1

首先，您需要將ListView放置在可訪問的位置，以便稍後再次找到引用。因此，不要將其聲明爲局部變量，而應將其聲明爲字段。

然後，添加項目，你只需要做：

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