在JavaFX中，如何以編程方式將Scrollpane滾動到底部？

Question

我一直在為我和一些朋友開發一個小型聊天客戶端，自學Java和JFX 8。 不幸的是，由於某種原因，我無法以編程方式滾動到聊天消息所在的ScrollPane的底部。

我有一個方法，我簡單地調用scrollToBottom（）執行以下代碼：

public void scrollToBottom() {
    Platform.runLater(() -> this.getChatView().vvalueProperty().setValue(1.0));
}

我有一個按鈕，使用此方法滾動到底部，但任何其他編程方法（甚至從其他方法觸發按鈕）不能正確更新滾動窗格的滾動條。 但是，當我在滾動窗口上調用getVvalue（）之后，它會返回正確的值，我試圖讓它滾動。 滾動窗格只是沒有滾動到所謂的值。

下面我有應用程序中唯一真正相關的類 - ChatBox類型只是VBox的擴展，它只使用擴展類型的Text。

public class MainScreenController {

    //Lists

    //Buttons
    private Button logoutButton;
    private Button btn1 = new Button("Test Button");
    private Button scrollButton = new Button("Scroll Button");

    //Numbers

    //Booleans
    private boolean isHosting;

    //Strings
    private String username = "";

    //Scene
    private Stage window;
    private GridPane layout = new GridPane();

    //Other Objects
    private TextArea chatField = new TextArea();
    private Label usernameLabel;
    private TextArea usersArea = new TextArea("Connected users: ");
    private VBox firstColumn = new VBox(10);
    private VBox secondColumn = new VBox(10);
    private ImageView mediaColumn = new ImageView();
    private Server server = new Server();
    private Client client = new Client();
    private TextField dlField = new TextField();
    private AudioHandler audioHandler = new AudioHandler();
    private ChatBox chatBox = new ChatBox();
    private ScrollPane chatView = new ScrollPane(this.chatBox);
    private HBox buttonBox = new HBox(10);

    private void initChatView() {

        this.getChatView().setMinSize(500, 500);
        this.getChatView().setPrefSize(500, 500);
        this.getChatView().setMaxSize(500, 500);
        this.getChatView().setStyle("-fx-focus-color: transparent; -fx-background-color: gainsboro");
        this.chatView.hbarPolicyProperty().set(ScrollBarPolicy.NEVER);
        this.chatView.vbarPolicyProperty().set(ScrollBarPolicy.AS_NEEDED);

        /*this.chatView.vvalueProperty().addListener(e -> {
              if(this.chatView.getVvalue() != 1) {
                  System.out.println("Pre: " + this.chatView.getVvalue());
                  this.chatView.vvalueProperty().set(1);
                  System.out.println("Post: " + this.chatView.getVvalue());
                }
        });*/

        this.scrollButton.setOnAction(e -> {
            scrollToBottom();
        });

    }

    private void initSecondColumn() {

        this.secondColumn.setStyle("-fx-background-color: gainsboro");
        this.secondColumn.setPrefSize(525, 550);
        this.secondColumn.setMinSize(450, 550);
        this.secondColumn.setMaxSize(525, 550);

        Button dlButton = new Button("Download link:");
        dlButton.setStyle("-fx-focus-color: transparent");
        dlButton.setOnAction(e -> {
            if (!this.dlField.getText().equals(null) || !this.dlField.getText().equals(null)) {
                try {
                    FileHandler.downloadFile(this.window, this.dlField.getText());
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
                this.dlField.clear();
            }
        });
        this.dlField.setPrefSize(450, 20);
        this.dlField.setMinSize(450, 20);
        this.dlField.setMaxSize(450, 20);

        this.mediaColumn.setFitHeight(475);
        this.mediaColumn.setPreserveRatio(true);
        this.mediaColumn.setStyle("-fx-border-color: red");
        this.mediaColumn.prefWidth(450);
        this.mediaColumn.prefHeight(475);
        this.mediaColumn.minWidth(450);
        this.mediaColumn.minHeight(475);
        this.mediaColumn.maxWidth(450);
        this.mediaColumn.maxHeight(475);
        this.secondColumn.getChildren().addAll(dlButton, this.dlField, mediaColumn);

    }

    private void initUsersArea() {

        this.usersArea.setPrefSize(500, 75);
        this.usersArea.setMinSize(500, 75);
        this.usersArea.setMaxSize(500, 75);
        this.usersArea.setEditable(false);
        this.usersArea.setStyle("-fx-focus-color: transparent; -fx-background-color: gainsboro");

    }

    public void scrollToBottom() {
        Platform.runLater(() -> this.getChatView().vvalueProperty().setValue(1.0));
        System.out.println(this.chatView.getVvalue());
    }

    public MainScreenController(GridPane layout, Stage window, Scene currentScene, Scene nextScene, WindowController windowController) throws URISyntaxException, IOException {

        new File(FileHandler.downloadsPath).mkdirs();
        this.layout = layout;
        this.window = window;
        this.initChatView();
        FileHandler.readLog(this.getChatBox());

    }

    private void initUsernameLabel() {

        this.usernameLabel = new Label();
        this.usernameLabel.setStyle("-fx-border-color: black; -fx-background-color: silver; -fx-focus-color: transparent");
        this.usernameLabel.setText(" Logged in as ");
        this.usernameLabel.setTextFill(Color.BLUE);

    }

    private void initLayout() {

        this.layout.setPadding(new Insets(10, 10, 10, 10));
        this.layout.setVgap(10);
        this.layout.setHgap(10);
        this.layout.getChildren().addAll(this.firstColumn, this.secondColumn);
        GridPane.setColumnIndex(this.firstColumn, 0);
        GridPane.setColumnIndex(this.secondColumn, 1);
        GridPane.setValignment(secondColumn, VPos.BOTTOM);
        this.buttonBox.getChildren().addAll(this.logoutButton, this.scrollButton);
        this.firstColumn.getChildren().addAll(this.buttonBox, this.usernameLabel, this.usersArea, this.chatView, this.getChatField());

    }

    public void initBtn1() {
        btn1.setStyle("-fx-focus-color: transparent");
        GridPane.setConstraints(btn1, 1, 0);
        GridPane.setValignment(btn1, VPos.BASELINE);
        this.layout.getChildren().add(btn1);
        btn1.addEventHandler(ActionEvent.ACTION, e -> {
            boolean b = false;
            if (!b) {
                audioHandler.startRecording();
                b = !b;
            } else if (b) {
                audioHandler.stopRecording();
                b = !b;
            }
        });
    }

    public void addMessage(String msg, String color) {

        FileHandler.writeToChatLog(msg);

        if (!msg.startsWith("*!") && !msg.startsWith("/")) {
            Platform.runLater(() -> {
                this.getChatBox().addText(new ChatText(msg, color));
                this.scrollButton.arm();
                this.scrollButton.fire();
            });
        }

    }

    private void initChatField() {

        this.getChatField().setPrefSize(500, 10);
        this.getChatField().setMaxHeight(10);
        this.getChatField().autosize();
        this.getChatField().setWrapText(true);
        this.getChatField().addEventHandler(KeyEvent.KEY_PRESSED, key -> {
            if (key.getCode() == KeyCode.ENTER) {
                key.consume();
                if (this.getChatField().getText().startsWith("/")) {
                    CommandParser.parse(this.getChatField().getText(), this);
                } else {
                    try {
                        this.getClient().getClientSendingData().writeUTF(this.getChatField().getText().trim());
                        this.getChatField().clear();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        });
        this.getChatField().setStyle("-fx-background-color: gainsboro");

    }

    private void initLogoutButton() {

        this.logoutButton = new Button();
        this.logoutButton.setText("Log out");
        this.logoutButton.setOnAction(e -> {
            try {
                this.client.getClientSendingData().writeUTF("*![System] " + SystemInfo.getDate() + ": " + this.client.getClientName() + " has disconnected.");
                System.out.println("Logging out.");
                window.close();
                new ChatClient().start(new Stage());
            } catch (Exception ex) {
                ex.printStackTrace();
            }
        });
        this.logoutButton.setStyle("-fx-focus-color: transparent");

    }

    public void initMainScreen() {

        initUsernameLabel();
        initLogoutButton();
        initChatField();
        initLayout();
        initUsersArea();
        initBtn1();
        initSecondColumn();

    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getUsername() {
        return this.username;
    }

    public Label getUsernameLabel() {
        return this.usernameLabel;
    }

    public GridPane getLayout() {
        return this.layout;
    }

    public void setIsHosting(boolean b) {
        this.isHosting = b;
    }

    public boolean getIsHosting() {
        return this.isHosting;
    }

    public Server getServer() {
        return this.server;
    }

    public void setServer(Server hostServer) {
        this.server = hostServer;
    }

    public Client getClient() {
        return this.client;
    }

    public void setClient(Client client) {
        this.client = client;
    }

    public ScrollPane getChatView() {
        return chatView;
    }

    public void setChatView(ScrollPane chatView) {
        this.chatView = chatView;
    }

    public TextArea getChatField() {
        return chatField;
    }

    public void setChatField(TextArea chatField) {
        this.chatField = chatField;
    }

    public TextArea getUsersArea() {
        return this.usersArea;
    }

    public ChatBox getChatBox() {
        return chatBox;
    }

    public void setChatBox(ChatBox chatBox) {
        this.chatBox = chatBox;
    }

}

如果您有任何其他一般性建議（我剛剛學習Java），歡迎提供所有提示。 ：） 謝謝！

Answer 1

我將TextArea中的文本滾動到底部的方法是，將文本中的插入符號設置為文本的末尾，如：

textArea.positionCaret(textArea.getText().length());

實際上，為了確保TextArea中的文本不向左水平滾動（例如，當TextArea中的最后一行非常長時），我將插入符號設置在文本中最后一個“\\ n”后面，像這樣：

String content = textArea.getText();
int indexOfLastLineFeed = content.lastIndexOf("\n");
if (indexOfLastLineFeed == -1)
    textArea.positionCaret(content.length());
else
    textArea.positionCaret(Math.min(indexOfLastLineFeed + 1, content.length()));

Answer 2

那個錯誤也發生在我身上，同時將ScrollPane與MasonryPane（來自JFoenix）混淆。 我找到的解決方案是調用scrollpane的layout（）方法及其內容。 層次結構：ScrollPane - > MasonryPane`

masonryPane.getChildren().addListener((ListChangeListener<Node>) c -> {
            masonryPane.layout();
            scrollPane.layout();
            scrollPane.setVvalue(1.0f);
        });

Answer 3

我發現問題是由多線程引起的。 對於任何感興趣的人，嘗試在執行scrollToBottom（）調用的線程上添加一個非常小的Thread.sleep（）; 我用10毫秒作為最低似乎工作。 感謝任何試圖提供幫助的人。