具体内容如下

首先进行一个微调：让表盘根据窗口大小自动调整大小：

在 ShowClock.start() 中，添加对面板长宽的监听。

pane.widthProperty().addListener(ov -> clock.setW(pane.getWidth()));
pane.heightProperty().addListener(ov -> clock.setH(pane.getHeight()));

添加对时间和钟表大小的更改方法

在 ClockPane 类中添加：

/** Construct a clock with specified hour, minute, and second */
 public ClockPane(int hour, int minute, int second) {
  this.hour = hour;
  this.minute = minute;
  this.second = second;
  paintClock();
 }

 /** Set a new hour */
 public void setHour(int hour) {
  this.hour = hour;
  paintClock();
 }

 /** Set a new minute */
 public void setMinute(int minute) {
  this.minute = minute;
  paintClock();
 }

 /** Set a new second */
 public void setSecond(int second) {
  this.second = second;
  paintClock();
 }

 /** Return clock pane's width */
 public double getW() {
  return w;
 }

 /** Set clock pane's width */
 public void setW(double w) {
  this.w = w;
  paintClock();
 }

 /** Return clock pane's height */
 public double getH() {
  return h;
 }

 /** Set clock pane's height */
 public void setH(double h) {
  this.h = h;
  paintClock();
 }

用 Timeline 实现动态钟表

在 ShowClock 类中添加：

//设置事件处理对象
EventHandler eventHandler = e -> {
   clock.setCurrentTime();
  };
//每秒结束后触发eventHandler
Timeline animation = new Timeline(
    new KeyFrame(Duration.millis(1000), eventHandler));
  animation.setCycleCount(Timeline.INDEFINITE); //无限循环
  animation.play(); //开始动画

就可以让时钟动起来了。

完整代码

ShowClock.java

package primier;

import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.scene.layout.*;
import javafx.scene.control.*;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.util.Duration;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;

public class ShowClock extends Application {
 @Override //Override the start method in the Application class
 public void start(Stage primaryStage) {
  ClockPane clock = new ClockPane();

  //设置事件处理对象
  EventHandler eventHandler = e -> {
   clock.setCurrentTime();
  };
  //每秒结束后触发eventHandler
  Timeline animation = new Timeline(
    new KeyFrame(Duration.millis(1000), eventHandler));
  animation.setCycleCount(Timeline.INDEFINITE); //无限循环
  animation.play(); //开始动画

  BorderPane pane = new BorderPane();
  pane.setCenter(clock);
  Scene scene = new Scene(pane, 250,250);
  primaryStage.setTitle("Display Clock");
  primaryStage.setScene(scene);
  primaryStage.show();

  pane.widthProperty().addListener(ov ->
    clock.setW(pane.getWidth()));
  pane.heightProperty().addListener(ov ->
    clock.setH(pane.getHeight()));
 }

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

ClockPane.java

package primier;

import java.util.Calendar;
import java.util.GregorianCalendar;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Line;
import javafx.scene.text.Text;

public class ClockPane extends Pane {
 private int hour;
 private int minute;
 private int second;

 // Clock pane's width and height
 private double w = 250, h = 250;

 /** Construct a default clock with the current time*/
 public ClockPane() {
  setCurrentTime();
 }

 /** Construct a clock with specified hour, minute, and second */
 public ClockPane(int hour, int minute, int second) {
  this.hour = hour;
  this.minute = minute;
  this.second = second;
  paintClock();
 }

 /** Return hour */
 public int getHour() {
  return hour;
 }

 /** Set a new hour */
 public void setHour(int hour) {
  this.hour = hour;
  paintClock();
 }

 /** Return minute */
 public int getMinute() {
  return minute;
 }

 /** Set a new minute */
 public void setMinute(int minute) {
  this.minute = minute;
  paintClock();
 }

 /** Return second */
 public int getSecond() {
  return second;
 }

 /** Set a new second */
 public void setSecond(int second) {
  this.second = second;
  paintClock();
 }

 /** Return clock pane's width */
 public double getW() {
  return w;
 }

 /** Set clock pane's width */
 public void setW(double w) {
  this.w = w;
  paintClock();
 }

 /** Return clock pane's height */
 public double getH() {
  return h;
 }

 /** Set clock pane's height */
 public void setH(double h) {
  this.h = h;
  paintClock();
 }

 /** Set the current time for the clock */
 public void setCurrentTime() {
  //Construct a calendar for the current date and time
  Calendar calendar = new GregorianCalendar();
  //Set current hour, minute and second
  this.hour = calendar.get(Calendar.HOUR_OF_DAY);
  this.minute = calendar.get(Calendar.MINUTE);
  this.second = calendar.get(Calendar.SECOND);
  paintClock();
 }

 /** Paint the clock */
 protected void paintClock() {
  // Initialize clock parameters
  double clockRadius = Math.min(w,h)*0.8*0.5;
  double centerX = w/2;
  double centerY = h/2;

  // Draw circle
  Circle circle = new Circle(centerX, centerY, clockRadius);
  circle.setFill(Color.WHITE);
  circle.setStroke(Color.BLACK);
  Text t1 = new Text(centerX-5, centerY-clockRadius+12,"12");
  Text t2 = new Text(centerX-clockRadius+3, centerY +5, "9");
  Text t3 = new Text(centerX+clockRadius-10, centerY+3, "3");
  Text t4 = new Text(centerX-3, centerY+clockRadius-3,"6");

  // Draw second hand
  double sLength = clockRadius * 0.8;
  double secondX = centerX + sLength * Math.sin(second * (2 * Math.PI / 60));
  double secondY = centerY - sLength * Math.cos(second * (2 * Math.PI / 60));
  Line sLine = new Line(centerX, centerY, secondX, secondY);
  sLine.setStroke(Color.GRAY);

  // Draw minute hand
  double mLength = clockRadius * 0.65;
  double minuteX = centerX + mLength * Math.sin(minute * (2 * Math.PI / 60));
  double minuteY = centerY - mLength * Math.cos(minute * (2 * Math.PI / 60));
  Line mLine = new Line(centerX, centerY, minuteX, minuteY);
  mLine.setStroke(Color.BLUE);

  // Draw hour hand
  double hLength = clockRadius * 0.5;
  double hourX = centerX + hLength *
    Math.sin((hour % 12 + minute / 60.0) * (2 * Math.PI / 12));
  double hourY = centerY - hLength *
    Math.cos((hour % 12 + minute / 60.0) * (2 * Math.PI / 12));
  Line hLine = new Line(centerX, centerY, hourX, hourY);
  sLine.setStroke(Color.GREEN);

  getChildren().clear();
  getChildren().addAll(circle, t1, t2, t3, t4, sLine, mLine, hLine);
 }
}