显示时间戳的答案
具体来说，关于时间戳的问题，请看下面的示例代码：
private Label createTimestampLabel() {
LocalDateTime now = LocalDateTime.now();
String formattedTimestamp = now.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME);
return new Label(formattedTimestamp);
}
它使用Oracle Date Time tutorial 中解释的java.time API 从 LocalDateTime 获取当前时间，并使用标准格式将其格式化为字符串。
它将格式化的时间戳字符串设置为标签节点的文本。
现在返回的元素是一个节点，它可以放置在场景图中而不会产生您在原始示例中看到的编译错误。
在您的问题中，使用java.time API 优于java.sql.Timestamp 和java.util.Date 代码。你没有使用 SQL，所以你不应该使用java.sql.Timestamp。 java.time 类还对其他 Java 包（如 java.util）中使用的过时日期和时间函数进行了许多改进。
通过重写示例代码在上下文中回答
所提供的示例应用程序有很多错误或惹恼我的地方。
所以我重新编写了它以更接近我通常编写此类应用程序的方式。
在选择如何实施重写时可能有一百个不同的小决定，在这里解释它们太冗长了。
希望您可以将重新编写的代码与您的原始代码进行比较，注意其中的一些差异，并从中学习一些东西。
GraphicControlApp.java
package org.example.javafx.demo.graphiccontrol;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class GraphicControlApp extends Application {
public void start(Stage stage) {
GraphicController graphicController = new GraphicController();
Scene scene = new Scene(graphicController.getUI());
stage.setScene(scene);
stage.setTitle("JavaFX Interactive Graphic Control Demonstration");
stage.show();
}
}
GraphicController.java
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.input.KeyEvent;
import javafx.scene.layout.*;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Rectangle;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
/**
* UI creator and controller for application logic.
*
* Normally, most UI elements would be defined externally in FXML,
* however, for a simple application, we define the UI via private functions in this class.
*/
public class GraphicController {
// amount to move the circle across the surface on interaction.
private static final double MOVEMENT_DELTA = 20.0;
// default spacing between UI elements.
private static final double SPACING = 10;
// normally the styles would be configured in an external css stylesheet,
// but we place the background definitions here for a simple application.
private static final Color SURFACE_COLOR = Color.rgb(190, 220, 190);
private static final Background surfaceBackground = createBackground(SURFACE_COLOR);
private static final Color APP_BACKGROUND_COLOR = Color.rgb(150, 200, 150);
private static final Background appBackground = createBackground(APP_BACKGROUND_COLOR);
private Button up;
private Button down;
/**
* @return the complete layout for the application with event handlers attached for logic control.
*/
public Pane getUI() {
Circle circle = new Circle(75, 100, 20);
Pane surface = createSurface(circle);
HBox controls = createControls(circle);
Label timestampLabel = createTimestampLabel();
Pane layout = createLayout(surface, controls, timestampLabel);
attachKeyboardHandlers(layout);
return layout;
}
/**
* Create a label formatted with the current time in ISO standard format (e.g. '2011-12-03T10:15:30')
*
* @return label with the current timestamp.
*/
private Label createTimestampLabel() {
LocalDateTime now = LocalDateTime.now();
String formattedTimestamp = now.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME);
return new Label(formattedTimestamp);
}
/**
* Create a surface on which a circle can move.
*
* @param circle the circle which can move on the surface.
* @return the created surface.
*/
private Pane createSurface(Circle circle) {
Pane surface = new Pane();
surface.setMinSize(100, 150);
surface.setBackground(surfaceBackground);
surface.getChildren().addAll(circle);
// we must define a clip on the surface to ensure that elements
// in the surface do not render outside the surface.
Rectangle clip = new Rectangle();
clip.widthProperty().bind(surface.widthProperty());
clip.heightProperty().bind(surface.heightProperty());
surface.setClip(clip);
return surface;
}
private VBox createLayout(Pane surface, HBox controls, Label timestampLabel) {
VBox layout = new VBox(SPACING, controls, surface, timestampLabel);
layout.setBackground(appBackground);
layout.setPadding(new Insets(SPACING));
VBox.setVgrow(surface, Priority.ALWAYS);
return layout;
}
/**
* Create controls which can control the movement of a circle.
*
* @param circle the circle which can be controlled
* @return the created controls with handlers attached for circle movement control.
*/
private HBox createControls(Circle circle) {
up = new Button("Up");
up.setOnAction(e -> moveVertically(circle, -MOVEMENT_DELTA));
down = new Button("Down");
down.setOnAction(e -> moveVertically(circle, MOVEMENT_DELTA));
return new HBox(SPACING, up, down);
}
private void moveVertically(Circle circle, double delta) {
double y = circle.getCenterY();
// we only restrict movement in the up direction,
// but allow unlimited movement in the down direction
// (even if that movement would mean that the circle would extend totally
// outside the current visible boundary of the surface).
if ((y + delta) < 0) {
return;
}
circle.setCenterY(y + delta);
}
/**
* Adds standard keyboard handling logic to the UI.
*
* Handlers are attached to the relevant scene whenever
* the scene containing the UI changes.
*
* @param layout the UI which will respond to keyboard input.
*/
private void attachKeyboardHandlers(Pane layout) {
EventHandler<KeyEvent> keyEventHandler = event -> {
switch (event.getCode()) {
case UP -> { up.requestFocus(); up.fire(); }
case DOWN -> { down.requestFocus(); down.fire(); }
}
};
layout.sceneProperty().addListener((observable, oldScene, newScene) -> {
if (oldScene != null) {
oldScene.removeEventFilter(
KeyEvent.KEY_PRESSED,
keyEventHandler
);
}
if (newScene != null) {
newScene.addEventFilter(
KeyEvent.KEY_PRESSED,
keyEventHandler
);
}
});
}
private static Background createBackground(Color surfaceColor) {
return new Background(new BackgroundFill(surfaceColor, null, null));
}
}