求助：实现JavaFX DatePicker今日日期点击按钮累加计数功能

Hey there! Let's figure out how to make your JavaFX DatePicker show an incrementing counter on today's date when you click that "selected" button. I'll walk you through the solution step by step, with code examples you can drop right into your project.

First, let's outline what we need to do:

• Track a counter that goes up by 1 every time the button is clicked
• Customize the DatePicker's date cells to display the counter only on today's date
• Refresh the DatePicker's display after each button click to show the updated counter

Here's a complete, working Controller class that handles all the logic. I've added comments to explain each part:

import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.DateCell;
import javafx.scene.control.DatePicker;
import javafx.util.Callback;
import java.time.LocalDate;

public class Controller {
    // Wire up the components from your FXML
    @FXML
    private DatePicker datePicker;
    @FXML
    private Button selected;

    // Counter to track button clicks
    private int clickCounter = 0;
    // Store today's date once to avoid recalculating it constantly
    private final LocalDate today = LocalDate.now();

    @FXML
    public void initialize() {
        // Set up the custom date cell factory when the controller loads
        setupCustomDateCells();
    }

    // Triggered when the "selected" button is clicked
    @FXML
    private void onSelectedButtonClick() {
        clickCounter++;
        // Refresh the DatePicker to update the cell display
        // Setting the value to itself forces a re-render of all cells
        datePicker.setValue(datePicker.getValue());
    }

    // Customize how each date cell in the DatePicker looks
    private void setupCustomDateCells() {
        Callback<DatePicker, DateCell> cellFactory = param -> new DateCell() {
            @Override
            public void updateItem(LocalDate item, boolean empty) {
                super.updateItem(item, empty);

                // Clear any existing text first
                setText(null);

                // Only render content if the cell isn't empty
                if (!empty && item != null) {
                    // Show the default day number for all dates except today
                    setText(String.valueOf(item.getDayOfMonth()));
                    
                    // Replace today's day number with the click counter
                    if (item.equals(today)) {
                        setText(String.valueOf(clickCounter));
                    }
                }
            }
        };
        datePicker.setDayCellFactory(cellFactory);
    }
}

Make sure your sample.fxml has the correct IDs and action binding for the components. Here's a minimal working example:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.DatePicker?>
<?import javafx.scene.layout.VBox?>

<VBox xmlns="http://javafx.com/javafx/17" xmlns:fx="http://javafx.com/fxml/1" fx:controller="Controller" spacing="10" padding="20">
    <DatePicker fx:id="datePicker"/>
    <Button fx:id="selected" text="selected" onAction="#onSelectedButtonClick"/>
</VBox>

• Counter Persistence: The clickCounter variable holds the number of clicks, and we increment it every time the button is pressed.
• Cell Factory: We override the DatePicker's default cell factory to control what each date cell displays. For today's date, we swap the day number with our counter.
• Forcing a Refresh: When we set datePicker.setValue(datePicker.getValue()), we're telling the DatePicker to re-render all its cells—this is how the updated counter shows up immediately after a click.
• Performance: Storing LocalDate.now() in a constant avoids recalculating today's date every time a cell updates, which keeps things efficient.

• If the counter doesn't show up: Double-check that your FXML's fx:id values match the @FXML variables in the Controller, and that the button's onAction is correctly linked to onSelectedButtonClick.
• If non-today dates lose their day numbers: Make sure you're calling setText(String.valueOf(item.getDayOfMonth())) for all non-today cells in the updateItem method.
• If the counter doesn't increment: Add a System.out.println(clickCounter); inside onSelectedButtonClick to confirm the method is actually being triggered when you click the button.

内容的提问来源于stack exchange，提问作者Joe Mau