如何在FXML中为JavaFX DatePicker设置默认值？

Question

在FXML级别上初始化DatePicker的默认值是否可行？

<children>
            <DatePicker fx:id="datePicker" value="2015-07-20"/>
            <Label fx:id="messageLabel" textAlignment="JUSTIFY" />
</children>

很明显会抛出异常，有可能调用LocalDate的构造函数吗？

例如：

        <DatePicker fx:id="datePicker" value="LocalDate.of(2015,07,20)"/>

- Palcente

---

我意识到我可以在控制器的初始化函数中填充它，但我想知道是否可以在FXML级别上填充它。 - Palcente

Answer 1

您可以通过控制器将日期的默认值设置为今天。以下代码对我有效：

您可以通过控制器将日期的默认值设置为今天。以下代码对我有效：

datePicker.setValue(LocalDate.now());

- venki

Answer 2

为了能够从FXML文件中实例化java.time.LocalDate，您需要创建并注册该类的自定义构建器。

1. Create a builder for LocalDate. A builder must implement javafx.util.Builder and its build method. Here is an example of a builder that takes three parameters (year, month, dayOfMonth):

   package util;
   import java.time.LocalDate;
   import javafx.util.Builder;
   
   public class LocalDateBuilder implements Builder<LocalDate>{
   
       private int year;
       private int month;
       private int dayOfMonth;
   
       @Override
       public LocalDate build() {
           return LocalDate.of(year, month, dayOfMonth);
       }
   
       public int getYear() {
           return year;
       }
       public void setYear(int year) {
           this.year = year;
       }
       public int getMonth() {
           return month;
       }
       public void setMonth(int month) {
           this.month = month;
       }
       public int getDayOfMonth() {
           return dayOfMonth;
       }
       public void setDayOfMonth(int dayOfMonth) {
           this.dayOfMonth = dayOfMonth;
       }
   }
   

2. Create a FactoryBuilder wrapper that decorates the default FactoryBuilder so that it will return your builder when a LocalDate builder is needed. Here is a sample FactoryBuilderWrapper class.

   package util;
   import java.time.LocalDate;
   import javafx.util.Builder;
   import javafx.util.BuilderFactory;
   
   public class BuilderFactoryWrapper implements BuilderFactory {
   
       private BuilderFactory builderFactory;
       public BuilderFactoryWrapper(BuilderFactory builderFactory) {
           this.builderFactory = builderFactory;
       }
   
       @Override
       public Builder<?> getBuilder(Class<?> klass) {
           if (klass == LocalDate.class) {
               // return our builder
               return new LocalDateBuilder();
           } else {
               // return the default builder
               return builderFactory.getBuilder(klass);
           }
       }
   }
   

3. In your application's start method, obtain the default FactoryBuilder, wrap it with your wrapper and reassign it to the FXMLLoader:

   @Override
   public void start(Stage stage) throws Exception {
       FXMLLoader loader = new FXMLLoader();
       loader.setLocation(getClass().getResource("myUI.fxml"));
       BuilderFactory builderFactory = loader.getBuilderFactory();
       // wrap the default BuilderFactory
       loader.setBuilderFactory(new    
               BuilderFactoryWrapper(builderFactory));
   
       Parent root = loader.load();
       Scene scene = new Scene(root);
       stage.setScene(scene);
       stage.show();
   }
   

以下是创建一个具有类型为LocalDate的birthDate属性的Person的FXML代码：（您需要导入java.time.LocalDate，但不需要导入构建器本身）

<?import model.Person?>
<?import java.time.LocalDate?>
...
<Person firstName="Jane" lastName="Citizen">
    <birthDate>
        <LocalDate year="1980" month="12" dayOfMonth="19"/>
    </birthDate>
</Person>

- Budi Kurniawan

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嘿，谢谢您详尽的回答！虽然有点晚，但仍然非常有价值！+1 - Palcente

你的控制器在哪里？你在哪里定义了<birthDate>？ - 7twenty7

Answer 3

我确定你无法在FXML级别上填充DatePicker，因为你不能在FXML级别上实例化LocalDate对象，原因如下：

1. LocalDate没有默认构造函数
2. LocalDate没有静态的valueOf(String)方法
3. javafx.fxml.JavaFXBuilderFactory#getBuilder(LocalDate.class)返回null，表示没有针对LocalDate的生成器

- Marcus Bleil

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非常好的答案，谢谢。我最终在控制器中进行了设置。 - Palcente

Answer 4

这个方法返回当前日期：

// Date Now  ### "To Date Picker"
    public static final LocalDate NOW_LOCAL_DATE (){
        String date = new SimpleDateFormat("dd-MM-  yyyy").format(Calendar.getInstance().getTime());
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy");
        LocalDate localDate = LocalDate.parse(date , formatter);
        return localDate;
    }

然后在initialize方法内调用它：

datePicker.setValue(NOW_LOCAL_DATE());

- Hussein Ahmed

Answer 5

如果您正在实现Initializable，则可以在控制器中执行以下操作：

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy", this.locale);
birthDate.setValue(LocalDate.parse(formatter.format(LocalDate.now())));

- Terry Carter