如何从比较 2 个 DatePickers 中获取 BooleanBinding？

Question

我在 GUI 上有两个 DatePickers 和一个 Button。每当第一个 datePicker 的日期在第二个 datePicker 的日期之前 NOT 时，我都需要禁用该按钮。即before 在以下 sn-p 中是 false：

LocalDate date1 = dpFromDate.getValue();
LocalDate date2 = dpToDate.getValue();
boolean before = date1.isBefore(date2);
button.setDisable(!before);

使用绑定 API。

BooleanBinding bb = ???;
button.disableProperty().bind(bb);

---

这是我的工作解决方案，但我相信有更好的 API 来处理这种情况：

BooleanBinding bb = Bindings.selectInteger(dpFromDate.valueProperty(), "year")
         .greaterThanOrEqualTo(Bindings.selectInteger(dpToDate.valueProperty(), "year"));

bb = bb.or(
       Bindings.selectInteger(dpFromDate.valueProperty(), "year")
       .isEqualTo(Bindings.selectInteger(dpToDate.valueProperty(), "year"))
  .and(Bindings.selectInteger(dpFromDate.valueProperty(), "monthValue")
       .greaterThanOrEqualTo(Bindings.selectInteger(dpToDate.valueProperty(), "monthValue")))
   );

bb = bb.or(
       Bindings.selectInteger(dpFromDate.valueProperty(), "year")
       .isEqualTo(Bindings.selectInteger(dpToDate.valueProperty(), "year"))
  .and(Bindings.selectInteger(dpFromDate.valueProperty(), "monthValue")
      .isEqualTo(Bindings.selectInteger(dpToDate.valueProperty(), "monthValue")))
  .and(Bindings.selectInteger(dpFromDate.valueProperty(), "dayOfMonth")
      .greaterThanOrEqualTo(Bindings.selectInteger(dpToDate.valueProperty(), "dayOfMonth")))
   );

Answer 1

只需根据比较两个日期的DatePicker 值创建一个BooleanBinding。这样您就不必自己编写功能，更重要的是 - 您无需创建如此复杂的绑定：

BooleanBinding bb = Bindings.createBooleanBinding(() -> {
    LocalDate from = dpFromDate.getValue();
    LocalDate to = dpToDate.getValue();

    // disable, if one selection is missing or from is not smaller than to
    return (from == null || to == null || (from.compareTo(to) >= 0));
}, dpFromDate.valueProperty(), dpToDate.valueProperty());

button.disableProperty().bind(bb);