首先你可以添加在Gender
一个新的枚举值表示未知性别:
public enum Gender { MALE, FEMALE, UNKNOWN }
。
然后你可以使用一个像ListChangeListener
:
this.people = FXCollections.observableArrayList(person -> new Observable[] {person.genderProperty()});
ListChangeListener<Person> listener = new ListChangeListener<Person>() {
private boolean checkCondition(ObservableList<Person> list, Person.Gender gender) {
int males = 0;
int females = 0;
for (Person person : list) {
switch (person.getGender()) {
case MALE: males++; break;
case FEMALE: females++; break;
default: break;
}
}
return ((males > 10 && gender == Person.Gender.MALE) ||
(females > 5 && gender == Person.Gender.FEMALE));
}
@Override
public void onChanged(Change<? extends Person> c) {
while (c.next()) {
if (c.wasAdded()) {
for (Person person : c.getAddedSubList()) {
if (checkCondition((ObservableList<Person>) c.getList(), person.getGender()))
c.getList().remove(person);
}
}
if (c.wasUpdated()) {
for (int update = c.getFrom(); update < c.getTo(); update++) {
Person person = c.getList().get(update);
if (checkCondition((ObservableList<Person>) c.getList(), person.getGender()))
person.setGender(Person.Gender.UNKNOWN);
}
}
}
}
};
people.addListener(listener);
唯一的问题与此解决方案,它并没有真正“恢复”的更新变化,但设置性别为新的未知值。
如果你想真正恢复更改,该解决方案可以是这样的:
this.people = FXCollections.observableArrayList();
ListChangeListener<Person> listener = new ListChangeListener<Person>() {
private boolean checkCondition(ObservableList<Person> list, Person.Gender gender) {
int males = 0;
int females = 0;
for (Person person : list) {
switch (person.getGender()) {
case MALE: males++; break;
case FEMALE: females++; break;
default: break;
}
}
return ((males > 10 && gender == Person.Gender.MALE) ||
(females > 5 && gender == Person.Gender.FEMALE));
}
@Override
public void onChanged(Change<? extends Person> c) {
while (c.next()) {
if (c.wasAdded()) {
for (Person person : c.getAddedSubList()) {
if (checkCondition((ObservableList<Person>) c.getList(), person.getGender()))
c.getList().remove(person);
else
person.genderProperty().addListener((obs, oldval, newval) -> {
if (checkCondition((ObservableList<Person>) c.getList(), newval))
person.setGender(oldval);
});
}
}
}
}
};
people.addListener(listener);
差异:提取已被删除,因为ListChangeListener
仅需添加元素的内部是覆盖。当添加一个新元素时,其genderProperty
上的侦听器已添加哪一个侦听性别更新,如果条件不满足,则生成器将恢复为原始状态。
您也可以通过不暴露列表实现相同的功能,但操作列表方法:addPersonAt
,removePersonAt
和updateGenderAt
。
我认为第二个选项对我来说很好。谢谢! – Jai