JavaFX FilteredList,基于列表中项目的属性进行过滤

Question

我有一个案例,我需要ObservableList<Item>根据项目的某些属性过滤一个(即条件是内部的而不是外部的).我发现javafx已经FilteredList尝试过了.我可以设置谓词和过滤工作,直到确定过滤的属性值发生变化.设置谓词现在完成如下:

list.setPredicate(t -> !t.filteredProperty().get())

由于谓词返回boolean而不是BooleanProperty,因此对该属性的更改不会反映在列表中.

这有什么简单的解决方案吗？我可以尝试做一些解决方法,例如创建一个单独的列表并同步它,或者每次属性更改一个项目时重置谓词,希望重新触发过滤,但我首先想问一下,如果有人知道一个漂亮的解决方案作为那些变通办法当然不是.

Answer 1

使用提取器创建基础列表.这将使基础列表在filteredProperty()任何元素发生更改时触发更新事件.在FilteredList将观察这些事件,因此将相应地更新:

ObservableList<Item> baseList = FXCollections.observableArrayList(item -> 
    new Observable[] {item.filteredProperty()});
FilteredList<Item> list = new FilteredList<>(baseList, t -> ! t.filteredProperty().get());

快速演示:

import java.util.stream.IntStream;

import javafx.beans.Observable;
import javafx.beans.property.BooleanProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.collections.FXCollections;
import javafx.collections.ListChangeListener.Change;
import javafx.collections.ObservableList;
import javafx.collections.transformation.FilteredList;


public class DynamicFilteredListTest {

    public static void main(String[] args) {

        ObservableList<Item> baseList = FXCollections.observableArrayList(item -> 
                new Observable[] {item.filteredProperty()});

        FilteredList<Item> list = new FilteredList<>(baseList, t -> ! t.isFiltered());

        list.addListener((Change<? extends Item> c) -> {
            while (c.next()) {
                if (c.wasAdded()) {
                    System.out.println(c.getAddedSubList()+ " added to filtered list");
                }
                if (c.wasRemoved()) {
                    System.out.println(c.getRemoved()+ " removed from filtered list");
                }
            }
        });

        System.out.println("Adding ten items to base list:\n");

        IntStream.rangeClosed(1, 10).mapToObj(i -> new Item("Item "+i)).forEach(baseList::add);

        System.out.println("\nFiltered list now:\n"+list);

        System.out.println("\nSetting filtered flag for alternate items in base list:\n");

        IntStream.range(0, 5).map(i -> 2*i).mapToObj(baseList::get).forEach(i -> i.setFiltered(true));

        System.out.println("\nFiltered list now:\n"+list);
    }


    public static class Item {
        private final StringProperty name = new SimpleStringProperty() ;
        private final BooleanProperty filtered = new SimpleBooleanProperty() ;

        public Item(String name) {
            setName(name);
        }

        public final StringProperty nameProperty() {
            return this.name;
        }

        public final String getName() {
            return this.nameProperty().get();
        }

        public final void setName(final String name) {
            this.nameProperty().set(name);
        }

        public final BooleanProperty filteredProperty() {
            return this.filtered;
        }

        public final boolean isFiltered() {
            return this.filteredProperty().get();
        }

        public final void setFiltered(final boolean filtered) {
            this.filteredProperty().set(filtered);
        }

        @Override
        public String toString() {
            return getName();
        }
    }
}