JavaFX中的多重布爾綁定

Question

我試圖將一個復選框綁定到多個復選框，如下所示：

private void bindPanelToPackages(CheckBox panel, CheckBox ...pkg){

    BooleanProperty panelBinding = null;
    BooleanBinding binder = null;

    for(CheckBox p: pkg){
        if(panelBinding == null){
            panelBinding = p.selectedProperty();
        }
        else{
            binder = panelBinding.and(p.selectedProperty());
        }
    }

    if(binder != null){
        panel.selectedProperty().bind(binder);
    }
    else if(panelBinding != null){
        panel.selectedProperty().bindBidirectional(panelBinding);
    }
}

我想要的是當'pkg'具有多個項目時允許雙向組綁定。 這樣，當我選擇包裝時，將自動選擇“面板”，或者如果我選擇“面板”，則將選擇/取消選擇所有“ pkg”。 我被困在：

panel.selectedProperty（）。bind（binder）;

並得到

“ JavaFX Application Thread” java.lang.RuntimeException：CheckBox.selected：不能設置綁定值。

因為我對“活頁夾”進行了單向綁定。 有什么辦法可以執行與此等效的操作嗎？：

panel.selectedProperty（）。bindBidirectional（binder）;

我似乎在文檔中找不到它，或者我不在正確的位置。 謝謝！

Answer 1

條件“選中所有復選框”只能表示為BooleanBinding ，而不能表示為BooleanProperty 。 基本上，問題在於沒有明確定義使該條件為false ：有許多方法可以做到這一點（即，取消選中所有復選框的任何非空子集）。 因此，您不能使用雙向綁定：您必須在兩個條件的每一個上使用偵聽器。

這是一個實現：

// must keep a reference to the Binding to prevent premature
// garbage collection:

BooleanBinding allSelected ;

private void bindPanelToPackages(CheckBox pane, CheckBox... packages) {

    // BooleanBinding that is true if and only if all check boxes in packages are selected:
    allSelected = Bindings.createBooleanBinding(() -> 
        // compute value of binding:
        Stream.of(packages).allMatch(CheckBox::isSelected), 
        // array of thing to observe to recompute binding - this gives the array
        // of all the check boxes' selectedProperty()s.
        Stream.of(packages).map(CheckBox::selectedProperty).toArray(Observable[]::new));

    // update pane's selected property if binding defined above changes
    allSelected.addListener((obs, wereAllSelected, areAllNowSelected) -> 
        pane.setSelected(areAllNowSelected));

    // use an action listener to listen for a direct action on pane, and update all checkboxes
    // in packages if this happens:
    pane.setOnAction(e -> 
        Stream.of(packages).forEach(box -> box.setSelected(pane.isSelected())));

}

和SSCCE：

import java.util.stream.IntStream;
import java.util.stream.Stream;

import javafx.application.Application;
import javafx.beans.Observable;
import javafx.beans.binding.Bindings;
import javafx.beans.binding.BooleanBinding;
import javafx.scene.Scene;
import javafx.scene.control.CheckBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class MultipleCheckBoxSelection extends Application {

    private BooleanBinding allSelected ;

    @Override
    public void start(Stage primaryStage) {
        CheckBox selectAll = new CheckBox("Select all");
        int numBoxes = 5 ;
        CheckBox[] boxes = IntStream
                .rangeClosed(1,  numBoxes)
                .mapToObj(i -> new CheckBox("Item "+i))
                .toArray(CheckBox[]::new);

        bindPanelToPackages(selectAll, boxes);


        VBox root = new VBox(10, selectAll);
        root.setStyle("-fx-padding: 15;");
        Stream.of(boxes).forEach(box -> box.setStyle("-fx-padding: 0 0 0 10;"));
        Stream.of(boxes).forEach(root.getChildren()::add);
        Scene scene = new Scene(root, 250, 400);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    private void bindPanelToPackages(CheckBox pane, CheckBox... packages) {

        // BooleanBinding that is true if and only if all check boxes in packages are selected:
        allSelected = Bindings.createBooleanBinding(() -> 
            // compute value of binding:
            Stream.of(packages).allMatch(CheckBox::isSelected), 
            // array of thing to observe to recompute binding - this gives the array
            // of all the check boxes' selectedProperty()s.
            Stream.of(packages).map(CheckBox::selectedProperty).toArray(Observable[]::new));

        // update pane's selected property if binding defined above changes
        allSelected.addListener((obs, wereAllSelected, areAllNowSelected) -> 
            pane.setSelected(areAllNowSelected));

        // use an action listener to listen for a direct action on pane, and update all checkboxes
        // in packages if this happens:
        pane.setOnAction(e -> 
            Stream.of(packages).forEach(box -> box.setSelected(pane.isSelected())));

    }

    public static void main(String[] args) {
        launch(args);
    }
}