JavaFX：将TextArea绑定到所选TreeItem的元素（包含在TreeView中）

Question

I'm building the following JavAFX and I'm pretty new to it altogether. Here's what it looks like:

http://i.imgur.com/nfzQzIY.png

As you can see there's a TreeView on the left as well as some TextArea s in the centre. Please ignore the rest.

The alphanumeric Strings on the left TreeView are PlugTreeItem class objects, which I've built to extend TreeItem and have an additional holder for a Plug item, like so:

public class PlugTreeItem<T> extends TreeItem{

    private Plug plugItem = null;

    //########################### PROCS ########################################

    public PlugTreeItem(Object t, Plug pl) {
        super(t);
        plugItem = pl;
    }

    public PlugTreeItem(Object t, Node node, Plug pl) {
        super(t, node);
        plugItem = pl;
    }

    public void setPlugItem(Plug plugItem) {
        this.plugItem = plugItem;
    }

    public Plug getPlugItem() {
        return plugItem;
    }
}

And the TreeView is built by reading Plug s off an SQL DB, creating PlugTreeItem objects, linking the plug to the PlugTreeItem then adding that to the tree's root node (which was created initially, as a dummy), out of which we make the TreeView : NOTE: result_set contains the SQL result matrix. MAC is the field that contains the addresses you see in left of the screenshot.

treeItemRoot = new PlugTreeItem<>("Active Plugs", new Plug());          //Root of the tree, contains a dummy Plug object.
selectedTreeItem = treeItemRoot;  //Holder of our currently selected TreeItem, see Listener below.

TreeView<String> treeView = new TreeView<>(treeItemRoot);

while(result_set.next()){
    Plug pl = null;                                         
    pl = new Plug(result_set.getString("SIHUid"), result_set.getString("sensorID"), result_set.getString("Location"), result_set.getString("Appliance"), result_set.getString("Type"), result_set.getString("connection"));
    PlugTreeItem<String> pti = new PlugTreeItem(pl.getMAC(),pl);
    treeItemRoot.getChildren().add(pti);
}

Finally, I've got some TextAreas as you see in the screenshot of the app. I want those to reflect the elements of the selected PlugTreeItem in the TreeView , let's just start with the Plug MAC TextArea that I want to reflect the same value that you see on the left.

I've added the following listener to selectedTreeItem so that every time the user clicks on a TreeItem , the selectedTreeItem gets updated and holds a reference to that specific PlugTreeItem :

treeView.getSelectionModel().selectedItemProperty().addListener( new ChangeListener() {     
            @Override
            public void changed(ObservableValue observable, Object oldValue, Object newValue) { 
                selectedTreeItem = (PlugTreeItem<String>) newValue;
                System.out.println("Selection plug MAC: " + selectedTreeItem.getPlugItem().getMAC());           //MARKER: REMOVE
                // do what ever you want 
            }
        });

Hopefully this does what I think it is. The System.out command confirms that whenever I click on different items on the tree, the MAC address that I clicked on gets printed.

How can I tell my TextAreas to "hey, listen to selectedTreeItem. Whenever it changes, get a specific value and set it as your text"?

I've tried adding a second Listener on a specific field of Plug that I've changed from String to StringProperty so that it becomes an ObservableValue . However, even after binding the TextArea's textProperty with the StringProperty, it doesn't change its contents.

I know I may have worded my question incorrectly due to its size. Please do not hesitate to ask me for any additional info or code I may have omitted or you deem imoprtant.

Answer 1

I would not make a subclass of TreeItem just for that. It's designed to be used with any object. For the TextArea bindings, just bind and unbind in the selection changed listener.

package treebind;

import javafx.application.Application;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.scene.Scene;
import javafx.scene.control.TextArea;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class TreeBind extends Application {

    @Override
    public void start(Stage primaryStage) {

        TreeItem<Plug> treeItemRoot = new TreeItem<>(new Plug("root","a"));
        TreeView<Plug> treeView = new TreeView<>(treeItemRoot);
        for (int i=0;i<10;i++)
            treeItemRoot.getChildren().add(new TreeItem<>(new Plug("name"+String.valueOf(i),"")));
        treeView.setMinWidth(150);

        final TextArea ta1 = new TextArea();

        treeView.getSelectionModel().selectedItemProperty().addListener(new ChangeListener() {
            @Override
            public void changed(ObservableValue observable, Object oldValue, Object newValue) {
                if (oldValue!=null){
                    ((TreeItem<Plug>)oldValue).getValue().s1.unbindBidirectional(ta1.textProperty());
                    ta1.clear();
                }
                if (newValue!=null){
                    ta1.setText(((TreeItem<Plug>)newValue).getValue().s1.getValue());
                    ((TreeItem<Plug>)newValue).getValue().s1.bindBidirectional(ta1.textProperty());
                }
            }
        });

        HBox root = new HBox();
        root.getChildren().addAll(treeView,ta1);
        Scene scene = new Scene(root, 400, 300);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    private class Plug{
        public final StringProperty name, s1;

        Plug(String name, String s1){
            this.name = new SimpleStringProperty(name);
            this.s1 = new SimpleStringProperty(s1);
        }
        @Override
        public String toString(){
            return name.getValue();
        }
    }
}