CODEWITHSUNDEEP
recursionjavafxtreeviewerase
Sargon1
Sargon1

Reputation: 874

How to delete branching TreeItems from a TreeView in javafx?

How would I implement the method

private void wipeTreeViewStructure(TreeItem node)

where "node" is a TreeItem which, along with all of its connected TreeItems, gets erased on execution? I tried something along the lines of

    private void wipeTreeViewStructure(TreeItem node) {
    for (TreeItem i : node.getChildren()) {
        wipeTreeViewStructure(i);
        i.delete();
    }
}

but that has two major flaws:

  1. I'm getting an "Incompatible types" error in the "i", which I don't know what to make out of.

  2. there is apparently no delete() or any similar method implemented for TreeItem.

With this many unknowns, I thought it would be better to just ask how it's done.

Upvotes: 0

Views: 2522

Answers (1)

James_D
James_D

Reputation: 209358

Your incompatible types error is (I think) because you are using raw types, instead of properly specifying the type of the object in the TreeItem. In other words, you should be using 

TreeItem<Something>

instead of just the raw

TreeItem

The Something is whatever you are using as data in your tree. Your IDE should be giving you lots of warnings over this.

You don't need recursion at all here. To remove the tree item, just remove it from its parent's list of child nodes. It will effectively take all its descendents with it. You can do

node.getParent().getChildren().remove(node);

and that should do everything you need. (If the node might be the root of the tree, then you should check for that first.)

SSCCE:

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

public class TreeViewWithDelete extends Application {

    @Override
    public void start(Stage primaryStage) {
        TreeItem<String> treeRoot = new TreeItem<>("Root");
        treeRoot.setExpanded(true);

        TreeView<String> tree = new TreeView<>(treeRoot);
        tree.getSelectionModel().select(treeRoot);

        Button delete = new Button("Delete");


        delete.setOnAction(e -> {
            TreeItem<String> selected = tree.getSelectionModel().getSelectedItem();
            selected.getParent().getChildren().remove(selected);
        });


        delete.disableProperty().bind(tree.getSelectionModel().selectedItemProperty().isNull()
                .or(tree.getSelectionModel().selectedItemProperty().isEqualTo(treeRoot)));

        TextField textField = new TextField();
        Button add = new Button("Add");
        EventHandler<ActionEvent> addAction = e -> {
            TreeItem<String> selected = tree.getSelectionModel().getSelectedItem();
            if (selected == null) {
                selected = treeRoot ;
            }
            String text = textField.getText();
            if (text.isEmpty()) {
                text = "New Item";
            }
            TreeItem<String> newItem = new TreeItem<>(text);
            selected.getChildren().add(newItem);
            newItem.setExpanded(true);
            tree.getSelectionModel().select(newItem);
        };
        textField.setOnAction(addAction);
        add.setOnAction(addAction);

        HBox controls = new HBox(5, textField, add, delete);
        controls.setAlignment(Pos.CENTER);
        controls.setPadding(new Insets(5));

        BorderPane root = new BorderPane(tree, null, null, controls, null);
        Scene scene = new Scene(root, 600, 600);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

Upvotes: 2

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