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  1. JDK
  2. JDK-8196326

NPE with Shape objects added to root node in start method

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      Description

      FULL PRODUCT VERSION :
      java version "9.0.4"
      Java(TM) SE Runtime Environment (build 9.0.4+11)
      Java HotSpot(TM) 64-Bit Server VM (build 9.0.4+11, mixed mode)

      ADDITIONAL OS VERSION INFORMATION :
      Microsoft Windows [Version 10.0.16299.192]

      A DESCRIPTION OF THE PROBLEM :
      Adding a Shape node to a Pane root in the start method of a JavaFX application, the JavaFX application window is presented with the Shape drawn as expected, but shortly after a NPE is generated.

      This occurs if passing the object to the Pane constructor, or if adding to the Pane object later with a root.getChildren().add(...) call.

      The NPE is generated, but the window seems to be drawn correctly.

      This is happening for multiple different Shape objects, but not a Text object.

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      In a simple JavaFX application's start method:

      - create a Rectangle object
      - create a Pane object containing this rectangle
      - create a Scene object containing this Pane
      - update the stage with this Scene object
      - wait briefly

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      I was expecting the window and its children to be drawn without an exception.
      ACTUAL -
      A NPE is produced for each Shape object added to the Pane.

      ERROR MESSAGES/STACK TRACES THAT OCCUR :
      Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
      at javafx.graphics/com.sun.glass.ui.win.WinAccessible.getUnignoredChildren(Unknown Source)
      at javafx.graphics/com.sun.glass.ui.win.WinAccessible.Navigate(Unknown Source)
      at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
      at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(Unknown Source)
      at java.base/java.lang.Thread.run(Unknown Source)

      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      package drawing;

      import javafx.application.*;
      import javafx.scene.*;
      import javafx.scene.layout.*;
      import javafx.scene.paint.*;
      import javafx.scene.shape.*;
      import javafx.scene.text.*;
      import javafx.stage.*;

      public class DrawBug extends Application
      {
          private Scene scene;
          private Pane root;
          
          public void start(Stage stage)
          {
              Rectangle rect = new Rectangle(0, 0, 300, 200);
              rect.setFill(Color.LIGHTGRAY);

              Text text = new Text(50, 50, "Hello");
              
              root = new Pane();
              root.getChildren().addAll(rect, text);
              // NOTE: Bug also happens with root = new Pane(rect, text);

              root.setPrefSize(400, 300);
              scene = new Scene(root);
              stage.setScene(scene);
              stage.show();
          }
      }

      ---------- END SOURCE ----------

      CUSTOMER SUBMITTED WORKAROUND :
      package drawing;

      import javafx.application.*;
      import javafx.scene.*;
      import javafx.scene.layout.*;
      import javafx.scene.paint.*;
      import javafx.scene.shape.*;
      import javafx.scene.text.*;
      import javafx.stage.*;

      public class DrawBugAvoided extends Application
      {
          private Scene scene;
          private Pane root;
          
          public void start(Stage stage)
          {
              Rectangle rect = new Rectangle(0, 0, 300, 200);
              rect.setFill(Color.LIGHTGRAY);

              Text text = new Text(50, 50, "Hello");
              
              root = new Pane();

              // Adding Shapes outside of the start method mostly works.
              // Though if you do move the mouse quickly onto the region of
              // the window that has the filled rectangle, it still generates the
              // NPE.
              root.setOnMouseEntered(event ->
              {
                  if (root.getChildren().size() == 0)
                      root.getChildren().addAll(rect, text);
              });

              root.setPrefSize(400, 300);
              scene = new Scene(root);
              stage.setScene(scene);
              stage.show();
          }
      }


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              • Assignee:
                pmangal Priyanka Mangal (Inactive)
                Reporter:
                webbuggrp Webbug Group
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                • Created:
                  Updated:
                  Resolved: