在Java FX 2.0中滾動錨定節點時始終可見？

Question

我想讓一個ScrollPane中存在的節點固定在頂部（固定在Y軸上），但能夠在X軸上滾動。 （在Java-FX 2.0中）

這可能嗎？

Answer 1

您可以使用綁定基於滾動條位置來調整這個特殊對象的位置，看下代碼：

public class FancyScrollPane extends Application { 

    @Override 
    public void start(Stage primaryStage) { 
     ScrollPane scrollPane = new ScrollPane(); 
     Pane content = new Pane(); 
     scrollPane.setContent(content); 

     // adding background 
     content.getChildren().add(new Rectangle(500, 500, Color.GREEN)); 

     Circle immovableObject = new Circle(30, Color.RED); 
     content.getChildren().add(immovableObject); 

     primaryStage.setScene(new Scene(scrollPane, 300, 300)); 
     primaryStage.show(); 

     // here we bind circle Y position 
     immovableObject.layoutYProperty().bind(
       // to vertical scroll shift (which ranges from 0 to 1) 
       scrollPane.vvalueProperty() 
        // multiplied by (scrollableAreaHeight - visibleViewportHeight) 
        .multiply(
         content.heightProperty() 
          .subtract(
           new ScrollPaneViewPortHeightBinding(scrollPane)))); 
    } 

    // we need this class because Bounds object doesn't support binding 
    private static class ScrollPaneViewPortHeightBinding extends DoubleBinding { 

     private final ScrollPane root; 

     public ScrollPaneViewPortHeightBinding(ScrollPane root) { 
      this.root = root; 
      super.bind(root.viewportBoundsProperty()); 
     } 

     @Override 
     protected double computeValue() { 
      return root.getViewportBounds().getHeight(); 
     } 
    } 

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