Question

我想保存TreeView组件的当前滚动状态并随时恢复该状态。

我尝试了很多东西来获得滚动位置并将其设置回来，但无法以任何方式完成。

这里的关键点是我们需要保存min，max，value，unitInc，blockInc值并在需要时恢复这些值。只有值或仅最小值和最大值不足以正确恢复。

更新

聆听垂直值更改并存储滚动状态

Set<Node> nodes = this.treeView.lookupAll(".scroll-bar");
for (Node node : nodes) {
    ScrollBar scrollBar = getScrollBar(node);
    if (scrollBar.getOrientation() == Orientation.VERTICAL) {
        scrollBar.valueProperty().addListener((observable, oldValue, newValue) -> {
            double value = newValue.doubleValue();
            if (value > 0) {
                scrollState.setMin(scrollBar.getMin());
                scrollState.setMax(scrollBar.getMax());
                scrollState.setUnitIncrement(scrollBar.getUnitIncrement());
                scrollState.setBlockIncrement(scrollBar.getBlockIncrement());
                scrollState.setVerticalValue(value);
            }
        });
    }
}

此处还存储滚动状态

private ScrollBar getScrollBar(Node node) {
    ScrollBar scrollBar = (ScrollBar) node;
    if (Objects.nonNull(scrollBar)) {
        scrollState.setMin(scrollBar.getMin());
        scrollState.setMax(scrollBar.getMax());
        scrollState.setUnitIncrement(scrollBar.getUnitIncrement());
        scrollState.setBlockIncrement(scrollBar.getBlockIncrement());
    }

    return scrollBar;
}

恢复存储的滚动状态

threadService.schedule(() -> { // run after some ms, it is important
    threadService.runActionLater(() -> { // run in ui thread

        Set<Node> nodes = this.treeView.lookupAll(".scroll-bar");
        for (Node node : nodes) {
            ScrollBar scrollBar = getScrollBar(node);
            if (scrollBar.getOrientation() == Orientation.VERTICAL) {
                double verticalValue = scrollState.getVerticalValue();
                if (verticalValue > 0) {
                    scrollBar.setMin(scrollState.getMin());
                    scrollBar.setMax(scrollState.getMax());
                    scrollBar.setUnitIncrement(scrollState.getUnitIncrement());
                    scrollBar.setBlockIncrement(scrollState.getBlockIncrement());
                    scrollBar.setValue(verticalValue);
                }
            }
        }
    }, true);
}, 50, TimeUnit.MILLISECONDS);

Answer 1

如果您只想在TreeView中滚动到索引，那么您可以使用scrollTo方法（例如，您保存所选索引，然后您滚动到这个指数后来）：

tree.scrollTo(5);

如果您确实希望存储然后恢复ScrollBar的位置，则可以使用Node类的lookupAll方法要查找.scroll-bar样式，然后将其设置为ScrollBar对象，该对象具有要存储的minProperty，maxProperty和valueProperty。

更新：

根据OP的发现，ScrollBar的{{3}}和unitIncrementProperty也应该存储和恢复，以便正确支持该操作。

示例

在示例中，我填充了TreeView一些虚拟数据。它包含一个Button，用于将水平位置和垂直ScrollBar保存到成员对象中，该成员对象可以存储位置的min，max，value，blockIncrement和unitIncrement值。它还有一个Button来恢复上次保存的滚动条位置。

public class TreeViewSample extends Application { // Members to store the horizontal and vertical positions private ScrollBarState hScrollBarState = null; private ScrollBarState vScrollBarState = null; TreeView<String> tree; public static void main(String[] args) { launch(args); } @Override public void start(Stage primaryStage) { primaryStage.setTitle("Tree View Sample with scrollbars"); TreeItem<String> rootItem = new TreeItem<String>("Items"); rootItem.setExpanded(true); for (int i = 1; i < 30; i++) { TreeItem<String> item = new TreeItem<String>("Long long long long long long long Item" + i); rootItem.getChildren().add(item); } tree = new TreeView<String>(rootItem); VBox root = new VBox(); Button buttonSave = new Button("Save ScrollBars!"); buttonSave.setOnAction((event) -> { // On save get the scrollbars and update the members (if the scrollbar is present) ScrollBar bar = getScrollBar(tree, Orientation.HORIZONTAL); if (bar != null) hScrollBarState = new ScrollBarState(bar.getMin(), bar.getMax(), bar.getValue(), bar.getBlockIncrement(), bar.getUnitIncrement()); bar = getScrollBar(tree, Orientation.VERTICAL); if (bar != null) vScrollBarState = new ScrollBarState(bar.getMin(), bar.getMax(), bar.getValue(), bar.getBlockIncrement(), bar.getUnitIncrement()); }); Button buttonRestore = new Button("Restore ScrollBars!"); buttonRestore.setOnAction((event) -> { restoreScrollBarPositions(getScrollBar(tree, Orientation.HORIZONTAL), hScrollBarState); restoreScrollBarPositions(getScrollBar(tree, Orientation.VERTICAL), vScrollBarState); }); root.getChildren().addAll(tree, buttonSave, buttonRestore); primaryStage.setScene(new Scene(root, 300, 250)); primaryStage.show(); } private ScrollBar getScrollBar(TreeView<?> tree, Orientation orientation) { // Get the ScrollBar with the given Orientation using lookupAll for (Node n : tree.lookupAll(".scroll-bar")) { if (n instanceof ScrollBar) { ScrollBar bar = (ScrollBar) n; if (bar.getOrientation().equals(orientation)) return bar; } } return null; } private void restoreScrollBarPositions(ScrollBar bar, ScrollBarState state) { // Set back the position values if they present if (bar != null && state != null) { bar.setMin(state.min); bar.setMax(state.max); bar.setValue(state.value); bar.setUnitIncrement(state.unitIncrement); bar.setBlockIncrement(state.blockIncrement); } } // Simple class to store the position values class ScrollBarState { double min; double max; double value; double blockIncrement; double unitIncrement; ScrollBarState(double min, double max, double value, double blockInc, double unitInc) { this.min = min; this.max = max; this.value = value; this.blockIncrement = blockInc; this.unitIncrement = unitInc; } } }

Answer 2

这可能对某人有用。我基于DVarga的解决方案创建了一个友好的状态对象。这是使用TextArea。

public class ScrollBarState
{
  private final TextArea textArea;
  private final Orientation orientation;
  private ScrollBar scrollBar;

  private double min;
  private double max;
  private double value;
  private double blockIncrement;
  private double unitIncrement;

  // ---------------------------------------------------------------------------------//
  // constructor
  // ---------------------------------------------------------------------------------//

  public ScrollBarState (TextArea textArea, Orientation orientation)
  {
    this.textArea = textArea;
    this.orientation = orientation;
  }

  // ---------------------------------------------------------------------------------//
  // reset
  // ---------------------------------------------------------------------------------//

  public void reset ()
  {
    scrollBar = null;
  }

  // ---------------------------------------------------------------------------------//
  // save
  // ---------------------------------------------------------------------------------//

  public void save ()
  {
    if (scrollBar == null && !setScrollBar ())
      return;

    this.min = scrollBar.getMin ();
    this.max = scrollBar.getMax ();
    this.value = scrollBar.getValue ();
    this.blockIncrement = scrollBar.getBlockIncrement ();
    this.unitIncrement = scrollBar.getUnitIncrement ();
  }

  // ---------------------------------------------------------------------------------//
  // restore
  // ---------------------------------------------------------------------------------//

  public void restore ()
  {
    if (scrollBar == null)
      return;

    scrollBar.setMin (min);
    scrollBar.setMax (max);
    scrollBar.setValue (value);
    scrollBar.setUnitIncrement (unitIncrement);
    scrollBar.setBlockIncrement (blockIncrement);
  }

  // ---------------------------------------------------------------------------------//
  // setScrollBar
  // ---------------------------------------------------------------------------------//

  private boolean setScrollBar ()
  {
    for (Node node : textArea.lookupAll (".scroll-bar"))
      if (node instanceof ScrollBar
          && ((ScrollBar) node).getOrientation ().equals (orientation))
      {
        scrollBar = (ScrollBar) node;
        return true;
      }
    return false;
  }
}

JavaFX TreeView还原滚动状态

2 个答案: