JavaFX: Show grid lines of TreeTableView

• Save the following to resources/MyApp.css:

  .tree-table-row-cell {
      -fx-background-color: -fx-table-cell-border-color, -fx-control-inner-background;
      -fx-background-insets: 0, 0 0 1 0;
      -fx-padding: 0.0em;
      -fx-text-fill: -fx-text-inner-color;
  }
  .tree-table-row-cell:selected {
      -fx-background-color: -fx-focus-color, -fx-cell-focus-inner-border, -fx-focus-color;
      -fx-background-insets: 0, 1, 2;
  }
  
  .tree-table-row-cell:odd {
      -fx-background-color: -fx-table-cell-border-color, derive(-fx-control-inner-background,-5%);
      -fx-background-insets: 0, 0 0 1 0;
  }
  
  .tree-table-row-cell:selected:odd {
      -fx-background-color: -fx-focus-color, -fx-cell-focus-inner-border, -fx-focus-color;
      -fx-background-insets: 0, 1, 2;
  }
  

• In your Java class, add the css to a scene.

  String css = getClass().getResource("/resources/MyApp.css").toExternalForm();
  scene.getStyleSheets().add(getClass().getResource(cs);