Eclipse RCP - ILazyTreeContentProvider实现意外地渴望

Question

我正在开发Eclipse RCP应用程序,并且我正在尝试使用ILazyTreeContentProvider实现,以便在特定时间仅显示可见项目.

代码:

在扩展ViewPart的类中:

public void createPartControl(Composite parent) {
        viewer = new TreeViewer(parent, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL | SWT.VIRTUAL);
        drillDownAdapter = new DrillDownAdapter(viewer);
        viewer.setContentProvider(new ViewContentProvider());
        viewer.setLabelProvider(new ViewLabelProvider());
        //viewer.setSorter(new NameSorter());
        viewer.setInput(getViewSite());

        // Create the help context id for the viewer's control
        PlatformUI.getWorkbench().getHelpSystem().setHelp(viewer.getControl(), "test.provider.lazy.viewer");
        makeActions();
        hookContextMenu();
        hookDoubleClickAction();
        contributeToActionBars();
    }

在ContentProvider中:

@Override
        public void updateElement(Object parent, int index) {
            System.out.println(updateElementCounter++);
            if (parent.equals(getViewSite())) {
                if (index == 0) {
                    TreeParent child = new TreeParent("Parent 1");
                    viewer.replace(parent, index, child);
                    viewer.setHasChildren(child, true);
                } else {
                    TreeParent child = new TreeParent("Parent 2");
                    viewer.replace(parent, index, child);
                    viewer.setHasChildren(child, true);
                    //viewer.setChildCount(child, 1);
                }
            } else {
                if (parent instanceof TreeParent) {
                    TreeParent treeParent = (TreeParent) parent;
                    if (treeParent.getName().equals("Parent 1")) {
                    TreeObject child = new TreeObject("Leaf "+index);
                    viewer.replace(treeParent, index, child);
                    viewer.setHasChildren(child, false);
                    //viewer.setChildCount(child, 0);
                    } else {
                        TreeObject child = new TreeObject("Special One");
                        viewer.replace(treeParent, index, child);
                        viewer.setHasChildren(child, false);
                        //viewer.setChildCount(child,0);
                    }

                }
            }
        }
        @Override
        public void updateChildCount(Object element, int currentChildCount) {
            if (element.equals(getViewSite())) {
                viewer.setChildCount(getViewSite(), 2);
            } else 
            if (element instanceof TreeParent) {
                TreeParent parent = (TreeParent) element;
                if (parent.getName().equals("Root")) {
                    viewer.setChildCount(parent, 2);
                } else if (parent.getName().equals("Parent 1")) {
                    viewer.setChildCount(parent, 20);
                } else {
                    viewer.setChildCount(parent, 1);
                }
            } else {
                viewer.setChildCount(element, 0);
            }

        }

问题是每次我扩展TreeItem的子节点时,它会加载所有子元素,而不仅仅是可见的子元素,而System.out.println(updateElementCounter++);命令打印出所有22个,尽管只有7个Tree Items可见.

不应该ILazyTreeContentProvider只加载那些可见的吗？(在这种情况下,它是7项)

我一定做错了什么...

无论如何,任何意见都非常感谢!

Answer 1

我将我的例子与这个例子进行了比较 ，我发现只有一个差异导致了所有的差异：

v.setUseHashlookup(true); //v is the TreeViewer

该方法在其文档中说明了什么：

配置此结构化查看器是否使用内部哈希表来加速元素和 SWT 项之间的映射。必须在向查看器提供输入（通过 setInput）之前调用此函数。

现在内容提供商其实很懒。只绘制可见的项目，而不是全部。