Eclipse RCP - ILazyTreeContentProvider实现是意外的渴望

问题描述

我正在开发一个Eclipse RCP应用程序，并尝试使用 ILazyTreeContentProvider 实现，以便在特定时间仅显示可见项目。

I am developing an Eclipse RCP application, and am trying to use a ILazyTreeContentProvider implementation in order to show only the visible items at a certain time.

代码：

在扩展ViewPart的类中：

Inside the class extending ViewPart:

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();
    }

ContentProvider内部：

Inside the ContentProvider:

@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);
            }

        }

问题是每次我展开TreeItem的子项，它加载所有的子元素，而不仅仅是可见的子元素，而 System.out.println（updateElementCounter ++）; 命令打印出所有22，尽管有只有7棵树项目可见。

The problem is that each time I expand the children of a TreeItem, it loads all the subelements, not just the visible ones, whereas the System.out.println(updateElementCounter++); command prints out all 22 despite having only 7 Tree Items visible.

不应该 ILazyTreeContentProvider 只加载可见的？ （在这种情况下它是7个项目）

Shouldn't the ILazyTreeContentProvider only load the ones that are visible? (In this case it's 7 items)

我必须做错事...

无论如何，任何意见非常感谢！

Anyways, any opinions are very appreciated!

推荐答案

我将我的例子与
我发现只有一个区别，所有的区别：

I have compared my example with this oneAnd I've found only one difference that made all the difference:

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

文档中说明的方法如下：

What the method states in its doc:

现在内容提供者实际上是懒惰的。只能画出可见物品，而不是全部。

Now the content provider is actually lazy. Only paints the visible items, not ALL of them.

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