java - 复选框树查看器 : Can't expand nodes by default

Question

我最近在自己的 Dialog 中实现了一个 CheckboxTreeViewer。到目前为止，这工作得很好，只是树默认不允许我扩展节点。它仅在我选中该复选框时才起作用，如下图所示:

这是默认的。正如您所看到的，尽管节点有子节点，但无法展开该节点:

选中复选框后，它就起作用了:

我已经尝试使用 setExpandPreCheckFilters ，但没有成功:

Composite container = (Composite) super.createDialogArea(parent);
tv = new CheckboxTreeViewer(container, SWT.MULTI | SWT.H_SCROLL| SWT.V_SCROLL);
GridData gridData = new GridData(GridData.FILL_BOTH);
tv.getTree().setLayoutData(gridData);
tv.setContentProvider(new FeaturePropertyDialogContentProvider());
tv.setLabelProvider(new FeaturePropertyDialogLabelProvider());
tv.setAutoExpandLevel(2);
tv.setExpandPreCheckFilters(true);

有什么想法吗？

--------------------------------更新------------------------ --------------------------

我找到了问题的原因。我忘记检查 hasChildren 方法中的每个元素。以下代码现在对我有用:

public boolean hasChildren(Object element) {
        if (element instanceof ProductLine) {
            ProductLine productLine = (ProductLine) element;
            if (productLine.getPropertyList() != null) {
                return true;
            } else {
                return false;
            }
        }
        if (element instanceof PropertyList) {
            PropertyList propertyList = (PropertyList) element;
            if (!(propertyList.getGeneralPlatforms().isEmpty())) {
                return true;
            } else {
                return false;
            }
        } else if (element instanceof GeneralPlatform) {
            GeneralPlatform platform = (GeneralPlatform) element;
            if (!(platform.getHardwareElements().isEmpty())) {
                return true;
            } else {
                return false;
            }
        } else if (element instanceof HardwareElement) {
            HardwareElement hw = (HardwareElement) element;
            if (!(hw.getHardwareElements().isEmpty())
                    || !(hw.getProperties().isEmpty())) {
                return true;
            } else {
                return false;
            }
        } else {
            return false;
        }
    }

感谢您的帮助!!

Answer 1

来自 setAutoExpandLevel 的 SWT javadoc:

The value 0 means that there is no auto-expand;

1 means that the invisible root element is expanded (since most concrete subclasses do not show the root element, there is usuallyno practical difference between using the values 0 and 1);

2 means that top-level elements are expanded, but not their children;

3 means that top-level elements are expanded, and their children, but not grandchildren;

因此您应该将自动展开级别设置为 3，而不是 2。

由于您发布的代码不完整，我还想提一下，当您调用 setAutoExpandLevel() 时，它也很重要。在内部，当输入更改时会调用它。所以应该在setRoot()之前调用。

下面是构建像您一样的树并扩展节点的示例代码:公共(public)类 CheckTreeSnippet {

public static void main(String[] args) {
    Display display = new Display();
    Shell shell = new Shell(display);
    shell.setLayout(new FillLayout());

    CheckboxTreeViewer tv = new CheckboxTreeViewer(shell, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL);
    GridData gridData = new GridData(GridData.FILL_BOTH);
    tv.getTree().setLayoutData(gridData);
    tv.setAutoExpandLevel(3);
    tv.setContentProvider(new FeaturePropertyDialogContentProvider());
    tv.setInput("root");

    shell.setSize(200, 200);
    shell.open();
    while (!shell.isDisposed()) {
        if (!display.readAndDispatch()) {
            display.sleep();
        }
    }
    display.dispose();
}

private static class FeaturePropertyDialogContentProvider implements ITreeContentProvider {

    @Override
    public Object[] getElements(Object inputElement) {
        return this.getChildren(inputElement);
    }

    @Override
    public Object[] getChildren(Object parentElement) {
        switch ((String) parentElement) {
            case "root":
                return new String[]{"Platform XYZ12", "Platform ZUPP"};
            case "Platform XYZ12":
                return new String[]{"Microcontroller TPU23"};
            case "Platform ZUPP":
                return new Object[]{"Sensor", "Precaler IO"};
            case "Sensor":
                return new Object[]{"unknown child 1", "unknown child 3"};
            default:
                return new String[0];
        }
    }

    @Override
    public Object getParent(Object element) {
        return null;
    }

    @Override
    public boolean hasChildren(Object element) {
        return this.getChildren(element).length > 0;
    }

    @Override
    public void dispose() {
    }

    @Override
    public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
    }
}

}