FeaturedItemProviderAdapterFactory

weixin_34319999

于 2017-12-07 22:25:00 发布

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CC 4.0 BY-SA版权

原文链接：https://yq.aliyun.com/articles/328820

本文介绍了一种不直接修改原始ItemProvider类的方法来过滤Viewer中显示的元素。通过创建自定义的ItemProvider适配器，可以实现仅展示特定类型的子元素。此方法避免了对现有代码造成影响，并保持了代码的整洁。

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如果想在viewer里过滤掉一些不需要的元素，除了直接修改XXXItemProvider（因为程序的其他地方也会用到这个类，修改它可能会带来问题），另一个办法是通过覆盖XXXItemProviderAdapterFactory，以使用自己继承自XXXItemProvider的ItemProvider，下面的例子是只显示一种类型的child：

/**
 * Adapter factory that only have one kind of child displayed
 * @author zhanghao
 *
 */
class FeaturedItemProviderAdapterFactory extends BMItemProviderAdapterFactory{
    EStructuralFeature feature;
    
    /**
     * @param feature
     */
    public FeaturedItemProviderAdapterFactory(EStructuralFeature feature) {
        super();
        this.feature = feature;
    }

    @Override
    public Adapter createBusinessModelAdapter() {
        if (businessModelItemProvider == null) {
            businessModelItemProvider = new FeaturedBusinessModelItemProvider(this, feature);
        }
        return businessModelItemProvider;
    }
    
    class FeaturedBusinessModelItemProvider extends BusinessModelItemProvider{
        EStructuralFeature feature;
        /**
         * @param adapterFactory
         */
        public FeaturedBusinessModelItemProvider(AdapterFactory adapterFactory, EStructuralFeature reference) {
            super(adapterFactory);
            this.feature=reference;
        }

        @Override
        public Collection getChildrenFeatures(Object object) {
            Collection collection = super.getChildrenFeatures(object);
            for (Iterator iterator = collection.iterator(); iterator.hasNext();) {
                EStructuralFeature feature = (EStructuralFeature) iterator.next();
                if(this.feature != feature)
                    iterator.remove();
            }
            return childrenFeatures;
        }
    }
}

使用的时候一般还是要用ComposedAdapterFactory：

List list = new ArrayList();
list.add(new ResourceItemProviderAdapterFactory());
list.add(new FeaturedItemProviderAdapterFactory(BMPackage.Literals.BUSINESS_MODEL__ENTITIES));//提供一个feature作为参数
list.add(new ReflectiveItemProviderAdapterFactory());
ComposedAdapterFactory factory=new ComposedAdapterFactory(list);
entityViewer.setContentProvider(new AdapterFactoryContentProvider(factory));

注：另一个方法是：

viewer.setInput(new ItemProvider(model.getXXXChildren()));

但这样一些notification会得不到响应，例如新增一个XXX元素后，viewer没有得到刷新。

本文转自博客园八进制的博客，原文链接：FeaturedItemProviderAdapterFactory，如需转载请自行联系原博主。