Question

我有两个类， PersonAdapter 和 AnimalAdapter 。

这两个类几乎完全相同，所以我试图减少尽可能多的锅炉板代码。

PersonAdapter 从 RecyclerView.Adapter 延伸。

AnimalAdapter 从 RecyclerView.Adapter 扩展而来。这两个类都实现了Filterable接口。

PersonAdapter 定义从 过滤器 扩展的内部类 PersonFilter 。

AnimalAdapter 定义从 过滤器 扩展的内部类 AnimalFilter 。

我想用某种泛型类替换 PersonFilter 和 AnimalFilter ，但我不知道如何将这两个类之间的差异：

PersonFilter 
    - works with a List<Person>
    - uses Person#getName() to make a string comparison

AnimalFilter 
    - works with a List<Animal>
    - uses Animal#getType() to make a string comparison

请快速查看两个课程：

PersonAdapter

public class PersonAdapter extends RecyclerView.Adapter<PersonViewHolder> implements Filterable {
    private List<Person> persons;
    private PersonFilter personFilter;

    public PersonAdapter(List<Person> persons) {
        this.persons = persons;
    }

    ...

    @Override
    public Filter getFilter() {
        if(personFilter == null)
            personFilter = new PersonFilter(this, persons);
        return personFilter;
    }


    public static class PersonFilter extends Filter {
        private final PersonAdapter adapter;

        private final List<Person> originalList;

        private final List<Person> filteredList;

        private PersonFilter(PersonAdapter adapter, List<Person> originalList) {
            super();
            this.adapter = adapter;
            this.originalList = new LinkedList<>(originalList);
            this.filteredList = new ArrayList<>();
        }

        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            filteredList.clear();
            final FilterResults results = new FilterResults();

            if (constraint.length() == 0) {
                filteredList.addAll(originalList);
            } else {
                final String filterPattern = constraint.toString().toLowerCase().trim();

                for (final Person person : originalList) {
                    if (person.getName().toLowerCase().contains(filterPattern.toLowerCase())) {
                        filteredList.add(person);
                    }
                }
            }
            results.values = filteredList;
            results.count = filteredList.size();
            return results;
        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            adapter.persons.clear();
            adapter.persons.addAll((ArrayList<Person>) results.values);
            adapter.notifyDataSetChanged();
        }
    }
}

AnimalAdapter

public class AnimalAdapter extends RecyclerView.Adapter<AnimalViewHolder> implements Filterable {
    private List<Animal> animals;
    private AnimalFilter animalFilter;

    public AnimalAdapter(List<Animal> animals) {
        this.animals = animals;
    }

    ...


    public static class AnimalFilter extends Filter {
        private final AnimalAdapter adapter;

        private final List<Animal> originalList;

        private final List<Animal> filteredList;

        private AnimalFilter(AnimalAdapter adapter, List<Animal> originalList) {
            super();
            this.adapter = adapter;
            this.originalList = new LinkedList<>(originalList);
            this.filteredList = new ArrayList<>();
        }

        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            filteredList.clear();
            final FilterResults results = new FilterResults();

            if (constraint.length() == 0) {
                filteredList.addAll(originalList);
            } else {
                final String filterPattern = constraint.toString().toLowerCase().trim();

                for (final Animal animal : originalList) {
                    if (animal.getType().toLowerCase().contains(filterPattern.toLowerCase())) {
                        filteredList.add(animal);
                    }
                }
            }
            results.values = filteredList;
            results.count = filteredList.size();
            return results;
        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            adapter.animals.clear();
            adapter.animals.addAll((ArrayList<Animal>) results.values);
            adapter.notifyDataSetChanged();
        }
    }
}

我应该如何创建一个与Animal和Person对象一起使用的Filter的通用子类，并且可以由PersonAdapter和AnimalAdapter使用？

Answer 1

这是一个过滤器，它使用泛型和谓词从问题中提取出两个过滤器。可以使用类似于Guava Iterable.filter()的方法进一步减少代码。

MyAdapterInterface需要是适配器的接口或共享父类，这些适配器共享此过滤器需要调用的所有适配器方法。

    public class MyFilter<A extends MyAdapterInterface,T> extends Filter {
        private final A adapter;
        private final Predicate<T> comparator; // Java 8 class - can easily be created by hand if you are using pre Java 8
        // see https://docs.oracle.com/javase/8/docs/api/java/util/function/Predicate.html

        private final List<T> originalList;
        private final List<T> filteredList;

        private MyFilter(A adapter, List<T> originalList, Predicate<T> predicate) {
            super();
            this.adapter = adapter;
            this.comparator = comparator;
            this.originalList = new LinkedList<>(originalList);
            this.filteredList = new ArrayList<>();
        }

        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            filteredList.clear();
            final FilterResults results = new FilterResults();

            if (constraint.length() == 0) {
                filteredList.addAll(originalList);
            } else {
                final String filterPattern = constraint.toString().toLowerCase().trim();

                for (final T animal : originalList) {
                    if (predicate.test(animal)) {
                        filteredList.add(animal);
                    }
                }
            }
            results.values = filteredList;
            results.count = filteredList.size();
            return results;
        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            adapter.clearResults();   // method to be added to MyAdapterInterface
            adapter.addResults(results.values);  // method to be added to MyAdapterInterface
            adapter.notifyDataSetChanged();
        }
    }

如何创建一个适用于两个不同对象的基类？

1 个答案: