课前准备

• 修改 ICategoryPagerCallback 的3个方法，添加参数 int categoryId

    //加载分类内容
    void onContentLoaded(List<HomePagerContent.DataBean > contents,int categoryId);
    //加载到了更多内容
    void onLoadMoreLoaded(List<HomePagerContent.DataBean > contents,int categoryId);
    //加载轮播图
    void onLooperListLoaded(List<HomePagerContent.DataBean > contents,int categoryId);

• 实现类 HomePagerFragment 也要修改

    @Override
    public void onContentLoaded(List<HomePagerContent.DataBean> contents,int categoryId) {
    }
    @Override
    public void onLoadMoreLoaded(List<HomePagerContent.DataBean> contents,int categoryId) {
    }
    @Override
    public void onLooperListLoaded(List<HomePagerContent.DataBean> contents,int categoryId) {
    }

课堂笔记

• 在 CategoryPagerPresenterImpl 创建 List< ICategoryPagerCallback > 泛型的集合，保存所有 viewpager 注册创建的接口，并在注销接口时移除

    private List<ICategoryPagerCallback> callbacks = new ArrayList<>();
    @Override
    public void registerViewCallback(ICategoryPagerCallback callback) {
        if (!callbacks.contains(callback)) {
            callbacks.add(callback);
        }
    }
    @Override
    public void unregisterViewCallback(ICategoryPagerCallback callback) {
        callbacks.remove(callback);
    }

• 数据请求成功时需要判断请求的结果是否为空（pagerContent 是 response.body()）

    private void handleHomePagerContentResult(HomePagerContent pagerContent, int categoryId) {
        for (ICategoryPagerCallback callback : callbacks) {
            if (pagerContent == null || pagerContent.getData().size() == 0) {
                callback.onEmpty(categoryId);
            } else {
                callback.onContentLoaded(pagerContent.getData(), categoryId);
            }
        }
    }

• 请求失败（网络错误）

    private void handleNetworkError(int categoryId) {
        for (ICategoryPagerCallback callback : callbacks) {
            callback.onError(categoryId);
        }
    }

• 请求刚开始，加载数据...

    @Override
    public void getContentByCategoryId(int categoryId) {
        for (ICategoryPagerCallback callback : callbacks) {
            callback.onLoading(categoryId);
        }
	.......
    }

• CategoryPagerPresenterImpl 完整代码

public class CategoryPagerPresenterImpl implements ICategoryPagerPresent {
    private static ICategoryPagerPresent mInstance = null;
    private CategoryPagerPresenterImpl() {
    }
    public static ICategoryPagerPresent getInstance() {
        if (mInstance == null) {
            mInstance = new CategoryPagerPresenterImpl();
        }
        return mInstance;
    }
    private static final int DEFAULT_PAGE = 1;
    private Map<Integer, Integer> pagesInfo = new HashMap<>();
    @Override
    public void getContentByCategoryId(int categoryId) {
        for (ICategoryPagerCallback callback : callbacks) {
            callback.onLoading(categoryId);
        }
        Retrofit retrofit = RetrofitManager.getInstance().getRetrofit();
        Api api = retrofit.create(Api.class);
        Integer targetPage = pagesInfo.get(categoryId);
        if (targetPage == null) {
            targetPage = DEFAULT_PAGE;
            pagesInfo.put(categoryId, targetPage);
        }
        String homePagerUrl = UrlUtils.createHomePagerUrl(categoryId, targetPage);
        Call<HomePagerContent> task = api.getHomePagerContent(homePagerUrl);
        task.enqueue(new Callback<HomePagerContent>() {
            @Override
            public void onResponse(Call<HomePagerContent> call, Response<HomePagerContent> response) {
                int code = response.code();
                if (code == HttpURLConnection.HTTP_OK) {
                    HomePagerContent pagerContent = response.body();
                    //请求成功
                    handleHomePagerContentResult(pagerContent, categoryId);
                } else {
                    //请求失败
                    handleNetworkError(categoryId);
                }
            }
            @Override
            public void onFailure(Call<HomePagerContent> call, Throwable t) {
                //请求失败
                handleNetworkError(categoryId);
            }
        });
    }
    private void handleNetworkError(int categoryId) {
        for (ICategoryPagerCallback callback : callbacks) {
            callback.onError(categoryId);
        }
    }
    private void handleHomePagerContentResult(HomePagerContent pagerContent, int categoryId) {
        for (ICategoryPagerCallback callback : callbacks) {
            if (pagerContent == null || pagerContent.getData().size() == 0) {
                callback.onEmpty(categoryId);
            } else {
                callback.onContentLoaded(pagerContent.getData(), categoryId);
            }
        }
    }
    @Override
    public void loadMore(int categoryId) {
    }
    @Override
    public void reload() {
    }
    private List<ICategoryPagerCallback> callbacks = new ArrayList<>();
    @Override
    public void registerViewCallback(ICategoryPagerCallback callback) {
        if (!callbacks.contains(callback)) {
            callbacks.add(callback);
        }
    }
    @Override
    public void unregisterViewCallback(ICategoryPagerCallback callback) {
        callbacks.remove(callback);
    }
}

• 在 HomePagerFragment 中根据对应的请求状态设置显示界面

@Override
    public void onContentLoaded(List<HomePagerContent.DataBean> contents,int categoryId) {
        setUpState(State.SUCCESS);
    }
    @Override
    public void onLoading(int categoryId) {
        setUpState(State.LOADING);
    }
    @Override
    public void onError(int categoryId) {
        setUpState(State.ERROR);
    }
    @Override
    public void onEmpty(int categoryId) {
        setUpState(State.EMPTY);
    }

观看视频