课堂笔记

添加控件

• 在 HomePagerFragment 添加 NestedScrollView 解决 RecyclerView 上滑问题
• 添加 TwinklingRefreshLayout 控件加载更多内容

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    ......
    <com.lcodecore.tkrefreshlayout.TwinklingRefreshLayout
        android:id="@+id/home_pager_refresh"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <androidx.core.widget.NestedScrollView
            android:layout_width="match_parent"
            android:layout_height="match_parent">
            <LinearLayout
                ......
                <RelativeLayout
                    ......
                </RelativeLayout>
                <!--  标题布局  -->
                <include layout="@layout/include_home_pager_title_part" />
                <androidx.recyclerview.widget.RecyclerView
            </LinearLayout>
        </androidx.core.widget.NestedScrollView>
    </com.lcodecore.tkrefreshlayout.TwinklingRefreshLayout>
</LinearLayout>

首页加载更多逻辑代码

• CategoryPagerPresenterImpl 加载更多时，也要用到 Call< HomePagerContent > ，所以我们把它从 getContentByCategoryId 抽取出来

    private Call<HomePagerContent> createTask(int categoryId,int page){
        Retrofit retrofit = RetrofitManager.getInstance().getRetrofit();
        Api api = retrofit.create(Api.class);
        String homePagerUrl = UrlUtils.createHomePagerUrl(categoryId, page);
        Call<HomePagerContent> task = api.getHomePagerContent(homePagerUrl);
        return task;
    }

• 加载更多时，我们要把加载内容的页面数 +1

    @Override
    public void loadMore(int categoryId) {
        mCurrentPage = pagesInfo.get(categoryId);
        if (mCurrentPage == null) {
            mCurrentPage = 1;
        }
        mCurrentPage++;
        Call<HomePagerContent> task = createTask(categoryId, mCurrentPage);
        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 loadMoreResult = response.body();
                    //加载更多成功
                    handleLoadMoreResult(loadMoreResult, categoryId);
                } else {
                    //加载更多网络错误
                    handleLoadMoreError(categoryId);
                }
            }
            @Override
            public void onFailure(Call<HomePagerContent> call, Throwable t) {
                //加载更多网络错误
                handleLoadMoreError(categoryId);
            }
        });
    }

• 加载更多失败时，页面数 -1

    private void handleLoadMoreError(int categoryId) {
        for (ICategoryPagerCallback callback : callbacks) {
            if (callback.getCategoryId() == categoryId) {
                callback.onLoadMoreError();
                mCurrentPage --;
            }
        }
    }

• 加载更多内容为空时，页面数也要 -1

    private void handleLoadMoreResult(HomePagerContent loadMoreResult, int categoryId) {
        for (ICategoryPagerCallback callback : callbacks) {
            if (callback.getCategoryId() == categoryId) {
                if (loadMoreResult == null || loadMoreResult.getData().size() == 0) {
                    //加载更多内容为空
                    callback.onLoadMoreEmpty();
                    mCurrentPage--;
                } else {
                    //成功加载更多数据
                    callback.onLoadMoreLoaded(loadMoreResult.getData());
                }
            }
        }
    }

首页加载更多数据显示

• 在 HomePagerFragment 绑定（找到）加载更多控件

    @BindView(R.id.home_pager_refresh)
    public TwinklingRefreshLayout twinklingRefreshLayout;

• initView 时，给 twinklingRefreshLayout 设置属性

    //设置不能下拉刷新
    twinklingRefreshLayout.setEnableRefresh(false);
    //设置可以上拉加载更多
    twinklingRefreshLayout.setEnableLoadmore(true);

• 在 initListener 给 twinklingRefreshLayout 添加加载更多的监听，并调用加载更多方法

        twinklingRefreshLayout.setOnRefreshListener(new RefreshListenerAdapter() {
            @Override
            public void onLoadMore(TwinklingRefreshLayout refreshLayout) {
                super.onLoadMore(refreshLayout);
                if (mCategoryPagerPresent != null) {
                    mCategoryPagerPresent.loadMore(mMaterialId);
                }
            }
        });

• 这样 View 层的 onLoadMoreLoaded 就有数据了，设置方法把数据给 HomePagerContentAdapter 显示

    @Override
    public void onLoadMoreLoaded(List<HomePagerContent.DataBean> contents) {
        mHomePagerContentAdapter.setLoadMoreData(contents);
        if (twinklingRefreshLayout != null) {
            //加载更多完成后，结束方法
            twinklingRefreshLayout.finishLoadmore();
        }
    }

• HomePagerContentAdapter 获取数据后，只更新获取到的数据部分

    public void setLoadMoreData(List<HomePagerContent.DataBean> contents) {
        int size = mData.size();
        mData.addAll(contents);
        notifyItemRangeChanged(size,contents.size());
    }

• 无论加载更多数据是否成功，都要结束加载更多方法

    @Override
    public void onLoadMoreError() {
        if (twinklingRefreshLayout != null) {
            twinklingRefreshLayout.finishLoadmore();
        }
    }
    @Override
    public void onLoadMoreEmpty() {
        if (twinklingRefreshLayout != null) {
            twinklingRefreshLayout.finishLoadmore();
        }
    }
    @Override
    public void onLoadMoreLoaded(List<HomePagerContent.DataBean> contents) {
        mHomePagerContentAdapter.setLoadMoreData(contents);
        if (twinklingRefreshLayout != null) {
            twinklingRefreshLayout.finishLoadmore();
        }
    }

创建 ToastUtil

• 防止同一时间多次出现 Toast 使 Toast 时间叠加

public class ToastUtil {
    private static Toast mToast;
    public static void showToast(String tips) {
        if (mToast == null) {
            mToast = Toast.makeText(BaseApplication.getAppContext(), tips, Toast.LENGTH_SHORT);
        } else {
            mToast.setText(tips);
        }
        mToast.show();
    }
}

• 其中 Context

public class BaseApplication extends Application {
    private static Context appContext;
    @Override
    public void onCreate() {
        super.onCreate();
        appContext = getBaseContext();
    }
    public static Context getAppContext() {
        return appContext;
    }
}

• 给 loadMore 的不同情况添加 Toast

    @Override
    public void onLoadMoreError() {
        ToastUtil.showToast("网络错误，请稍后重试。。。");
        twinklingRefreshLayout.finishLoadmore();
    }
    @Override
    public void onLoadMoreEmpty() {
        ToastUtil.showToast("没有更多内容了");
        twinklingRefreshLayout.finishLoadmore();
    }
    @Override
    public void onLoadMoreLoaded(List<HomePagerContent.DataBean> contents) {
        mHomePagerContentAdapter.setLoadMoreData(contents);
        if (twinklingRefreshLayout != null) {
            twinklingRefreshLayout.finishLoadmore();
        }
        ToastUtil.showToast("加载了"+contents.size()+"个宝贝");
    }

课后感悟

• 网上的 ToastUtil 工具类，就是 Context 不同
• 视频：Android Toast工具类

课程视频

• 【领券联盟】36-NestedScrollView 解决 RecyclerView 上滑问题
• 【领券联盟】37-加载更多控件介绍
• 【领券联盟】38-首页加载更多的逻辑代码
• 【领券联盟】39-首页加载更多数据显示
• 【领券联盟】40-创建ToastUtil处理异常情况