仿9GAG制作过程(四)

有话要说:

这次主要讲述主页面下拉刷新和上拉加载功能的实现。

主要是使用了SwipeRefreshLayout的布局方式,并在此基础上通过RecyclerView的特性增加了上拉加载的功能。

成果:

实现方式:

页面布局:

 1 <android.support.v4.widget.SwipeRefreshLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     android:id="@+id/swipeRefreshView"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent">
 5     <android.support.v7.widget.RecyclerView
 6         android:id="@+id/recyclerView"
 7         android:background="#f0f0f0"
 8         android:layout_width="match_parent"
 9         android:layout_height="match_parent"/>
10 </android.support.v4.widget.SwipeRefreshLayout>

 

通过SwipeRefreshLayout来实现下拉刷新功能。

下拉刷新:

 1       SwipeRefreshLayout swipeRefreshLayout;        
 2       // 下拉刷新控件
 3         swipeRefreshLayout = getView().findViewById(R.id.swipeRefreshView);
 4         // 设置下拉控件背景色
 5         swipeRefreshLayout.setProgressBackgroundColorSchemeColor(Color.WHITE);
 6         // 设置下来控件主色
 7         swipeRefreshLayout.setColorSchemeResources(R.color.colorAccent);
 8         // 设置下拉刷新事件
 9         swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
10             @Override
11             public void onRefresh() {
12                 new Thread(new Runnable() {
13                     @Override
14                     public void run() {
15                         try {
16                             Thread.sleep(1000);
17                         } catch (InterruptedException e) {
18                             e.printStackTrace();
19                         }
20                         String url = baseUrl + (++currentPage);
21                         OkHttpClient client = new OkHttpClient();
22                         Request request = new Request.Builder()
23                                 .url(url)
24                                 .build();
25                         try {
26                             Response response = client.newCall(request).execute();
27                             String json = response.body().string();
28                             if (json != null) {
29                                 Gson gson = new Gson();
30                                 List<NewsBean> newDatas = gson.fromJson(json, new TypeToken<List<NewsBean>>(){}.getType());
31                                 if (newsBeans != null && newsBeans.size() > 0) {
32                                     newsBeans.addAll(0, newDatas);
33                                 }
34                             }
35                             Message message = new Message();
36                             message.what = UPDATE_NEWS;
37                             handler.sendMessage(message);
38                         } catch (IOException e) {
39                             e.printStackTrace();
40                         }
41                     }
42                 }).start();
43             }
44         });

通过setProgressBackgroundColorSchemeColor来设置下拉控件的背景色,也就是圈圈的主体颜色。

通过setColorSchemeResources来设置下拉控件中间的线条颜色。

通过setOnRefreshListener来定义下拉刷新事件。

然后通过currentPage来实现下拉刷新之后获取的数据是下一页的数据,再添加到集合开头。

 1 private Handler handler = new Handler() {
 2         @Override
 3         public void handleMessage(Message msg) {
 4             switch (msg.what) {
 5                 case QUERY_NEWS:
 6                     recyclerView.getAdapter().notifyDataSetChanged();
 7                     break;
 8                 case UPDATE_NEWS:
 9                     recyclerView.getAdapter().notifyDataSetChanged();
10                     swipeRefreshLayout.setRefreshing(false);
11                     break;
12                 case LOAD_MORE:
13                     ((NewsAdapter)recyclerView.getAdapter()).changeStatus(NewsAdapter.UNLOADING);
14                     currentState = NewsAdapter.UNLOADING;
15                     break;
16             }
17         }
18     };

刷新完成之后,通过notifyDataSetChanged告诉RecyclerView数据改变了,进而更改页面显示。通过setRefreshing来控制下拉刷新控件的显示。

由此,完成了下拉刷新的实现。

上拉加载:

由于SwipeRefreshLayout并不提供上拉加载的功能,于是准备利用RecyclerView灵活的特性来实现上拉加载功能。

  1 package com.example.lanxingren.imitating9gag.adapter;
  2 
  3 import android.content.Context;
  4 import android.support.annotation.NonNull;
  5 import android.support.v7.widget.CardView;
  6 import android.support.v7.widget.RecyclerView;
  7 import android.view.LayoutInflater;
  8 import android.view.View;
  9 import android.view.ViewGroup;
 10 import android.widget.ImageView;
 11 import android.widget.TextView;
 12 
 13 import com.example.lanxingren.imitating9gag.R;
 14 import com.example.lanxingren.imitating9gag.bean.NewsBean;
 15 import com.example.lanxingren.imitating9gag.util.GlideApp;
 16 
 17 import java.util.List;
 18 
 19 public class NewsAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
 20 
 21     private List<NewsBean> myNewsList;
 22     private Context myContext;
 23 
 24     // 是否加载
 25     public static final int LOADING = 1;
 26     public static final int UNLOADING = 2;
 27 
 28     private int mStatus = UNLOADING;// 当前加载状态
 29 
 30     // item的viewType
 31     private final int ITEM = 1;
 32     private final int FOOTER = 2;
 33 
 34     static class NewsHolder extends RecyclerView.ViewHolder {
 35         CardView cardView;
 36         TextView titleView;
 37         ImageView imageView;
 38         TextView pointView;
 39         ImageView likeImageView;
 40         ImageView unlikeImageView;
 41 
 42 
 43         private NewsHolder (View view) {
 44             super(view);
 45             cardView = (CardView) view;
 46             titleView = view.findViewById(R.id.item_title);
 47             imageView = view.findViewById(R.id.item_image);
 48             pointView = view.findViewById(R.id.item_point);
 49             likeImageView = view.findViewById(R.id.item_like);
 50             unlikeImageView = view.findViewById(R.id.item_unlike);
 51         }
 52     }
 53 
 54     static class FooterHolder extends RecyclerView.ViewHolder {
 55         CardView cardView;
 56         private FooterHolder (View view) {
 57             super(view);
 58             cardView = view.findViewById(R.id.cardView_footer);
 59         }
 60     }
 61 
 62     public NewsAdapter (List<NewsBean> newsList) {
 63         this.myNewsList = newsList;
 64     }
 65 
 66     @Override
 67     public int getItemCount() {
 68         int count = 0;
 69         if (myNewsList != null) {
 70             count = myNewsList.size() + 1;
 71         }
 72         return count;
 73     }
 74 
 75     @NonNull
 76     @Override
 77     public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
 78         if (myContext == null) {
 79             myContext = parent.getContext();
 80         }
 81 
 82         if (viewType == ITEM) {
 83             View view = LayoutInflater.from(myContext).inflate(R.layout.item_news, parent, false);
 84             return new NewsHolder(view);
 85         } else {
 86             View view = LayoutInflater.from(myContext).inflate(R.layout.item_footer, parent, false);
 87             return new FooterHolder(view);
 88         }
 89     }
 90 
 91     @Override
 92     public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
 93         if (holder instanceof NewsHolder) {
 94             final NewsHolder newsHolder = (NewsHolder)holder;
 95             final NewsBean newsBean = myNewsList.get(position);
 96 
 97             // 设置标题
 98             String title = "9GAG#" + newsBean.getId();
 99             if (newsBean.getTitle() != null && newsBean.getTitle().length() > 0) {
100                 title = newsBean.getTitle();
101             }
102             newsHolder.titleView.setText(title);
103 
104             // 屏幕宽度
105             int screenWidth = myContext.getResources()
106                     .getDisplayMetrics()
107                     .widthPixels;
108             // 屏幕高度
109             int screenHeight = myContext.getResources()
110                     .getDisplayMetrics()
111                     .heightPixels;
112 
113             // 设置图片,不知道为什么override这样设置就可以让图片正正好显示,有时间研究一下?
114             if (newsBean.getUrls() != null && newsBean.getUrls().size() > 0) {
115                 GlideApp.with(myContext)
116                         .load(newsBean.getUrls().get(0))
117                         .override(screenWidth, screenHeight)
118                         .into(newsHolder.imageView);
119             }
120 
121             // 设置点赞数
122             String point = Integer.toString(newsBean.getLike() - newsBean.getUnlike());
123             newsHolder.pointView.setText(point);
124 
125             // 设置点赞图标显示
126             int accentColor = myContext.getResources().getColor(R.color.colorAccent);
127             int defaultColor = myContext.getResources().getColor(R.color.defaultColor);
128             switch (newsBean.getIsLiked()) {
129                 case -1:
130                     newsHolder.likeImageView.setColorFilter(defaultColor);
131                     newsHolder.unlikeImageView.setColorFilter(accentColor);
132                     break;
133                 case 0:
134                     newsHolder.likeImageView.setColorFilter(defaultColor);
135                     newsHolder.unlikeImageView.setColorFilter(defaultColor);
136                     break;
137                 case 1:
138                     newsHolder.likeImageView.setColorFilter(accentColor);
139                     newsHolder.unlikeImageView.setColorFilter(defaultColor);
140                     break;
141             }
142 
143             // 初始化监听事件
144             newsHolder.likeImageView.setOnClickListener(new View.OnClickListener() {
145                 @Override
146                 public void onClick(View v) {
147                     newsBean.setIsLiked(1);
148                     notifyDataSetChanged();
149                 }
150             });
151             newsHolder.unlikeImageView.setOnClickListener(new View.OnClickListener() {
152                 @Override
153                 public void onClick(View v) {
154                     newsBean.setIsLiked(-1);
155                     notifyDataSetChanged();
156                 }
157             });
158 
159         } else if (holder instanceof FooterHolder) {
160             switch (mStatus) {
161                 case UNLOADING:
162                     ((FooterHolder) holder).cardView.setVisibility(View.GONE);
163                     break;
164                 case LOADING:
165                     ((FooterHolder) holder).cardView.setVisibility(View.VISIBLE);
166                     break;
167             }
168         }
169     }
170 
171     @Override
172     public int getItemViewType(int position) {
173         if (position + 1 == getItemCount()) {
174             return FOOTER;
175         } else {
176             return ITEM;
177         }
178     }
179 
180     public void changeStatus(int status) {
181         this.mStatus = status;
182         notifyDataSetChanged();
183     }
184 }

在适配器中定义了两个布局,一个是普通布局,一个是尾布局(footer)。

下面是footer的具体布局:

 1 <android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
 2     android:layout_width="match_parent"
 3     android:layout_height="wrap_content"
 4     xmlns:app="http://schemas.android.com/apk/res-auto"
 5     android:layout_marginTop="10dp"
 6     android:layout_marginBottom="0dp"
 7     app:cardCornerRadius="0dp"
 8     android:elevation="0dp"
 9     android:id="@+id/cardView_footer">
10     <ProgressBar
11         android:layout_width="wrap_content"
12         android:layout_height="100dp"
13         android:layout_gravity="center_horizontal"
14         />
15 </android.support.v7.widget.CardView>

 

注意点:

  1. 通过mStatus来判断尾布局是否展示
  2. ITEM代表的是普通布局,即段子的布局;FOOTER代表的是尾布局
  3. 由于增加了一个item,故getItemCount得在原先的基础上加上一
  4. 在onCreateViewHolder中通过viewType来创建不同的viewHolder
  5. 实现getItemViewType方法,根据position的值来确定viewType
  6. 在onBindViewHolder中先判断viewHolder的类型,如果是尾布局(footer)的话,再根据mStatus来判断是否展示
  7. changeStatus主要是给外面用的,通过该方法可以控制footer的显示

使用上拉加载:

 1 private void initLoadMoreListener() {
 2         recyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
 3             @Override
 4             public void onScrollStateChanged(final RecyclerView recyclerView, int newState) {
 5                 super.onScrollStateChanged(recyclerView, newState);
 6 
 7                 // 获取当前可见的item位置
 8                 int lastVisiblePosition = 0;
 9                 RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
10                 if (layoutManager instanceof LinearLayoutManager) {
11                     lastVisiblePosition = ((LinearLayoutManager) layoutManager).findLastVisibleItemPosition();
12                 }
13 
14                 // 当前加载状态是UNLOADING && 当前可见的item位置是最后一条时
15                 if (currentState == NewsAdapter.UNLOADING
16                         && lastVisiblePosition + 1 == recyclerView.getAdapter().getItemCount()) {
17                     // 改变footer的可见性
18                     ((NewsAdapter)recyclerView.getAdapter()).changeStatus(NewsAdapter.LOADING);
19                     currentState = NewsAdapter.LOADING;
20 
21                     new Thread(new Runnable() {
22                         @Override
23                         public void run() {
24                             try {
25                                 Thread.sleep(1000);
26                             } catch (InterruptedException e) {
27                                 e.printStackTrace();
28                             }
29 
30                             String url = baseUrl + (++currentPage);
31                             OkHttpClient client = new OkHttpClient();
32                             Request request = new Request.Builder()
33                                     .url(url)
34                                     .build();
35                             try {
36                                 Response response = client.newCall(request).execute();
37                                 String json = response.body().string();
38                                 if (json != null) {
39                                     Gson gson = new Gson();
40                                     List<NewsBean> newDatas = gson.fromJson(json, new TypeToken<List<NewsBean>>(){}.getType());
41                                     if (newsBeans != null && newsBeans.size() > 0) {
42                                         newsBeans.addAll(newsBeans.size(), newDatas);
43                                     }
44                                 }
45                                 Message message = new Message();
46                                 message.what = LOAD_MORE;
47                                 handler.sendMessage(message);
48                             } catch (IOException e) {
49                                 e.printStackTrace();
50                             }
51                         }
52                     }).start();
53                 }
54             }
55         });
56     }

通过给recyclerView加上滚动事件来实现下拉加载功能,具体逻辑如下:

获取页面可见最下面的item位置

→判断当前尾布局的加载状态

→如果尾布局现在的状态是UNLOADING && item位置为最后一个,则开线程加载数据

→将尾布局展示,即开始转圈动画

→请求网络,获取数据,放入数据集

→根据handler的处理,告诉RecyclerView数据改变,然后将footer隐藏

 

通过以上的过程就可以实现上拉加载的效果。

参考:

SwipeRefreshLayout详解和自定义上拉加载更多SwipeRefreshLayout + RecyclerView 实现 上拉刷新 和 下拉刷新

结束语:

本次学习了Android的下拉刷新以及上拉加载的实现,对RecyclerView有了进一步的了解。

接下来准备实现点赞功能以及GIF的暂停功能。

 

大家如果有什么疑问或者建议可以通过评论或者邮件的方式联系我,欢迎大家的评论~

posted @ 2018-06-12 15:26 懒星人 阅读(...) 评论(...) 编辑 收藏