RecyclerView 实现下拉刷新和自动加载

魔鬼旋律 8年前

来自： http://android.jobbole.com/82442/

RecyclerView是 Android 兼容包V21中新推出的列表类，它的自定义化强的优点足以让它能够取代GridView和ListView，本文将结合SwipeRefreshLayout与RecyclerView讲解如何实现下拉刷新和自动加载的代码

需要的依赖

以下版本自行更新

Java 

compile 'com.android.support:appcompat-v7:21.0.0'  compile 'com.android.support:recyclerview-v7:21.0.0'  compile 'com.android.support:cardview-v7:21.0.0'  compile 'com.android.support:support-v4:21.0.0'
compile 'com.android.support:appcompat-v7:21.0.0'  compile 'com.android.support:recyclerview-v7:21.0.0'  compile 'com.android.support:cardview-v7:21.0.0'  compile 'com.android.support:support-v4:21.0.0'
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需要解决的问题

  • [x] 下拉刷新
  • [x] 自动加载
  • [x] 网络请求异步加载

技术处理

下拉刷新

采用 android.support.v4.widget.SwipeRefreshLayout 来实现

具体可以搜索这个class，我们按照官方文档，布局如下

Java 

<view xmlns:android="http://schemas.android.com/apk/res/android"  android:id="@+id/swipeRefreshLayout"  class="android.support.v4.widget.SwipeRefreshLayout"  android:layout_width="match_parent"  android:layout_height="match_parent">        <view xmlns:android="http://schemas.android.com/apk/res/android"          android:id="@+id/recylerView"          class="android.support.v7.widget.RecyclerView"          android:layout_width="wrap_content"          android:layout_height="wrap_content"></view>  </view>
<viewxmlns:android="http://schemas.android.com/apk/res/android"  android:id="@+id/swipeRefreshLayout"  class="android.support.v4.widget.SwipeRefreshLayout"  android:layout_width="match_parent"  android:layout_height="match_parent">         <viewxmlns:android="http://schemas.android.com/apk/res/android"          android:id="@+id/recylerView"          class="android.support.v7.widget.RecyclerView"          android:layout_width="wrap_content"          android:layout_height="wrap_content"></view>  </view>
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然后对 swipeRefreshLayout 设置监听即可

Java 

swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {          @Override          public void onRefresh() {              if(isrefreshing){                  Log.d(TAG,"ignore manually update!")；              } else{                   loadPage();              }          }      });
swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {          @Override          public void onRefresh() {              if(isrefreshing){                  Log.d(TAG,"ignore manually update!")；              } else{                  loadPage();              }          }      });
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自动加载

RecyclerView是一个新兴事物，伸手党们还找不到 endless-RecyclerView 这样的开源神器，只好自己找方法了，同ListView一样，还是重写 OnScrollListener 这个方法

Java 

recyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {              @Override              public void onScrolled(RecyclerView recyclerView, int dx, int dy) {                  super.onScrolled(recyclerView, dx, dy);                  int lastVisibleItem = ((LinearLayoutManager) mLayoutManager).findLastVisibleItemPosition();                  int totalItemCount = mLayoutManager.getItemCount();                  //lastVisibleItem >= totalItemCount - 4 表示剩下4个item自动加载，各位自由选择                  // dy>0 表示向下滑动                  if (lastVisibleItem >= totalItemCount - 4 && dy > 0) {                      if(isLoadingMore){                           Log.d(TAG,"ignore manually update!");                      } else{                           loadPage();//这里多线程也要手动控制isLoadingMore                          isLoadingMore = false;                      }                  }              }          });
recyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {              @Override              public void onScrolled(RecyclerViewrecyclerView, int dx, int dy) {                  super.onScrolled(recyclerView, dx, dy);                  int lastVisibleItem = ((LinearLayoutManager) mLayoutManager).findLastVisibleItemPosition();                  int totalItemCount = mLayoutManager.getItemCount();                  //lastVisibleItem >= totalItemCount - 4 表示剩下4个item自动加载，各位自由选择                  // dy>0 表示向下滑动                  if (lastVisibleItem >= totalItemCount - 4 && dy > 0) {                      if(isLoadingMore){                          Log.d(TAG,"ignore manually update!");                      } else{                          loadPage();//这里多线程也要手动控制isLoadingMore                          isLoadingMore = false;                      }                  }              }          });
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如果想用GridView，可以试试这个，注意例子里的span_count =2

Java 

@Override        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {          super.onScrolled(recyclerView, dx, dy);          int[] visibleItems = mLayoutManager.findLastVisibleItemPositions(null);          int lastitem = Math.max(visibleItems[0],visibleItems[1]);          Log.d(TAG,"visibleItems =" + visibleItems);          Log.d(TAG,"lastitem =" + lastitem);          Log.d(TAG,"adapter.getItemCount() =" + adapter.getItemCount());          if (dy > 0 && lastitem > adapter.getItemCount() - 5 && !isLoadingMore) {            Log.d(TAG,"will loadNewFeeds");          }        }
 @Override        public void onScrolled(RecyclerViewrecyclerView, int dx, int dy) {          super.onScrolled(recyclerView, dx, dy);          int[] visibleItems = mLayoutManager.findLastVisibleItemPositions(null);          int lastitem = Math.max(visibleItems[0],visibleItems[1]);          Log.d(TAG,"visibleItems =" + visibleItems);          Log.d(TAG,"lastitem =" + lastitem);          Log.d(TAG,"adapter.getItemCount() =" + adapter.getItemCount());          if (dy > 0 && lastitem > adapter.getItemCount() - 5 && !isLoadingMore) {            Log.d(TAG,"will loadNewFeeds");          }        }
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网络请求异步加载

我这里的 loadPage 是基于 Retrofit 构建的，输入参数是一个Map,它的回调功能非常实用,可以直接控制UI更新,流程图如下,大家可以参考一下设计

loadPage 流程图

参考文献

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