Android App使用RecyclerView实现上拉和下拉刷新的方法
关于RecyclerView
RecyclerView在Android 5.0以来被引入,以前经常使用的ListView 继承的是AbsListView,而RecyclerView则直接继承 ViewGroup,并实现了ScrollingView 和 NestedScrollingChild接口,RecyclerView相比ListView,是一次彻底的改变。
RecyclerView比listview更先进更灵活,对于很多的视图它就是一个容器,可以有效的重用和滚动。当数据动态变化的时候请使用它。
RecyclerView使用起来很方便因为它提供:
1、它为item的定位提供一个layoutmanager
2、为item的操作提供一个缺省的animations
3、还可以灵活地定义这个小部件的自定义布局管理器和动画
实现上拉刷新和下拉刷新
布局文件:
<android.support.v4.widget.SwipeRefreshLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/swipe_refresh_widget" android:layout_width="match_parent" android:layout_height="match_parent" > <android.support.v7.widget.RecyclerView android:id="@android:id/list" android:layout_width="match_parent" android:layout_height="match_parent" android:cacheColorHint="@null" android:scrollbars="vertical" /> </android.support.v4.widget.SwipeRefreshLayout>
在Activity中引用这个布局并初始化
@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mSwipeRefreshWidget = (SwipeRefreshLayout) findViewById(R.id.swipe_refresh_widget); mRecyclerView = (RecyclerView) findViewById(android.R.id.list); mSwipeRefreshWidget.setColorScheme(R.color.color1, R.color.color2, R.color.color3, R.color.color4); mSwipeRefreshWidget.setOnRefreshListener(this); // 这句话是为了,第一次进入页面的时候显示加载进度条 mSwipeRefreshWidget.setProgressViewOffset(false, 0, (int) TypedValue .applyDimension(TypedValue.COMPLEX_UNIT_DIP, 24, getResources() .getDisplayMetrics())); mRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() { @Override public void onScrollStateChanged(RecyclerView recyclerView, int newState) { super.onScrollStateChanged(recyclerView, newState); if (newState == RecyclerView.SCROLL_STATE_IDLE && lastVisibleItem + 1 == adapter.getItemCount()) { mSwipeRefreshWidget.setRefreshing(true); // 此处在现实项目中,请换成网络请求数据代码,sendRequest ..... handler.sendEmptyMessageDelayed(0, 3000); } } @Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); lastVisibleItem = mLayoutManager.findLastVisibleItemPosition(); } }); mRecyclerView.setHasFixedSize(true); mLayoutManager = new LinearLayoutManager(this); mRecyclerView.setLayoutManager(mLayoutManager); mRecyclerView.setItemAnimator(new DefaultItemAnimator()); adapter = new SampleAdapter(); mRecyclerView.setAdapter(adapter); // 此处在现实项目中,请换成网络请求数据代码,sendRequest ..... handler.sendEmptyMessageDelayed(0, 3000); }
SwipeRefreshLayout里面需要注意的Api:
1、setOnRefreshListener(OnRefreshListener listener) 设置下拉监听,当用户下拉的时候会去执行回调
2、setColorSchemeColors(int... colors) 设置 进度条的颜色变化,最多可以设置4种颜色
3、setProgressViewOffset(boolean scale, int start, int end) 调整进度条距离屏幕顶部的距离
4、setRefreshing(boolean refreshing) 设置SwipeRefreshLayout当前是否处于刷新状态,一般是在请求数据的时候设置为true,在数据被加载到View中后,设置为false。
RecyclerView的实现:
第一种,下拉刷新和上拉刷新都用SwipeRefreshLayout 自带的进度条
mRecyclerView = (RecyclerView) findViewById(android.R.id.list); mRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() { @Override public void onScrollStateChanged(RecyclerView recyclerView, int newState) { super.onScrollStateChanged(recyclerView, newState); if (newState == RecyclerView.SCROLL_STATE_IDLE && lastVisibleItem + 1 == adapter.getItemCount()) { mSwipeRefreshWidget.setRefreshing(true); // 此处在现实项目中,请换成网络请求数据代码,sendRequest ..... handler.sendEmptyMessageDelayed(0, 3000); } } @Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); lastVisibleItem = mLayoutManager.findLastVisibleItemPosition(); } }); mRecyclerView.setHasFixedSize(true); mLayoutManager = new LinearLayoutManager(this); mRecyclerView.setLayoutManager(mLayoutManager); mRecyclerView.setItemAnimator(new DefaultItemAnimator()); adapter = new SampleAdapter(); mRecyclerView.setAdapter(adapter);
第二种实现下拉刷新用SwipeRefreshLayout 自带的进度条, 上拉刷新用类似ListView的刷新 提示“加载中”等信息。
我们可以给RecyclerView 也添加一个类似FooterView的item。
我们在Adapter中实现:
public class SampleAdapter extends RecyclerView.Adapter<ViewHolder> { private List<Integer> list; private static final int TYPE_ITEM = 0; private static final int TYPE_FOOTER = 1; public List<Integer> getList() { return list; } public SampleAdapter() { list = new ArrayList<Integer>(); } // RecyclerView的count设置为数据总条数+ 1(footerView) @Override public int getItemCount() { return list.size() + 1; } @Override public int getItemViewType(int position) { // 最后一个item设置为footerView if (position + 1 == getItemCount()) { return TYPE_FOOTER; } else { return TYPE_ITEM; } } @Override public void onBindViewHolder(ViewHolder holder, final int position) { if (holder instanceof ItemViewHolder) { ((ItemViewHolder) holder).textView.setText(String.valueOf(list .get(position))); } } @Override public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { if (viewType == TYPE_ITEM) { View view = LayoutInflater.from(parent.getContext()).inflate( R.layout.list_item_text, null); view.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT)); return new ItemViewHolder(view); } // type == TYPE_FOOTER 返回footerView else if (viewType == TYPE_FOOTER) { View view = LayoutInflater.from(parent.getContext()).inflate( R.layout.footerview, null); view.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT)); return new FooterViewHolder(view); } return null; } class FooterViewHolder extends ViewHolder { public FooterViewHolder(View view) { super(view); } } class ItemViewHolder extends ViewHolder { TextView textView; public ItemViewHolder(View view) { super(view); textView = (TextView) view.findViewById(R.id.text); } } }
这样我们就可以针对footerview的布局做一些处理了,比如提示“加载中,”,“已经全部加载”等信息。更加灵活一点