下拉刷新和上拉加载更多，从设计层面上来说，就不是同一个层面上的，从Google官方推出的下拉刷新控件SwipeRefreshLayout就可以看出。
一般来说，下拉刷新是以包裹整个列表控件的容器来实现的，而上拉加载更多是以列表控件的一部分扩展（footerView）来实现的。
下拉刷新
- Google官方的SwipeRefreshLayout
xml中控件初始化：
<android.support.v4.widget.SwipeRefreshLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</android.support.v4.widget.SwipeRefreshLayout>
java类中实现
// 设置下拉出现小圆圈是否是缩放出现，出现的位置，最大的下拉位置
mySwipeRefreshLayout.setProgressViewOffset(true, 50, 200);
// 设置下拉圆圈的大小，两个值 LARGE， DEFAULT
mySwipeRefreshLayout.setSize(SwipeRefreshLayout.LARGE);
// 设置下拉圆圈上的颜色，蓝色、绿色、橙色、红色
mySwipeRefreshLayout.setColorSchemeResources(
android.R.color.holo_blue_bright,
android.R.color.holo_green_light,
android.R.color.holo_orange_light,
android.R.color.holo_red_light);
// 通过 setEnabled(false) 禁用下拉刷新
mySwipeRefreshLayout.setEnabled(false);
// 设定下拉圆圈的背景
mSwipeLayout.setProgressBackgroundColor(R.color.red);
/*
* 设置手势下拉刷新的监听
*/
mySwipeRefreshLayout.setOnRefreshListener(
new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
// 刷新动画开始后回调到此方法
}
}
);
- 使用第三方下拉刷新控件，可以更好地支持自定义下拉样式。
这里推荐一个比较好的第三方控件：android-Ultra-Pull-To-Refresh
compile 'in.srain.cube:ultra-ptr:1.0.10'
xml中控件初始化：
<in.srain.cube.views.ptr.PtrFrameLayout
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/refreshView"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:ptr_duration_to_close="200"
app:ptr_duration_to_close_header="1000"
app:ptr_keep_header_when_refresh="true"
app:ptr_pull_to_fresh="false"
app:ptr_ratio_of_header_height_to_refresh="1.2"
app:ptr_resistance="1.7">
<com.zdf.zhihu.view.widget.LoadMoreRecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="wrap_content">
</com.zdf.zhihu.view.widget.LoadMoreRecyclerView>
</in.srain.cube.views.ptr.PtrFrameLayout>
java类中实现：
private void initRefreshView() {
// 这里可以完全自定义各种样式，只要实现PtrUIHandler，
// 具体请参考官方文档也源码
MaterialHeader header = new MaterialHeader(getContext());
refreshView.setHeaderView(header);
refreshView.addPtrUIHandler(header);
refreshView.setPtrHandler(new PtrDefaultHandler() {
@Override
public void onRefreshBegin(PtrFrameLayout ptrFrameLayout) {
page = 0;
requestTopMovies();
}
});
}
@Override
public void autoRefresh() {
handler.postDelayed(new Runnable() {
@Override
public void run() {
refreshView.autoRefresh();
}
}, 100);
}
@Override
public void refreshComplete() {
handler.post(new Runnable() {
@Override
public void run() {
refreshView.refreshComplete();
}
});
}
上拉加载更多
以列表控件的一部分扩展实现，这里以RecyclerView为例，新建一个类LoadMoreRecyclerView，继承至RecyclerView，主要的功能就是实现加载更多逻辑和显示控件：
/**
* 集成了上拉加载更多的RecyclerView
*
* Created by XiaoFeng on 2017/2/3.
*/
public class LoadMoreRecyclerView extends RecyclerView {
private final int STATE_NONE = 0x00;
private final int STATE_LOADING = 0x01;
private final int STATE_FAILURE = 0x02;
private final int STATE_COMPLETE = 0x03;
// 滑到底部里最后一个个数的阀值
private static final int VISIBLE_THRESHOLD = 1;
private int state;
private boolean loadMoreEnabled = true;
private OnLoadMoreListener listener;
private SuperAdapter superAdapter;
private LoadMoreView loadMoreView;
private LinearLayoutManager layoutManager;
public LoadMoreRecyclerView(Context context) {
this(context, null);
}
public LoadMoreRecyclerView(Context context, @Nullable AttributeSet attrs) {
this(context, attrs, 0);
}
public LoadMoreRecyclerView(Context context, @Nullable AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public void initLoadMore(@NonNull OnLoadMoreListener listener) {
this.listener = listener;
if (getAdapter() instanceof SuperAdapter) {
superAdapter = (SuperAdapter) getAdapter();
}
loadMoreView = new LoadMoreView(getContext());
layoutManager = (LinearLayoutManager) getLayoutManager();
addOnScrollListener(new OnScrollListener() {
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (canLoadMore() && dy >= 0) {
int totalItemCount = layoutManager.getItemCount();
int lastVisibleItem = layoutManager.findLastVisibleItemPosition();
if (lastVisibleItem + VISIBLE_THRESHOLD >= totalItemCount) {
onLoadMore(recyclerView);
}
}
}
});
}
public void setLoadMoreEnabled(boolean enabled) {
this.loadMoreEnabled = enabled;
}
private boolean canLoadMore() {
return state != STATE_LOADING && loadMoreEnabled;
}
private void onLoadMore(RecyclerView recyclerView) {
state = STATE_LOADING;
if (loadMoreView != null) {
loadMoreView.loading();
}
recyclerView.post(new Runnable() {
@Override
public void run() {
if (state == STATE_LOADING) {
if (superAdapter != null && loadMoreView != null) {
superAdapter.addFooterView(loadMoreView);
}
}
}
});
if (listener != null) {
listener.onLoadMore();
}
}
public void loadMoreFailed() {
state = STATE_FAILURE;
if (loadMoreView != null) {
loadMoreView.failure();
}
if (superAdapter != null) {
superAdapter.removeFooterView();
}
}
public void loadMoreComplete() {
state = STATE_COMPLETE;
if (loadMoreView != null) {
loadMoreView.complete();
}
if (superAdapter != null) {
superAdapter.removeFooterView();
}
}
}
上面出现的SuperAdapter是使用了一个第三方封装的万能Adapter，同时支持ListView和RecyclerView，个人感觉比鸿洋大神封装的万能Adapter要好一些，但是基本原理都是一样的。原理可以看他们各自的文章介绍，已经写的很详细了，这里就不多说了。
http://www.jianshu.com/p/d6a76fd3ea5b
http://blog.csdn.net/lmj623565791/article/details/38902805
http://blog.csdn.net/lmj623565791/article/details/51118836
关于分页加载
伴随着上拉加载更多功能的，往往是分页加载，关于分页加载的页数是在列表控件内部自动控制？还是在列表控件外部自己控制？我个人认为应该放在列表控件外部自己来控制页数，因为这个页数不光是在上拉加载更多时会使用到，在下拉刷新的时候也会使用到，并且对页数需要清零。
这里提供一种在列表控件外部控制页数的实现逻辑：
// 分页页数
private int page = 0;
// 初始化下拉刷新控件
private void initRefreshView() {
MaterialHeader header = new MaterialHeader(getContext());
refreshView.setHeaderView(header);
refreshView.addPtrUIHandler(header);
refreshView.setPtrHandler(new PtrDefaultHandler() {
@Override
public void onRefreshBegin(PtrFrameLayout ptrFrameLayout) {
page = 0;
requestTopMovies();
}
});
}
// 初始化RecyclerView，包含上拉加载更多
private void initRecyclerView() {
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
adapter = new SubjectAdapter(getContext());
recyclerView.setAdapter(adapter);
recyclerView.initLoadMore(new OnLoadMoreListener() {
@Override
public void onLoadMore() {
page++;
requestTopMovies();
}
});
}
// 具有分页操作的网络请求
private void requestTopMovies() {
Subscriber subscriber = new RxCallback<List<Movie>>() {
@Override
public void onSuccess(List<Movie> movieList) {
if (adapter != null) {
if (page == 0) {
adapter.clear();
} else {
recyclerView.loadMoreComplete();
}
adapter.addAll(movieList);
}
}
@Override
public void onFinished() {
refreshComplete();
}
};
RxRetrofitClient.getInstance().requestTop250Movies(subscriber, page, 10);
}
参考:
https://github.com/hanks-zyh/SwipeRefreshLayout
http://www.jianshu.com/p/d6a76fd3ea5b
http://blog.csdn.net/lmj623565791/article/details/38902805
http://blog.csdn.net/lmj623565791/article/details/51118836
