前言：
我们在项目开发过程中一般都有"分页加载"的需求，分页加载就是以列表的方式显示数据，在有网络的前提下，我们可以通过下拉刷新手动获取更多的数据；没有更多的数据的时候，会提醒我们没有更多数据。
用到的知识点：
- Retrofit实现网络请求
- Recyclerview展示列表信息
- Swiperefreshlayout实现下拉刷新，上拉加载更多
- Picasso加载图片
实现代码
1.配置gradle依赖
//retrofit
compile 'com.squareup.retrofit2:retrofit:2.0.2'
compile 'com.squareup.retrofit2:converter-gson:2.0.2'
//recyclerview
compile 'com.android.support:recyclerview-v7:25.0.1'
//picasso
compile 'com.squareup.picasso:picasso:2.3.2'2.在layout布局文件中添加SwipyRefreshLayout
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:my="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#FFECECEB"
android:orientation="vertical">
<uk.co.common.ui.pull.SwipyRefreshLayout
android:id="@+id/refreshLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
my:direction="both">
<!--解决RecyclerView与TextView控件冲突-->
<android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v7.widget.RecyclerView
android:id="@+id/rv_offer_personal_loans"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_marginTop="10dp"
android:divider="#FFFFFFFD" />
<TextView
android:id="@+id/tv_bottom_text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_marginTop="10dp"
android:text="I am bottom text."
android:textColor="#384f6f"
android:textSize="14sp"
android:visibility="gone" />
</LinearLayout>
</android.support.v4.widget.NestedScrollView>
</uk.co.common.ui.pull.SwipyRefreshLayout>
</LinearLayout>3.适配器的代码
public class OfferLoansRVAdapter extends RecyclerView.Adapter<OfferLoansRVAdapter.ViewHolder> implements View.OnClickListener {
public List<Offer_personal_loans.LoansBean> LoansBeens;
public Context context;
public OfferLoansRVAdapter(Context context, List<Offer_personal_loans.LoansBean> loansBeans) {
super();
this.context = context;
this.LoansBeens = loansBeans;
}
//声明OnRecyclerViewListener对象
private OfferLoansRVAdapter.OnRecyclerViewListener mOnRecyclerViewListener = null;
@Override
public void onClick(View v) {
if (mOnRecyclerViewListener != null) {
mOnRecyclerViewListener.onItemClick(v, (int) v.getTag());
}
}
//定义OnReccyclerViewListener接口
public interface OnRecyclerViewListener {
void onItemClick(View view, int position);
}
//设置监听器用来传递数据给上面定义的接口对象的方法
public void setOnItemClickListener(OfferLoansRVAdapter.OnRecyclerViewListener listener) {
this.mOnRecyclerViewListener = listener;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
//R.layout.common_loan_item:item的布局文件
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.common_loan_item, parent, false);
OfferLoansRVAdapter.ViewHolder vh = new OfferLoansRVAdapter.ViewHolder(view);
view.setOnClickListener(this);
return vh;
}
@Override
public void onBindViewHolder(ViewHolder holder, final int position) {
RecyclerView.ViewHolder viewHolder = holder;
try {
String logo_url = LoansBeens.get(position).getLogo_url();
Picasso.with(Global.mContext).load(logo_url).into(holder.imgLoanLogo);
...
holder.imgLoanCheck.setVisibility(View.VISIBLE);
//将position保存在itemView的标记中，以便实现点击事件
holder.itemView.setTag(position);
} catch (Exception e) {
}
}
/*
*这是重要的方法，在分页加载数据的时候用来添加List数据
*/
public void addItem(List<Offer_personal_loans.LoansBean> loansBeans) {
try {
for (Offer_personal_loans.LoansBean loansBean : loansBeans)
LoansBeens.add(loansBean);
} catch (ConcurrentModificationException e) {
e.printStackTrace();
}
}
@Override
public int getItemCount() {
return LoansBeens == null ? 0 : LoansBeens.size();
}
public Offer_personal_loans.LoansBean getItem(int position) {
return LoansBeens.get(position);
}
public class ViewHolder extends RecyclerView.ViewHolder {
private ImageView imgLoanLogo;
...
public ViewHolder(View view) {
super(view);
imgLoanLogo = (ImageView) view.findViewById(R.id.img_loan_logo);
...
}
}
}
4.在Fragment实现的代码
public class OfferPersonalLoansFragment extends BaseFragment implements SwipyRefreshLayout.OnRefreshListener {
private SwipyRefreshLayout refreshLayout;
private RecyclerView rvOfferPersonalLoans;
private Offer_personal_loans offerPersonalLoans;
private List<Offer_personal_loans.LoansBean> personalLoansBeen;
private List<List<Offer_personal_loans.LoansBean>> offerPersonalLoansList;
private OfferLoansRVAdapter offerPersonalLoansRVAdapter;
private TextView tvBottomText;
//Presenter
private CommonPresenter commonPresenter;
//偏移量
private int offset = 0;
//限制条数
private int limit = 5;
@Override
public int getLayoutRes() {
return R.layout.offer_personal_loans;
}
@Override
public void initView() {
refreshLayout = (SwipyRefreshLayout) findView(R.id.refreshLayout);
refreshLayout.setOnRefreshListener(this);
rvOfferPersonalLoans = (RecyclerView) findView(R.id.rv_offer_personal_loans);
rvOfferPersonalLoans.setLayoutManager(new LinearLayoutManager(getActivity()));
tvBottomText = (TextView) findView(R.id.tv_bottom_text);
}
@Override
public void initListener() {
}
@Override
public void initData() {
//网络请求数据
showProgressDialog("", "Please wait...");
commonPresenter = new CommonPresenter(this);
commonPresenter.getOfferPersonalLoans(uuid, offset * limit, limit);
}
}
@Override
public void onClick(View v, int id) {
}
/*
*网络请求成功后调用的方法
*/
@Override
public void onHttpSuccess(int reqType, Message msg) {
if (reqType == IHttpService.HTTP_GET_OFFER_PERSONAL_LOANS) {
hideProgressDialog();
offerPersonalLoans = (Offer_personal_loans) msg.obj;
try {
personalLoansBeen = offerPersonalLoans.getLoans();
offerPersonalLoansList = new ArrayList<>();
offerPersonalLoansList.add(personalLoansBeen);
} catch (Exception e) {
e.printStackTrace();
}
initLoanRecyclerView();
tvBottomText.setVisibility(View.VISIBLE);
}
}
private void initLoanRecyclerView() {
if (offerPersonalLoansRVAdapter == null) {//判空
offerPersonalLoansRVAdapter = new OfferLoansRVAdapter(getActivity(), personalLoansBeen);
rvOfferPersonalLoans.setAdapter(offerPersonalLoansRVAdapter);
} else {
//之前已经有加载数据了,手动刷新/分页加载数据的时候,这里是添加List数据
offerPersonalLoansRVAdapter.addItem(personalLoansBeen);
offerPersonalLoansRVAdapter.notifyDataSetChanged();
}
refreshLayout.setRefreshing(false);//这一句要记得加上
//统一处理点击事件
offerPersonalLoansRVAdapter.setOnItemClickListener(new OfferLoansRVAdapter.OnRecyclerViewListener() {
@Override
public void onItemClick(View view, int position) {
...
}
});
}
/*
*上拉刷新，请求接口
*/
@Override
public void onRefresh(int index) {
commonPresenter = new CommonPresenter(this);
commonPresenter.getOfferPersonalLoans(uuid, offset * limit, limit);
}
/*
*分页加载，请求接口
*/
@Override
public void onLoad(int index) {
String uuid = SharedPreUtil.getString(Global.mContext, "membership_uuid", "");
if (!TextUtils.isEmpty(uuid)) {
commonPresenter = new CommonPresenter(this);
offset++;//每次请求接口，偏移量+1（根据接口来设计）
commonPresenter.getOfferPersonalLoans(uuid, offset * limit, limit);
}
}
/*
*网络请求失败后调用的方法
*/
@Override
public void onHttpError(int reqType, ArrayList<String> error) {
if (reqType == IHttpService.HTTP_GET_OFFER_PERSONAL_LOANS) {
hideProgressDialog();
}
}
/*
*网络timeout调用的方法
*/
@Override
public void onHttpFailure(int reqType, String error) {
if (reqType == IHttpService.HTTP_GET_OFFER_PERSONAL_LOANS) {
hideProgressDialog();
}
}
/*
*服务器错误调用的方法
*/
@Override
public void onServerError(int reqType) {
if (reqType == IHttpService.HTTP_GET_OFFER_PERSONAL_LOANS) {
hideProgressDialog();
}
}
}5.总结：分页加载就是一页一页加载数据，当滑动到底部、没有更多数据加载的时候，我们可以手动调用接口，重新刷新RecyclerView。上拉功能就不能用 ，只有下拉刷新过后，才能重新上拉加载数据，这样的话不仅能够减轻服务器的负担，也能让用户节省流量，从而提高用户体验。