1. 实现网络数据分页加载
我们在前面已经知道，Paging库主要由三大组件构成：PagingList， PagedListAdapter以及
PagingDataSource。实现了这三大组件，分页加载功能也就实现了。
1.1 三大组件初始化
首先在Fragment或者Activity的onCreate或者onCreateView中初始化PagingList以及Paging，
在这个过程中，将PagingList、PagedListAdapter以及PagingDataSource一并初始化了。
PagingSearchFragment.java
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
new SearchPresenter(mContext,this, Injection.provideSchedulerProvider());
return super.onCreateView(inflater, container, savedInstanceState);
}
//initData方法在父类的onCreateView方法中被调用
@Override
public void initData() {
mPagedList = makePageList(null);
pagingListAdpater = new ContactsPagingListAdpater(mContext);
resultListView.setAdapter(pagingListAdpater);
......
......
pagingListAdpater.submitList(mPagedList);
}
1.2 PagingList构建
PagingList初始化具体在makePageList中实现，PagingList主要通过PagedList.Config配置参数，通过PagedList.Builder完成构造，具体参数设置以及构造设置参考代码中的注释。
private PagedList mPagedList;
private PagedList makePageList(String searchStr) {
mDataSource = new PagingDataSource(mPresenter, searchStr);
PagedList.Config mPagedListConfig = new PagedList.Config.Builder()
.setPageSize(20) //分页数据的数量。在后面的DataSource之loadRange中，count即为每次加载的这个设定值。
//.setPrefetchDistance(10) //def pageSize
.setEnablePlaceholders(false)//加载数据Item为null时占位
.setInitialLoadSizeHint(40)
.build();
return new PagedList.Builder(mDataSource, mPagedListConfig)
.setNotifyExecutor(new BackgroundThreadTask()) //初始化阶段启用
.setFetchExecutor(new MainThreadTask()) //初始化阶段启动
.setInitialKey(Integer.valueOf(1)) //设置初始化页码
.build();
}
1.3 PagingDataSource实现
这里我们根据业务需求，选取PageKeyedDataSource作为数据源，这个数据源主要需要传递Int型的PageNum作为参数实现每一页数据的请求，具体实现请看下面的代码。
public class PagingDataSource extends PageKeyedDataSource<Integer, ContactInfo>{
private static final String TAG = PagingDataSource.class.getSimpleName();
private BaseIPVTApiPresenter mBaseIPVTApiPresenter;
private String mSearchKey;
int mPageTotal = 1;
public PagingDataSource(BaseIPVTApiPresenter baseIPVTApiPresenter, String searchKey){
mBaseIPVTApiPresenter = baseIPVTApiPresenter;
mSearchKey = searchKey;
}
//DataSource执行build()的时候调用
@Override
public void loadInitial(@NonNull LoadInitialParams<Integer> params, @NonNull LoadInitialCallback<Integer, ContactInfo> callback) {
//加载第一页
Logger.d(TAG,"[loadInitial]params requestedSize = "+params.requestedLoadSize);//pageSize
Logger.d(TAG,"[loadInitial]current ThreadName = "+Thread.currentThread().getName());
if(TextUtils.isEmpty(mSearchKey)){
return;
}
mBaseIPVTApiPresenter.reqOnePageContactList(null, "1", mSearchKey,
new RequestCallback<HttpOnePage<ContactInfo>>() {
@Override
public void processData(HttpOnePage<ContactInfo> data) {
List<ContactInfo> firstPage = data.list();
int pageNum = data.pageNum();
int pageSize = data.pageSize();
int pageTotal = data.pageTotal();
mPageTotal = pageTotal;
Integer prevPageNum = pageNum;
Integer nextPageNum = pageNum;
if(pageNum <= 1 ){
prevPageNum = null;
}else{
prevPageNum = pageNum -1;
}
if(pageTotal <=1){
nextPageNum = null;
} else {
nextPageNum = pageNum +1;
}
Logger.d(TAG,"[loadInitial]prePageNum = "+prevPageNum+", nextPageNum = "+nextPageNum);
callback.onResult(firstPage, prevPageNum, nextPageNum);
}
@Override
public void processErrorCode(String errcode) {
}
@Override
public void processException(int errNo) {
}
});
}
@Override
public void loadBefore(@NonNull LoadParams<Integer> params, @NonNull LoadCallback<Integer, ContactInfo> callback) {
//加载之前
Logger.d(TAG,"loadBefore");
}
@Override
public void loadAfter(@NonNull LoadParams<Integer> params, @NonNull LoadCallback<Integer, ContactInfo> callback) {
if(TextUtils.isEmpty(mSearchKey)){
return;
}
Logger.d(TAG,"[loadAfter]current ThreadName = "+Thread.currentThread().getName());
Logger.d(TAG,"[loadAfter]params key = "+params.key+",requestedLoadSize = "+params.requestedLoadSize);
//加载后面的每一页
mBaseIPVTApiPresenter.reqOnePageContactList(null, String.valueOf(params.key), mSearchKey,
new RequestCallback<HttpOnePage<ContactInfo>>() {
@Override
public void processData(HttpOnePage<ContactInfo> data) {
Integer nextPage = params.key;
if(params.key<mPageTotal){
nextPage = nextPage+1;
}else{
nextPage = null;
}
Logger.d(TAG,"next Page = "+nextPage);
callback.onResult(data.list(), nextPage);
}
@Override
public void processErrorCode(String errcode) {
}
@Override
public void processException(int errNo) {
}
});
}
}
PagingDataSource 继承自PageKeyedDataSource，实现了loadInitial、loadAfter、loadBefore方法，
其中
-
loadInitial初始加载数据 -
loadAfter向后分页加载数据 -
loadBefore向前分页加载数据
这三个方法都有两个参数，一个params和一个callback。
其中params包装了分页加载的参数，loadInitial中的params为LoadInitialParams包含了requestedLoadSize和placeholdersEnabled两个属性，requestedLoadSize为加载的数据量，placeholdersEnabled是是否显示占位及当数据为null时显示占位的view
loadBefore和loadAfter中的params为LoadParams包含了key和requestedLoadSize，key即为DataSource<Key, Value>中的key，在这里即为页数
callback 为数据加载完成的回调，loadInitial 中调用调用IPVTApiPresenter加载数据，然后调用callback.onResult告诉调用者数据加载完成。
public abstract void onResult(@NonNull List<Value> data, @Nullable Key previousPageKey,
@Nullable Key nextPageKey);
onResult 有三个参数，第一个为数据，后面两个即为上一页和下一页
如果我们当前页为第一页即没有上一页，则上一页为null，下一页为2，此时加载的时候会加载当前页和调用loadAfter加载第二页，但不会调用loadBefore因为没有上一页，即previousPageKey为null不会加载上一页
如果我们初始加载的是第三页，则上一页是2，下一页是4，此时加载的时候会加载当前页和调用loadAfter加载第4页，调用loadBefore加载第二页
分页加载的时候会将previousPageKey或nextPageKey传递到loadAfter或loadBefore中的params.key
loadAfter 、loadBefore中的params中的key即为我们要加载页的数据，加载完后回调中告知下一次加载数据页数+1或者-1
1.4 PagedListAdapter实现
ContactsPagingListAdpater实现代码如下，这里主要是要实现DiffUtil.ItemCallback接口，然后传给父类PagedListAdapter，用于监听Item数据项变化来更新列表
public class ContactsPagingListAdpater extends PagedListAdapter<ContactInfo, ContactViewHolder>{
private final Context mContext;
private int curFragmentType = ProContactsActivity.FRAGMENT_TYPE_CONTACT;
private boolean isCheckBoxVisible = false;
private final static DiffUtil.ItemCallback<ContactInfo> mDiffCallback = new DiffUtil.ItemCallback<ContactInfo>() {
@Override
public boolean areItemsTheSame(ContactInfo oldItem, ContactInfo newItem) {
Logger.d("DiffCallback", "areItemsTheSame");
return oldItem.contactId() == newItem.contactId();
}
@Override
public boolean areContentsTheSame(ContactInfo oldItem, ContactInfo newItem) {
return oldItem.equals(newItem);
}
};
public ContactsPagingListAdpater(Context context){
super(mDiffCallback);
mContext = context;
}
@NonNull
@Override
public ContactViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(mContext).inflate(R.layout.contacts_item_layout, parent, false);
ContactViewHolder holder = new ContactViewHolder(view);
return holder;
}
// 事件回调监听
private ContactsPagingListAdpater.OnItemClickListener onItemClickListener;
// 定义点击回调接口
public interface OnItemClickListener {
void onItemClick(View view, int position);
}
// 定义一个设置点击监听器的方法
public void setOnItemClickListener(ContactsPagingListAdpater.OnItemClickListener listener) {
this.onItemClickListener = listener;
}
@Override
public void onBindViewHolder(@NonNull ContactViewHolder holder, int position) {
ContactInfo itemInfo = getItem(position);
Integer type = itemInfo.type();
if (type != null && type==1) {
holder.contactImage.setImageResource(R.drawable.public_equipment_icon);
} else {
holder.contactImage.setImageResource(R.drawable.contacts_icon);
}
holder.contactName.setText(itemInfo.name());
if (!isCheckBoxVisible || curFragmentType == ProContactsActivity.FRAGMENT_TYPE_SEARCH) {
holder.contactCheckBox.setVisibility(View.GONE);
} else {
holder.contactCheckBox.setVisibility(View.VISIBLE);
}
String state = String.valueOf(itemInfo.state());
if (state != null) {
if (state.equals("1")) {
holder.stateImage.setImageResource(R.drawable.contact_state_online_green);
} else if (state.equals("2")) {
holder.stateImage.setImageResource(R.drawable.contact_state_busy_red);
} else {
holder.stateImage.setImageResource(R.drawable.contact_state_offline_grey);
}
} else {
holder.stateImage.setImageResource(R.drawable.contact_state_offline_grey);
}
/*if (checkedContacts.contains(itemInfo)) {
holder.contactCheckBox.setChecked(true);
} else {*/
holder.contactCheckBox.setChecked(false);
//}
//return convertView;
holder.mItemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
onItemClickListener.onItemClick(view,position);
}
});
}
}
1.5 网络数据获取
网络数据获取，主要使用一些三方库实现，RxJava用于异步处理，Retrofit+Okhttp用于网络数据
获取，Google AutoValue用于JavaBean处理，moshi Json用于Json解析。
BaseIPVTApiPresenterImpl.java
@Override
public void reqOnePageContactList(String departmentId, String pageNum, String searchKey,
RequestCallback<HttpOnePage<ContactInfo>> callback) {
int expNo = preProcessBeforeRequest();
if(expNo > NetErrorCode.EXP_NONE){
callback.processException(expNo);
return;
}
Map<String, String> contactListParams = RequestParamManager.getInstance().
onePageContactParamsMap(mContext,departmentId,pageNum,searchKey);
Disposable disposable = Single.defer(()->ServiceGenerator.createService(IPVTService.class)
.reqContactsPageData(RequestParamManager.getInstance().onePageContactParamsMap(mContext,departmentId,pageNum,searchKey)))
.compose(relogin())
.subscribeOn(mSchedulerProvider.io())
.observeOn(mSchedulerProvider.ui())
.compose(RxProgress.bindToLifecycle(mActivity, R.string.load_msg))
.subscribe(listHttpPageResult -> {
processResult(listHttpPageResult, callback);
}, throwable -> {
processException(throwable, callback);
});
mCompositeDisposable.add(disposable);
}
Retrofit API 接口如下：
//query contacts page list/ 20 per page
@GET("pro/contacts/userlist")
Single<HttpResult<HttpOnePage<ContactInfo>>> reqContactsPageData(@QueryMap Map<String, String> map);
在该Api中，返回的json格式如下：
{
"data": {
"list": [{
"contactId": 19425,
"departmentId": 0,
"name": "121",
"proAccount": "121",
"state": 1,
"type": 1
}
......
......
, {
"contactId": 19423,
"departmentId": 0,
"name": "mmey",
"proAccount": "123",
"state": 0,
"type": 1
}],
"pageNum": 2,
"pageSize": 20,
"pageTotal": 2,
"searchContent": "1"
},
"retCode": "0",
"timeStamp": "20180829010007"
}
