在前面章節介紹了Jetpack中的Paging的基本使用,在閱讀本文前,若不知Paging的基本使用的朋友,可以查看筆者之前的文章Android Jetpack架構組件-Paging介紹及實踐
知道了Paging的基本使用,但並不滿足實際開發,雖然Paging可以實現分頁加載,但Paging在數據請求的時,只要有一次返回的數據爲空及PagedList爲空,則再不會進行分頁
這顯然是不友好的,因爲返回數據爲空有多種原因,可能是網絡或者查詢數據格式等,返回的PageList爲空,這個時候如果將分頁結束掉,則顯然不能接受;
或者Paging實現的分頁加載,如果滑動很快的話,則會出現加載明顯卡頓的效果,且無任何友好UI效果展示,如下圖所示:
在實際開發中,我們希望是慢慢滑動的時候,Paging幫我們處理分頁邏輯,而當快速滑動的時候,我們自己接管Paging的分頁加載邏輯,出現加載更多的loading,如下效果所示:
接下來,按照上面需求,實現當正常慢慢活動的時候,Paging幫我們分頁,當快速滑動的時候,則我們接管Paging的分頁加載,
示例以Jetpack中的
ViewModel、DataSource、Paging、PagingListAdapter並且配合SmartRefreshLayout來完成上拉加載和下拉刷新
- 當然監聽RecycleView加載更多的視圖的有很多種方法,這裏直接使用SmartRefreshLayout
在開始之前,先通過ViewModel+DataSource+PagingListAdapter將數據綁定到RecycleView上,若看過之前的基本使用,則以下基本使用部分可以略過
Paging的基本使用
- 1、先將Paging的基本使用及數據加載完成,則Activity中的代碼如下所示:
package com.onexzgj.inspur.pageingsample.pagingpro;
public class PagingProActivity extends AppCompatActivity implements OnRefreshListener, OnLoadMoreListener {
@SuppressLint("RestrictedApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_paging_pro);
recyclerView.setLayoutManager(new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false));
adapter = new PagingProAdapter(this);
recyclerView.setAdapter(adapter);
paingProViewModel = new ViewModelProvider.NewInstanceFactory().create(PaingProViewModel.class);
paingProViewModel.getPageData().observe(this, new Observer<PagedList<ResponseArticle.DataBean.Article>>() {
@Override
public void onChanged(PagedList<ResponseArticle.DataBean.Article> articles) {
submitList(articles);
}
});
}
public void submitList(PagedList<ResponseArticle.DataBean.Article> result) {
if (result.size() > 0) {
adapter.submitList(result);
}
}
}
- 2、再來看看PaingProViewModel中的實現
package com.onexzgj.inspur.pageingsample.pagingpro;
/**
* author:onexzgj
* time:2020/5/4
*/
public class PaingProViewModel extends AbsPagingProViewModel<ResponseArticle.DataBean.Article> {
private AtomicBoolean loadAfter = new AtomicBoolean(false);
private int mPageIndex = 0;
public int getmPageIndex() {
return mPageIndex;
}
@Override
protected DataSource createDataSource() {
return new ArticleDataSource();
}
class ArticleDataSource extends PageKeyedDataSource<Integer, ResponseArticle.DataBean.Article> {
@Override
public void loadInitial(@NonNull LoadInitialParams<Integer> params, @NonNull LoadInitialCallback<Integer, ResponseArticle.DataBean.Article> callback) {
loadData(0, callback, null);
}
@Override
public void loadBefore(@NonNull LoadParams<Integer> params, @NonNull LoadCallback<Integer, ResponseArticle.DataBean.Article> callback) {
callback.onResult(Collections.emptyList(), 0);
}
@Override
public void loadAfter(@NonNull LoadParams<Integer> params, @NonNull LoadCallback<Integer, ResponseArticle.DataBean.Article> callback) {
loadData(params.key, null, callback);
}
}
//簡單的請求網絡業務邏輯
@SuppressLint("RestrictedApi")
private void loadData(int pageIndex, PageKeyedDataSource.LoadInitialCallback<Integer, ResponseArticle.DataBean.Article> initCallback, PageKeyedDataSource.LoadCallback<Integer, ResponseArticle.DataBean.Article> callback) {
mPageIndex = pageIndex;
if (pageIndex > 0) {
loadAfter.set(true);
}
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder().url("https://www.wanandroid.com/article/list/" + pageIndex + "/json").build();
try {
Response response = null;
response = client.newCall(request).execute();
if (response.isSuccessful()) {
ResponseArticle responseArticle = JSON.parseObject(response.body().string(), ResponseArticle.class);
if (initCallback != null) {
initCallback.onResult(responseArticle.getData().getDatas(), pageIndex - 1, pageIndex + 1);
} else {
callback.onResult(responseArticle.getData().getDatas(), pageIndex + 1);
}
if (pageIndex > 0) {
//通過BoundaryPageData發送數據 告訴UI層 是否應該主動關閉上拉加載分頁的動畫
((MutableLiveData) getBoundaryPageData()).postValue(responseArticle.getData().getDatas().size() > 0);
loadAfter.set(false);
}
mPageIndex = pageIndex + 1;
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
- 3、通過PagedListAdapter將數據綁定到RecycleView上
import com.onexzgj.inspur.pageingsample.R;
/**
* author:onexzgj
* time:2020/5/4
*/
public class PagingProAdapter extends PagedListAdapter<ResponseArticle.DataBean.Article, PagingProAdapter.ViewHolder> {
public Context mContext;
protected PagingProAdapter(Context context) {
super(new DiffUtil.ItemCallback<ResponseArticle.DataBean.Article>() {
@Override
public boolean areItemsTheSame(@NonNull ResponseArticle.DataBean.Article oldItem, @NonNull ResponseArticle.DataBean.Article newItem) {
return oldItem == newItem;
}
@Override
public boolean areContentsTheSame(@NonNull ResponseArticle.DataBean.Article oldItem, @NonNull ResponseArticle.DataBean.Article newItem) {
return oldItem.getId() == newItem.getId();
}
});
this.mContext= context;
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(mContext).inflate(R.layout.item, parent, false);
return new ViewHolder(itemView);
}
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
holder.bindData(getItem(position));
}
class ViewHolder extends RecyclerView.ViewHolder {
private TextView nameView;
public ViewHolder(@NonNull View itemView) {
super(itemView);
nameView = itemView.findViewById(R.id.tv_info);
}
public void bindData(ResponseArticle.DataBean.Article item) {
nameView.setText(item.getTitle());
}
}
}
到這裏Paging的基本使用則已經完成,接下來,我們將實現手動接管Paging的上拉加載與下來刷新
實現上拉加載和下拉刷新
- 1、通過SmartRefreshLayout,來監聽RecycleView的下拉刷新與上拉加載更多的監聽,如何使用SmartRefreshLayout這裏不做詳述
...
smartRefreshLayout.setEnableRefresh(true);
smartRefreshLayout.setEnableLoadMore(true);
smartRefreshLayout.setOnRefreshListener(this);
smartRefreshLayout.setOnLoadMoreListener(this);
...
- 2、刷新邏輯實現
通過實現smartRefreshLayout的onRefresh(),將DataSource重新初始化一下即可,即如下所示:
@Override
public void onRefresh(@NonNull RefreshLayout refreshLayout) {
paingProViewModel.getDataSource().invalidate();
}
- 3、 加載更多邏輯實現
通過實現smartRefreshLayout的loadMore()中的實現邏輯,如下所示:
@Override
public void onLoadMore(@NonNull RefreshLayout refreshLayout) {
//若列表數據爲空,則不觸發上拉加載更多數據
final PagedList<ResponseArticle.DataBean.Article> currentList = adapter.getCurrentList();
if (currentList == null || currentList.size() <= 0) {
finishRefresh(false);
return;
}
//需要注意這裏,在PaingProViewModel中自實現loadAfter方法,實現請求分頁數據的邏輯
paingProViewModel.loadAfter(paingProViewModel.getmPageIndex(),new PageKeyedDataSource.LoadCallback<Integer, ResponseArticle.DataBean.Article>(){
@Override
public void onResult(@NonNull List<ResponseArticle.DataBean.Article> data, @Nullable Integer adjacentPageKey) {
PagedList.Config config = currentList.getConfig();
if (data != null && data.size() > 0) {
//這裏 咱們手動接管 分頁數據加載的時候 使用MutableItemKeyedDataSource也是可以的。
//由於當且僅當 paging不再幫我們分頁的時候,我們纔會接管。所以 就不需要ViewModel中創建的DataSource繼續工作了,所以使用新的DataSource對象,這裏是MutablePageKeyedDataSource
MutablePageKeyedDataSource dataSource = new MutablePageKeyedDataSource();
//這裏要把列表上已經顯示的先添加到dataSource.data中
//而後把本次分頁回來的數據再添加到dataSource.data中
dataSource.data.addAll(currentList);
dataSource.data.addAll(data);
PagedList pagedList = dataSource.buildNewPagedList(config);
submitList(pagedList);
}
}
});
}
可以看到我們通過,在PaingProViewModel中定義loadAfter方法,實現接管Paging分頁加載的請求數據邏輯,
- 4、實現PaingProViewModel中的自定義的方法loadAfter()
@SuppressLint("RestrictedApi")
public void loadAfter(int pageIndex, PageKeyedDataSource.LoadCallback<Integer, ResponseArticle.DataBean.Article> callback) {
Log.d("TAG", "loadAfter: pageIndex" + pageIndex);
//是否加載更多的表示位
if (loadAfter.get()) {
callback.onResult(Collections.emptyList(), 0);
return;
}
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder().url("https://www.wanandroid.com/article/list/" + pageIndex + "/json").build();
ArchTaskExecutor.getIOThreadExecutor().
execute(new Runnable() {
@Override
public void run() {
try {
Response response = null;
response = client.newCall(request).execute();
if (response.isSuccessful()) {
ResponseArticle responseArticle = JSON.parseObject(response.body().string(), ResponseArticle.class);
callback.onResult(responseArticle.getData().getDatas(), pageIndex + 1);
if (pageIndex > 0) {
//通過BoundaryPageData發送數據 告訴UI層 是否應該主動關閉上拉加載分頁的動畫
((MutableLiveData) getBoundaryPageData()).postValue(responseArticle.getData().getDatas().size() > 0);
loadAfter.set(false);
}
mPageIndex = pageIndex + 1;
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
);
}
loadAfter爲設置是否是Paging上拉加載的標記位,只有Paging進行過上拉加載的時候,才接管上拉加載,即加載的頁碼大於0的時候才接管,否則返回空的PagedList即可。
- 5、自定義的MutablePageKeyedDataSource的實現
package com.onexzgj.inspur.pageingsample.pagingpro;
@SuppressLint("RestrictedApi")
public class MutablePageKeyedDataSource<Value> extends PageKeyedDataSource<Integer, Value> {
public List<Value> data = new ArrayList<>();
public PagedList<Value> buildNewPagedList(PagedList.Config config) {
PagedList<Value> pagedList = new PagedList.Builder<Integer, Value>(this, config)
.setFetchExecutor(ArchTaskExecutor.getIOThreadExecutor())
.setNotifyExecutor(ArchTaskExecutor.getMainThreadExecutor())
.build();
return pagedList;
}
@Override
public void loadInitial(@NonNull LoadInitialParams<Integer> params, @NonNull LoadInitialCallback<Integer, Value> callback) {
callback.onResult(data, null, null);
}
@Override
public void loadBefore(@NonNull LoadParams<Integer> params, @NonNull LoadCallback<Integer, Value> callback) {
callback.onResult(Collections.emptyList(), null);
}
@Override
public void loadAfter(@NonNull LoadParams<Integer> params, @NonNull LoadCallback<Integer, Value> callback) {
callback.onResult(Collections.emptyList(), null);
}
}
作用相當於重新創建一個新的DataSource,且綁定數據集合構建出一個PagedList對象,供Paging使用。
總結
到這裏,Paging自定義上拉加載更多介紹完了,建檔總結,即通過SmartRefreshLayout監聽RecycleView的loadMore方法,通過在ViewModel中自定義loadAfter來加載數據,且重新創建DataSource和將集合數據List,和重新構建出一個PageList即可,文章中的示例代碼已上Jetpack/pagingpro
該倉庫爲演示Jetpack的組件的倉庫,分別對Lifecyele、LiveData、ViewModel、Room、WorkManager、Paging的介紹和使用
##詳細介紹文章