Concert

public class Concert {    private String title;    private String content;    private String author;    public String getTitle() {        return title;    }    public void setTitle(String title) {        this.title = title;    }    public String getContent() {        return content;    }    public void setContent(String content) {        this.content = content;    }    public String getAuthor() {        return author;    }    public void setAuthor(String author) {        this.author = author;    }    @Override    public boolean equals(Object obj) {        if (this == obj) {            return true;        }        if (obj == null) {            return false;        }        if (this.getClass() == obj.getClass()) {            return true;        }        Concert concert = (Concert) obj;        return Objects.equals(title, concert.title) && Objects.equals(content, concert.content) && Objects.equals(author, concert.author);    }    @Override    public int hashCode() {        return Objects.hash(title, content, author);    }}

PagedListAdapter

参考：
https://developer.android.google.cn/topic/libraries/architecture/paging/ui

这个Adapter就是一个RecyclerView的Adapter。

不过我们在使用paging实现RecyclerView的分页加载效果，不能直接继承RecyclerView的Adapter，而是需要继承PagedListAdapter。

public class RecyclerAdapter extends PagedListAdapter<Concert, RecyclerAdapter.RecyclerViewHolder> {    protected RecyclerAdapter() {        super(DIFF_CALLBACK);    }    @NonNull    @Override    public RecyclerViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recyclerview, parent, false);        return new RecyclerViewHolder(view);    }    @Override    public void onBindViewHolder(@NonNull RecyclerViewHolder holder, int position) {        Concert concert = getItem(position);        if (concert != null) {            holder.mTitleTextView.setText(concert.getTitle());            holder.mAuthorTextView.setText(concert.getAuthor());            holder.mContentTextView.setText(concert.getContent());        }    }    public static class RecyclerViewHolder extends RecyclerView.ViewHolder {        TextView mTitleTextView;        TextView mAuthorTextView;        TextView mContentTextView;        public RecyclerViewHolder(View itemView) {            super(itemView);            mTitleTextView = itemView.findViewById(R.id.title);            mAuthorTextView = itemView.findViewById(R.id.author);            mContentTextView = itemView.findViewById(R.id.content);        }    }    //需要oldConcert与新 newConcert 比较才能得出变化的数据    private static DiffUtil.ItemCallback<Concert> DIFF_CALLBACK =            new DiffUtil.ItemCallback<Concert>() {                // 判断Item是否已经存在                @Override                public boolean areItemsTheSame(Concert oldConcert, Concert newConcert) {                    return oldConcert.getTitle().equals(newConcert.getTitle());                }                // 如果Item已经存在则会调用此方法，判断Item的内容是否一致                @Override                public boolean areContentsTheSame(Concert oldConcert, Concert newConcert) {                    return oldConcert.equals(newConcert);                }            };}

ConcertDataSource

/** * DataSource:顾名思义，数据源，获取数据是通过它实现的。 * 官方文档上，实现的是ItemKeyedDataSource,而我这里实现的是PositionalDataSource */public class ConcertDataSource extends PositionalDataSource<Concert> {    /**     * 加载初始化数据，可以这么来理解，加载的是第一页的数据。     * 形象的说，当我们第一次打开页面，需要回调此方法来获取数据。     */    @Override    public void loadInitial(@NonNull LoadInitialParams params, @NonNull final LoadInitialCallback<Concert> callback) {        callback.onResult(fetchItems(0, 20), 0, 10000);    }    /**     * 当有了初始化数据之后，滑动的时候如果需要加载数据的话，会调用此方法。     */    @Override    public void loadRange(@NonNull LoadRangeParams params, @NonNull final LoadRangeCallback<Concert> callback) {        callback.onResult(fetchItems(params.startPosition, params.loadSize));    }    private List<Concert> fetchItems(int startPosition, int pageSize) {        List<Concert> list = new ArrayList<>();        for (int i = startPosition; i < startPosition + pageSize; i++) {            Concert concert = new Concert();            concert.setAuthor("author = " + i);            concert.setContent("content = " + i);            concert.setTitle("title = " + i);            list.add(concert);        }        return list;    }}

ConcertFactory

public class ConcertFactory extends DataSource.Factory<Integer, Concert> {    private MutableLiveData<ConcertDataSource> mSourceLiveData =            new MutableLiveData<>();    @Override    public DataSource<Integer, Concert> create() {        ConcertDataSource concertDataSource = new ConcertDataSource();        mSourceLiveData.postValue(concertDataSource);        return concertDataSource;    }}

ConcertViewModel

/** * PagedList: 数据源获取的数据最终靠PagedList来承载。 * 对于PagedList,我们可以这样来理解，它就是一页数据的集合。 * 每请求一页，就是新的一个PagedList对象。 */public class ConcertViewModel extends ViewModel {    private final LiveData<PagedList<Concert>> convertList;    private DataSource<Integer, Concert> concertDataSource;    public ConcertViewModel() {        ConcertFactory concertFactory = new ConcertFactory();        concertDataSource = concertFactory.create();        convertList = new LivePagedListBuilder<>(concertFactory, 20).build();    }    public void invalidateDataSource() {        concertDataSource.invalidate();    }    public LiveData<PagedList<Concert>> getConvertList() {        return convertList;    }}

MainActivity

public class MainActivity extends AppCompatActivity {    private RecyclerView mRecyclerView;    private RecyclerAdapter adapter;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mRecyclerView = findViewById(R.id.recyclerView);        adapter = new RecyclerAdapter();        ConcertViewModel viewModel =                ViewModelProviders.of(this).get(ConcertViewModel.class);        //        viewModel.getConvertList().observe(this, concerts -> adapter.submitList(concerts));        viewModel.getConvertList().observe(this, new Observer<PagedList<Concert>>() {            @Override            public void onChanged(@Nullable PagedList<Concert> concerts) {                adapter.submitList(concerts);                Log.i("hongx","数据更新了");            }        });        mRecyclerView.setAdapter(adapter);        mRecyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));    }}

Github：
https://github.com/345166018/HxJetpack/tree/master/HxPaging

Android(安卓)Jetpack-Paging使用

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