Paging分页库-无限滚动(添加Header和Footer) 笔记

导入依赖库：

compile 'android.arch.paging:runtime:1.0.1'

使用Paging实现无限滚动，实现清空、更新、初始化功能，并且添加header和footer

public class PagingActivity extends AppCompatActivity { public class Student{ public int id; public String name; } @BindView(R.id.recyclerViewId) RecyclerView mRecyclerView; MyAdpater adpater; PagedList.Config config; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_paging); ButterKnife.bind(this); adpater = new MyAdpater(); config = new PagedList.Config.Builder() .setEnablePlaceholders(false)//配置是否启动PlaceHolders，这里设置是否设置PagedList中的占位符,如果设置为true,我们的数据数量必须固定,由于网络数据数量不固定,所以设置false .setInitialLoadSizeHint(20)//初始化加载的数量 .setPageSize(10)//配置分页加载的数量 //.setPrefetchDistance(2)//距离底部还有多少条数据时开始预加载 .build(); LiveData> liveData = https://www.it610.com/article/new LivePagedListBuilder(MyDataSourceFactory,config).build(); liveData.observe(this, new Observer>() { @Override public void onChanged(@Nullable PagedList students) { adpater.submitList(students); } }); mRecyclerView.setLayoutManager(new LinearLayoutManager(this)); mRecyclerView.setAdapter(adpater); }@OnClick(R.id.clearBtn) public void onClearClicked(){ adpater.submitList(null); //清空数据 }@OnClick(R.id.initBtn) public void onInitClicked(){//初始化数据 LiveData【Paging分页库-无限滚动(添加Header和Footer)】> liveData = https://www.it610.com/article/new LivePagedListBuilder(MyDataSourceFactory,config).build(); liveData.observe(this, new Observer>() { @Override public void onChanged(@Nullable PagedList students) { adpater.submitList(students); } }); }@OnClick(R.id.updateBtn) public void onUpdateClicked(){//更新数据 adpater.getCurrentList().get(8).name="修改了姓名"; adpater.notifyItemChanged(8); }DataSource.Factory MyDataSourceFactory = new DataSource.Factory() { @Override public DataSource create() { return new MyDataSource(); } }; class MyDataSource extends PositionalDataSource{@Override public void loadInitial(@NonNull LoadInitialParams params, @NonNull LoadInitialCallback callback) { callback.onResult(loadData(0,20),0,100); //setEnablePlaceholders为false：忽略总计数（非必填），true:总共请求totalCount(必填) }@Override public void loadRange(@NonNull LoadRangeParams params, @NonNull LoadRangeCallback callback) { //if(params.startPosition<100) { callback.onResult(loadData(params.startPosition, 10)); //} } }class MyDataSource2 extends PageKeyedDataSource{@Override public void loadInitial(@NonNull LoadInitialParams params, @NonNull LoadInitialCallback callback) { callback.onResult(loadData(0,20),0,100,0,10); }@Override public void loadBefore(@NonNull LoadParams params, @NonNull LoadCallback callback) { //callback.onResult(loadData(params.key,10),params.key-1); }@Override public void loadAfter(@NonNull final LoadParams params, @NonNull LoadCallback callback) { runOnUiThread(new Runnable() { @Override public void run() { Toast.makeText(getApplicationContext(),params.key/10+"",Toast.LENGTH_SHORT).show(); } }); callback.onResult(loadData(params.key,10),params.key+10); } }/** * 假设这里需要做一些后台线程的数据加载任务。 * * @param startPosition * @param count * @return */ private List loadData(int startPosition,int count) { List list = new ArrayList(); for (int i = 0; i < count; i++) { Student data = https://www.it610.com/article/new Student(); data.id = startPosition + i; data.name ="姓名：abc" + data.id; list.add(data); }return list; }DiffUtil.ItemCallback diffCallback = new DiffUtil.ItemCallback() { @Override public boolean areItemsTheSame(Student oldItem, Student newItem) { return oldItem.id == newItem.id; }@Override public boolean areContentsTheSame(Student oldItem, Student newItem) { return oldItem.equals(newItem); } }; class MyAdpater extends PagedListAdapter{public MyAdpater(){ super(diffCallback); }@Override public int getItemViewType(int position) { int itemCount = getItemCount() - 1; if(position == 0){ return ITEM_TYPE_HEADER; }else if(position == itemCount){ return ITEM_TYPE_FOOTER; }else{ return super.getItemViewType(position); } }@Override public int getItemCount() { return super.getItemCount() + 2; }@Nullable @Override protected Student getItem(int position) { return super.getItem(position-1); }@NonNull @Override public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) { switch(viewType){ case ITEM_TYPE_HEADER: TextView headerTv = new TextView(getApplicationContext()); ViewGroup.LayoutParams params = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,150); headerTv.setLayoutParams(params); headerTv.setTextSize(28); headerTv.setText("I am header"); headerTv.setTextColor(Color.WHITE); headerTv.setBackgroundColor(Color.BLUE); headerTv.setGravity(Gravity.CENTER); return new HeaderViewHolder(headerTv); case ITEM_TYPE_FOOTER: TextView footTv = new TextView(getApplicationContext()); footTv.setText("I am footer"); return new FooterViewHolder(footTv); default: View view = LayoutInflater.from(getApplicationContext()).inflate(R.layout.list_item_layout,null); return new MyViewHolder(view); } }@Override public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) { if(holder instanceof MyViewHolder) { ((MyViewHolder)holder).nameTv.setText(getItem(position).name); ((MyViewHolder)holder).idTv.setText(getItem(position).id + ""); } } //添加header和footer,重写AdapterDataObserver @Override public void registerAdapterDataObserver(@NonNull RecyclerView.AdapterDataObserver observer) { super.registerAdapterDataObserver(new AdapterDataObserverProxy(observer,1)); }private static final int ITEM_TYPE_HEADER = -99; private static final int ITEM_TYPE_FOOTER = -100; } class MyViewHolder extends RecyclerView.ViewHolder{ public TextView nameTv,idTv; public MyViewHolder(View itemView) { super(itemView); nameTv = itemView.findViewById(R.id.nameTv); idTv = itemView.findViewById(R.id.idTv); } }class HeaderViewHolder extends RecyclerView.ViewHolder{ public HeaderViewHolder(View itemView) { super(itemView); } } class FooterViewHolder extends RecyclerView.ViewHolder{ public FooterViewHolder(View itemView) { super(itemView); } } }

重写AdapterDataObserver

// 1.新建一个 AdapterDataObserverProxy 类继承 RecyclerView.AdapterDataObserver class AdapterDataObserverProxy extends RecyclerView.AdapterDataObserver { RecyclerView.AdapterDataObserver adapterDataObserver; int headerCount; public AdapterDataObserverProxy(RecyclerView.AdapterDataObserver adapterDataObserver, int headerCount) { this.adapterDataObserver = adapterDataObserver; this.headerCount = headerCount; } @Override public void onChanged() { adapterDataObserver.onChanged(); } @Override public void onItemRangeChanged(int positionStart, int itemCount) { adapterDataObserver.onItemRangeChanged(positionStart + headerCount, itemCount); } @Override public void onItemRangeChanged(int positionStart, int itemCount, @Nullable Object payload) { adapterDataObserver.onItemRangeChanged(positionStart + headerCount, itemCount, payload); }// 当第n个数据被获取，更新第n+1个position @Override public void onItemRangeInserted(int positionStart, int itemCount) { adapterDataObserver.onItemRangeInserted(positionStart + headerCount, itemCount); } @Override public void onItemRangeRemoved(int positionStart, int itemCount) { adapterDataObserver.onItemRangeRemoved(positionStart + headerCount, itemCount); } @Override public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) { super.onItemRangeMoved(fromPosition + headerCount, toPosition + headerCount, itemCount); } }