Android Jetpack

Paging：分页库

Posted by alonealice on 2020-05-25

Paging是Google官方推出了一个新的分页组件。

添加依赖

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implementation "android.arch.paging:runtime:1.0.1"
//Paging对RxJava2的原生支持
implementation "android.arch.paging:rxjava2:1.0.1"

使用

创建PageKeyedDataSource，用以获取数据源：

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class PagingDataSource extends PageKeyedDataSource<String, String> {

    @Override
    public void loadInitial(@NonNull LoadInitialParams<String> params, @NonNull LoadInitialCallback<String, String> callback) {
        List<String> list = new ArrayList<>();
        for (int i = 0; i < 20; i++) {
            list.add("第"+i);
        }
        callback.onResult(list,0,2000,"","");
    }

    @Override
    public void loadBefore(@NonNull LoadParams<String> params, @NonNull LoadCallback<String, String> callback) {

    }

    @Override
    public void loadAfter(@NonNull LoadParams<String> params, @NonNull LoadCallback<String, String> callback) {
        List<String> list = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            list.add("第"+i);
        }
        callback.onResult(list, "");
    }
}

创建DataSource.Factory：

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class PagingDataSourceFactory extends DataSource.Factory<String, String> {

    @NonNull
    @Override
    public DataSource<String, String> create() {
        PagingDataSource dataSource = new PagingDataSource();
        return dataSource;
    }
}

创建LivePagedListBuilder，用以绑定数据源和UI：

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textAdapter = new TextAdapter(new DiffUtil.ItemCallback<String>() {
    @Override
    public boolean areItemsTheSame(@NonNull String oldItem, @NonNull String newItem) {
        return oldItem.equals(newItem);
    }

    @Override
    public boolean areContentsTheSame(@NonNull String oldItem, @NonNull String newItem) {
        return oldItem.equals(newItem);
    }
});
recyclerView.setAdapter(textAdapter);
PagedList.Config config = new PagedList.Config.Builder()
        .setInitialLoadSizeHint(20)//设置首次加载的数量
        .setPageSize(20)//设置每页加载的数量
        .setPrefetchDistance(2)//设置距离每页最后数据项来时预加载下一页数据
        .build();
LiveData<PagedList<String>> build = new LivePagedListBuilder<>(factory, config).build();
build.observe(this, strings -> textAdapter.submitList(strings));

创建adpter：

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class TextAdapter extends PagedListAdapter<String, TextViewHolder> {

    protected TextAdapter(@NonNull DiffUtil.ItemCallback<String> diffCallback) {
        super(diffCallback);
    }

    @NonNull
    @Override
    public TextViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        return new TextViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_paging, parent, false));
    }

    @Override
    public void onBindViewHolder(@NonNull TextViewHolder holder, int position) {
        holder.textView.setText(getItem(position));
    }
}



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