# Legacy usage and screenshots

These are the original usage notes and historical screenshots. Current sources use AndroidX imports. The pagination helpers and footer states shown here belong to the sample apps, not a paging engine in the library. Use these notes to understand an existing integration. Always check RecyclerView.NO_POSITION before indexing data; do not combine the legacy position helpers with ConcatAdapter.

## Introduction

HeaderAndFooterRecyclerView is a RecyclerView solution that supports addHeaderView, addFooterView to a RecyclerView.

Through this library, you can implement RecyclerView's Page Loading by dynamically modify the FooterView's State, such as "loading", "loading error", "loading success", "slipping to the bottom".

## How to Use It

* Add HeaderView, FooterView
```java
    mHeaderAndFooterRecyclerViewAdapter = new HeaderAndFooterRecyclerViewAdapter(mDataAdapter);
    mRecyclerView.setAdapter(mHeaderAndFooterRecyclerViewAdapter);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));

    //add a HeaderView
    RecyclerViewUtils.setHeaderView(mRecyclerView, new SampleHeader(this));

    //add a FooterView
    RecyclerViewUtils.setFooterView(mRecyclerView, new SampleFooter(this));
```
* LinearLayout / GridLayout / StaggeredGridLayout layout of RecyclerView paging load

```java
mRecyclerView.addOnScrollListener(mOnScrollListener);
```

```java
private EndlessRecyclerOnScrollListener mOnScrollListener = new EndlessRecyclerOnScrollListener() {

        @Override
        public void onLoadNextPage(View view) {
            super.onLoadNextPage(view);

            LoadingFooter.State state = RecyclerViewStateUtils.getFooterViewState(mRecyclerView);
            if(state == LoadingFooter.State.Loading) {
                Log.d("@Cundong", "the state is Loading, just wait..");
                return;
            }

            mCurrentCounter = mDataList.size();

            if (mCurrentCounter < TOTAL_COUNTER) {
                // loading more
                RecyclerViewStateUtils.setFooterViewState(EndlessLinearLayoutActivity.this, mRecyclerView, REQUEST_COUNT, LoadingFooter.State.Loading, null);
                requestData();
            } else {
                //the end
                RecyclerViewStateUtils.setFooterViewState(EndlessLinearLayoutActivity.this, mRecyclerView, REQUEST_COUNT, LoadingFooter.State.TheEnd, null);
            }
        }
    };
```

## Attention

If you have already added a HeaderView for RecyclerView by ```RecyclerViewUtils.setHeaderView(mRecyclerView, view);``` , then call the ViewHolder 's ```getAdapterPosition()```、```getLayoutPosition()```, ,the returned value will be affected by the addition of the HeaderView (the return position is the real position + headerCounter).

Therefore, in this case, please use: ```RecyclerViewUtils.getAdapterPosition(mRecyclerView, ViewHolder.this)```, ```RecyclerViewUtils.getLayoutPosition(mRecyclerView, ViewHolder.this)```.

## Demo

* Add HeaderView, FooterView

![Screenshots][1]

* Support for ply loading of the LinearLayout layout RecyclerView

![Screenshots][2]

* Support for paging loads of GridLayout layout RecyclerView

![Screenshots][3]

* Supports paging loads of StaggeredGridLayout layout RecyclerView

![Screenshots][4]

* The page load fails when the GridLayout layout is RecyclerView

![Screenshots][5]

[1]: ../art/art1.png
[2]: ../art/art2.png
[3]: ../art/art3.png
[4]: ../art/art4.png
[5]: ../art/art5.png