How implement sticky footer in recyclerview

问题:

I have RecyclerView and I need next behavior:

• if there are a lot of items (more then fits screen) - footer is last item
• if few item/no item - footer is located at screen bottom

Please advise how can I implement this behavior.

回答1:

You can use RecyclerView.ItemDecoration to implement this behavior.

public class StickyFooterItemDecoration extends RecyclerView.ItemDecoration {

    /**
     * Top offset to completely hide footer from the screen and therefore avoid noticeable blink during changing position of the footer.
     */
    private static final int OFF_SCREEN_OFFSET = 5000;

    @Override
    public void getItemOffsets(Rect outRect, final View view, final RecyclerView parent, RecyclerView.State state) {
        int adapterItemCount = parent.getAdapter().getItemCount();
        if (isFooter(parent, view, adapterItemCount)) {
            //For the first time, each view doesn't contain any parameters related to its size,
            //hence we can't calculate the appropriate offset.
            //In this case, set a big top offset and notify adapter to update footer one more time.
            //Also, we shouldn't do it if footer became visible after scrolling.
            if (view.getHeight() == 0 && state.didStructureChange()) {
                hideFooterAndUpdate(outRect, view, parent);
            } else {
                outRect.set(0, calculateTopOffset(parent, view, adapterItemCount), 0, 0);
            }
        }
    }

    private void hideFooterAndUpdate(Rect outRect, final View footerView, final RecyclerView parent) {
        outRect.set(0, OFF_SCREEN_OFFSET, 0, 0);
        footerView.post(new Runnable() {
            @Override
            public void run() {
                parent.getAdapter().notifyDataSetChanged();
            }
        });
    }

    private int calculateTopOffset(RecyclerView parent, View footerView, int itemCount) {
        int topOffset = parent.getHeight() - visibleChildsHeightWithFooter(parent, footerView, itemCount);
        return topOffset < 0 ? 0 : topOffset;
    }

    private int visibleChildsHeightWithFooter(RecyclerView parent, View footerView, int itemCount) {
        int totalHeight = 0;
        //In the case of dynamic content when adding or removing are possible itemCount from the adapter is reliable,
        //but when the screen can fit fewer items than in adapter, getChildCount() from RecyclerView should be used.
        int onScreenItemCount = Math.min(parent.getChildCount(), itemCount);
        for (int i = 0; i < onScreenItemCount - 1; i++) {
            totalHeight += parent.getChildAt(i).getHeight();
        }
        return totalHeight + footerView.getHeight();
    }

    private boolean isFooter(RecyclerView parent, View view, int itemCount) {
        return parent.getChildAdapterPosition(view) == itemCount - 1;
    }
}

Make sure to set match_parent for the RecyclerView height.

Please have a look at the sample application https://github.com/JohnKuper/recyclerview-sticky-footer and how it works http://sendvid.com/nbpj0806

A Huge drawback of this solution is it works correctly only after notifyDataSetChanged() throughout an application(not inside decoration). With more specific notifications it won't work properly and to support them, it requires a way more logic. Also, you can get insights from the library recyclerview-stickyheaders by eowise and improve this solution.

回答2:

Improvising on Dmitriy Korobeynikov and solving the problem of calling notify dataset changed

public class StickyFooterItemDecoration extends RecyclerView.ItemDecoration {

  @Override
  public void getItemOffsets(Rect outRect, final View view, final RecyclerView parent,
      RecyclerView.State state) {

    int position = parent.getChildAdapterPosition(view);
    int adapterItemCount = parent.getAdapter().getItemCount();
    if (adapterItemCount == RecyclerView.NO_POSITION || (adapterItemCount - 1) != position) {
      return;
    }
    outRect.top = calculateTopOffset(parent, view, adapterItemCount);
  }


  private int calculateTopOffset(RecyclerView parent, View footerView, int itemCount) {
    int topOffset =
        parent.getHeight() - parent.getPaddingTop() - parent.getPaddingBottom()
            - visibleChildHeightWithFooter(parent, footerView, itemCount);
    return topOffset < 0 ? 0 : topOffset;
  }



  private int visibleChildHeightWithFooter(RecyclerView parent, View footerView, int itemCount) {
    int totalHeight = 0;
    int onScreenItemCount = Math.min(parent.getChildCount(), itemCount);
    for (int i = 0; i < onScreenItemCount - 1; i++) {
      RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) parent.getChildAt(i)
          .getLayoutParams();
      int height =
          parent.getChildAt(i).getHeight() + layoutParams.topMargin
              + layoutParams.bottomMargin;
      totalHeight += height;
    }
    int footerHeight = footerView.getHeight();
    if (footerHeight == 0) {
      fixLayoutSize(footerView, parent);
      footerHeight = footerView.getHeight();
    }
    footerHeight = footerHeight + footerView.getPaddingBottom() + footerView.getPaddingTop();

    return totalHeight + footerHeight;
  }

  private void fixLayoutSize(View view, ViewGroup parent) {
    // Check if the view has a layout parameter and if it does not create one for it
    if (view.getLayoutParams() == null) {
      view.setLayoutParams(new ViewGroup.LayoutParams(
          ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
    }

    // Create a width and height spec using the parent as an example:
    // For width we make sure that the item matches exactly what it measures from the parent.
    //  IE if layout says to match_parent it will be exactly parent.getWidth()
    int widthSpec = View.MeasureSpec.makeMeasureSpec(parent.getWidth(), View.MeasureSpec.EXACTLY);
    // For the height we are going to create a spec that says it doesn't really care what is calculated,
    //  even if its larger than the screen
    int heightSpec = View.MeasureSpec
        .makeMeasureSpec(parent.getHeight(), View.MeasureSpec.UNSPECIFIED);

    // Get the child specs using the parent spec and the padding the parent has
    int childWidth = ViewGroup.getChildMeasureSpec(widthSpec,
        parent.getPaddingLeft() + parent.getPaddingRight(), view.getLayoutParams().width);
    int childHeight = ViewGroup.getChildMeasureSpec(heightSpec,
        parent.getPaddingTop() + parent.getPaddingBottom(), view.getLayoutParams().height);

    // Finally we measure the sizes with the actual view which does margin and padding changes to the sizes calculated
    view.measure(childWidth, childHeight);

    // And now we setup the layout for the view to ensure it has the correct sizes.
    view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());
  }
}

回答3:

I am using a Linearlayout with weights. I created multiple values for the footer weight, it works perfectly.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/white"
    android:orientation="vertical"

<include layout="@layout/header" />

    <android.support.v7.widget.RecyclerView
    android:id="@+id/recycleView"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="0.5"
    tools:layout_height="0dp"
    tools:listitem="@layout/row" />

<TextView
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="@dimen/footer_weight"
    android:padding="@dimen/extra_padding"
    android:paddingEnd="@dimen/small_padding"
    android:paddingLeft="@dimen/small_padding"
    android:paddingRight="@dimen/small_padding"
    android:paddingStart="@dimen/small_padding"
    android:text="@string/contact"
    android:textColor="@color/grey" />

 </LinearLayout>

回答4:

All these solutions don't work. When you minimize app and open it again, footer flies lower than the bottom of the screen and you need to scroll to see it, even if there are just 1-2 items. You can add footer view below your recycler view in xml.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/white">

<android.support.v4.widget.NestedScrollView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fillViewport="true"
    android:overScrollMode="never"
    android:scrollbars="none">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <android.support.v7.widget.RecyclerView
            android:id="@+id/recyclerView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />

        <android.support.v4.widget.Space
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:minHeight="1dp" />

        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">

            <include layout="@layout/recyclerView_footer" />
        </FrameLayout>
    </LinearLayout>
</android.support.v4.widget.NestedScrollView>

pay attention - I used NestedScrollView with

    recyclerView.isNestedScrollingEnabled = false

and SpaceView has weight 1 and height = 0dp and all this stuff inside of linear layout and NestedScrollView has height = match_parent, now I have footer stuck to the bottom and it is moving further when list become larger

回答5:

I know, that this is an old question, but I'll add an answer for those who would search for such decision in future. It is POSSIBLE to keep last item at the bottom of the screen in case you have only few or no items and make the last item to scroll with the recyclerview when you have many items.

How to achieve. Your RecyclerView adapter should apply several view types: views, which should be shown as a list item; view, which should be shown as footer; an empty view. You may check how to put items with different views to the RecyclerView here: https://stackoverflow.com/a/29362643/6329995 Locate an empty view between your main list and the footer view. Then in onBindViewHolder for the empty view check whether your main list views and footer view take all screen. If yes - set empty view height to zero, otherwise set it to the height which appears to be not taken by items and footer. That's all. You may also update that height dynamically, when you delete/add rows. Just call notifyItemChanged for your empty space item after you update the list.

You'd also set your RecyclerView height to match_parent or exact height, NOT wrap_content!

Hope this helps.

回答6:

If you cannot forget about RecyclerView and use ListView, then go check this link out Is there an addHeaderView equivalent for RecyclerView? it has everything you need. It's about header, but it's pretty much the same, except that header is in the beginning of your list and footer is in the end.