Android 如何在recyclerview中实现粘性页脚

我有RecyclerView，我需要下一个行为：

• 如果有很多项目（超过屏幕尺寸），则页脚是最后一项
• 如果少项/无项-页脚位于屏幕底部

---

请告知我如何实现此行为。

如果您不能忘记RecyclerView并使用ListView，请查看此链接，它提供了您所需的一切。这是关于页眉的问题，但基本相同，只是页眉在列表的开头，页脚在列表的末尾。

我知道，这是一个老问题，但我将为那些将来会搜索此类决策的人添加一个答案。可以将最后一个项目保留在屏幕底部，以防您只有很少或没有项目，并在您有很多项目时使用recyclerview滚动最后一个项目

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;
    }
}

如何实现。您的RecyclerView适配器应应用几种视图类型：视图，应显示为列表项；视图，应显示为页脚；空旷的景色。您可以在此处检查如何将具有不同视图的项目放入RecyclerView： 在主列表和页脚视图之间找到一个空视图。 然后在空视图的onBindViewHolder中检查主列表视图和页脚视图是否占据所有屏幕。如果是-将空视图高度设置为零，否则将其设置为项目和页脚似乎不采用的高度。这就是全部。 在删除/添加行时，还可以动态更新该高度。更新列表后，只需调用notifyItemChanged即可为您的空空间项更改

您还可以将RecyclerView高度设置为与父项或确切高度相匹配，而不是包装内容

---

希望这有帮助。

您可以使用RecyclerView.ItemDecoration来实现此行为

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;
    }
}

公共类StickyFooterItemDecoration扩展了RecyclerView.ItemDecoration{
/**
*顶部偏移，以完全隐藏屏幕上的页脚，从而避免在更改页脚位置时出现明显的闪烁。
*/
专用静态最终int关闭屏幕偏移量=5000；
@凌驾
public void getItemOffset（Rect outRect、final View视图、final RecyclerView父级、RecyclerView.State）{
int adapterItemCount=parent.getAdapter（）.getItemCount（）；
if（isFooter（父项、视图、adapterItemCount））{
//第一次，每个视图都不包含与其大小相关的任何参数，
//因此，我们无法计算适当的偏移量。
//在这种情况下，设置一个较大的顶部偏移量，并通知适配器再次更新页脚。
//此外，如果在滚动后页脚变得可见，我们也不应该这样做。
if（view.getHeight（）==0&&state.didStructureChange（））{
hideFooterAndUpdate（outRect、view、parent）；
}否则{
outRect.set（0，calculateTopOffset（父项、视图、适配器项计数），0，0）；
}
}
}
私有void hideFooterAndUpdate（Rect outRect、最终视图footerView、最终回收视图父级）{
outRect.set（0，离屏偏移，0，0）；
footerView.post（新的Runnable（）{
@凌驾
公开募捐{
parent.getAdapter（）.notifyDataSetChanged（）；
}
});
}
私有int calculateTopOffset（RecyclerView父级、视图页脚视图、int itemCount）{
int-topOffset=parent.getHeight（）-visibleChildsHeightWithFooter（parent、footerView、itemCount）；
返回topOffset<0？0:topOffset；
}
私有int visibleChildsHeightWithFooter（RecyclerView父级、View footerView、int itemCount）{
int totalHeight=0；
//在添加或删除动态内容时，适配器的itemCount是可靠的，
//但是，当屏幕可以容纳的项目少于适配器中的项目时，应该使用RecyclerView中的getChildCount（）。
int-onScreenItemCount=Math.min（parent.getChildCount（），itemCount）；
对于（int i=0；i

确保为RecyclerView高度设置匹配父项

请看一下示例应用程序及其工作原理

---

此解决方案的一个巨大缺点是，只有在整个应用程序（而不是内部装饰）中notifyDataSetChanged（）之后，它才能正常工作。对于更具体的通知，它将无法正常工作，为了支持它们，它需要一种更具逻辑性的方法。此外，您还可以通过eowise从库recyclerview stickyheaders中获得见解，并改进此解决方案。

我正在使用带权重的线性布局。我为页脚权重创建了多个值，效果非常好

<?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>

对Dmitry Kornikov进行了改进，解决了调用notify数据集的问题

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());
  }
}

公共类StickyFooterItemDecoration扩展了RecyclerView.ItemDecoration{
@凌驾
public void getItemOffset（Rect outRect、final View视图、final RecyclerView父级、，
RecyclerView.State）{
int position=parent.getChildAdapterPosition（视图）；
int adapterItemCount=parent.getAdapter（）.getItemCount（）；
如果（adapterItemCount==RecyclerView.NO_位置| |（adapterItemCount-1）！=位置）{
返回；
}
outRect.top=calculateTopOffset（父项、视图、适配器项计数）；
}
私有int calculateTopOffset（RecyclerView父级、视图页脚视图、int itemCount）{
整数拓扑偏移=
parent.getHeight（）-parent.getPaddingTop（）-parent.getPaddingBottom（）
-VisibleChightWithFooter（父项、页脚视图、项计数）；
返回topOffset<0？0:topOffset；
}
私密儿童医院
    recyclerView.isNestedScrollingEnabled = false

class FooterViewHolder(private val parent: ViewGroup) {

...

fun bind(item: Item) {
    ...
    itemView.post(::adjustTop)
}

private fun adjustTop() {
    val parent = parent as RecyclerView
    var topOffset = parent.height
    for (child in parent.children) topOffset -= child.height
    (itemView.layoutParams as ViewGroup.MarginLayoutParams)
        .setMargins(0, topOffset.coerceAtLeast(0), 0, 0)
}
}

<ConsraintLayout>
    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:clipToPadding="false"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"/>

    <-- This is your footer and it can be anything you want -->
    <TextView
        android:id="@+id/yourFooter"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"/>

</ConstraintLayout>

view.doOnPreDraw {
    val footerheight = yourFooter.height
    recyclerView.updatePadding(bottom = footerHeight)
    ...
}

view.doOnPreDraw {
    val footerheight = yourFooter.height
    recyclerView.updatePadding(bottom = footerHeight)

    recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
        override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
            val range = recyclerView.computeVerticalScrollRange()
            val extent = recyclerView.computeVerticalScrollExtent()
            val offset = recyclerView.computeVerticalScrollOffset()
            val threshHold = range - footerHeight
            val currentScroll = extent + offset
            val excess = currentScroll - threshHold
            yourFooter.transalationX = if (excess > 0)
                footerHeight * (excess.toFloat()/footerHeight.toFloat()) else 0F
        }
    })
}