RecyclerView在最后一项之后删除分隔符/装饰器

时间：2017-09-14 09:47:41

标签： android android-recyclerview divider

我有一个非常简单的RecyclerView。 这就是我设置分隔符的方法

DividerItemDecoration itemDecorator = new DividerItemDecoration(getContext(), DividerItemDecoration.VERTICAL);
itemDecorator.setDrawable(ContextCompat.getDrawable(getActivity(), R.drawable.news_divider));
recyclerView.addItemDecoration(itemDecorator);

这是drawable / news_divider.xml 

<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle">
    <solid android:color="@color/white_two"/>
    <size android:height="1dp"/>
</shape>

问题是由于一些愚蠢的原因，分隔符不仅仅是在项目之间创建的。但也是在最后一项之后。而且我只想在不是每个项目之后的项目之间。

知道如何防止分隔符出现在最后一项之后吗？

干杯谢谢

10 个答案:

答案 0 :(得分：52)

尝试使用此代码，它不会显示最后一项的分隔符。

public class DividerItemDecorator extends RecyclerView.ItemDecoration {
    private Drawable mDivider;

    public DividerItemDecorator(Drawable divider) {
        mDivider = divider;
    }

    @Override
    public void onDraw(Canvas canvas, RecyclerView parent, RecyclerView.State state) {
        int dividerLeft = parent.getPaddingLeft();
        int dividerRight = parent.getWidth() - parent.getPaddingRight();

        int childCount = parent.getChildCount();
        for (int i = 0; i <= childCount - 2; i++) {
            View child = parent.getChildAt(i);

            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();

            int dividerTop = child.getBottom() + params.bottomMargin;
            int dividerBottom = dividerTop + mDivider.getIntrinsicHeight();

            mDivider.setBounds(dividerLeft, dividerTop, dividerRight, dividerBottom);
            mDivider.draw(canvas);
        }
    }
}

<强> divider.xml： 

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <size
        android:width="1dp"
        android:height="1dp" />
    <solid android:color="@color/grey_300" />
</shape>

将分隔符设置为：

RecyclerView.ItemDecoration dividerItemDecoration = new DividerItemDecorator(ContextCompat.getDrawable(context, R.drawable.divider));
recyclerView.addItemDecoration(dividerItemDecoration);

答案 1 :(得分：32)

建议here你可以像这样扩展DividerItemDecoration：

recyclerView.addItemDecoration(
    new DividerItemDecoration(context, layoutManager.getOrientation()) {
        @Override
        public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
            int position = parent.getChildAdapterPosition(view);
            // hide the divider for the last child
            if (position == parent.getAdapter().getItemCount() - 1) {
                outRect.setEmpty();
            } else {
                super.getItemOffsets(outRect, view, parent, state);
            }
        }
    }
);

<强> [UPDATE]
@Rebecca Hsieh指出：

当RecyclerView中的项目视图没有透明背景时，此有效，例如，

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:background="#ffffff">
    ... 
</LinearLayout>

RecyclerItemDecoration.getItemOffsets由RecyclerView调用以测量子位置。此解决方案将最后一个分隔符放在最后一个项目后面。因此，RecyclerView中的项目视图应该有一个背景来覆盖最后一个分隔符，这使它看起来像隐藏。

其他解决方案

如果你不喜欢被分开的分隔符，你可以简单地复制或扩展DividerItemDecoration类并通过将for (int i = 0; i < childCount; i++)修改为for (int i = 0; i < childCount - 1; i++)来改变其绘图行为

答案 2 :(得分：5)

接受的答案并没有为装饰分配空间，因为它没有覆盖getItemOffsets()

我调整了支持库中的DividerItemDecoration，以排除最后一项的装饰

public class DividerItemDecorator extends RecyclerView.ItemDecoration {

    private Drawable mDivider;
    private final Rect mBounds = new Rect();

    public DividerItemDecorator(Drawable divider) {
        mDivider = divider;
    }

    @Override
    public void onDraw(Canvas canvas, RecyclerView parent, RecyclerView.State state) {
        canvas.save();
        final int left;
        final int right;
        if (parent.getClipToPadding()) {
            left = parent.getPaddingLeft();
            right = parent.getWidth() - parent.getPaddingRight();
            canvas.clipRect(left, parent.getPaddingTop(), right,
                    parent.getHeight() - parent.getPaddingBottom());
        } else {
            left = 0;
            right = parent.getWidth();
        }

        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount - 1; i++) {
            final View child = parent.getChildAt(i);
            parent.getDecoratedBoundsWithMargins(child, mBounds);
            final int bottom = mBounds.bottom + Math.round(child.getTranslationY());
            final int top = bottom - mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
        canvas.restore();
    }

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

        if (parent.getChildAdapterPosition(view) == state.getItemCount() - 1) {
            outRect.setEmpty();
        } else
            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
    }
}

要应用装饰器，请使用

RecyclerView.ItemDecoration dividerItemDecoration = new DividerItemDecorator(dividerDrawable);
recyclerView.addItemDecoration(dividerItemDecoration);

可以在此处找到包含方向的来源 https://gist.github.com/abdulalin/146f8ca42aa8322692b15663b8d508ff

答案 3 :(得分：5)

这是 接受的答案 的Kotlin版本：

class DividerItemDecorator(private val divider: Drawable?) : RecyclerView.ItemDecoration() {

    override fun onDrawOver(canvas: Canvas, parent: RecyclerView, state: RecyclerView.State) {
        val dividerLeft = parent.paddingLeft
        val dividerRight = parent.width - parent.paddingRight
        val childCount = parent.childCount
        for (i in 0..childCount - 2) {
            val child: View = parent.getChildAt(i)
            val params =
                child.layoutParams as RecyclerView.LayoutParams
            val dividerTop: Int = child.bottom + params.bottomMargin
            val dividerBottom = dividerTop + (divider?.intrinsicHeight?:0)
            divider?.setBounds(dividerLeft, dividerTop, dividerRight, dividerBottom)
            divider?.draw(canvas)
        }
    }
}

答案 4 :(得分：3)

Kotlin的扩展功能：

fun RecyclerView.addItemDecorationWithoutLastDivider() {

    if (layoutManager !is LinearLayoutManager)
        return

    addItemDecoration(object :
        DividerItemDecoration(context, (layoutManager as LinearLayoutManager).orientation) {

        override fun getItemOffsets( outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
            super.getItemOffsets(outRect, view, parent, state)

            if (parent.getChildAdapterPosition(view) == state.itemCount - 1)
                outRect.setEmpty()
            else
                super.getItemOffsets(outRect, view, parent, state)
        }
    })
}

您可以轻松使用它：

recyclerView.addItemDecorationWithoutLastDivider()

答案 5 :(得分：2)

创建自己的Divider类（Example here）

在绘制分隔符的代码中，首先检查是否为列表中的最后一项绘制分隔符。如果是这样，请不要画画。

请注意，如果您覆盖OnDrawOver，则会在您的视图的顶部绘制，包括滚动条等。最好坚持OnDraw。 Google上有很多例子，但this是一个关于创建自己的装饰器的好教程。

答案 6 :(得分：2)

以下是我在我的应用中使用的DividerDecorator类，它删除了最后一项的底线。

public class DividerDecorator extends RecyclerView.ItemDecoration {
    private Drawable mDivider;

    public DividerDecorator(Context context) {
        mDivider = context.getResources().getDrawable(R.drawable.recyclerview_divider);
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        int left = parent.getPaddingLeft();
        int right = parent.getWidth() - parent.getPaddingRight();

        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);

            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();

            int top = child.getBottom() + params.bottomMargin;
            int bottom = top + mDivider.getIntrinsicHeight();

            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }
}

您可以使用以下代码将其设置为RecyclerView：

mRecyclerViewEvent.addItemDecoration(new DividerDecorator(context));

这是recyclerview_divider.xml 

<size
    android:width="1dp"
    android:height="1dp" />

<solid android:color="@color/DividerColor" />

答案 7 :(得分：1)

这是Android支持DividerItemDecoration的自定义版本，忽略了最后一项：

  

https://gist.github.com/mohsenoid/8ffdfa53f0465533833b0b44257aa641

主要区别是：

private fun drawVertical(canvas: Canvas, parent: RecyclerView) {
    canvas.save()
    val left: Int
    val right: Int

    if (parent.clipToPadding) {
        left = parent.paddingLeft
        right = parent.width - parent.paddingRight
        canvas.clipRect(left, parent.paddingTop, right,
                parent.height - parent.paddingBottom)
    } else {
        left = 0
        right = parent.width
    }

    val childCount = parent.childCount
    for (i in 0 until childCount - 1) {
        val child = parent.getChildAt(i)
        parent.getDecoratedBoundsWithMargins(child, mBounds)
        val bottom = mBounds.bottom + Math.round(child.translationY)
        val top = bottom - mDivider!!.intrinsicHeight
        mDivider!!.setBounds(left, top, right, bottom)
        mDivider!!.draw(canvas)
    }
    canvas.restore()
}

private fun drawHorizontal(canvas: Canvas, parent: RecyclerView) {
    canvas.save()
    val top: Int
    val bottom: Int

    if (parent.clipToPadding) {
        top = parent.paddingTop
        bottom = parent.height - parent.paddingBottom
        canvas.clipRect(parent.paddingLeft, top,
                parent.width - parent.paddingRight, bottom)
    } else {
        top = 0
        bottom = parent.height
    }

    val childCount = parent.childCount
    for (i in 0 until childCount - 1) {
        val child = parent.getChildAt(i)
        parent.layoutManager.getDecoratedBoundsWithMargins(child, mBounds)
        val right = mBounds.right + Math.round(child.translationX)
        val left = right - mDivider!!.intrinsicWidth
        mDivider!!.setBounds(left, top, right, bottom)
        mDivider!!.draw(canvas)
    }
    canvas.restore()
}

答案 8 :(得分：0)

Kotlin 版本和 使用 AbdulAli 的工作答案的原始 DividerItemDecorator 类的新签名函数进行更新：

class DividerItemDecorator(private val mDivider: Drawable) : ItemDecoration() {
    private val mBounds: Rect = Rect()

    override fun onDraw(canvas: Canvas, parent: RecyclerView, state: RecyclerView.State) {
        canvas.save()
        val left: Int
        val right: Int
        if (parent.clipToPadding) {
            left = parent.paddingLeft
            right = parent.width - parent.paddingRight
            canvas.clipRect(
                left, parent.paddingTop, right,
                parent.height - parent.paddingBottom
            )
        } else {
            left = 0
            right = parent.width
        }
        val childCount = parent.childCount
        for (i in 0 until childCount - 1) {
            val child: View = parent.getChildAt(i)
            parent.getDecoratedBoundsWithMargins(child, mBounds)
            val bottom: Int = mBounds.bottom + Math.round(child.getTranslationY())
            val top = bottom - mDivider.intrinsicHeight
            mDivider.setBounds(left, top, right, bottom)
            mDivider.draw(canvas)
        }
        canvas.restore()
    }

    override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
        if (parent.getChildAdapterPosition(view) == state.itemCount - 1) {
            outRect.setEmpty()
        } else outRect.set(0, 0, 0, mDivider.intrinsicHeight)
    }
}

答案 9 :(得分：-2)

如果您已经使用以下设置：

    DividerItemDecoration dividerItemDecoration;
    dividerItemDecoration  = new DividerItemDecoration(context, 
    DividerItemDecoration.VERTICAL);
    mRecyclerView.addItemDecoration(dividerItemDecoration);

，如果要删除：

    mRecyclerView.removeItemDecoration(dividerItemDecoration);
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