Android - 如何为RecyclerView添加虚线/点线分隔线？

Question

我已经使用了这个答案中的代码来为我的RecyclerView创建一个坚实的分隔线。

然而，我想要将这条线变成虚线/点线。

我已经有一个line_dashed.xml资源文件，我在应用的其他地方使用它。

<shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="line" >

    <stroke
        android:color="@color/blue"
        android:dashGap="12dp"
        android:dashWidth="12dp"
        android:width="1dp" />

</shape>

但是，如果我尝试将此作为可通过我的recyclerView.addItemDecoration(new SimpleDividerItemDecoration(getContext()))调用访问的可绘制资源应用，则根本不会绘制任何线条。

如何解决，以便显示虚线？

- ban-geoengineering

Answer 1

只需将您的可绘制资源添加到此项装饰器中即可。

DividerItemDecoration decorator = new DividerItemDecoration(ContextCompat.getDrawable(getContext(), R.drawable.line_dashed));
recyclerView.addItemDecoration(decorator);

和DividerItemDecorator类：

public class DividerItemDecoration extends RecyclerView.ItemDecoration {

    private Drawable mDivider;
    private int mPaddingLeft;

    public DividerItemDecoration(Drawable divider) {
        mDivider = divider;
        mPaddingLeft = 0;
    }

    public DividerItemDecoration(Drawable divider, int paddingLeft) {
        mDivider = divider;
        mPaddingLeft = paddingLeft;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        if (mDivider == null) return;
        if (parent.getChildAdapterPosition(view) < 1) return;

        if (getOrientation(parent) == LinearLayoutManager.VERTICAL) {
            outRect.top = mDivider.getIntrinsicHeight();
        } else {
            outRect.left = mDivider.getIntrinsicWidth();
        }
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        if (mDivider == null) {
            super.onDrawOver(c, parent, state);
            return;
        }

        if (getOrientation(parent) == LinearLayoutManager.VERTICAL) {
            final int left = parent.getPaddingLeft() + mPaddingLeft;
            final int right = parent.getWidth() - parent.getPaddingRight();
            final int childCount = parent.getChildCount();

            for (int i = 1; i < childCount; i++) {
                final View child = parent.getChildAt(i);
                final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
                final int size = mDivider.getIntrinsicHeight();
                final int top = child.getTop() - params.topMargin;
                final int bottom = top + size;
                mDivider.setBounds(left, top, right, bottom);
                mDivider.draw(c);
            }

        } else { //horizontal
            final int top = parent.getPaddingTop();
            final int bottom = parent.getHeight() - parent.getPaddingBottom();
            final int childCount = parent.getChildCount();

            for (int i = 1; i < childCount; i++) {
                final View child = parent.getChildAt(i);
                final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
                final int size = mDivider.getIntrinsicWidth();
                final int left = child.getLeft() - params.leftMargin;
                final int right = left + size;
                mDivider.setBounds(left, top, right, bottom);
                mDivider.draw(c);
            }
        }
    }

    private int getOrientation(RecyclerView parent) {
        if (parent.getLayoutManager() instanceof LinearLayoutManager) {
            LinearLayoutManager layoutManager = (LinearLayoutManager) parent.getLayoutManager();
            return layoutManager.getOrientation();
        } else
            throw new IllegalStateException("DividerItemDecoration can only be used with a LinearLayoutManager.");
    }
}

我测试过，应该是可以正常工作的。

更新：

    android:layerType="software"

在xml中为RecyclerView添加此参数。同时，在您的形状可绘制项中添加大小：

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

- Mykhailo

---

它对我有用 - 只是需要做一个更改：我不得不在line_dashed.xml中添加 <size android:height="2dp"/> 才能看到它 - 也就是说，我必须指定高度为 2dp 而不是 1dp。有任何想法为什么会这样吗？ - ban-geoengineering

我也不得不指定高度为2dp而不是1dp才能使其正常工作。有任何想法吗？ - Ozeetee

是的，确切地说，只有在高度为2dp而不是1dp时才起作用。 - Deepak Goyal

@DeepakGoyal - 一些设备尺寸在转换计算中会将1dp转换为<1像素。在这种情况下，像您所做的那样将其设置为1px或2dp通常是一个好主意。 - Mitch Ware

它正常工作，但 android:layerType="software" 禁用卡片视图的阴影。 - Mohamed Moamen

Answer 2

目前您可以使用来自框中的DividerItemDecoration。

recyclerView.apply {
        layoutManager = LinearLayoutManager([e-mail])
        adapter = [e-mail]
        addItemDecoration(
            DividerItemDecoration(
                [e-mail],
                DividerItemDecoration.VERTICAL
            ).apply {
                context.getDrawable(R.drawable.divider)?.let {
                    setDrawable(it)
                }
            }
        )
    }

请使用下面的形状XML：

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="line">

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

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

    <stroke
        android:width="0.5dp"
        android:color="@color/primary"
        android:dashWidth="5dp"
        android:dashGap="5dp" />
</shape>

注意: 笔画宽度必须小于线的高度。否则，线将无法绘制。

- Alex

---

这一点对我来说非常关键：注意：线条的宽度必须小于线的高度。否则，线将无法绘制。 - trod

Answer 3

在Android中绘制虚线并不是一件容易的事情。像你展示的那样绘制可绘制对象，甚至只是在画布上绘制点线（canvas.drawLine(..., paintWithDashEffect)）并不总是有效（并非所有设备都适用）。您可以使用android:layerType="software"或绘制路径。在我看来，更好的解决方案是根本不绘制虚线（只绘制实线）。但是，如果您真的需要虚线，可以使用@fearless的答案或类似这样的东西：

public class DividerItemDecoration extends RecyclerView.ItemDecoration {

private Paint mPaint;
private int mDividerSize;

public DividerItemDecoration(int dividerSize) {
    mDividerSize = dividerSize;
    mPaint = new Paint();
    mPaint.setColor(ContextCompat.getColor(context, R.color.colorAccent));
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeWidth(dividerSize);
    mPaint.setPathEffect(new DashPathEffect(new float[]{dashGap,dashWidth},0));
}

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
    outRect.bottom = mDividerSize;
}

@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();
    Path path = new Path();
    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 + mDividerSize/2;

        path.moveTo(left, top);
        path.lineTo(right, top);
    }
    c.drawPath(path, mPaint);
}

}

- Roman_D