Android -如何为RecyclerView添加虚线/点分隔线

Question

我已经使用这个答案中的代码为我的RecyclerView创建了一个实分隔线。

但是，我希望这条线是虚线/虚线。

我已经有一个line_dashed.xml资源，我在我的应用程序的其他地方使用:

<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应用为通过调用recyclerView.addItemDecoration(new SimpleDividerItemDecoration(getContext()))访问的可绘制资源，则根本没有绘制线。

如何解决，所以虚线显示?

Answer 1

只需将您的可绘制资源添加到此项目装饰器中。

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.");
    }
}

应该可以工作，我测试过了。

更新:

    android:layerType="software"

在xml中为recyclerView添加这个参数还可以为可绘制的形状添加大小:

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

Answer 2

目前你可以从框中使用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)
                }
            }
        )
    }

使用下一个形状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:笔画宽度必须小于行高。在另一种情况下，线将不被绘制。

Answer 3

在Android中画虚线并不是那么容易的事情。像你所展示的那样，甚至只是在canwas (canvas.drawLine(..., paintWithDashEffect))上画虚线，并不总是有效(不是所有设备)。您可以使用android:layerType="software"或绘制路径。恕我直言，更好的解决方案是根本不画虚线(只画一条线)。但如果你真的需要虚线，你可以使用@fearless answer或类似的东西:

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);
}
}