java - 在元素顶部添加 DividerItemDecoration

Question

我正在尝试在 RecyclerView 中的元素顶部添加分隔线。

根据google我成功添加了一个DividerItemDecoration，代码如下:

DividerItemDecoration:

public class DividerItemDecoration extends RecyclerView.ItemDecoration {

private static final int[] ATTRS = new int[]{
        android.R.attr.listDivider
};

public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;
public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;
private Drawable mDivider;
private int mOrientation;

public DividerItemDecoration(Context context, int orientation) {
    final TypedArray a = context.obtainStyledAttributes(ATTRS);
    mDivider = a.getDrawable(0);
    a.recycle();
    setOrientation(orientation);
}

public void setOrientation(int orientation) {
    if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST) {
        throw new IllegalArgumentException("invalid orientation");
    }
    mOrientation = orientation;
}

@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
    if (mOrientation == VERTICAL_LIST) {
        drawVertical(c, parent);
    } else {
        drawHorizontal(c, parent);
    }
}

public void drawVertical(Canvas c, RecyclerView parent) {
    final int left = parent.getPaddingLeft();
    final int right = parent.getWidth() - parent.getPaddingRight();

    final int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                .getLayoutParams();
        final int top = child.getBottom() + params.bottomMargin;
        final int bottom = top + mDivider.getIntrinsicHeight();
        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(c);
    }
}

public void drawHorizontal(Canvas c, RecyclerView parent) {
    final int top = parent.getPaddingTop();
    final int bottom = parent.getHeight() - parent.getPaddingBottom();

    final int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                .getLayoutParams();
        final int left = child.getRight() + params.rightMargin;
        final int right = left + mDivider.getIntrinsicHeight();
        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(c);
    }
}

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
    if (mOrientation == VERTICAL_LIST) {
        outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
    } else {
        outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
    }
}
}

结果:

我想要完成的事情:

我尝试使用偏移量和索引，但没有得到预期的结果。

如何在我的元素之上添加相同的项目分隔符？

此外，如果有必要，我会留下我的行布局，这是代码:

行:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <TextView
        android:id="@+id/tvDescrizione"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:textStyle="italic"
        android:textColor="#000"
        android:textSize="18sp"/>

    <TextView
        android:id="@+id/tvBarcode"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tvDescrizione"
        android:textColor="#000"
        android:textSize="18sp"/>

    <TextView
        android:id="@+id/tvData"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tvDescrizione"
        android:layout_alignParentEnd="true"
        android:textColor="#000"
        android:textSize="18sp"/>

</RelativeLayout>

Answer 1

说明:在这个答案中，我在 RecyclerView 中的每个项目上方和 RecyclerView 本身之后添加了一个分隔线。这样你就不会出现“过度绘制”，其中 2 条线相互重叠绘制。为此我使用了 View 标签，它从 xml 中绘制了一条简单的线。

行文件:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <View android:layout_height="2dp"
        android:layout_width="match_parent"
        android:layout_marginBottom="5dp"
        android:background="@color/colorPrimary"/>

    <TextView
        android:id="@+id/tvDescrizione"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:textStyle="italic"
        android:textColor="#000"
        android:textSize="18sp"/>

    <TextView
        android:id="@+id/tvBarcode"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tvDescrizione"
        android:textColor="#000"
        android:textSize="18sp"/>

    <TextView
        android:id="@+id/tvData"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tvDescrizione"
        android:layout_alignParentEnd="true"
        android:textColor="#000"
        android:textSize="18sp"/>

</RelativeLayout>

主文件:

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

        <android.support.v7.widget.RecyclerView
            android:id="@+id/repository_rv"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            tools:listitem="@layout/tmp3"
            android:layout_marginTop="30dp"/>

        <View
            android:id="@+id/bottomLine"
            android:layout_height="2dp"
            android:layout_marginTop="5dp"
            android:layout_width="match_parent"
            android:background="@color/colorPrimary"/>

 </LinearLayout>