这是之前在ListView类中使用divider和dividerHeight参数实现的一个例子:
<ListView
android:id="@+id/activity_home_list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:divider="@android:color/transparent"
android:dividerHeight="8dp"/>
然而，在RecyclerView类中我没有看到这样的可能性。
<android.support.v7.widget.RecyclerView
android:id="@+id/activity_home_recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical"/>
在这种情况下，是否可以定义边距和/或直接添加自定义分隔符视图到列表项的布局中，或者是否有更好的方法来实现我的目标?
只需添加
recyclerView.addItemDecoration(new DividerItemDecoration(getContext(),
DividerItemDecoration.VERTICAL));
此外，您可能还需要添加依赖项
实现“com.android.support: recyclerview-v7:28.0.0”
为了自定义它，你可以添加一个自定义drawable:
DividerItemDecoration itemDecorator = new DividerItemDecoration(getContext(), DividerItemDecoration.VERTICAL);
itemDecorator.setDrawable(ContextCompat.getDrawable(getContext(), R.drawable.divider));
你可以自由地使用任何自定义绘图，例如:
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<solid android:color="@color/colorPrimary"/>
<size android:height="0.5dp"/>
</shape>
下面是我在Kotlin中如何做的，在项目之间设置一个默认大小为10dp的简单空间:
class SimpleItemDecoration(context: Context, space: Int = 10) : RecyclerView.ItemDecoration() {
private val spaceInDp = ConvertUtil.dpToPx(context, space)
override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
outRect.left = spaceInDp
outRect.right = spaceInDp
outRect.bottom = spaceInDp
// Add top margin only for the first item to avoid double space between items
if (parent.getChildAdapterPosition(view) == 0) {
outRect.top = spaceInDp
}
}
}
这是dpToPx方法:
fun dpToPx(context: Context, dp: Int): Int {
return (dp * context.resources.displayMetrics.density).toInt()
}
然后像这样将它添加到RecyclerView中:(感谢@MSpeed)
recyclerView.addItemDecoration(SimpleItemDecoration(context))
如果有人只想在项目之间添加10dp的间距，你可以通过设置一个drawable到DividerItemDecoration来实现:
DividerItemDecoration dividerItemDecoration = new DividerItemDecoration(
recyclerView.getContext(),
layoutManager.getOrientation()
);
dividerItemDecoration.setDrawable(
ContextCompat.getDrawable(getContext(), R.drawable.divider_10dp)
);
recyclerView.addItemDecoration(dividerItemDecoration);
其中，divider_10dpis一个可绘制资源，包含:
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle">
<size android:height="10dp"/>
<solid android:color="@android:color/transparent"/>
</shape>
如果你想为物品添加相同的空间，最简单的方法是为RecycleView添加顶部+左侧填充，为卡片物品添加右侧+底部空白。
文件dimens.xml
<resources>
<dimen name="divider">1dp</dimen>
</resources>
文件list_item.xml
<CardView
android:layout_marginBottom="@dimen/divider"
android:layout_marginRight="@dimen/divider">
...
</CardView>
文件list.xml
<RecyclerView
...
android:paddingLeft="@dimen/divider"
android:paddingTop="@dimen/divider" />
我从一个旧的要点中分叉了DividerItemDecoration，并简化了它以适应我的用例，我还修改了它，以在ListView中绘制的方式绘制分隔符，包括在最后一个列表项之后的分隔符。这也会处理垂直的ItemAnimator动画:
1)将这个类添加到你的项目中:
public class DividerItemDecoration extends RecyclerView.ItemDecoration {
private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
private Drawable divider;
public DividerItemDecoration(Context context) {
try {
final TypedArray a = context.obtainStyledAttributes(ATTRS);
divider = a.getDrawable(0);
a.recycle();
} catch (Resources.NotFoundException e) {
// TODO Log or handle as necessary.
}
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
if (divider == null) return;
if (parent.getChildAdapterPosition(view) < 1) return;
if (getOrientation(parent) == LinearLayoutManager.VERTICAL)
outRect.top = divider.getIntrinsicHeight();
else
throw new IllegalArgumentException("Only usable with vertical lists");
}
@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
if (divider == null) {
super.onDrawOver(c, parent, state);
return;
}
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 size = divider.getIntrinsicHeight();
final int top = (int) (child.getTop() - params.topMargin - size + child.getTranslationY());
final int bottom = top + size;
divider.setBounds(left, top, right, bottom);
divider.draw(c);
if (i == childCount - 1) {
final int newTop = (int) (child.getBottom() + params.bottomMargin + child.getTranslationY());
final int newBottom = newTop + size;
divider.setBounds(left, newTop, right, newBottom);
divider.draw(c);
}
}
}
private int getOrientation(RecyclerView parent) {
if (!(parent.getLayoutManager() instanceof LinearLayoutManager))
throw new IllegalStateException("Layout manager must be an instance of LinearLayoutManager");
return ((LinearLayoutManager) parent.getLayoutManager()).getOrientation();
}
}
2)添加装饰器到你的RecylerView:
recyclerView.addItemDecoration(new DividerItemDecoration(getActivity()));
