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?
我觉得需要一个简单的、不使用XML的、基于代码的答案
DividerItemDecoration dividerItemDecoration = new DividerItemDecoration(recyclerView.getContext(), DividerItemDecoration.VERTICAL);
ShapeDrawable shapeDrawableForDivider = new ShapeDrawable(new RectShape());
int dividerThickness = // (int) (SomeOtherView.getHeight() * desiredPercent);
shapeDrawableForDivider.setIntrinsicHeight(dividerThickness);
shapeDrawableForDivider.setAlpha(0);
dividerItemDecoration.setDrawable(shapeDrawableForDivider);
recyclerView.addItemDecoration(dividerItemDecoration);
我非常喜欢这个答案，我用Kotlin的单一表达式重新写了一遍:
recyclerView.addItemDecoration(DividerItemDecoration(this,DividerItemDecoration.VERTICAL).also { deco ->
with (ShapeDrawable(RectShape())){
intrinsicHeight = (resources.displayMetrics.density * 24).toInt()
alpha = 0
deco.setDrawable(this)
}
})
这和@Nerdy最初的答案是一样的，只是它将分隔线的高度设置为24dp，而不是另一个视图高度的百分比。
这里有一个装饰，可以让你设置项目之间的间距以及边缘的间距。这适用于水平和垂直布局。
class LinearSpacingDecoration(
@Px private val itemSpacing: Int,
@Px private val edgeSpacing: Int = 0
): RecyclerView.ItemDecoration() {
override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
val count = parent.adapter?.itemCount ?: 0
val position = parent.getChildAdapterPosition(view)
val leading = if (position == 0) edgeSpacing else itemSpacing
val trailing = if (position == count - 1) edgeSpacing else 0
outRect.run {
if ((parent.layoutManager as? LinearLayoutManager)?.orientation == LinearLayout.VERTICAL) {
top = leading
bottom = trailing
} else {
left = leading
right = trailing
}
}
}
}
用法:
recyclerView.addItemDecoration(LinearSpacingDecoration(itemSpacing = 10, edgeSpacing = 20))
为了在RecylerView中实现项目之间的间隔，我们可以使用ItemDecorators:
addItemDecoration(object : RecyclerView.ItemDecoration() {
override fun getItemOffsets(
outRect: Rect,
view: View,
parent: RecyclerView,
state: RecyclerView.State,
) {
super.getItemOffsets(outRect, view, parent, state)
if (parent.getChildAdapterPosition(view) > 0) {
outRect.top = 8.dp // Change this value with anything you want. Remember that you need to convert integers to pixels if you are working with dps :)
}
}
})
对于我粘贴的代码，有几件事需要考虑:
You don't really need to call super.getItemOffsets but I chose to, because I want to extend the behavior defined by the base class. If the library got an update doing more logic behind the scenes, we would miss it.
As an alternative to adding top spacing to the Rect, you could also add bottom spacing, but the logic related to getting the last item of the adapter is more complex, so this might be slightly better.
I used an extension property to convert a simple integer to dps: 8.dp. Something like this might work:
val Int.dp: Int
get() = (this * Resources.getSystem().displayMetrics.density + 0.5f).toInt()
// Extension function works too, but invoking it would become something like 8.dp()
对于那些只在RecyclerView中寻找项目之间的空间的人，请参阅我的方法，在所有项目之间获得相等的空间，除了在第一个和最后一个项目中，我给出了较大的填充。我只应用填充左/右在水平的LayoutManager和顶部/底部在垂直的LayoutManager。
public class PaddingItemDecoration extends RecyclerView.ItemDecoration {
private int mPaddingPx;
private int mPaddingEdgesPx;
public PaddingItemDecoration(Activity activity) {
final Resources resources = activity.getResources();
mPaddingPx = (int) resources.getDimension(R.dimen.paddingItemDecorationDefault);
mPaddingEdgesPx = (int) resources.getDimension(R.dimen.paddingItemDecorationEdge);
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
final int itemPosition = parent.getChildAdapterPosition(view);
if (itemPosition == RecyclerView.NO_POSITION) {
return;
}
int orientation = getOrientation(parent);
final int itemCount = state.getItemCount();
int left = 0;
int top = 0;
int right = 0;
int bottom = 0;
/** Horizontal */
if (orientation == LinearLayoutManager.HORIZONTAL) {
/** All positions */
left = mPaddingPx;
right = mPaddingPx;
/** First position */
if (itemPosition == 0) {
left += mPaddingEdgesPx;
}
/** Last position */
else if (itemCount > 0 && itemPosition == itemCount - 1) {
right += mPaddingEdgesPx;
}
}
/** Vertical */
else {
/** All positions */
top = mPaddingPx;
bottom = mPaddingPx;
/** First position */
if (itemPosition == 0) {
top += mPaddingEdgesPx;
}
/** Last position */
else if (itemCount > 0 && itemPosition == itemCount - 1) {
bottom += mPaddingEdgesPx;
}
}
if (!isReverseLayout(parent)) {
outRect.set(left, top, right, bottom);
} else {
outRect.set(right, bottom, left, top);
}
}
private boolean isReverseLayout(RecyclerView parent) {
if (parent.getLayoutManager() instanceof LinearLayoutManager) {
LinearLayoutManager layoutManager = (LinearLayoutManager) parent.getLayoutManager();
return layoutManager.getReverseLayout();
} else {
throw new IllegalStateException("PaddingItemDecoration can only be used with a LinearLayoutManager.");
}
}
private int getOrientation(RecyclerView parent) {
if (parent.getLayoutManager() instanceof LinearLayoutManager) {
LinearLayoutManager layoutManager = (LinearLayoutManager) parent.getLayoutManager();
return layoutManager.getOrientation();
} else {
throw new IllegalStateException("PaddingItemDecoration can only be used with a LinearLayoutManager.");
}
}
}
文件dimens.xml
<resources>
<dimen name="paddingItemDecorationDefault">10dp</dimen>
<dimen name="paddingItemDecorationEdge">20dp</dimen>
</resources>
