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?
这很简单，你不需要这么复杂的代码:
DividerItemDecoration divider = new DividerItemDecoration(
mRVMovieReview.getContext(), DividerItemDecoration.VERTICAL
);
divider.setDrawable(
ContextCompat.getDrawable(getBaseContext(), R.drawable.line_divider)
);
mRVMovieReview.addItemDecoration(divider);
将它添加到你的drawable: line_divide .xml中
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<size android:height="1dp" />
<solid android:color="@android:color/black" />
</shape>
从谷歌搜索，添加这个ItemDecoration到你的RecyclerView:
public class DividerItemDecoration extends RecyclerView.ItemDecoration {
private Drawable mDivider;
private boolean mShowFirstDivider = false;
private boolean mShowLastDivider = false;
public DividerItemDecoration(Context context, AttributeSet attrs) {
final TypedArray a = context
.obtainStyledAttributes(attrs, new int[]{android.R.attr.listDivider});
mDivider = a.getDrawable(0);
a.recycle();
}
public DividerItemDecoration(Context context, AttributeSet attrs, boolean showFirstDivider,
boolean showLastDivider) {
this(context, attrs);
mShowFirstDivider = showFirstDivider;
mShowLastDivider = showLastDivider;
}
public DividerItemDecoration(Drawable divider) {
mDivider = divider;
}
public DividerItemDecoration(Drawable divider, boolean showFirstDivider,
boolean showLastDivider) {
this(divider);
mShowFirstDivider = showFirstDivider;
mShowLastDivider = showLastDivider;
}
@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.getChildPosition(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;
}
// Initialization needed to avoid compiler warning
int left = 0, right = 0, top = 0, bottom = 0, size;
int orientation = getOrientation(parent);
int childCount = parent.getChildCount();
if (orientation == LinearLayoutManager.VERTICAL) {
size = mDivider.getIntrinsicHeight();
left = parent.getPaddingLeft();
right = parent.getWidth() - parent.getPaddingRight();
} else { // Horizontal
size = mDivider.getIntrinsicWidth();
top = parent.getPaddingTop();
bottom = parent.getHeight() - parent.getPaddingBottom();
}
for (int i = mShowFirstDivider ? 0 : 1; i < childCount; i++) {
View child = parent.getChildAt(i);
RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
if (orientation == LinearLayoutManager.VERTICAL) {
top = child.getTop() - params.topMargin;
bottom = top + size;
} else { // Horizontal
left = child.getLeft() - params.leftMargin;
right = left + size;
}
mDivider.setBounds(left, top, right, bottom);
mDivider.draw(c);
}
// Show the last divider
if (mShowLastDivider && childCount > 0) {
View child = parent.getChildAt(childCount - 1);
RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
if (orientation == LinearLayoutManager.VERTICAL) {
top = child.getBottom() + params.bottomMargin;
bottom = top + size;
} else { // hHorizontal
left = child.getRight() + params.rightMargin;
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.");
}
}
}
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>
以下是我的偷懒方法，但它很有效:
将CardView包装在一个布局中，并在父布局上设置一个填充/边距来模拟分隔符，并强制将普通分隔符设置为null。
文件list_item.xml
<LinearLayout
android:id="@+id/entry_item_layout_container"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:paddingBottom="<divider_size>" > // This is the divider
<CardView
android:layout_width="<width_size>"
android:layout_height="<height_size>">
...
</CardView>
</LinearLayout
文件list.xml
<RecyclerView
android:divider="@null"
android:layout_width="<width_size>"
android:layout_height="<height_size>"
...
/>
我们可以使用附加到recyclerview的各种装饰器来装饰物品，例如:
简单地使用下面的…从答案中提取
public class DividerItemDecoration extends RecyclerView.ItemDecoration {
private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
private Drawable mDivider;
/**
* Default divider will be used
*/
public DividerItemDecoration(Context context) {
final TypedArray styledAttributes = context.obtainStyledAttributes(ATTRS);
mDivider = styledAttributes.getDrawable(0);
styledAttributes.recycle();
}
/**
* Custom divider will be used
*/
public DividerItemDecoration(Context context, int resId) {
mDivider = ContextCompat.getDrawable(context, resId);
}
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
int left = parent.getPaddingLeft();
int right = parent.getWidth() - parent.getPaddingRight();
int childCount = parent.getChildCount();
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;
int bottom = top + mDivider.getIntrinsicHeight();
mDivider.setBounds(left, top, right, bottom);
mDivider.draw(c);
}
}
}
然后用上面的方法如下:
RecyclerView.ItemDecoration itemDecoration = new DividerItemDecoration(this, DividerItemDecoration.VERTICAL_LIST);
recyclerView.addItemDecoration(itemDecoration);
这将在列表中的每个项目之间显示分隔符，如下所示:
对于那些想要了解更多细节的人，可以看看这个指南Using the recyclerview_ CodePath Android Cliffnotes。
这里的一些答案建议使用边距，但问题是:
如果你同时添加了上边距和下边距，它们将在项目之间显示为添加的，而且它们将太大。如果只添加其中之一，则整个列表的顶部或底部都没有边距。如果你在上面加上一半的距离，在下面加上一半的距离，外层的边缘就太小了。
因此，唯一美观上正确的解决方案是系统知道在哪里正确应用的分隔符:项目之间，但不是项目的上面或下面。
