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?
实现它自己的RecyclerView版本。ItemDecoration
public class SpacingItemDecoration extends RecyclerView.ItemDecoration {
private int spacingPx;
private boolean addStartSpacing;
private boolean addEndSpacing;
public SpacingItemDecoration(int spacingPx) {
this(spacingPx, false, false);
}
public SpacingItemDecoration(int spacingPx, boolean addStartSpacing, boolean addEndSpacing) {
this.spacingPx = spacingPx;
this.addStartSpacing = addStartSpacing;
this.addEndSpacing = addEndSpacing;
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
if (spacingPx <= 0) {
return;
}
if (addStartSpacing && parent.getChildLayoutPosition(view) < 1 || parent.getChildLayoutPosition(view) >= 1) {
if (getOrientation(parent) == LinearLayoutManager.VERTICAL) {
outRect.top = spacingPx;
} else {
outRect.left = spacingPx;
}
}
if (addEndSpacing && parent.getChildAdapterPosition(view) == getTotalItemCount(parent) - 1) {
if (getOrientation(parent) == LinearLayoutManager.VERTICAL) {
outRect.bottom = spacingPx;
} else {
outRect.right = spacingPx;
}
}
}
private int getTotalItemCount(RecyclerView parent) {
return parent.getAdapter().getItemCount();
}
private int getOrientation(RecyclerView parent) {
if (parent.getLayoutManager() instanceof LinearLayoutManager) {
return ((LinearLayoutManager) parent.getLayoutManager()).getOrientation();
} else {
throw new IllegalStateException("SpacingItemDecoration can only be used with a LinearLayoutManager.");
}
}
}
Here is a simple hack to add a divider
Just add a background to the layout of your recycler item as follows
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/shape_border"
android:gravity="center"
android:orientation="horizontal"
android:padding="5dp">
<ImageView
android:id="@+id/imageViewContactLogo"
android:layout_width="60dp"
android:layout_height="60dp"
android:layout_marginRight="10dp"
android:src="@drawable/ic_user" />
<LinearLayout
android:id="@+id/linearLayout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="0.92"
android:gravity="center|start"
android:orientation="vertical">
<TextView
android:id="@+id/textViewContactName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:singleLine="true"
android:text="Large Text"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="@+id/textViewStatusOrNumber"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="5dp"
android:singleLine="true"
android:text=""
android:textAppearance="?android:attr/textAppearanceMedium" />
</LinearLayout>
<TextView
android:id="@+id/textViewUnreadCount"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:padding="5dp"
android:text=""
android:textAppearance="?android:attr/textAppearanceMedium"
android:textColor="@color/red"
android:textSize="22sp" />
<Button
android:id="@+id/buttonInvite"
android:layout_width="54dp"
android:layout_height="wrap_content"
android:background="@drawable/ic_add_friend" />
</LinearLayout>
在drawable文件夹中创建以下shape_border.xml文件:
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle" >
<gradient
android:angle="270"
android:centerColor="@android:color/transparent"
android:centerX="0.01"
android:startColor="#000" />
</shape>
这是最终的结果-一个带分隔符的RecyclerView。
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。
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>
