RecyclerView 现在可以说是很常用了吧？RecyclerView 自然是很方便的控件，但用多了有时候对一些重复性代码也是感觉挺麻烦的，于是乎我就将一些重复性代码封装了起来，从而使 RecyclerView 的使用更加的简便
本篇博客包含的内容有：
- 通用的单布局 RecyclerView.Adapter
- 通用的多布局 RecyclerView.Adapter
- 通用的 RecyclerView.ItemDecoration
- RecyclerView 的单击和长按事件监听
- 带头部与底部View的 RecyclerView
- SnapHelper 的使用
一、通用 RecyclerView.Adapter
CommonRecyclerViewAdapter 是一个抽象类，利用泛型构造了一个通用的Adapter，并通过 MultiTypeSupport 接口来实现对多布局的支持。
此外，有时候我们在刷新数据时，改变的数据可能只是List集合中的单个数据，如果都采用 Adapter.notifyDataSetChanged() 来刷新整个视图，无疑是浪费资源的，此处采用了 DiffUtil 来对比前后两个数据集，寻找出旧数据集与新数据集的最小变化量，从而对数据进行定向刷新，可以只刷新相应的Item，使得视图的刷新过程更为高效，且增添和删除数据时都伴随有相应的动画效果
/**
* 作者：叶应是叶
* 时间：2017/12/21 21:50
* 说明：通用RecyclerView Adapter
*/
public abstract class CommonRecyclerViewAdapter<T> extends RecyclerView.Adapter<CommonRecyclerViewHolder> {
//省略一些代码
......
private DiffUtil.Callback callback = new DiffUtil.Callback() {
@Override
public int getOldListSize() {
return getItemCount();
}
@Override
public int getNewListSize() {
return newDataList.size();
}
@Override
public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
return CommonRecyclerViewAdapter.this.areItemsTheSame(oldItemPosition, newItemPosition);
}
@Override
public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
return CommonRecyclerViewAdapter.this.areContentsTheSame(oldItemPosition, newItemPosition);
}
@Nullable
@Override
public Object getChangePayload(int oldItemPosition, int newItemPosition) {
return CommonRecyclerViewAdapter.this.getChangePayload(oldItemPosition, newItemPosition);
}
};
public void setData(final List<T> dataList) {
new Thread(new Runnable() {
@Override
public void run() {
newDataList.clear();
newDataList = CommonRecyclerViewAdapter.this.clone(dataList);
DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(callback, true);
Message message = new Message();
message.what = DIFF_UTIL_UPDATE;
message.obj = diffResult;
handler.sendMessage(message);
}
}).start();
}
@Override
public int getItemViewType(int position) {
if (multiTypeSupport != null) {
return multiTypeSupport.getLayoutId(dataList.get(position), position);
}
return DEFAULT_ITEM_VIEW_TYPE;
}
@Override
public CommonRecyclerViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
if (multiTypeSupport != null) {
layoutId = viewType;
}
return new CommonRecyclerViewHolder(layoutInflater.inflate(layoutId, parent, false));
}
@Override
public void onBindViewHolder(CommonRecyclerViewHolder holder, int position, List<Object> payloads) {
if (payloads.isEmpty()) {
onBindViewHolder(holder, position);
} else {
Bundle bundle = (Bundle) payloads.get(0);
partialBindData(holder, bundle);
}
}
@Override
public void onBindViewHolder(CommonRecyclerViewHolder holder, int position) {
entirelyBindData(holder, dataList.get(position));
if (clickListener != null) {
holder.setClickListener(clickListener);
}
if (longClickListener != null) {
holder.setLongClickListener(longClickListener);
}
}
//省略一些代码
......
private List<T> clone(List<T> dataList) {
List<T> tempDataList = new ArrayList<>(dataList.size());
for (T data : dataList) {
tempDataList.add(clone(data));
}
return tempDataList;
}
/**
* clone 指定对象，以此获得对象副本
*
* @param data 要复制的对象
* @return 对象副本
*/
protected abstract T clone(T data);
/**
* 判断数据列表刷新前后指定索引的位置是否指向同一条数据
* 此处只对比两者是否指向同一条数据，而不关心其数据内容是否有变化
*
* @param oldItemPosition 更新前的数据索引
* @param newItemPosition 更新后的数据索引
* @return 是否指向同一条数据
*/
protected abstract boolean areItemsTheSame(int oldItemPosition, int newItemPosition);
/**
* 此处来判断指向同一条数据的前后两个索引位置，其数据内容是否相同
* 只在 areItemsTheSame 返回 true 时才会调用本方法
*
* @param oldItemPosition 更新前的数据索引
* @param newItemPosition 更新后的数据索引
* @return 数据内容是否有变化
*/
protected abstract boolean areContentsTheSame(int oldItemPosition, int newItemPosition);
/**
* 获取同条数据在刷新前后是哪些数据内容发生了变化
* 只在 areContentsTheSame 返回 false 时才会调用本方法
*
* @param oldItemPosition 更新前的数据索引
* @param newItemPosition 更新后的数据索引
* @return 数据变化内容
*/
@NonNull
protected abstract Bundle getChangePayload(int oldItemPosition, int newItemPosition);
/**
* 对刷新前后的数据进行定向更新，即只更新数据发生了变化的View
*
* @param holder Holder
* @param bundle getChangePayload 方法的返回值
*/
protected abstract void partialBindData(CommonRecyclerViewHolder holder, @NonNull Bundle bundle);
/**
* 对数据进行完全绑定
*
* @param holder Holder
* @param data Data
*/
protected abstract void entirelyBindData(CommonRecyclerViewHolder holder, T data);
}
此处还需要使用到一个通用的 RecyclerView.ViewHolder
/**
* 作者：叶应是叶
* 时间：2017/12/21 21:52
* 说明：通用RecyclerView ViewHolder
*/
public class CommonRecyclerViewHolder extends RecyclerView.ViewHolder {
public interface OnClickListener {
void onClick(int position);
}
public interface OnLongClickListener {
void onLongClick(int position);
}
private OnClickListener clickListener;
private OnLongClickListener longClickListener;
//用来存放View以减少findViewById的次数
private SparseArray<View> viewSparseArray;
CommonRecyclerViewHolder(View view) {
super(view);
viewSparseArray = new SparseArray<>();
view.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (clickListener != null) {
clickListener.onClick(getAdapterPosition());
}
}
});
view.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
if (longClickListener != null) {
longClickListener.onLongClick(getAdapterPosition());
}
return true;
}
});
}
void setClickListener(OnClickListener clickListener) {
this.clickListener = clickListener;
}
void setLongClickListener(OnLongClickListener longClickListener) {
this.longClickListener = longClickListener;
}
/**
* 根据 ID 来获取 View
*
* @param viewId viewID
* @param <T> 泛型
* @return 将结果强转为 View 或 View 的子类型
*/
private <T extends View> T getView(@IdRes int viewId) {
// 先从缓存中找，找到的话则直接返回
// 如果找不到则findViewById，再把结果存入缓存中
View view = viewSparseArray.get(viewId);
if (view == null) {
view = itemView.findViewById(viewId);
if (view != null) {
viewSparseArray.put(viewId, view);
}
}
return (T) view;
}
public CommonRecyclerViewHolder setText(@IdRes int viewId, CharSequence text) {
TextView textView = getView(viewId);
if (textView != null) {
textView.setText(text);
}
return this;
}
//省略一些代码
......
}
二、通用单布局 Adapter 使用示例
先来新建一个Model
/**
* 作者：叶应是叶
* 时间：2017/12/21 21:55
* 说明：
*/
public class New {
private int index;
private String title;
private String content;
public New(int index, String title, String content) {
this.index = index;
this.title = title;
this.content = content;
}
//省略一些代码
......
}
每个子项的布局包含一个索引TextView、一个标题TextView、一个内容TextView
<?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="#439af1"
android:orientation="vertical">
<TextView
android:id="@+id/tv_index"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:padding="6dp"
android:textSize="25sp"
android:textStyle="bold" />
<TextView
android:id="@+id/tv_title"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:padding="5dp"
android:textSize="28sp"
android:textStyle="bold" />
<TextView
android:id="@+id/tv_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="start"
android:padding="10dp"
android:textSize="22sp" />
</LinearLayout>
之后就是继承 CommonRecyclerViewAdapter ，泛型指定为 New ，在构造函数里直接指定要使用的布局为 R.layout.item_new，再实现几个抽象方法即可。
/**
* 作者：叶应是叶
* 时间：2017/12/21 21:55
* 说明：单个布局
*/
public class NewCommonAdapter extends CommonRecyclerViewAdapter<New> {
public NewCommonAdapter(Context context, List<New> dataList) {
super(context, dataList, R.layout.item_new);
}
@Override
protected New clone(New data) {
return new New(data.getIndex(), data.getTitle(), data.getContent());
}
@Override
protected boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
return dataList.get(oldItemPosition).getIndex() == newDataList.get(newItemPosition).getIndex();
}
@Override
protected boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
String title = dataList.get(oldItemPosition).getTitle();
String content = dataList.get(oldItemPosition).getContent();
String newTitle = newDataList.get(newItemPosition).getTitle();
String newContent = newDataList.get(newItemPosition).getContent();
return title.equals(newTitle) && content.equals(newContent);
}
@NonNull
@Override
protected Bundle getChangePayload(int oldItemPosition, int newItemPosition) {
Bundle bundle = new Bundle();
String title = dataList.get(oldItemPosition).getTitle();
String content = dataList.get(oldItemPosition).getContent();
String newTitle = newDataList.get(newItemPosition).getTitle();
String newContent = newDataList.get(newItemPosition).getContent();
if (!title.equals(newTitle)) {
bundle.putString("Title", newTitle);
}
if (!content.equals(newContent)) {
bundle.putString("Content", newContent);
}
return bundle;
}
@Override
protected void partialBindData(CommonRecyclerViewHolder holder, @NonNull Bundle bundle) {
for (String key : bundle.keySet()) {
switch (key) {
case "Title":
holder.setText(R.id.tv_title, bundle.getString(key));
break;
case "Content":
holder.setText(R.id.tv_content, bundle.getString(key));
break;
}
}
}
@Override
protected void entirelyBindData(CommonRecyclerViewHolder holder, New data) {
holder.setText(R.id.tv_title, data.getTitle())
.setText(R.id.tv_content, data.getContent());
}
}
这里省略 Activity 中对 RecyclerView 的各种初始化操作，只展现最终效果，具体代码看最下方 GitHub 地址
单布局.gif
三、通用多布局 Adapter 使用示例
在 CommonRecyclerViewAdapter 类当中，为了支持多布局，通过 MultiTypeSupport 接口来返回相应的布局文件ID，这里除了使用 单布局 中使用的 R.layout.item_new 布局文件外，同时使用另外一个布局文件 R.layout.item_new_multi ，仅仅是背景色不同而已
想要让子 Adapter 支持多布局，只要实现 CommonRecyclerViewAdapter 的另外一个构造函数即可。这里在索引为单数时使用 R.layout.item_new 布局，双数时使用 R.layout.item_new_multi 布局
/**
* 作者：叶应是叶
* 时间：2017/12/21 21:56
* 说明：多布局
*/
public class NewCommonMultiAdapter extends CommonRecyclerViewAdapter<New> {
public NewCommonMultiAdapter(Context context, List<New> dataList) {
super(context, dataList, new CommonRecyclerViewAdapter.MultiTypeSupport<New>() {
@Override
public int getLayoutId(New item, int position) {
return item.getIndex() % 2 == 0 ? R.layout.item_new_multi : R.layout.item_new;
}
});
}
//省略一些代码
......
@Override
protected void partialBindData(CommonRecyclerViewHolder holder, @NonNull Bundle bundle) {
if (bundle.size() > 0) {
int index = bundle.getInt("Index");
for (String key : bundle.keySet()) {
switch (key) {
case "Title":
if (index % 2 == 0) {
holder.setText(R.id.tv_multi_title, bundle.getString(key));
} else {
holder.setText(R.id.tv_title, bundle.getString(key));
}
break;
case "Content":
if (index % 2 == 0) {
holder.setText(R.id.tv_multi_content, bundle.getString(key));
} else {
holder.setText(R.id.tv_content, bundle.getString(key));
}
break;
}
}
}
}
@Override
protected void entirelyBindData(CommonRecyclerViewHolder holder, New data) {
if (data.getIndex() % 2 == 0) {
holder.setText(R.id.tv_multi_title, data.getTitle())
.setText(R.id.tv_multi_content, data.getContent())
.setText(R.id.tv_multi_index, String.valueOf(data.getIndex()));
} else {
holder.setText(R.id.tv_title, data.getTitle())
.setText(R.id.tv_content, data.getContent())
.setText(R.id.tv_index, String.valueOf(data.getIndex()));
}
}
}
多布局.gif
四、添加头部与底部 View
为了实现带头部与底部View的 RecyclerView ，需要自定义一个Adapter来包裹实际的Adapter，重写 getItemViewType(int position) 方法，返回不同的值以区分头部View与底部View，并向外开放添加和移除头部底部View的方法
/**
* 作者：叶应是叶
* 时间：2017/12/21 21:53
* 说明：可添加头部View与底部View的RecyclerView Adapter
*/
public class WrapRecyclerViewAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private RecyclerView.Adapter<RecyclerView.ViewHolder> innerAdapter;
private SparseArray<View> headerViewArray;
private SparseArray<View> footerViewArray;
//头部View类型开始位置,用于viewType
private static int BASE_VIEW_TYPE_HEADER = 1000;
//底部View类型开始位置,用于viewType
private static int BASE_VIEW_TYPE_FOOTER = 2000;
private RecyclerView.AdapterDataObserver dataObserver = new RecyclerView.AdapterDataObserver() {
@Override
public void onChanged() {
super.onChanged();
notifyDataSetChanged();
}
@Override
public void onItemRangeChanged(int positionStart, int itemCount) {
super.onItemRangeChanged(positionStart, itemCount);
notifyItemRangeChanged(positionStart + getHeaderViewCount(), itemCount);
}
@Override
public void onItemRangeInserted(int positionStart, int itemCount) {
super.onItemRangeInserted(positionStart, itemCount);
notifyItemRangeInserted(positionStart + getHeaderViewCount(), itemCount);
}
@Override
public void onItemRangeRemoved(int positionStart, int itemCount) {
super.onItemRangeRemoved(positionStart, itemCount);
notifyItemRangeRemoved(positionStart + getHeaderViewCount(), itemCount);
}
@Override
public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
super.onItemRangeMoved(fromPosition, toPosition, itemCount);
int headerViewsCountCount = getHeaderViewCount();
notifyItemRangeChanged(fromPosition + headerViewsCountCount, toPosition + headerViewsCountCount + itemCount);
}
};
public WrapRecyclerViewAdapter(RecyclerView.Adapter innerAdapter) {
headerViewArray = new SparseArray<>();
footerViewArray = new SparseArray<>();
setAdapter(innerAdapter);
}
private void setAdapter(RecyclerView.Adapter<RecyclerView.ViewHolder> adapter) {
innerAdapter = adapter;
innerAdapter.registerAdapterDataObserver(dataObserver);
}
@Override
public int getItemViewType(int position) {
if (isHeaderPosition(position)) {
return headerViewArray.keyAt(position);
}
if (isFooterPosition(position)) {
return footerViewArray.keyAt(position - headerViewArray.size() - getDataItemCount());
}
return innerAdapter.getItemViewType(position - headerViewArray.size());
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
if (isHeaderView(viewType)) {
return new ViewHolder(headerViewArray.get(viewType));
}
if (isFooterView(viewType)) {
return new ViewHolder(footerViewArray.get(viewType));
}
return innerAdapter.onCreateViewHolder(parent, viewType);
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
int headerViewsCountCount = getHeaderViewCount();
if (position >= headerViewsCountCount && position < headerViewsCountCount + innerAdapter.getItemCount()) {
innerAdapter.onBindViewHolder(holder, position - headerViewsCountCount);
}
}
@Override
public int getItemCount() {
return getHeaderViewCount() + getDataItemCount() + getFooterViewCount();
}
private int getDataItemCount() {
return innerAdapter == null ? 0 : innerAdapter.getItemCount();
}
public int getHeaderViewCount() {
return headerViewArray.size();
}
public int getFooterViewCount() {
return footerViewArray.size();
}
public RecyclerView.Adapter getInnerAdapter() {
return innerAdapter;
}
/**
* 判断是否是头部View
*
* @param viewType ViewType
* @return 是否是头部View
*/
private boolean isHeaderView(int viewType) {
return headerViewArray.indexOfKey(viewType) > -1;
}
/**
* 判断是否是底部View
*
* @param viewType ViewType
* @return 是否是底部View
*/
private boolean isFooterView(int viewType) {
return footerViewArray.indexOfKey(viewType) > -1;
}
/**
* 判断是否是头部View
*
* @param view View
* @return 是否是头部View
*/
public boolean isHeaderView(View view) {
return headerViewArray.indexOfValue(view) > -1;
}
/**
* 判断是否是底部View
*
* @param view View
* @return 是否是底部View
*/
public boolean isFooterView(View view) {
return footerViewArray.indexOfValue(view) > -1;
}
/**
* 根据索引判断该位置的View是否是头部View
*
* @param position 索引
* @return 是否是头部View
*/
private boolean isHeaderPosition(int position) {
return position >= 0 && position < getHeaderViewCount();
}
/**
* 根据索引判断该位置的View是否是底部View
*
* @param position 索引
* @return 是否是底部View
*/
private boolean isFooterPosition(int position) {
return position >= (getHeaderViewCount() + getDataItemCount())
&& position < (getHeaderViewCount() + getDataItemCount() + getFooterViewCount());
}
/**
* 添加头部View
*
* @param view 头部View
*/
public void addHeaderView(View view) {
if (headerViewArray.indexOfValue(view) < 0) {
headerViewArray.put(BASE_VIEW_TYPE_HEADER++, view);
notifyItemInserted(headerViewArray.size() - 1);
}
}
/**
* 添加底部View
*
* @param view 底部View
*/
public void addFooterView(View view) {
if (footerViewArray.indexOfValue(view) < 0) {
footerViewArray.put(BASE_VIEW_TYPE_FOOTER++, view);
notifyItemInserted(getHeaderViewCount() + getDataItemCount() + getFooterViewCount() - 1);
}
}
/**
* 移除头部View
*
* @param view View
*/
public void removeHeaderView(View view) {
int index = headerViewArray.indexOfValue(view);
if (index > -1) {
headerViewArray.removeAt(index);
notifyItemRemoved(index);
}
}
/**
* 移除底部View
*
* @param view View
*/
public void removeFooterView(View view) {
int index = footerViewArray.indexOfValue(view);
if (index > -1) {
footerViewArray.removeAt(index);
notifyItemRemoved(getHeaderViewCount() + getDataItemCount() + index);
}
}
private class ViewHolder extends RecyclerView.ViewHolder {
ViewHolder(View itemView) {
super(itemView);
}
}
}
WrapRecyclerViewAdapter 的使用方法也很简单，只要将实际的Adapter作为参数来构造 WrapRecyclerViewAdapter 对象，然后再传给 RecyclerView 即可，之后就可以通过 addHeaderView 和 addFooterView 方法来添加头部和底部View
RecyclerView rv_wrapDataList = (RecyclerView) findViewById(R.id.rv_wrapDataList);
NewCommonAdapter adapter = new NewCommonAdapter(this, newList);
WrapRecyclerViewAdapter wrapRecyclerViewAdapter = new WrapRecyclerViewAdapter(adapter);
rv_wrapDataList.setLayoutManager(new LinearLayoutManager(this));
rv_wrapDataList.setAdapter(wrapRecyclerViewAdapter);
带头部和底部View.gif
五、单击和长按事件监听
RecyclerView 的单击和长按事件一直是一个比较麻烦的地方，毕竟没有官方提供的接口，不过此处 CommonRecyclerViewAdapter 也已经提供了相应的设置方法
NewCommonMultiAdapter newCommonMultiAdapter = new NewCommonMultiAdapter(this, newList);
newCommonMultiAdapter.setClickListener(new CommonRecyclerViewHolder.OnClickListener() {
@Override
public void onClick(int position) {
toast("单击" + "\n" + newList.get(position).getTitle() + "\n" + newList.get(position).getContent());
}
});
newCommonMultiAdapter.setLongClickListener(new CommonRecyclerViewHolder.OnLongClickListener() {
@Override
public void onLongClick(int position) {
toast("长按" + "\n" + newList.get(position).getTitle() + "\n" + newList.get(position).getContent());
}
});
点击事件.gif
六、通用 RecyclerView.ItemDecoration
想要实现Item之间的分割线，需要继承 RecyclerView.ItemDecoration 在相应的位置进行绘制，这里提供一个通用的分隔线
/**
* 作者：叶应是叶
* 时间：2017/12/21 21:52
* 说明：通用分隔线
*/
public class CommonItemDecoration extends RecyclerView.ItemDecoration{
private int orientation = LinearLayoutManager.HORIZONTAL;
private Drawable drawable;
public CommonItemDecoration(Context context, int orientation) {
this.orientation = orientation;
int[] attrs = new int[]{android.R.attr.listDivider};
TypedArray typedArray = context.obtainStyledAttributes(attrs);
drawable = typedArray.getDrawable(0);
typedArray.recycle();
}
public CommonItemDecoration(Drawable drawable, int orientation) {
this.drawable = drawable;
this.orientation = orientation;
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
if (orientation == LinearLayoutManager.HORIZONTAL) {
outRect.set(0, 0, drawable.getIntrinsicWidth(), 0);
} else if (orientation == LinearLayoutManager.VERTICAL) {
outRect.set(0, 0, 0, drawable.getIntrinsicHeight());
}
}
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
super.onDraw(c, parent, state);
if (orientation == LinearLayoutManager.HORIZONTAL) {
drawVerticalDivider(c, parent);
} else if (orientation == LinearLayoutManager.VERTICAL) {
drawHorizontalDivider(c, parent);
}
}
private void drawVerticalDivider(Canvas c, RecyclerView parent) {
for (int i = 0; i < parent.getChildCount(); i++) {
View child = parent.getChildAt(i);
// RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
// //受 child layout_marginEnd 属性的影响
// int left = child.getRight() + params.rightMargin;
//不受 child layout_marginEnd 属性的影响，会直接绘制在 child 右侧
int left = child.getRight();
int top = child.getTop();
int right = left + drawable.getIntrinsicWidth();
int bottom = child.getBottom();
drawable.setBounds(left, top, right, bottom);
drawable.draw(c);
}
}
private void drawHorizontalDivider(Canvas c, RecyclerView parent) {
for (int i = 0; i < parent.getChildCount(); i++) {
View child = parent.getChildAt(i);
int left = child.getLeft();
//不受 child layout_marginBottom 属性的影响，会直接绘制在 child 底部
int top = child.getBottom();
int right = child.getRight();
int bottom = top + drawable.getIntrinsicHeight();
//会受 child layout_marginBottom 属性的影响
//RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
//int top = child.getBottom() + params.bottomMargin;
drawable.setBounds(left, top, right, bottom);
drawable.draw(c);
}
}
}
在之前的几张效果图中，其实是已经为 RecyclerView 添加了一条白色分隔线的
RecyclerView rv_commonMultiDataList = (RecyclerView) findViewById(R.id.rv_commonMultiDataList);
CommonItemDecoration commonItemDecoration = new CommonItemDecoration(ContextCompat.getDrawable(this, R.drawable.divider), LinearLayoutManager.VERTICAL);
rv_commonMultiDataList.addItemDecoration(commonItemDecoration);
这里也可以传入不同的 Drawable 对象，从而实现多种风格的分隔线
分隔线.gif
七、SnapHelper的使用
顺带在这里对 SnapHelper 进行一个简单的介绍，SnapHelper 是在 Android 24.2.0 的support 包中新添加的一个支持库，是对RecyclerView的拓展。SnapHelper旨在支持RecyclerView的对齐方式，通过计算对齐RecyclerView中TargetView 的指定点或者容器中的任何像素点，可以使RecyclerView实现类似于 ViewPager 的切换效果
SnapHelper是一个抽象类，官方提供了 LinearSnapHelper 和 PagerSnapHelper 两个具体实现，这里来实现类似于第一次使用App时显示的引导页的效果
/**
* 作者：叶应是叶
* 时间：2017/12/21 22:02
* 说明：
*/
public class SnapRecyclerViewActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_snap_recycler_view);
RecyclerView rv_snap = (RecyclerView) findViewById(R.id.rv_snap);
SnapAdapter snapAdapter = new SnapAdapter(this, getData());
rv_snap.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false));
// rv_snap.setLayoutManager(new LinearLayoutManager(this));
rv_snap.setAdapter(snapAdapter);
// LinearSnapHelper snapHelper = new LinearSnapHelper();
// snapHelper.attachToRecyclerView(rv_snap);
PagerSnapHelper pagerSnapHelper=new PagerSnapHelper();
pagerSnapHelper.attachToRecyclerView(rv_snap);
}
private List<Image> getData() {
List<Image> imageList = new ArrayList<>();
imageList.add(new Image(0, R.drawable.drawable_1));
imageList.add(new Image(1, R.drawable.drawable_0));
imageList.add(new Image(2, R.drawable.drawable_1));
imageList.add(new Image(3, R.drawable.drawable_0));
imageList.add(new Image(4, R.drawable.drawable_1));
imageList.add(new Image(5, R.drawable.drawable_0));
imageList.add(new Image(6, R.drawable.drawable_1));
imageList.add(new Image(7, R.drawable.drawable_0));
return imageList;
}
}
image
源代码我也已经放到了GitHub上，点击查看：Android RecyclerView 的简便写法
