在ListView中，可以添加头部和尾部，其添加方法也是十分的简单，直接调用listview.addHeaderView(view);和listview.addFooterView(view);即可，但在RecyclerView中却没有这样的方法，那么要在RecyclerView中使用这种方法怎么办呢，这就是本文要讲明的地方
原理
查看ListView源代码，得知其头部和尾部，实质上就是对原来的adapter添加了一个头和一个尾，也就是包装了一层，那么我们要在RecyclerView中使用头部和尾部的话，可以按照ListView的方法，依葫芦画瓢做一个头，做一个尾
实现
自定义一个RecyclerView布局，增加头部和尾部的添加方法
public class WrapRecyclerView extends RecyclerView {
private ArrayList<View> mHeaderViewInfos = new ArrayList<View>();
private ArrayList<View> mFooterViewInfos = new ArrayList<View>();
private Adapter mAdapter;
public WrapRecyclerView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
public void addHeaderView(View v) {
mHeaderViewInfos.add(v);
if (mAdapter != null) {
if (!(mAdapter instanceof HeaderViewRecyclerAdapter)) {
mAdapter = new HeaderViewRecyclerAdapter(mHeaderViewInfos, mFooterViewInfos, mAdapter);
}
}
}
public void addFooterView(View v) {
mFooterViewInfos.add(v);
if (mAdapter != null) {
if (!(mAdapter instanceof HeaderViewRecyclerAdapter)) {
mAdapter = new HeaderViewRecyclerAdapter(mHeaderViewInfos, mFooterViewInfos, mAdapter);
}
}
}
@Override
public void setAdapter(Adapter adapter) {
if (mHeaderViewInfos.size() > 0|| mFooterViewInfos.size() > 0) {
mAdapter = new HeaderViewRecyclerAdapter(mHeaderViewInfos, mFooterViewInfos, adapter);
} else {
mAdapter = adapter;
}
super.setAdapter(mAdapter);
}
}
布局中使用到的适配器
public class HeaderViewRecyclerAdapter extends Adapter {
private Adapter mAdapter;
ArrayList<View> mHeaderViewInfos;
ArrayList<View> mFooterViewInfos;
public HeaderViewRecyclerAdapter(ArrayList<View> headerViewInfos,
ArrayList<View> footerViewInfos, Adapter adapter) {
mAdapter = adapter;
if (headerViewInfos == null) {
mHeaderViewInfos = new ArrayList<View>();
} else {
mHeaderViewInfos = headerViewInfos;
}
if (footerViewInfos == null) {
mFooterViewInfos = new ArrayList<View>();
} else {
mFooterViewInfos = footerViewInfos;
}
}
@Override
public int getItemCount() {
if (mAdapter != null) {
return getFootersCount() + getHeadersCount() + mAdapter.getItemCount();
} else {
return getFootersCount() + getHeadersCount();
}
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
int numHeaders = getHeadersCount();
//head
if (position < numHeaders) {
return;
}
//body
final int adjPosition = position - numHeaders;
int adapterCount = 0;
if (mAdapter != null) {
adapterCount = mAdapter.getItemCount();
if (adjPosition < adapterCount) {
mAdapter.onBindViewHolder(holder, adjPosition);
return;
}
}
//footer
}
@Override
public int getItemViewType(int position) {
//判断当前条目是什么类型
int numHeaders = getHeadersCount();
if (position < numHeaders) {
return RecyclerView.INVALID_TYPE;
}
final int adjPosition = position - numHeaders;
int adapterCount = 0;
if (mAdapter != null) {
adapterCount = mAdapter.getItemCount();
if (adjPosition < adapterCount) {
return mAdapter.getItemViewType(adjPosition);
}
}
return RecyclerView.INVALID_TYPE - 1;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
//header
if (viewType == RecyclerView.INVALID_TYPE) {
return new HeaderViewHolder(mHeaderViewInfos.get(0));
} else if (viewType == RecyclerView.INVALID_TYPE - 1) {//footer
return new HeaderViewHolder(mFooterViewInfos.get(0));
}
//Footer
return mAdapter.onCreateViewHolder(parent, viewType);
}
public int getHeadersCount() {
return mHeaderViewInfos.size();
}
public int getFootersCount() {
return mFooterViewInfos.size();
}
private static class HeaderViewHolder extends ViewHolder {
public HeaderViewHolder(View view) {
super(view);
}
}
}
在布局文件中使用增加的自定义布局
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.cj5785.wraprecyclerview.WrapRecyclerView
android:id="@+id/wrap_recyclerview"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</RelativeLayout>
编写适配器
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
private List<String> list;
public MyAdapter(List<String> list) {
this.list = list;
}
class MyViewHolder extends RecyclerView.ViewHolder{
private TextView textView;
public MyViewHolder(View view) {
super(view);
textView = (TextView) view.findViewById(R.id.tv);
}
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
View view = layoutInflater.inflate(R.layout.list_item,parent,false);
MyViewHolder holder = new MyViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
holder.textView.setText(list.get(position));
}
@Override
public int getItemCount() {
return list.size();
}
}
适配器的Item布局
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/tv"
android:layout_marginTop="10dp"
android:layout_marginBottom="10dp"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center" />
在主活动在调用
public class MainActivity extends AppCompatActivity {
private WrapRecyclerView wrapRecyclerView;
private LayoutParams params;
private List<String> list;
private MyAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
wrapRecyclerView = (WrapRecyclerView) findViewById(R.id.wrap_recyclerview);
params = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
TextView header = new TextView(this);
header.setGravity(Gravity.CENTER);
header.setLayoutParams(params);
header.setText("Header");
wrapRecyclerView.addHeaderView(header);
TextView footer = new TextView(this);
footer.setGravity(Gravity.CENTER);
footer.setLayoutParams(params);
footer.setText("Footer");
wrapRecyclerView.addFooterView(footer);
list = new ArrayList<>();
for (int i = 0; i < 10; i++) {
list.add("item " + i);
}
adapter = new MyAdapter(list);
wrapRecyclerView.setLayoutManager(new LinearLayoutManager(this));
wrapRecyclerView.setAdapter(adapter);
}
}
运行结果
