RecyclerView添加Header和Footer

本文轉載地址：https://www.jianshu.com/p/e9dfb7167f87

RecyclerView雖然作爲ListView的替代者有着較好的性能提升，但是ListView的一些常用功能卻沒有提供，比如我們平時會經常用到的addHeaderView，addFooterView，既然RecyclerView沒有提供這個方法，我們應該如何爲列表添加頭部和底部呢？通過看ListView的源碼可以知道ListView的添加Header和Footer是靠Adapter裏面動態添加的，所以我們按照這個思路也給RecyclerView添加HeaderView和FooterView，先看一下效果

 

這裏寫圖片描述

這裏寫圖片描述

RecyclerView實現添加HeaderView和FooterView的核心就是在Adapter裏面的onCreateViewHolder根據viewType來判斷是列表項還是HeaderView來分別加載不同的佈局文件，當然viewType的判斷規則也是由我們定義的，廢話不多說，看一下具體的實現效果。
1：Gradle配置 build.gradle

 

compile 'com.android.support:recyclerview-v7:23.1.1'
compile 'com.android.support:cardview-v7:23.1.1'

2：主佈局文件 activity_main.xml 很簡單裏面一個RecyclerView

 

<?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="match_parent">
  <android.support.v7.widget.RecyclerView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/rv_list"
    />
</LinearLayout>

3：列表項佈局 rv_item.xml 外面一個CardView的卡片式容器裏面一個TextView

 

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
xmlns:card_view="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="8dp"
android:id="@+id/cv_item"
android:foreground="?android:attr/selectableItemBackground"
card_view:cardCornerRadius="4dp"
card_view:cardElevation="4dp"
>
<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/tv_item_text"
        android:text="test"
        android:layout_margin="8dp"
        />
</LinearLayout>

</android.support.v7.widget.CardView>

4：列表頭部佈局 rv_header.xml

 

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
xmlns:card_view="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="8dp"
android:id="@+id/cv_item"
android:foreground="?android:attr/selectableItemBackground"
card_view:cardCornerRadius="4dp"
card_view:cardElevation="4dp"
card_view:cardBackgroundColor="#4CAF50"
>
<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="150dp"
    >
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Header"
        android:textSize="30sp"
        android:textColor="#ffffff"
        android:gravity="center"
        />
</LinearLayout>
</android.support.v7.widget.CardView>

5：列表底部佈局 rv_footer.xml

 

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
xmlns:card_view="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="8dp"
android:id="@+id/cv_item"
android:foreground="?android:attr/selectableItemBackground"
card_view:cardCornerRadius="4dp"
card_view:cardElevation="4dp"
card_view:cardBackgroundColor="#E91E63"
>
<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="150dp"
    >
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Footer"
        android:textSize="30sp"
        android:textColor="#ffffff"
        android:gravity="center"
        />

</LinearLayout>
</android.support.v7.widget.CardView>

*6：HeaderBottomAdapter.java，RecyclerView的Adapter，在getItemViewType方法裏面判斷了當前Item的類型，然後在onCreateViewHolder跟據item的類型分別加載不同的佈局以實現HeaderView和FooterView，其他方法的含義可以參考註釋
**

 

public class HeaderBottomAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

//item類型
public static final int ITEM_TYPE_HEADER = 0;
public static final int ITEM_TYPE_CONTENT = 1;
public static final int ITEM_TYPE_BOTTOM = 2;
//模擬數據
public String [] texts={"java","python","C++","Php",".NET","js","Ruby","Swift","OC"};
private LayoutInflater mLayoutInflater;
private Context mContext;
private int mHeaderCount=1;//頭部View個數
private int mBottomCount=1;//底部View個數

public HeaderBottomAdapter(Context context) {
    mContext = context;
    mLayoutInflater = LayoutInflater.from(context);
}

//內容長度
public int getContentItemCount(){
    return texts.length;
}
//判斷當前item是否是HeadView
public boolean isHeaderView(int position) {
    return mHeaderCount != 0 && position < mHeaderCount;
}
//判斷當前item是否是FooterView
public boolean isBottomView(int position) {
    return mBottomCount != 0 && position >= (mHeaderCount + getContentItemCount());
}


//判斷當前item類型
@Override
public int getItemViewType(int position) {
    int dataItemCount = getContentItemCount();
    if (mHeaderCount != 0 && position < mHeaderCount) {
        //頭部View
        return ITEM_TYPE_HEADER;
    } else if (mBottomCount != 0 && position >= (mHeaderCount + dataItemCount)) {
        //底部View
        return ITEM_TYPE_BOTTOM;
    } else {
        //內容View
        return ITEM_TYPE_CONTENT;
    }
}

//內容 ViewHolder
public static class ContentViewHolder extends RecyclerView.ViewHolder {
    private TextView textView;
    public ContentViewHolder(View itemView) {
        super(itemView);
        textView=(TextView)itemView.findViewById(R.id.tv_item_text);
    }
}
//頭部 ViewHolder
public static class HeaderViewHolder extends RecyclerView.ViewHolder {

    public HeaderViewHolder(View itemView) {
        super(itemView);
    }
}
//底部 ViewHolder
public static class BottomViewHolder extends RecyclerView.ViewHolder {

    public BottomViewHolder(View itemView) {
        super(itemView);
    }
}

@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    if (viewType ==ITEM_TYPE_HEADER) {
        return new HeaderViewHolder(mLayoutInflater.inflate(R.layout.rv_header, parent, false));
    } else if (viewType == ITEM_TYPE_CONTENT) {
        return  new ContentViewHolder(mLayoutInflater.inflate(R.layout.rv_item, parent, false));
    } else if (viewType == ITEM_TYPE_BOTTOM) {
        return new BottomViewHolder(mLayoutInflater.inflate(R.layout.rv_footer, parent, false));
    }
    return null;
}

@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    if (holder instanceof HeaderViewHolder) {

    } else if (holder instanceof ContentViewHolder) {
        ((ContentViewHolder) holder).textView.setText(texts[position - mHeaderCount]);

    } else if (holder instanceof BottomViewHolder) {

    }
}

@Override
public int getItemCount() {
   return mHeaderCount + getContentItemCount() + mBottomCount;
}

}

7：最後一步，MainActivity.java

 

public class MainActivity extends AppCompatActivity {
private RecyclerView mRecyclerView;
private HeaderBottomAdapter adapter;
GridLayoutManager gridLayoutManager;
LinearLayoutManager layoutManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mRecyclerView=(RecyclerView)findViewById(R.id.rv_list);
    //List佈局
    layoutManager=new LinearLayoutManager(this);
    layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
    mRecyclerView.setLayoutManager(layoutManager);
    mRecyclerView.setAdapter(adapter=new HeaderBottomAdapter(this));

    //Grid佈局 
//        gridLayoutManager=new GridLayoutManager(MainActivity.this, 2);
//        mRecyclerView.setLayoutManager(gridLayoutManager);//這裏用線性宮格顯示 類似於grid view
//        mRecyclerView.setAdapter(adapter=new HeaderBottomAdapter(this));
//
//
//            gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
//                @Override
//                public int getSpanSize(int position) {
//                    return (adapter.isHeaderView(position) || adapter.isBottomView(position)) ? gridLayoutManager.getSpanCount() : 1;
//                }
//            });


    }

}

這裏注意一點，如果你的RecyclerView使用Grid類型列表在設置Adapter後需要調用這個方法，根據當前Item類型來判斷佔據的橫向格數，這也是Adapter裏面實現isHeaderView和isBottomView的緣故

 

 gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
            @Override
            public int getSpanSize(int position) {
                return (adapter.isHeaderView(position) || adapter.isBottomView(position)) ? gridLayoutManager.getSpanCount() : 1;
            }
       });