RecyclerView的刷新和加载更多

1.RecyclerView :出现也不知道多久了，没怎么使用过，上次写的笔记乱七八糟的，再次仔细的整理下。

  使用需加入依赖 

compile 'com.android.support:recyclerview-v7:25.2.0'

2.总结一下内容

　　<1>可以实现横向滑动

　　<2>可以实现纵向滑动

　　<3>可以实现瀑布流

　　<4>可以实现吸顶模式

　　<5>加入自定义分割线

　　<6>实现数据分组效果

 

3.先实现ListView的效果图，实现下拉刷新，上划加载更多

  实现下拉刷新需要借助SwipeRefreshLayout 嵌套在recyclerView的外部

android.support.v4.widget.SwipeRefreshLayout

上划加载更多可以依靠recyclerView的自身监听 addOnScrollListener 当newState==RecyclerView.SCROLL_STATE_IDLE则代表滑动到了底部，然后执行加载 更多的操作。效果图：

4.看实现代码：

布局还有一个recyclerView和SwipeRefreshLayout

    <android.support.v4.widget.SwipeRefreshLayout
        android:layout_height="match_parent"
        android:layout_width="match_parent"
        android:id="@+id/swipeRefreshLayout">
    <android.support.v7.widget.RecyclerView
        android:layout_height="match_parent"
        android:layout_width="match_parent"
        android:id="@+id/recyclerView"/>
    </android.support.v4.widget.SwipeRefreshLayout>

条目布局一个ImageView和一个textView

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:orientation="horizontal"
              android:layout_height="60dp">
    <ImageView
        android:layout_height="60dp"
        android:layout_width="60dp"
        android:id="@+id/imageView"
        android:scaleType="centerCrop"
        android:src="@mipmap/image"/>
    <TextView
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:gravity="center_horizontal|center_vertical"
        android:textColor="@color/colorPrimary"
        android:id="@+id/textView"/>
</LinearLayout>

adapter继承了RecyclerView.Adapter其泛型为ViewHolder,viewholder继承RecyclerView.ViewHolder。

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

    List<String> data;
    Context context;

    public RecyclerViewAdapter(Context context, List<String> data) {
        this.context = context;
        this.data = data;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view= LayoutInflater.from(context).inflate(R.layout.recycleritem_layout,parent,false);
        final ViewHolder holder=new ViewHolder(view);
        holder.imageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int position=holder.getAdapterPosition();
                Toast.makeText(context,"点击了第"+position+"个图片",Toast.LENGTH_SHORT).show();
            }
        });
        holder.textView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int position=holder.getAdapterPosition();
                Toast.makeText(context,"点击了第"+position+"个文字条目",Toast.LENGTH_SHORT).show();
            }
        });
        return holder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {

        String s=data.get(position);
        holder.textView.setText(s);
    }

    @Override
    public int getItemCount() {
        return data.size();
    }

    class ViewHolder extends RecyclerView.ViewHolder{

        View viewItem;
        ImageView imageView;
        TextView textView;
        public ViewHolder(View itemView) {
            super(itemView);
            viewItem=itemView;
            imageView= (ImageView) itemView.findViewById(R.id.imageView);
            textView= (TextView) itemView.findViewById(R.id.textView);

        }
    }
}

在activity中初始了数据，并加载，其中

 linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);

设置了recyclerView的滑动方向为垂直，这里也可以设置为水平方向的滑动。

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "MainActivity";
    RecyclerView recyclerView;
    List<String>data=new ArrayList<>();
    SwipeRefreshLayout swipeRefreshLayout;
     RecyclerViewAdapter recyclerViewAdapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        recyclerView= (RecyclerView) findViewById(R.id.recyclerView);
        swipeRefreshLayout= (SwipeRefreshLayout) findViewById(R.id.swipeRefreshLayout);

        for(int i=0;i<15;i++){
            data.add("第"+i+"项数据");
        }

        LinearLayoutManager linearLayoutManager=new LinearLayoutManager(this);
        linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(linearLayoutManager);

       recyclerViewAdapter=new RecyclerViewAdapter(this,data);
        recyclerView.setAdapter(recyclerViewAdapter);
        /**
         * 刷新
         */
        swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {

                handler.sendEmptyMessageDelayed(100,100);
            }
        });

        /**
         * 加载更多
         */
        recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
　　　　　　　　　　// 这里在加入判断，判断是否滑动到底部
                if(newState==RecyclerView.SCROLL_STATE_IDLE){
                    List<String> dataNew=new  ArrayList<>();
                    for(int i=0;i<30;i++){
                        dataNew.add("加载更多后第"+i+"项数据");
                    }
                    data.addAll(dataNew);
                    recyclerViewAdapter.notifyDataSetChanged();
                }
            }
        });

    }

    Handler handler=new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);

            List<String> dataNew=new  ArrayList<>();
            for(int i=0;i<30;i++){
                dataNew.add("刷新后第"+i+"项数据");
            }
            data.clear();
           data.addAll(0,dataNew);
          //data.add(0, "下拉刷新出来的数据");
            swipeRefreshLayout.setRefreshing(false);
            recyclerViewAdapter.notifyDataSetChanged();

        }
    };

}

 5.判断是否滑动到底部

 在滑动停止时，判断是否滑动到底部，然后在判断是否需要加载更多

 public static boolean isSlideToBottom(RecyclerView recyclerView) {
        if (recyclerView == null) return false;
        if (recyclerView.computeVerticalScrollExtent() + recyclerView.computeVerticalScrollOffset()
                >= recyclerView.computeVerticalScrollRange())
            return true;
        return false;
    }

5.给Recyclerview加上头布局和底部布局。

重新recyclerViewAdapter里面的getItemViewType方法，判断itemview是内容还是头布局或底部布局。

    @Override
    public int getItemViewType(int position) {

        if (headeraccount != 0 && position < headeraccount) {
            /**
             * 头部
             */
            return ITEM_TYPE_HEADER;
        } else if (footaccount != 0 && position >= (headeraccount + data.size())) {

            /**
             * 尾部
             */
            return ITEM_TYPE_BOTTOM;
        } else {
            /**
             * 有效数据
             */

            return ITEM_TYPE_CONTENT;
        }

    }

adapter代码：

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

    List<String> data;
    Context context;
    int headeraccount=1;
    int footaccount=1;
    //item类型
    public static final int ITEM_TYPE_HEADER = 0;
    public static final int ITEM_TYPE_CONTENT = 1;
    public static final int ITEM_TYPE_BOTTOM = 2;

    @Override
    public int getItemViewType(int position) {

        if (headeraccount != 0 && position < headeraccount) {
            /**
             * 头部
             */
            return ITEM_TYPE_HEADER;
        } else if (footaccount != 0 && position >= (headeraccount + data.size())) {

            /**
             * 尾部
             */
            return ITEM_TYPE_BOTTOM;
        } else {
            /**
             * 有效数据
             */

            return ITEM_TYPE_CONTENT;
        }

    }

    public RecyclerViewAdapter(Context context, List<String> data) {
        this.context = context;
        this.data = data;
    }

    @Override
    public RecyclerView.ViewHolder  onCreateViewHolder(ViewGroup parent, int viewType) {
        if (viewType == ITEM_TYPE_HEADER) {
            return new HeaderViewHolder(LayoutInflater.from(context).inflate(R.layout.header_layout, parent, false));

        }
        if (viewType == ITEM_TYPE_BOTTOM) {
            return new HeaderViewHolder(LayoutInflater.from(context).inflate(R.layout.header_layout, parent, false));

        }
        if (viewType == ITEM_TYPE_CONTENT) {
            View view = LayoutInflater.from(context).inflate(R.layout.recycleritem_layout, parent, false);
            final ContextViewHolder holder = new ContextViewHolder(view);
            holder.imageView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    int position = holder.getAdapterPosition();
                    Toast.makeText(context, "点击了第" + position + "个图片", Toast.LENGTH_SHORT).show();
                }
            });
            holder.textView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    int position = holder.getAdapterPosition();
                    Toast.makeText(context, "点击了第" + position + "个文字条目", Toast.LENGTH_SHORT).show();
                }
            });
            return holder;
        }

        return  null;

    }

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

        }else if(holder instanceof  FootViewHolder){

        }else if(holder instanceof  ContextViewHolder){
               String s= data.get(position-headeraccount);
            ((ContextViewHolder) holder).textView.setText(s);
        }

    }

    @Override
    public int getItemCount() {
        return data.size()+headeraccount+footaccount;
    }

     class   ContextViewHolder extends RecyclerView.ViewHolder{

        View viewItem;
        ImageView imageView;
        TextView textView;
        public ContextViewHolder(View itemView) {
            super(itemView);
            viewItem=itemView;
            imageView= (ImageView) itemView.findViewById(R.id.imageView);
            textView= (TextView) itemView.findViewById(R.id.textView);

        }
    }
    class FootViewHolder extends RecyclerView.ViewHolder{

        public FootViewHolder(View itemView) {
            super(itemView);
        }
    }
    class HeaderViewHolder extends RecyclerView.ViewHolder{

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

}

头布局和底部布局都只是一个imageView

<?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="100dp">
<ImageView
    android:layout_height="100dp"
    android:layout_width="match_parent"
    android:scaleType="centerCrop"
    android:src="@mipmap/img"/>
</LinearLayout>

实现效果图：

6.给recyclerView添加item分割线

继承 RecyclerView.ItemDecoration

public class SpacesItemDecoration  extends RecyclerView.ItemDecoration{
    private int dividerHeight;
    private Paint paint;
    public SpacesItemDecoration(Context context) {
        dividerHeight = context.getResources().getDimensionPixelSize(R.dimen.margin);
        paint=new Paint();
        paint.setColor(context.getResources().getColor(R.color.colorAccent));
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        /**
         * 类似加了一个bottom的padding
         */
        outRect.bottom = dividerHeight;
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDraw(c, parent, state);
        int childCount = parent.getChildCount();
        int left = parent.getPaddingLeft();
        int right = parent.getWidth() - parent.getPaddingRight();

        for (int i = 0; i < childCount - 1; i++) {
            View view = parent.getChildAt(i);
            float top = view.getBottom();
            float bottom = view.getBottom() + dividerHeight;
            /**
             * 绘制的矩形也就是从，item的左上角，到右下角，类似于背景，
             * 正好显示出一个横线，就是getItemOffsets空出来的范围
             *
             */
            c.drawRect(left, top, right, bottom, paint);
        }
    }

}

 　　　　recyclerView.setAdapter(recyclerViewAdapter);
        SpacesItemDecoration decoration=new SpacesItemDecoration(getApplicationContext());
        recyclerView.addItemDecoration(decoration);

效果图：