recyclerview

文章目录

一、概述

这篇文章记录：

  • recyclerView的基本用法
  • 为recyclerview添加点击事件
  • 添加上拉加载更多
  • 拖拽排序&滑动删除（初稿）

二、recyclerview基本用法：

  • 写item和recyclerview布局
  • 写Adapter
  • 绑定数据、适配器、recyclerview

1、基本操作

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mRecyclerView = findView(R.id.id_recyclerview);
	//2、设置布局管理器
mRecyclerView.setLayoutManager(layout);
	//3、设置adapter
mRecyclerView.setAdapter(adapter)
	//4、设置Item动画
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
	//5、添加分割线
mRecyclerView.addItemDecoration(new DividerItemDecoration( getActivity(), DividerItemDecoration.HORIZONTAL_LIST));
   	//6、保持固定的大小,提高性能
mRecyclerView.setHasFixedSize(true);

2、适配器&ViewHolder

  • 继承RecyclerView.Adapter
  • 复写下面三个方法：
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public RecyclerView.ViewHolder (ViewGroup viewGroup, int i){}

public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int i){}

public int getItemCount(){}
  • 写ViewHolder继承RecyclerView.ViewHolder

3、Click和LongClick事件

  • 1、在Adapter中定义如下接口：
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public static interface OnRecyclerViewItemClickListener {
    void onItemClick(View view , String data);
}
  • 2、在onCreateViewHolder()中为每个item添加点击事件
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@Override
    public ViewHolder (ViewGroup viewGroup,  int viewType) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.item, viewGroup, false);
        ViewHolder vh = new ViewHolder(view);
        //将创建的View注册点击事件
        view.setOnClickListener(this);
        return vh;
    }
  • 3、将点击事件转移给外面的调用者：
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     @Override
    public void onClick(View v) {
        if (mOnItemClickListener != null) {
            //注意这里使用getTag方法获取数据
            mOnItemClickListener.onItemClick(v,(String)v.getTag());
        }
    }

注意： onBindViewHolder()方法中设置和item相关的数据

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@Override
    public void onBindViewHolder(ViewHolder viewHolder,  int position) {
        viewHolder.mTextView.setText(datas[position]);
        //将数据保存在itemView的Tag中，以便点击时进行获取
        viewHolder.itemView.setTag(datas[position]);
    }
  • 4、最后暴露给外面的调用者，定义一个设置Listener的方法（）
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public void setOnItemClickListener(OnRecyclerViewItemClickListener listener) {
        this.mOnItemClickListener = listener;
    }

4、上拉加载更多

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recyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
         @Override
         public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
             super.onScrolled(recyclerView, dx, dy);
             int lastVisibleItem = ((LinearLayoutManager) mLayoutManager).findLastVisibleItemPosition();
             int totalItemCount = mLayoutManager.getItemCount();
             //lastVisibleItem >= totalItemCount - 4 表示剩下4个item自动加载，各位自由选择
             // dy>0 表示向下滑动
             if (lastVisibleItem >= totalItemCount - 4 && dy > 0) {
                 if(isLoadingMore){
                      Log.d(TAG,"ignore manually update!");
                 } else{
                      loadPage();//这里多线程也要手动控制isLoadingMore
                     isLoadingMore = false;
                 }
             }
         }
     });

5、ItemTouchHelper

大专栏  recyclerviewlity_class_to_add_swipe_to_dismiss_and_drag__26amp_3B_drop_support_to_RecyclerView_28from_google_docs_29" class="headerlink" title="This is a utility class to add swipe to dismiss and drag & drop support to RecyclerView(from google docs)">This is a utility class to add swipe to dismiss and drag & drop support to RecyclerView(from google docs)

  • 类的大概声明

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    public class ItemTouchHelper extends RecyclerView.ItemDecoration
            implements RecyclerView.OnChildAttachStateChangeListener {
            
            //构造函数
            public ItemTouchHelper(Callback callback) {//传入一个Callback，两个内部类可用
            mCallback = callback;
        }
        //与recyclerview绑定
        public void attachToRecyclerView(RecyclerView recyclerView){}
            
            //some code here

     public abstract static class Callback {}	//嵌套类
     public abstract static class SimpleCallback extends Callback{} 	//嵌套类
    }

  • SimpleCallback

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    /**
     *dragDirs- 表示拖拽的方向，有六个类型的值：LEFT、RIGHT、START、END、UP、DOWN
     *swipeDirs- 表示滑动的方向，有六个类型的值：LEFT、RIGHT、START、END、UP、DOWN
     */
    ItemTouchHelper.Callback mCallback = new ItemTouchHelper.SimpleCallback(int dragDirs, int swipeDirs) {
        /**
         * @param recyclerView
         * @param viewHolder 拖动的ViewHolder
         * @param target 目标位置的ViewHolder
         * @return
         */
        @Override
        public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
            //...
            return false;
        }
        /**
         * @param viewHolder 滑动的ViewHolder
         * @param direction 滑动的方向
         */
        @Override
        public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
            //...
        }
    };

  • Examples

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//0则不执行拖动或者滑动
ItemTouchHelper.Callback mCallback = new ItemTouchHelper.SimpleCallback(ItemTouchHelper.UP|ItemTouchHelper.DOWN,ItemTouchHelper.RIGHT) {

  @Override
  public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
    int fromPosition = viewHolder.getAdapterPosition();//得到拖动ViewHolder的position
    int toPosition = target.getAdapterPosition();//得到目标ViewHolder的position
    if (fromPosition < toPosition) {
      //分别把中间所有的item的位置重新交换
      for (int i = fromPosition; i < toPosition; i++) {
        Collections.swap(datas, i, i + 1);
      }
    } else {
      for (int i = fromPosition; i > toPosition; i--) {
        Collections.swap(datas, i, i - 1);
      }
    }
    mAdapter.notifyItemMoved(fromPosition, toPosition);
    //返回true表示执行拖动
    return true;
  }
  @Override
  public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
    int position = viewHolder.getAdapterPosition();
    datas.remove(position);
    mAdapter.notifyItemRemoved(position);
  }
  @Override//画每一个Item时回调
  public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
    super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
    if(actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
      //滑动时改变Item的透明度
      final float alpha = 1 - Math.abs(dX) / (float)viewHolder.itemView.getWidth();
      viewHolder.itemView.setAlpha(alpha);
      viewHolder.itemView.setTranslationX(dX);
    }
  }
};
ItemTouchHelper itemTouchHelper = new ItemTouchHelper(mCallback);
itemTouchHelper.attachToRecyclerView(mRecyclerView);

参考链接：

https://github.com/devunwired/recyclerview-playground

https://github.com/AleBarreto/DragRecyclerView.git

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原文地址：https://www.cnblogs.com/lijianming180/p/12286184.html