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