RecyclerView使用详解

RecyclerView是Android 5.x版本中新添加的一个全新控件，他比ListView，GridView更加的灵活，我们能够使用RecyclerView就完成ListView，GridView所做的工作，同时使用RecyclerView也能非常方便的实现瀑布流的效果。

一.竖屏ListView，横屏GridView效果

MainActivity代码：

public class MainActivity extends Activity implements MyRecyclerViewAdapter.OnItemClickListener{private RecyclerView recyclerView;private List<string> dataList;private MyRecyclerViewAdapter adapter;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Display disPlay = getWindowManager().getDefaultDisplay(); Point size = new Point(); disPlay.getSize(size); int width = size.x; int height = size.y; System.out.println(width+","+height);dataList = new ArrayList<string>();initValues();recyclerView = (RecyclerView) findViewById(R.id.recycler_view);if(width < height){LinearLayoutManager llm = new LinearLayoutManager(this,LinearLayoutManager.VERTICAL, false);initRecyclerView(llm,new DividerItemDecoration(this, LinearLayoutManager.VERTICAL));}else if(width > height){LinearLayoutManager llm = new GridLayoutManager(this, 4);initRecyclerView(llm,new DividerGridItemDecoration(this));}recyclerView.setItemAnimator(new DefaultItemAnimator());adapter.setOnItemClickListener(this);}private void initRecyclerView(LayoutManager llm,ItemDecoration itemDecoration) {recyclerView.setLayoutManager(llm);adapter = new MyRecyclerViewAdapter(this,dataList);recyclerView.setAdapter(adapter);recyclerView.addItemDecoration(itemDecoration);}private void initValues() {for (int i = 0; i <= 50; i++) {dataList.add("item"+i);}}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {getMenuInflater().inflate(R.menu.main, menu);return true;}@Overridepublic boolean onOptionsItemSelected(MenuItem item) {int id = item.getItemId();if (id == R.id.action_settings) {return true;}return super.onOptionsItemSelected(item);}@Overridepublic void onItemClick(View view, int position) {Toast.makeText(MainActivity.this, "点击了"+position, Toast.LENGTH_SHORT).show();Intent intent = new Intent(MainActivity.this,StaggeredGridLayoutActivity.class);startActivity(intent);}@Overridepublic void onItemLongClick(View view, int position) {Toast.makeText(MainActivity.this, "删除了"+position, Toast.LENGTH_SHORT).show();adapter.removeData(position);adapter.notifyItemRangeChanged(position, adapter.getItemCount());}}</string></string>

首先获取到手机屏幕的宽高，如果width<height，那就展示一个ListView，如果width>height,那就展示一个4列的GridView。

MyRecyclerViewAdapter代码：

class MyRecyclerViewAdapter extendsRecyclerView.Adapter<myrecyclerviewadapter myviewholder> {private List<string> dataList;private Context mContext;public interface OnItemClickListener {void onItemClick(View view, int position);void onItemLongClick(View view, int position);}private OnItemClickListener mOnItemClickListener;public void setOnItemClickListener(OnItemClickListener mOnItemClickListener) {this.mOnItemClickListener = mOnItemClickListener;}public MyRecyclerViewAdapter(Context mContext, List<string> dataList) {this.mContext = mContext;this.dataList = dataList;}class MyViewHolder extends ViewHolder {TextView tv;FrameLayout root_view;public MyViewHolder(View view) {super(view);tv = (TextView) view.findViewById(R.id.tv);root_view = (FrameLayout) view.findViewById(R.id.root_view);}}@Overridepublic int getItemCount() {return dataList.size();}@Overridepublic void onBindViewHolder(final MyViewHolder holder, final int position) {holder.tv.setText(dataList.get(position));if(null != mOnItemClickListener){holder.root_view.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View view) {mOnItemClickListener.onItemClick(view, position);}});holder.root_view.setOnLongClickListener(new OnLongClickListener() {@Overridepublic boolean onLongClick(View view) {mOnItemClickListener.onItemLongClick(view, position);return true;}});}}public void addData(int position){dataList.add(position, "Insert One");notifyItemInserted(position);}public void removeData(int position){dataList.remove(position);notifyItemRemoved(position);}@Overridepublic MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {View view = LayoutInflater.from(mContext).inflate(R.layout.recycler_view_item, parent, false);MyViewHolder holder = new MyViewHolder(view);return holder;}}</string></string></myrecyclerviewadapter>

由于RecyclerView并没有像ListView一样给每个Item设置点击监听事件，所以我们需要自己实现对RecyclerView的点击监听。实现的方法可以是在我们的MyRecyclerViewAdapter中去为点击事件提供一个回调。

DividerItemDecoration代码（为ListView添加分割线）：

public class DividerItemDecoration extends ItemDecoration {private static final int[] ATTRS = new int[]{android.R.attr.listDivider};public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;private Drawable mDivider;private int mOrientation;public DividerItemDecoration(Context context,int orientation){final TypedArray typedArray = context.obtainStyledAttributes(ATTRS);mDivider = typedArray.getDrawable(0);typedArray.recycle();setOrientation(orientation);}public void setOrientation(int orientation) {if(orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST){try {throw new InterruptedIOException("invalid orientation");} catch (InterruptedIOException e) {e.printStackTrace();}}mOrientation = orientation;}@Overridepublic void onDraw(Canvas c, RecyclerView parent, State state) {if(mOrientation == VERTICAL_LIST){drawVertical(c,parent);}else{drawHorizontal(c,parent);}}private void drawHorizontal(Canvas c, RecyclerView parent) {int top = parent.getPaddingTop();int bottom = parent.getHeight()-parent.getPaddingBottom();final int childCount = parent.getChildCount();for(int i =0;i<childCount;i++){final View child = parent.getChildAt(i);final RecyclerView.LayoutParams params = (LayoutParams) child.getLayoutParams();final int left = child.getRight()+params.rightMargin;final int right = left+mDivider.getIntrinsicHeight();mDivider.setBounds(left, top, right, bottom);mDivider.draw(c);}}private void drawVertical(Canvas c, RecyclerView parent) {int left = parent.getPaddingLeft();int right = parent.getWidth()-parent.getPaddingRight();final int childCount = parent.getChildCount();for(int i =0;i<childCount;i++){final View child = parent.getChildAt(i);final RecyclerView.LayoutParams params = (LayoutParams) child.getLayoutParams();final int top = child.getBottom()+params.bottomMargin;final int bottom = top+mDivider.getIntrinsicHeight();mDivider.setBounds(left, top, right, bottom);mDivider.draw(c);}}@Overridepublic void getItemOffsets(Rect outRect, View view, RecyclerView parent,State state) {if(mOrientation == VERTICAL_LIST){outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());}else{outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);}}}

DividerGridItemDecoration代码（为GridView添加分割线）：

public class DividerGridItemDecoration extends ItemDecoration {private static final int[] ATTRS = new int[] { android.R.attr.listDivider };private Drawable mDivider;public DividerGridItemDecoration(Context context) {final TypedArray typedArray = context.obtainStyledAttributes(ATTRS);mDivider = typedArray.getDrawable(0);typedArray.recycle();}@Overridepublic void onDraw(Canvas c, RecyclerView parent, State state) {drawHorizontal(c, parent);drawVertical(c, parent);}private void drawVertical(Canvas c, RecyclerView parent) {final int childCount = parent.getChildCount();for (int i = 0; i < childCount; i++) {final View child = parent.getChildAt(i);RecyclerView.LayoutParams params = (LayoutParams) child.getLayoutParams();final int top = child.getTop() - params.topMargin;final int bottom = child.getBottom() + params.bottomMargin;final int left = child.getRight() + params.rightMargin;final int right = left + mDivider.getIntrinsicWidth();mDivider.setBounds(left, top, right, bottom);mDivider.draw(c);}}private void drawHorizontal(Canvas c, RecyclerView parent) {final int childCount = parent.getChildCount();for (int i = 0; i < childCount; i++) {final View child = parent.getChildAt(i);RecyclerView.LayoutParams params = (LayoutParams) child.getLayoutParams();final int left = child.getLeft() - params.leftMargin;final int right = child.getRight() + params.rightMargin+ mDivider.getIntrinsicWidth();final int top = child.getBottom() + params.bottomMargin;final int bottom = top + mDivider.getIntrinsicHeight();mDivider.setBounds(left, top, right, bottom);mDivider.draw(c);}}private int getSpanCount(RecyclerView parent) {int spanCount = -1;LayoutManager layoutManager = parent.getLayoutManager();if (layoutManager instanceof GridLayoutManager) {spanCount = ((GridLayoutManager) layoutManager).getSpanCount();} else if (layoutManager instanceof StaggeredGridLayoutManager) {spanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount();}return spanCount;}private boolean isLastColum(RecyclerView parent, int pos, int spanCount,int childCount) {LayoutManager layoutManager = parent.getLayoutManager();if (layoutManager instanceof GridLayoutManager) {if ((pos + 1) % spanCount == 0){return true;}} else if (layoutManager instanceof StaggeredGridLayoutManager) {int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();if (orientation == StaggeredGridLayoutManager.VERTICAL) {if ((pos + 1) % spanCount == 0){return true;}} else {childCount = childCount - childCount % spanCount;if (pos >= childCount)return true;}}return false;}private boolean isLastRaw(RecyclerView parent, int pos, int spanCount,int childCount) {LayoutManager layoutManager = parent.getLayoutManager();if (layoutManager instanceof GridLayoutManager) {childCount = childCount - childCount % spanCount;if (pos >= childCount)return true;} else if (layoutManager instanceof StaggeredGridLayoutManager) {int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();if (orientation == StaggeredGridLayoutManager.VERTICAL) {childCount = childCount - childCount % spanCount;if (pos >= childCount)return true;} else{if ((pos + 1) % spanCount == 0) {return true;}}}return false;}@Overridepublic void getItemOffsets(Rect outRect, int itemPosition,RecyclerView parent) {int spanCount = getSpanCount(parent);int childCount = parent.getAdapter().getItemCount();if (isLastRaw(parent, itemPosition, spanCount, childCount)){outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);} else if (isLastColum(parent, itemPosition, spanCount, childCount)){outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());} else {outRect.set(0, 0, mDivider.getIntrinsicWidth(),mDivider.getIntrinsicHeight());}}}

RecyclerView本身并不支持divider属性，所以如果我们不做定制，RecyclerView的每个Item之间是不会有分割线的，但是我们可以通过addItemDecoration()来定制自己的分割线，addItemDecoration()接收的参数是个ItemDecoration对象，我们可以自定义一个DividerItemDecoration类继承自ItemDecoration，在这个类中完成分割线的定制。

二.实现瀑布流效果

StaggeredGridActivity代码：

public class StaggeredGridActivity extends Activity implements StaggeredGridAdapter.OnItemClickListener{private RecyclerView recyclerView;private List<string> dataList;private StaggeredGridAdapter adapter;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);recyclerView = (RecyclerView) findViewById(R.id.recycler_view);dataList = new ArrayList<string>();initValues();adapter = new StaggeredGridAdapter(this, dataList);recyclerView.setLayoutManager(new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL));recyclerView.setItemAnimator(new DefaultItemAnimator());recyclerView.setAdapter(adapter);adapter.setOnItemClickListener(this);}private void initValues() {for (int i = 0; i < 50; i++) {dataList.add("item"+i);}}@Overridepublic void onItemClick(View view, int position) {Toast.makeText(StaggeredGridLayoutActivity.this, "点击了"+position, Toast.LENGTH_SHORT).show();}@Overridepublic void onItemLongClick(View view, int position) {Toast.makeText(StaggeredGridLayoutActivity.this, "删除了"+position, Toast.LENGTH_SHORT).show();adapter.removeItem(position);adapter.notifyItemRangeChanged(position, adapter.getItemCount());}}</string></string>

StaggeredGridAdapter代码：

public class StaggeredGridAdapter extendsRecyclerView.Adapter<staggeredgridadapter myviewholder> {private List<string> dataList;private List<integer> mHeights;private Context mContext;public interface OnItemClickListener{void onItemClick(View view,int position);void onItemLongClick(View view,int position);}private OnItemClickListener mOnItemClickListener;public void setOnItemClickListener(OnItemClickListener mOnItemClickListener){this.mOnItemClickListener = mOnItemClickListener;}public StaggeredGridAdapter(Context mContext, List<string> dataList) {this.dataList = dataList;this.mContext = mContext;mHeights = new ArrayList<integer>();for(int i = 0;i<dataList.size();i++){mHeights.add((int)(100+Math.random()*300));}}@Overridepublic int getItemCount() {return dataList.size();}@Overridepublic void onBindViewHolder(final MyViewHolder holder, final int position) {LayoutParams params = (LayoutParams) holder.tv.getLayoutParams();params.height = mHeights.get(position);holder.tv.setLayoutParams(params);holder.tv.setText(dataList.get(position));if(mOnItemClickListener != null){holder.root_view.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View view) {mOnItemClickListener.onItemClick(view, position);}});holder.root_view.setOnLongClickListener(new OnLongClickListener() {@Overridepublic boolean onLongClick(View view) {mOnItemClickListener.onItemLongClick(view, position);return true;}});}}public void addItem(int position){dataList.add(position, "Insert One");mHeights.add( (int) (100 + Math.random() * 300));notifyItemInserted(position);}public void removeItem(int position){dataList.remove(position);notifyItemRemoved(position);}@Overridepublic MyViewHolder onCreateViewHolder(ViewGroup parent, int arg1) {View view = LayoutInflater.from(mContext).inflate(R.layout.stagger_recycler_view_item, parent, false);MyViewHolder holder = new MyViewHolder(view);return holder;}class MyViewHolder extends ViewHolder {TextView tv;FrameLayout root_view;public MyViewHolder(View view) {super(view);tv = (TextView) view.findViewById(R.id.tv);root_view = (FrameLayout) view.findViewById(R.id.root_view);}}}</integer></string></integer></string></staggeredgridadapter>

其实瀑布流的实现和GridView的实现基本一致，只是瀑布流的每个Item的高不一样，所以这里在Adapter中动态的设置每个Item的高，在onBindViewHolder()中我们用到了LayoutParams方法，这里需要注意的是LayoutParams有很多不同的包，导包的时候一定要导对应的包。不然会报类型不匹配的错误。

三.添加、删除Item

1.删除：

notifyItemRemoved(int position)

2.添加：

notifyItemInserted(int position)

设置动画：

recyclerView.setItemAnimator(new DefaultItemAnimator())

四.点击监听（onClick，onLongClick）

如何实现RecyclerView的点击事件在上面的代码已经给出，上面的代码中如果是点击，则显示一条Toast，如果是长按则删除对应的Item。

点击事件处理中遇到的2个问题：

1.长按删除后也会显示非长按点击的Toast：

原因：一开始在setOnLongClickListener中返回了false，这样这个点击事件还会在向下传递，就会传递到setClickListener中，如果返回了true，则代表这次点击事件在setOnLongClickListener中就被消费了，不会再往下传递。（个人理解，有待验证...）可以参考下之前的文章 

OnTouch事件ACTION_DOWN,ACTION_MOVE,ACTION_UP的事件拦截

解决：setOnLongClickListener中return true。

2.长按删除后出现数据错乱：

原因：在StaggeredGridAdapter的removeItem()方法中，我们对Item的删除使用了notifyItemRemoved(int position)方法，这是RecyclerView为我们提供的带动画的删除方法，但是这个方法只是删除了界面上的Item，为保持数据的一致，我们还需要删除数据源中对应的数据，即dataList.remove(position)。如果对Item的删除仅仅这样处理的话，你会发现再去做删除操作时会发生数据的错乱，导致这个的原因是，我们在做完删除处理后并没有对RecyclerView进行刷新，所以会导致RecyclerView显示的数据与数据源不一致。

解决：解决这个问题的办法就是在删除数据后我们就对RecyclerView刷新一次。RecyclerView和ListView一样，有notifyDataSetChanged()方法，但是使用这个方法进行刷新我们就无法看到删除动画了，原因是调用notifyDataSetChanged()刷新屏幕上显示的所有item的话，必然也会刷新当前正在执行动画的那个Item，这样导致的结果是前面的动画还没执行完，它马上又被刷新了，动画就看不见了。这里我们可以用notifyItemRangeChanged(int position, int itemCount())方法，只需要从被删除的Item后面开始刷新就可以了，这样就保持了原有的删除动画。