RecyclerView一个可以代替ListView和GridView的控件，那么RecyclerView到底比他们好在哪里？

RecyclerView架构提供了一种插拔式的体验，所以实现了代码的高度解耦，使用起来也异常的灵活。

我们可以通过设置它的LayoutManager控制其显示的方式，通过ItemDecoration控制Item间的间隔，通过ItemAnimator控制Item的增删动画

RecyclerView.LayoutManager提供了三个实现类其中LinearLayoutManager 现行管理器，支持横向、纵向，GridLayoutManager 网格布局管理器，StaggeredGridLayoutManager 瀑布就式布局管理器

那么先从LinearLayoutManager看起

先在gradle中引用compile 'com.android.support:recyclerview-v7:23.4.0'

Activity布局文件如下：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:tools="http://schemas.android.com/tools"  android:layout_width="match_parent"  android:layout_height="match_parent"  tools:context="com.lg.recyclerviewdemo.LinearActivity">  <android.support.v7.widget.RecyclerView  android:id="@+id/linear_recycler"  android:layout_width="match_parent"  android:layout_height="match_parent"/>  </RelativeLayout>

item布局文件：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  android:layout_width="match_parent"  android:layout_height="match_parent">  <LinearLayout  android:layout_width="match_parent"  android:layout_height="match_parent"  android:gravity="center">  <ImageView  android:layout_width="70dp"  android:layout_height="70dp"  android:src="@drawable/android" />  <TextView  android:id="@+id/recycler_item_tv"  android:layout_width="wrap_content"  android:layout_height="100dp"  android:layout_marginLeft="20dp"  android:gravity="center"  android:textColor="@color/colorPrimary"  android:textSize="20sp"  android:textStyle="bold" />  </LinearLayout>
</RelativeLayout>

在Acitvity中初始化数据：

mDatas = new ArrayList<String>();
for (int i = 1; i <= 65; i++) {  mDatas.add("item"+i);
}

核心代码：

recyclerAdapter = new RecyclerAdapter();
//设置布局管理器
linear_recycler.setLayoutManager(new LinearLayoutManager(this));
//设置adapter
linear_recycler.setAdapter(recyclerAdapter);
//添加分割线
linear_recycler.addItemDecoration(new DividerLinearItemDecoration(this, DividerLinearItemDecoration.VERTICAL_LIST));

接下来自制adapter：

public class RecyclerAdapter extends RecyclerView.Adapter<LinearHolder> {  private View view;  @Override  public LinearHolder onCreateViewHolder(ViewGroup parent, int viewType) {  //利用反射将item的布局加载出来  view = LayoutInflater.from(parent.getContext()).inflate(R.layout.recycler_item, null);  //new一个我们的ViewHolder，findViewById操作都在LinearHolder的构造方法中进行了  return new LinearHolder(view);  }  @Override  public void onBindViewHolder(LinearHolder holder, int position) {  holder.recycler_item.setText(MainActivity.mDatas.get(position));  }  @Override  public int getItemCount() {  return MainActivity.mDatas.size();  }
}  class LinearHolder extends RecyclerView.ViewHolder {  TextView recycler_item;  public LinearHolder(View itemView) {  super(itemView);  recycler_item = (TextView) itemView.findViewById(R.id.recycler_item_tv);  }

再绘画它的分割线：

public class DividerLinearItemDecoration extends RecyclerView.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 DividerLinearItemDecoration(Context context, int orientation) {  final TypedArray a = context.obtainStyledAttributes(ATTRS);  mDivider = a.getDrawable(0);  a.recycle();  setOrientation(orientation);  }  public void setOrientation(int orientation) {  if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST) {  throw new IllegalArgumentException("invalid orientation");  }  mOrientation = orientation;  }  @Override  public void onDraw(Canvas c, RecyclerView parent) {  if (mOrientation == VERTICAL_LIST) {  drawVertical(c, parent);  } else {  drawHorizontal(c, parent);  }  }  public void drawVertical(Canvas c, RecyclerView parent) {  final int left = parent.getPaddingLeft();  final int right = parent.getWidth() - parent.getPaddingRight();  final int childCount = parent.getChildCount();  for (int i = 0; i < childCount; i++) {  final View child = parent.getChildAt(i);  RecyclerView v = new RecyclerView(parent.getContext());  final RecyclerView.LayoutParams params = (RecyclerView.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);  }  }  public void drawHorizontal(Canvas c, RecyclerView parent) {  final int top = parent.getPaddingTop();  final 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 = (RecyclerView.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);  }  }  @Override  public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {  if (mOrientation == VERTICAL_LIST) {  outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());  } else {  outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);  }  }
}

好了，我们来看看效果：

嘛，貌似和ListView没什么区别，还这么麻烦

别急，我们试试GridLayoutManager

很简单，我们只需要改变LayoutManager和ItemDecoration就行了：

grid_recycler.setLayoutManager(new GridLayoutManager(this,2));
grid_recycler.addItemDecoration(new DividerGridItemDecoration(this));

DividerGridItemDecoration代码：

public class DividerGridItemDecoration extends RecyclerView.ItemDecoration {  private static final int[] ATTRS = new int[] { android.R.attr.listDivider };  private Drawable mDivider;  public DividerGridItemDecoration(Context context)  {  final TypedArray a = context.obtainStyledAttributes(ATTRS);  mDivider = a.getDrawable(0);  a.recycle();  }  @Override  public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state)  {  drawHorizontal(c, parent);  drawVertical(c, parent);  }  private int getSpanCount(RecyclerView parent)  {  // 列数  int spanCount = -1;  RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();  if (layoutManager instanceof GridLayoutManager)  {  spanCount = ((GridLayoutManager) layoutManager).getSpanCount();  } else if (layoutManager instanceof StaggeredGridLayoutManager)  {  spanCount = ((StaggeredGridLayoutManager) layoutManager)  .getSpanCount();  }  return spanCount;  }  public void drawHorizontal(Canvas c, RecyclerView parent)  {  int childCount = parent.getChildCount();  for (int i = 0; i < childCount; i++)  {  final View child = parent.getChildAt(i);  final RecyclerView.LayoutParams params = (RecyclerView.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);  }  }  public void drawVertical(Canvas c, RecyclerView parent)  {  final int childCount = parent.getChildCount();  for (int i = 0; i < childCount; i++)  {  final View child = parent.getChildAt(i);  final RecyclerView.LayoutParams params = (RecyclerView.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 boolean isLastColum(RecyclerView parent, int pos, int spanCount,  int childCount)  {  RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();  if (layoutManager instanceof GridLayoutManager)  {  if ((pos + 1) % spanCount == 0)// 如果是最后一列，则不需要绘制右边  {  return true;  }  } else if (layoutManager instanceof StaggeredGridLayoutManager)  {  int orientation = ((StaggeredGridLayoutManager) layoutManager)  .getOrientation();  if (orientation == StaggeredGridLayoutManager.VERTICAL)  {  if ((pos + 1) % spanCount == 0)// 如果是最后一列，则不需要绘制右边  {  return true;  }  } else  {  childCount = childCount - childCount % spanCount;  if (pos >= childCount)// 如果是最后一列，则不需要绘制右边  return true;  }  }  return false;  }  private boolean isLastRaw(RecyclerView parent, int pos, int spanCount,  int childCount)  {  RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();  if (layoutManager instanceof GridLayoutManager)  {  childCount = childCount - childCount % spanCount;  if (pos >= childCount)// 如果是最后一行，则不需要绘制底部  return true;  } else if (layoutManager instanceof StaggeredGridLayoutManager)  {  int orientation = ((StaggeredGridLayoutManager) layoutManager)  .getOrientation();  // StaggeredGridLayoutManager 且纵向滚动  if (orientation == StaggeredGridLayoutManager.VERTICAL)  {  childCount = childCount - childCount % spanCount;  // 如果是最后一行，则不需要绘制底部  if (pos >= childCount)  return true;  } else  // StaggeredGridLayoutManager 且横向滚动  {  // 如果是最后一行，则不需要绘制底部  if ((pos + 1) % spanCount == 0)  {  return true;  }  }  }  return false;  }  @Override  public void getItemOffsets(Rect outRect, int itemPosition,  RecyclerView parent)  {  int spanCount = getSpanCount(parent);  int childCount = parent.getAdapter().getItemCount();  if (isLastRaw(parent, itemPosition, spanCount, childCount))// 如果是最后一行，则不需要绘制底部  {  outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);  } else if (isLastColum(parent, itemPosition, spanCount, childCount))// 如果是最后一列，则不需要绘制右边  {  outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());  } else  {  outRect.set(0, 0, mDivider.getIntrinsicWidth(),  mDivider.getIntrinsicHeight());  }  }
}

看下效果吧：

渍，有点意思，不过也没那么神乎其神啊

别忘了，我们还有个StaggeredGridLayoutManager没用

展示了那么多纵向的，我们来个横向的，同样改变LayoutManager

stag_grid_recycler.setLayoutManager(new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.HORIZONTAL));

看下效果：

一个RecyclerView就能实现这么多功能，确实强大啊

不过，你以为这样就完了？下来要放大招了

看标题，瀑布流有木有，你用ListView不会那么简单就实现吧，但是用RecyclerView分分钟

稍微改变item布局，让图片放在字的上面

我们在onBindViewHolder给item设置随机高度：

LayoutParams layoutParams = holder.sg_item.getLayoutParams();
layoutParams.height = heights.get(position);

看下大招效果：

我就问你6不6，6的话还不快关注我(嘎嘎)

好吧，可能吓到你了，什么？点击事件？

好吧，很不幸告诉你，要自己写，对，就是要自己写。

前面已经说过了，RecyclerView实现了高度解耦，非常的灵活(你要干什么，自己去写)。那就写吧！

先写个接口：

public interface OnItemClickLitener {  /*点击事件*/  void onItemClick(View view, int position);  /*长按事件*/  void onItemLongClick(View view, int position);
}

在adapter中加入代码：

private OnItemClickLitener mOnItemClickLitener;  public void setOnItemClickLitener(OnItemClickLitener mOnItemClickLitener) {  this.mOnItemClickLitener = mOnItemClickLitener;
}

onBindViewHolder方法中加入：

holder.sg_item.setOnClickListener(new View.OnClickListener() {  @Override  public void onClick(View v) {  int pos = holder.getLayoutPosition();  mOnItemClickLitener.onItemClick(holder.itemView, pos);  }  });
holder.sg_item.setOnLongClickListener(new View.OnLongClickListener() {  @Override  public boolean onLongClick(View v) {  int pos = holder.getLayoutPosition();  mOnItemClickLitener.onItemLongClick(holder.itemView, pos);  return false;  }
});

然后在Activity中调用：

staggeredGridAdapter.setOnItemClickLitener(new OnItemClickLitener() {  @Override  public void onItemClick(View view, int position) {  staggeredGridAdapter.notifyItemRemoved(position);  }  @Override  public void onItemLongClick(View view, final int position) {  android.support.v7.app.AlertDialog.Builder builder = new AlertDialog.Builder(StaggeredGridVActivity.this);  builder.setTitle("Delete?")  .setNegativeButton("no", null)  .setPositiveButton("yes", new DialogInterface.OnClickListener() {  @Override  public void onClick(DialogInterface dialog, int which) {  staggeredGridAdapter.notifyItemRemoved(position);  Toast.makeText(StaggeredGridVActivity.this,MainActivity.mDatas.get(position),Toast.LENGTH_SHORT).show();  }  }).show();  }  });

效果图：

怎么样？厉害吧。不过你以为这样就完了？

如果我想要将item托拉拽再加上侧滑删除呢？

首先，如果要实现托拉拽功能，那item长按事件还是不要写代码的，避免事件冲突

然后在Activity中加入代码：

ItemTouchHelper itemTouchHelper = new ItemTouchHelper(callback);
itemTouchHelper.attachToRecyclerView(stag_v_recycler);

callback代码：

ItemTouchHelper.Callback callback = new ItemTouchHelper.Callback() {  //这个方法是用来设置我们拖动的方向以及侧滑的方向的@Override  public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {  //设置拖拽方向为上下左右  final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN |  ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;  //设置侧滑方向为从左到右和从右到左都可以  final int swipeFlags = ItemTouchHelper.START | ItemTouchHelper.END;  //将方向参数设置进去  return makeMovementFlags(dragFlags, swipeFlags);  }  /** * @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) {  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(MainActivity.mDatas, i, i + 1);  }  } else {  for (int i = fromPosition; i > toPosition; i--) {  Collections.swap(MainActivity.mDatas, i, i - 1);  }  }  staggeredGridAdapter.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();  staggeredGridAdapter.notifyItemRemoved(position);  }  @Override  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);  }  }  };

OK，我们来看看效果：

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