概述
RecyclerView出现已经有一段时间了，相信大家肯定不陌生了，大家可以通过导入support-v7对其进行使用。
据官方的介绍，该控件用于在有限的窗口中展示大量数据集，其实这样功能的控件我们并不陌生，例如：ListView、GridView。
那么有了ListView、GridView为什么还需要RecyclerView这样的控件呢？
整体上看RecyclerView架构，提供了一种插拔式的体验，高度的解耦，异常的灵活，通过设置它提供的不同LayoutManager，ItemDecoration , ItemAnimator实现令人瞠目的效果。
- 你想要控制其显示的方式，请通过布局管理器LayoutManager
- 你想要控制Item间的间隔（可绘制），请通过ItemDecoration
- 你想要控制Item增删的动画，请通过ItemAnimator
- 你想要控制点击、长按事件，请自己写！
RecyclerView基本的使用代码：
mRecyclerView = findView(R.id.id_recyclerview);
mRecyclerView.setLayoutManager(layout);//设置布局管理器
mRecyclerView.setAdapter(adapter)//设置adapter
mRecyclerView.setItemAnimator(new DefaultItemAnimator());//设置Item增加、移除动画
mRecyclerView.addItemDecoration(new DividerItemDecoration(getActivity(), DividerItemDecoration.HORIZONTAL_LIST));//添加分割线 相比较于ListView的代码，ListView可能只需要去设置一个adapter就能正常使用了。而RecyclerView基本需要上面一系列的步骤，那么为什么会添加这么多的步骤呢？
那么就必须解释下RecyclerView的这个名字了，从它类名上看，RecyclerView代表的意义是，我只管Recycler View，也就是说RecyclerView只管回收与复用View，其他的你可以自己去设置。可以看出其高度的解耦，给予你充分的定制自由（所以你才可以轻松的通过这个控件实现ListView,GirdView，瀑布流等效果）。
分割线 ItemDecoration
RecyclerView并没有支持divider这样的属性，你可以给Item的布局去设置margin、background等方式来间接添加分割线，但这种方式不够优雅，我们的分割线可以在代码中通过以下方法添加。
mRecyclerView.addItemDecoration()
该方法的参数为RecyclerView.ItemDecoration，该类为抽象类，官方目前并没有提供默认的实现类。
public static abstract class ItemDecoration {
public void onDraw(Canvas c, RecyclerView parent, State state) {
onDraw(c, parent);
}
public void onDrawOver(Canvas c, RecyclerView parent, State state) {
onDrawOver(c, parent);
}
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) {
getItemOffsets(outRect, ((LayoutParams) view.getLayoutParams()).getViewLayoutPosition(), parent);
}
@Deprecated
public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {
outRect.set(0, 0, 0, 0);
}
} 若我们调用mRecyclerView.addItemDecoration()方法添加分割线，则RecyclerView在绘制的时候，会 去 绘制 Decoration ，即调用该类的onDraw和onDrawOver方法：
- onDraw 方法在drawChildren之前
- onDrawOver在drawChildren之后，一般我们选择复写其中一个即可。
- getItemOffsets 可以通过outRect.set()为每个Item设置一定的偏移量，主要用于绘制Decorator。
代码 Activity
public class MainActivity extends ActionBarActivity implements MyOnItemClickLitener {
private RecyclerView mRecyclerView;
private List<String> mDatas;//数据
private List<Integer> mHeights;//高度
private MyRecyclerViewAdapter mRecyclerViewAdapter;//适配器
private MyStaggeredAdapter mStaggeredAdapter;
private ItemDecoration decoration1;//分割线
private ItemDecoration decoration2;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mRecyclerView = new android.support.v7.widget.RecyclerView(this);
setContentView(mRecyclerView);
initData();
initAdapter();
initRecylerView();
}
protected void initData() {
mDatas = new ArrayList<String>();
for (int i = 'A'; i < 'z'; i++) {
mDatas.add("" + (char) i);
}
mHeights = new ArrayList<Integer>();
for (int i = 0; i < mDatas.size(); i++) {
mHeights.add((int) (100 + Math.random() * 500));
}
}
private void initAdapter() {
mRecyclerViewAdapter = new MyRecyclerViewAdapter(this, mDatas);
mStaggeredAdapter = new MyStaggeredAdapter(this, mDatas, mHeights);
mRecyclerViewAdapter.setOnItemClickLitener(this);
mStaggeredAdapter.setOnItemClickLitener(this);
}
private void initRecylerView() {
decoration1 = new DividerItemDecoration(this, 0);
decoration2 = new DividerItemDecoration(this, 1);
mRecyclerView.setPadding(10, 10, 10, 10);
mRecyclerView.setAdapter(mRecyclerViewAdapter);//设置adapter
mRecyclerView.setLayoutManager(new GridLayoutManager(this, 3));//设置布局管理器
mRecyclerView.addItemDecoration(decoration1);//添加一个分割线
mRecyclerView.addItemDecoration(decoration2);//还可以再添加一个分割线
mRecyclerView.setItemAnimator(new DefaultItemAnimator());//设置Item增加、移除动画。github上有很多动画效果，如RecyclerViewItemAnimators
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
mRecyclerView.removeItemDecoration(decoration1);//移除分割线，即使没有显示也可以移除
mRecyclerView.removeItemDecoration(decoration2);
switch (item.getItemId()) {
case R.id.add:
mRecyclerViewAdapter.addData(new Random().nextInt(5));
break;
case R.id.delete:
mRecyclerViewAdapter.removeData(new Random().nextInt(5));
break;
//通过RecyclerView去实现ListView、GridView、瀑布流的效果基本上没有什么区别，仅仅通过设置不同的LayoutManager即可实现
case R.id.listview:
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
break;
case R.id.gridview:
mRecyclerView.setLayoutManager(new GridLayoutManager(this, 3));
break;
case R.id.staggeredHorizontalGridView://Staggered：错列的，叉排的。
mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(5, StaggeredGridLayoutManager.HORIZONTAL));//5行
break;
case R.id.staggeredVerticalGridview:
mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL));//3列
break;
case R.id.staggeredAdapter:
mRecyclerView.setAdapter(mStaggeredAdapter);
break;
case R.id.recyclerViewAdapter:
mRecyclerView.setAdapter(mRecyclerViewAdapter);
break;
}
return true;
}
@Override
public void onItemClick(View view, int position) {
Toast.makeText(MainActivity.this, position + " 被点击了", Toast.LENGTH_SHORT).show();
}
@Override
public void onItemLongClick(View view, int position) {
Toast.makeText(MainActivity.this, position + "被长按了", Toast.LENGTH_SHORT).show();
}
} 固定宽高的Adapter
public class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyRecyclerViewAdapter.MyViewHolder> {
private Context context;
private List<String> mDatas;
private MyOnItemClickLitener mOnItemClickLitener;
public void setOnItemClickLitener(MyOnItemClickLitener mOnItemClickLitener) {
this.mOnItemClickLitener = mOnItemClickLitener;
}
public MyRecyclerViewAdapter(Context context, List<String> datas) {
this.context = context;
mDatas = datas;
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
return new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.item, parent, false));
}
@Override
public void onBindViewHolder(final MyViewHolder holder, final int position) {
holder.tv.setText(mDatas.get(position));
RecyclerView.LayoutParams lp = (RecyclerView.LayoutParams) holder.tv.getLayoutParams();
lp.setMargins(5, 5, 5, 5);//设置边距
holder.tv.setLayoutParams(lp);
// 如果设置了回调，则设置点击事件
if (mOnItemClickLitener != null) {
holder.itemView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
int pos = holder.getLayoutPosition();
mOnItemClickLitener.onItemClick(holder.itemView, pos);
}
});
holder.itemView.setOnLongClickListener(new OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
int pos = holder.getLayoutPosition();
mOnItemClickLitener.onItemLongClick(holder.itemView, pos);
removeData(pos);
return false;
}
});
}
}
@Override
public int getItemCount() {
return mDatas.size();
}
/**添加并更新数据，同时具有动画效果*/
public void addData(int position) {
mDatas.add(position, "Insert One");
notifyItemInserted(position);//更新数据集，注意不是用adapter.notifyDataSetChanged()，否则没有动画效果
}
/**移除并更新数据，同时具有动画效果*/
public void removeData(int position) {
mDatas.remove(position);
notifyItemRemoved(position);
}
class MyViewHolder extends RecyclerView.ViewHolder {
TextView tv;
public MyViewHolder(View view) {
super(view);
tv = (TextView) view.findViewById(R.id.id_num);
}
}
} 随机宽高的Adapter
/**和MyAdapter唯一的区别就是：在代码中动态设置了TextView的高度(宽度)*/
public class MyStaggeredAdapter extends RecyclerView.Adapter<MyStaggeredAdapter.MyViewHolder> {
private Context context;
private List<String> mDatas;
private List<Integer> mHeights;//高度
private MyOnItemClickLitener mOnItemClickLitener;
public void setOnItemClickLitener(MyOnItemClickLitener mOnItemClickLitener) {
this.mOnItemClickLitener = mOnItemClickLitener;
}
public MyStaggeredAdapter(Context context, List<String> datas, List<Integer> heights) {
this.context = context;
this.mDatas = datas;
this.mHeights = heights;
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
return new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.item, parent, false));
}
@Override
public void onBindViewHolder(final MyViewHolder holder, final int position) {
RecyclerView.LayoutParams lp = (RecyclerView.LayoutParams) holder.tv.getLayoutParams();
lp.setMargins(5, 5, 5, 5);
//横向时，item的宽度需要设置；纵向时，item的高度需要设置
lp.height = mHeights.get(position);//******************************************************************************************唯一的区别在这里！
lp.width = mHeights.get(position);//*******************************************************************************************唯一的区别在这里！
holder.tv.setLayoutParams(lp);
holder.tv.setText(mDatas.get(position));
// 如果设置了回调，则设置点击事件
if (mOnItemClickLitener != null) {
holder.itemView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
int pos = holder.getLayoutPosition();
mOnItemClickLitener.onItemClick(holder.itemView, pos);
}
});
holder.itemView.setOnLongClickListener(new OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
int pos = holder.getLayoutPosition();
mOnItemClickLitener.onItemLongClick(holder.itemView, pos);
removeData(pos);
return false;
}
});
}
}
@Override
public int getItemCount() {
return mDatas.size();
}
public void addData(int position) {
mDatas.add(position, "Insert One");
mHeights.add((int) (100 + Math.random() * 300));
notifyItemInserted(position);
}
public void removeData(int position) {
mDatas.remove(position);
notifyItemRemoved(position);
}
class MyViewHolder extends RecyclerView.ViewHolder {
TextView tv;
public MyViewHolder(View view) {
super(view);
tv = (TextView) view.findViewById(R.id.id_num);
}
}
} 点击事件回调接口
/**系统没有提供ClickListener和LongClickListener，我们自己通过接口回调处理 */
public interface MyOnItemClickLitener {
void onItemClick(View view, int position);
void onItemLongClick(View view, int position);
} 分割线示例
/**zhy写的分割线，Item如果为最后一列则右边无间隔线，如果为最后一行则底部无分割线*/
public class MyGridItemDecoration extends RecyclerView.ItemDecoration {
private Drawable mDivider;
public MyGridItemDecoration(Context context) {
//通过读取系统主题中的 Android.R.attr.listDivider属性，将其作为Item间的分割线， <item name="android:listDivider">@drawable/divider_bg</item>
TypedArray typedArray = context.obtainStyledAttributes(new int[] { android.R.attr.listDivider });
mDivider = typedArray.getDrawable(0);
typedArray.recycle();//回收TypedArray，以便后面重用。This TypedArray should be recycled after use with recycle()
}
@Override
/**判断如果是最后一行，则不需要绘制底部；如果是最后一列，则不需要绘制右边，整个判断也考虑到了StaggeredGridLayoutManager的横向和纵向*/
public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {
int spanCount = getSpanCount(parent);
int itemCount = parent.getAdapter().getItemCount();
//使用outRect设置绘制的范围。一般如果仅仅是希望有空隙，还是去设置item的margin方便
if (isLastRaw(parent, itemPosition, spanCount, itemCount)) { // 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, itemCount)) { // 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());
}
}
@Override
public void onDraw(Canvas c, RecyclerView parent, State state) {
drawHorizontal(c, parent);
drawVertical(c, parent);
}
//******************************************************************************************
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);
}
}
//******************************************************************************************
/**获取RecyclerView有多少列*/
private int getSpanCount(RecyclerView parent) {
int spanCount = -1; // 列数
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 isLastRaw(RecyclerView parent, int pos, int spanCount, int childCount) {
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;
if (pos >= childCount) return true;// 如果是最后一行，则不需要绘制底部
} else { // StaggeredGridLayoutManager 且横向滚动
if ((pos + 1) % spanCount == 0) return true;// 如果是最后一行，则不需要绘制底部
}
}
return false;
}
private boolean isLastColum(RecyclerView parent, int pos, int spanCount, int childCount) {
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;
}
} 附件列表