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;
@Override
protected 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);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public 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);
}
@Override
public 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 extends
RecyclerView.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);
}
}
@Override
public int getItemCount() {
return dataList.size();
}
@Override
public void onBindViewHolder(final MyViewHolder holder, final int position) {
holder.tv.setText(dataList.get(position));
if(null != mOnItemClickListener){
holder.root_view.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
mOnItemClickListener.onItemClick(view, position);
}
});
holder.root_view.setOnLongClickListener(new OnLongClickListener() {
@Override
public 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);
}
@Override
public 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;
}
@Override
public 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);
}
}
@Override
public 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();
}
@Override
public 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;
}
@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))
{
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;
@Override
protected 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);
}
}
@Override
public void onItemClick(View view, int position) {
Toast.makeText(StaggeredGridLayoutActivity.this, "点击了"+position, Toast.LENGTH_SHORT).show();
}
@Override
public 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 extends
RecyclerView.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));
}
}
@Override
public int getItemCount() {
return dataList.size();
}
@Override
public 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() {
@Override
public void onClick(View view) {
mOnItemClickListener.onItemClick(view, position);
}
});
holder.root_view.setOnLongClickListener(new OnLongClickListener() {
@Override
public 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);
}
@Override
public 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
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。
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