概述
RecyclerView出現已經有一段時間了，相信大家肯定不陌生了，大家可以通過導入support-v7對其進行使用。
據官方的介紹，該控件用於在有限的窗口中展示大量數據集，其實這樣功能的控件我們並不陌生，例如：ListView、GridView。
那么有了ListView、GridView為什么還需要RecyclerView這樣的控件呢？
整體上看RecyclerView架構，提供了一種插拔式的體驗，高度的解耦，異常的靈活，通過設置它提供的不同LayoutManager，ItemDecoration , ItemAnimator實現令人瞠目的效果。
- 你想要控制其顯示的方式，請通過布局管理器LayoutManager
- 你想要控制Item間的間隔（可繪制），請通過ItemDecoration
- 你想要控制Item增刪的動畫，請通過ItemAnimator
- 你想要控制點擊、長按事件，請自己寫！
RecyclerView基本的使用代碼：
mRecyclerView = findView(R.id.id_recyclerview);
mRecyclerView.setLayoutManager(layout);//設置布局管理器
mRecyclerView.setAdapter(adapter)//設置adapter
mRecyclerView.setItemAnimator(new DefaultItemAnimator());//設置Item增加、移除動畫
mRecyclerView.addItemDecoration(new DividerItemDecoration(getActivity(), DividerItemDecoration.HORIZONTAL_LIST));//添加分割線
相比較於ListView的代碼，ListView可能只需要去設置一個adapter就能正常使用了。而RecyclerView基本需要上面一系列的步驟，那么為什么會添加這么多的步驟呢？
那么就必須解釋下RecyclerView的這個名字了，從它類名上看，RecyclerView代表的意義是，我只管Recycler View，也就是說RecyclerView只管回收與復用View，其他的你可以自己去設置。可以看出其高度的解耦，給予你充分的定制自由（所以你才可以輕松的通過這個控件實現ListView,GirdView，瀑布流等效果）。
分割線 ItemDecoration
RecyclerView並沒有支持divider這樣的屬性，你可以給Item的布局去設置margin、background等方式來間接添加分割線，但這種方式不夠優雅，我們的分割線可以在代碼中通過以下方法添加。
mRecyclerView.addItemDecoration()
該方法的參數為RecyclerView.ItemDecoration，該類為抽象類，官方目前並沒有提供默認的實現類。
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);
}
}
若我們調用mRecyclerView.addItemDecoration()方法添加分割線，則RecyclerView在繪制的時候，會
去
繪制
Decoration
，即調用該類的onDraw和onDrawOver方法：
- onDraw 方法在drawChildren之前
- onDrawOver在drawChildren之后，一般我們選擇復寫其中一個即可。
- getItemOffsets 可以通過outRect.set()為每個Item設置一定的偏移量，主要用於繪制Decorator。
代碼 Activity
public class MainActivity extends ActionBarActivity implements MyOnItemClickLitener {
private RecyclerView mRecyclerView;
private List<String> mDatas;//數據
private List<Integer> mHeights;//高度
private MyRecyclerViewAdapter mRecyclerViewAdapter;//適配器
private MyStaggeredAdapter mStaggeredAdapter;
private ItemDecoration decoration1;//分割線
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);//設置adapter
mRecyclerView.setLayoutManager(new GridLayoutManager(this, 3));//設置布局管理器
mRecyclerView.addItemDecoration(decoration1);//添加一個分割線
mRecyclerView.addItemDecoration(decoration2);//還可以再添加一個分割線
mRecyclerView.setItemAnimator(new DefaultItemAnimator());//設置Item增加、移除動畫。github上有很多動畫效果，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);//移除分割線，即使沒有顯示也可以移除
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;
//通過RecyclerView去實現ListView、GridView、瀑布流的效果基本上沒有什么區別，僅僅通過設置不同的LayoutManager即可實現
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：錯列的，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 + " 被點擊了", Toast.LENGTH_SHORT).show();
}
@Override
public void onItemLongClick(View view, int position) {
Toast.makeText(MainActivity.this, position + "被長按了", Toast.LENGTH_SHORT).show();
}
}
固定寬高的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);//設置邊距
holder.tv.setLayoutParams(lp);
// 如果設置了回調，則設置點擊事件
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();
}
/**添加並更新數據，同時具有動畫效果*/
public void addData(int position) {
mDatas.add(position, "Insert One");
notifyItemInserted(position);//更新數據集，注意不是用adapter.notifyDataSetChanged()，否則沒有動畫效果
}
/**移除並更新數據，同時具有動畫效果*/
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);
}
}
}
隨機寬高的Adapter
/**和MyAdapter唯一的區別就是：在代碼中動態設置了TextView的高度(寬度)*/
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);
//橫向時，item的寬度需要設置；縱向時，item的高度需要設置
lp.height = mHeights.get(position);//******************************************************************************************唯一的區別在這里！
lp.width = mHeights.get(position);//*******************************************************************************************唯一的區別在這里！
holder.tv.setLayoutParams(lp);
holder.tv.setText(mDatas.get(position));
// 如果設置了回調，則設置點擊事件
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);
}
}
}
點擊事件回調接口
/**系統沒有提供ClickListener和LongClickListener，我們自己通過接口回調處理 */
public interface MyOnItemClickLitener {
void onItemClick(View view, int position);
void onItemLongClick(View view, int position);
}
分割線示例
/**zhy寫的分割線，Item如果為最后一列則右邊無間隔線，如果為最后一行則底部無分割線*/
public class MyGridItemDecoration extends RecyclerView.ItemDecoration {
private Drawable mDivider;
public MyGridItemDecoration(Context context) {
//通過讀取系統主題中的 Android.R.attr.listDivider屬性，將其作為Item間的分割線， <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
/**判斷如果是最后一行，則不需要繪制底部；如果是最后一列，則不需要繪制右邊，整個判斷也考慮到了StaggeredGridLayoutManager的橫向和縱向*/
public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {
int spanCount = getSpanCount(parent);
int itemCount = parent.getAdapter().getItemCount();
//使用outRect設置繪制的范圍。一般如果僅僅是希望有空隙，還是去設置item的margin方便
if (isLastRaw(parent, itemPosition, spanCount, itemCount)) {// 如果是最后一行，則不需要繪制底部
outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
} else if (isLastColum(parent, itemPosition, spanCount, itemCount)) {// 如果是最后一列，則不需要繪制右邊
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);
}
}
//******************************************************************************************
/**獲取RecyclerView有多少列*/
private int getSpanCount(RecyclerView parent) {
int spanCount = -1; // 列數
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，則不需要繪制底部
return true;
} else if (layoutManager instanceof StaggeredGridLayoutManager) {
int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();
// StaggeredGridLayoutManager 且縱向滾動
if (orientation == StaggeredGridLayoutManager.VERTICAL) {
childCount = childCount - childCount % spanCount;
if (pos >= childCount) return true;// 如果是最后一行，則不需要繪制底部
} else { // StaggeredGridLayoutManager 且橫向滾動
if ((pos + 1) % spanCount == 0) return true;// 如果是最后一行，則不需要繪制底部
}
}
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，則不需要繪制右邊
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，則不需要繪制右邊
return true;
}
} else {
childCount = childCount - childCount % spanCount;
if (pos >= childCount) // 如果是最后一列，則不需要繪制右邊
return true;
}
}
return false;
}
}
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