一 、前言
最近實在太忙，一個多禮拜沒有更新文章了，于是今晚加班加點把demo寫出來，現在都12點了才開始寫文章。
1.我們的目標
把RecyclerView下拉刷新上拉加載更多加入到我們的開發者頭條APP中。
2.效果圖
3.實現步驟
二 、具體實現
1.尋找RecyclerView上拉刷新下載加載開源庫
我們找開源項目肯定首選github，去搜索一下一大堆，如果效果圖是你想要的功能的話，然后找排名靠前，收藏比較多的項目吧，我找的項目是CommonPullToRefresh,支持ListView，RecyclerView，GridView，SwipeRefreshLayout等常用控件。我跑了一下Demo，沒啥bug，挺好用的。
2.加入項目中
1).module導入進來，然后主項目依賴一下，這里有不會的看我另外一篇文章Android Studio 入門，里面有講到Android Studio添加項目依賴。
2).代碼實現,我們這邊就是修改SelectedFragment
首先我們看布局文件的變化,在RecyclerView外面包裹了自定義的一個類PtrClassicFrameLayout,內部實現了下拉刷新，上拉加載更多。還可以設置自定義屬性，都是啥意思我就不解釋了，有興趣的點擊github上那個鏈接，講解的很詳細。
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <com.chanven.lib.cptr.PtrClassicFrameLayout xmlns:cube_ptr="http://schemas.android.com/apk/res-auto" android:id="@+id/test_recycler_view_frame" android:layout_width="match_parent" android:layout_height="match_parent" android:background="#f0f0f0" cube_ptr:ptr_duration_to_close="200" cube_ptr:ptr_duration_to_close_header="700" cube_ptr:ptr_keep_header_when_refresh="true" cube_ptr:ptr_pull_to_fresh="false"cube_ptr:ptr_ratio_of_header_height_to_refresh="1.2" cube_ptr:ptr_resistance="1.8"> <android.support.v7.widget.RecyclerView android:id="@+id/test_recycler_view" android:layout_width="match_parent" android:layout_height="match_parent"android:background="@android:color/white"/> </com.chanven.lib.cptr.PtrClassicFrameLayout></LinearLayout>
再來看onCreateView方法，這個代碼就不解釋了。
@Override public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState){ View rootView = LayoutInflater.from(getActivity()).inflate(R.layout.fragment_selected, null); ptrClassicFrameLayout = (PtrClassicFrameLayout) rootView.findViewById(R.id.test_recycler_view_frame); mRecyclerView = (RecyclerView) rootView.findViewById(R.id.test_recycler_view); mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity())); init(); return rootView; }在onCreateView里面調用了init()方法，我們來瞧瞧怎么實現的。這里解釋一下為什么要對適配器進行包裝，這樣的目的在包裝類里面處加入頭部，底部View，處理點擊事件。大家拿到源碼了之后自己也可以看看。
private void init() { //初始化適配器 selectedAdapter = new SelectedRecyclerAdapter(getActivity()); //對適配器進行封裝 mAdapter = new RecyclerAdapterWithHF(selectedAdapter); //把滾動Banner加入頭部 mAdapter.addCarouse(initCarouselHead()); mRecyclerView.setAdapter(mAdapter); ptrClassicFrameLayout.setPtrHandler(ptrDefaultHandler);//設置下拉監聽 ptrClassicFrameLayout.setOnLoadMoreListener(onLoadMoreListener);//設置上拉監聽 ptrClassicFrameLayout.setLoadMoreEnable(true);//設置可以加載更多 }mAdapter.addCarouse(initCarouselHead()); 初始化一個滾動Banner，然后加入適配器頭部。這個我前面的教程應該已經講過了。。
//初始化 private View initCarouselHead(){ View headView = LayoutInflater.from(getActivity()).inflate(R.layout.fragment_selected_header,mRecyclerView,false); tvContent=(TextView) headView.findViewById(R.id.tv_content); tvContent.setText(carousePageStr[0]); viewPager = (ViewPager)headView.findViewById(R.id.viewpager); selectedPagerAdapter=new SelectedPagerAdapter(getActivity(),carousePagerSelectView); viewPager.setOffscreenPageLimit(2); viewPager.setCurrentItem(0); viewPager.addOnPageChangeListener(onPageChangeListener); viewPager.setAdapter(selectedPagerAdapter); ViewGroup group = (ViewGroup) headView.findViewById(R.id.viewGroup);// 初始化底部顯示控件 tips = new ImageView[3]; for (int i = 0; i < tips.length; i++){ ImageView imageView = new ImageView(getActivity()); if (i == 0) { imageView.setBackgroundResource(R.mipmap.page_indicator_focused); } else { imageView.setBackgroundResource(R.mipmap.page_indicator_unfocused); } tips[i] = imageView; LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT)); layoutParams.leftMargin = 10;// 設置點點點view的左邊距 layoutParams.rightMargin = 10;// 設置點點點view的右邊距 group.addView(imageView, layoutParams); } timer = new Timer(true);//初始化計時器 timer.schedule(task, 0, CAROUSEL_TIME);//延時0ms后執行,3000ms執行一次 return headView; }SelectedRecyclerAdapter 必須繼承RecyclerView.Adapter
這玩意跟ListView的適配器差不多，用過ListView適配器的應該一看就懂了。
首先會調用getItemCount，知道我要顯示多少item。
知道了行數然后就是循環調用onCreateViewHolder跟onBindViewHolder了，onCreateViewHolder就是創建一個item的View,onBindViewHolder就會把上次創建的item的View傳入進來，還有一個下標，這樣我們就能給每一行賦值，這兩個方法都是先后一起調用。item回收重用的機制應該跟ListView一樣的。
public class SelectedRecyclerAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> { private List<SelectedArticle> selectedArticles; private LayoutInflater inflater; public SelectedRecyclerAdapter(Context context) { super(); inflater = LayoutInflater.from(context); selectedArticles = new ArrayList<SelectedArticle>(); initData(); } private void initData() { for (int i = 0; i < 10; i++) { SelectedArticle selectedArticle = new SelectedArticle(i, "Android開發666", i, i, ""); selectedArticles.add(selectedArticle); } } public void loadMore(int page) { for (int i = 0; i < 5; i++) { SelectedArticle selectedArticle = new SelectedArticle(i, "第" + page + "頁數據", i, i, ""); selectedArticles.add(selectedArticle); } } public void getFirst() { selectedArticles.clear(); initData(); } @Override public int getItemCount() { return selectedArticles.size(); } @Override public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) { SelectedRecyclerHolder holder = (SelectedRecyclerHolder) viewHolder; SelectedArticle selectedArticle = selectedArticles.get(position); holder.title.setText(selectedArticle.getTitle()); holder.like.setText("" + selectedArticle.getLikeNumber()); holder.comment.setText("" + selectedArticle.getCommentNumber()); } @Override public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewHolder, int position) { View view = inflater.inflate(R.layout.fragment_selected_item, null); return new SelectedRecyclerHolder(view); } public class SelectedRecyclerHolder extends RecyclerView.ViewHolder { private TextView title;//標題 private TextView like;//喜歡數量 private TextView comment;評論數量 public SelectedRecyclerHolder(View view) { super(view); title = (TextView) view.findViewById(R.id.tv_title); like = (TextView) view.findViewById(R.id.tv_like); comment = (TextView) view.findViewById(R.id.tv_comment); } }}3.解決整合進來的bug
滑動沖突
當我們上拉到頂部把標題欄擠出屏幕外的時候,進行下拉會觸發RecyclerView的下拉事件，正確的情況應該是顯示Toolbar.
1).RecyclerView下拉刷新的時候先判斷Toolbar有沒有顯示。如果Toolbar沒有顯示就不處理。
2).AppBarLayout有一個addOnOffsetChangedListener方法,在AppBarLayout的布局偏移量發生改變時被調用。
在MainFragment里面進行監聽
appBarLayout= (AppBarLayout) rootView.findViewById(R.id.appBarLayout);appBarLayout.addOnOffsetChangedListener(onOffsetChangedListener);
然后在回調函數中，把值給SelectedFragment，
private AppBarLayout.OnOffsetChangedListener onOffsetChangedListener=new AppBarLayout.OnOffsetChangedListener() { @Override public void onOffsetChanged(AppBarLayout appBarLayout, int i){ //i>=0 Toolbar全部顯示 selectedFragment.setPullRefresh(i>=0); System.out.println("i值:"+i); } };3).在SelectedFragment中，繼續把值傳給PtrFrameLayout
public void setPullRefresh(boolean pullRefresh) { ptrClassicFrameLayout.setPullRefresh(pullRefresh); }4.在PtrFrameLayout里面用一個實例變量接收這個值
private boolean pullRefresh=true; public void setPullRefresh(boolean pullRefresh) { this.pullRefresh = pullRefresh; }4).找到PtrFrameLayout類的dispatchTouchEvent事件,這個方法是處理屏幕的觸摸事件的。
@Override public boolean dispatchTouchEvent(MotionEvent e) { if (!isEnabled() || mContent == null || mHeaderView == null) { System.out.println("都是空的..."); return dispatchTouchEventSupper(e); } int action = e.getAction(); switch (action) { case MotionEvent.ACTION_UP: System.out.println("彈起..."); case MotionEvent.ACTION_CANCEL: System.out.println("取消...");// if(pullRefresh){ mPtrIndicator.onRelease(); if (mPtrIndicator.hasLeftStartPosition()) { if (DEBUG) { PtrCLog.d(LOG_TAG, "call onRelease when user release"); } System.out.println("call onRelease when user release"); onRelease(false); if (mPtrIndicator.hasMovedAfterPressedDown()) { sendCancelEvent(); return true; } } return dispatchTouchEventSupper(e);// } case MotionEvent.ACTION_DOWN: System.out.println("按下..."); mHasSendCancelEvent = false; mPtrIndicator.onPressDown(e.getX(), e.getY()); mScrollChecker.abortIfWorking(); mPreventForHorizontal = false; // The cancel event will be sent once the position is moved. // So let the event pass to children. // fix #93, #102 return dispatchTouchEventSupper(e); case MotionEvent.ACTION_MOVE: System.out.println("移動..."); if(pullRefresh){//Toolbar顯示 mLastMoveEvent = e; mPtrIndicator.onMove(e.getX(), e.getY()); float offsetX = mPtrIndicator.getOffsetX(); float offsetY = mPtrIndicator.getOffsetY(); if (mDisableWhenHorizontalMove && !mPreventForHorizontal && (Math.abs(offsetX) > mPagingTouchSlop && Math.abs(offsetX) > Math.abs(offsetY))) { if (mPtrIndicator.isInStartPosition()) { mPreventForHorizontal = true; } } if (mPreventForHorizontal) { return dispatchTouchEventSupper(e); } boolean moveDown = offsetY > 0; boolean moveUp = !moveDown; boolean canMoveUp = mPtrIndicator.hasLeftStartPosition(); if (DEBUG) { boolean canMoveDown = mPtrHandler != null && mPtrHandler.checkCanDoRefresh(this, mContent, mHeaderView); PtrCLog.v(LOG_TAG, "ACTION_MOVE: offsetY:%s, currentPos: %s, moveUp: %s, canMoveUp: %s, moveDown: %s: canMoveDown: %s", offsetY, mPtrIndicator.getCurrentPosY(), moveUp, canMoveUp, moveDown, canMoveDown); } // disable move when header not reach top if (moveDown && mPtrHandler != null && !mPtrHandler.checkCanDoRefresh(this, mContent, mHeaderView)) { return dispatchTouchEventSupper(e); } if ((moveUp && canMoveUp) || moveDown) {// System.out.println("是否下拉刷新:"+pullRefresh+"偏移量是多少:"+offsetY); movePos(offsetY); return true; } } } return dispatchTouchEventSupper(e); }我就改了一行代碼，在action==MotionEvent.ACTION_MOVE的時候，先判斷我們傳入的pullRefresh是否為true。。。
頂部加入輪播
RecyclerView頭部底部加入View，前面我們介紹過了，都是適配器的封裝類RecyclerAdapterWithHF來控制。從效果圖中，我們可以看出，輪播的View是加入頭部的，找到RecyclerAdapterWithHF類，看看源碼依葫蘆畫瓢就可以了。
1).得有一個保存View的集合，其實用一個變量也行，因為我們只有一個輪播View.
private List<View> mCarouse = new ArrayList<View>();//保存輪播View //可以添加輪播View public void addCarouse(View view){ mCarouse.add(view); }2).定義一個常量，用于類型判斷
public static final int TYPE_CAROUSE = 7900;
3).在getItemViewType里面加入輪播的類型
@Override public final int getItemViewType(int position) { // check what type our position is, based on the assumption that the // order is headers > items > footers if (isHeader(position)) { return TYPE_HEADER; } else if (mCarouse.size()>0&&mHeaders.size()==position){ //判斷集合個數&&position==0 這個時候mHeaders里面是沒有值的 return TYPE_CAROUSE; }else if (isFooter(position)) { return TYPE_FOOTER; } int type = getItemViewTypeHF(getRealPosition(position)); if (type == TYPE_HEADER || type == TYPE_FOOTER|| type == TYPE_CAROUSE) { throw new IllegalArgumentException("Item type cannot equal " + TYPE_HEADER + " or " + TYPE_FOOTER); } return type; }4).onCreateViewHolder里面也要修改一下，就是在if里面多加了個&&.無論是頭部，底部，輪播的View，都是添加到FrameLayout里面的。
@Override public final RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int type) { // if our position is one of our items (this comes from // getItemViewType(int position) below) if (type != TYPE_HEADER && type != TYPE_FOOTER && type != TYPE_CAROUSE) { ViewHolder vh = onCreateViewHolderHF(viewGroup, type); return vh; // else we have a header/footer } else { // create a new framelayout, or inflate from a resource FrameLayout frameLayout = new FrameLayout(viewGroup.getContext()); // make sure it fills the space frameLayout.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT)); return new HeaderFooterViewHolder(frameLayout); } }5).onBindViewHolder這里為item綁定數據，其實就是第四步返回的ItemView綁定數據.
@Override public final void onBindViewHolder(final RecyclerView.ViewHolder vh, int position){ // check what type of view our position is if (isHeader(position)) { View v = mHeaders.get(position); // add our view to a header view and display it prepareHeaderFooter((HeaderFooterViewHolder) vh, v); }else if(mCarouse.size()>0&&position==mHeaders.size()){//這個時候mHeaders.size()值為0// System.out.println("有多少個頭View:"+mHeaders.size()+"值等于多少:"+(mHeaders.size()-1)); View v = mCarouse.get(mHeaders.size());//取出輪播的View prepareHeaderFooter((HeaderFooterViewHolder) vh, v); } else if (isFooter(position)) { View v = mFooters.get(position - getItemCountHF() - mHeaders.size()); // add our view to a footer view and display it prepareHeaderFooter((HeaderFooterViewHolder) vh, v); } else { vh.itemView.setOnClickListener(new MyOnClickListener(vh)); vh.itemView.setOnLongClickListener(new MyOnLongClickListener(vh)); // it's one of our items, display as required onBindViewHolderHF(vh, getRealPosition(position)); } }6).我們從第五步看到頭部底部輪播View最后都會調用prepareHeaderFooter方法?？吹竭@方法的源碼，其實就是把類型對應的View，添加到Item中.
private void prepareHeaderFooter(HeaderFooterViewHolder vh, View view) { // if it's a staggered grid, span the whole layout if (mManagerType == TYPE_MANAGER_STAGGERED_GRID) { StaggeredGridLayoutManager.LayoutParams layoutParams = new StaggeredGridLayoutManager.LayoutParams (ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.WRAP_CONTENT); layoutParams.setFullSpan(true); vh.itemView.setLayoutParams(layoutParams); } // if the view already belongs to another layout, remove it if (view.getParent() != null) { ((ViewGroup) view.getParent()).removeView(view); } // empty out our FrameLayout and replace with our header/footer vh.base.removeAllViews(); vh.base.addView(view); }以上就是本文的全部內容，希望本文的內容對大家的學習或者工作能帶來一定的幫助，同時也希望多多支持武林網！
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