Android仿XListView支持下拉刷新和上劃加載更多的自定義RecyclerView

首先給大家展示下效果圖，感覺還不錯，請繼續往下閱讀：

下拉刷新：

上劃加載

在項目更新的過程中，遇到了一個將XListView換成recyclerView的需求，而且更換完之後大體效果不能變，但是對於下拉刷新這樣的效果，谷歌給出的解決方案是把RecyclerView放在一個SwipeRefreshLayout中，但是這樣其實是拉下一個小圓形控件實現的，和XListView的header效果不同。在網上找了很多的別人代碼，都沒有實現我想要的效果，於是自己動手寫了一個。

具體實現的效果有以下幾條

下拉刷新功能：

1、實現一個有彈性的拖出效果：思路參考XListView，recyclerView的position=0的位置放一個header布局，這個布局的margin top默認為負的布局高度，所以這塊布局就一直處於屏幕外部，在下拉的時候通過onTouchListener根據手指的移動動態修改margin top，慢慢的拖出，當拖出的距離也就是margin top變為正數以後，就蓋面header布局的狀態，改變箭頭的方向並改變提示語

2、實現有彈性的回彈效果：用timerTask寫了一個動態修改的header布局的margin top的動畫，每隔一定的時間減小margin top的值，當用戶松手的時候通過一個函數updateHeaderHeight（）來執行這個動畫。

3、實現用戶非手動拖拉的自動刷新效果：這個recyclerView還有一個方法叫forceRefresh（），就是不需要用戶手動下拉，頭部自己滾動出來，然後刷新完再自己收回去，自動下拉也是用一個timerTask每隔十幾毫秒增加margin top的值讓頭部慢慢露出來

上劃加載更多功能：

1、實現滾動到底部自動停住效果： 有時候recyclerVIew滾動太快，滾到底部的時候會根據慣性向上飄，這個地方到底的時候監控recyclerView滾動速度，如果非常快說明是慣性滾動，就不修改footer布局的高度

2、實現向上拖動效果：復寫了recyclerView的onScrollListener，在手指向上滾動的時候，通過updateFooterHeight（）方法動態修改底部footerView的margin bottom，同headerView一樣，在手指移動的時候讓這個margin跟著變大，以增加footer布局的高度，而且手指移動的越網上，增加的margin的高度就越小，實現一個有彈性的上拉效果，防止誤操作。

3、實現自動回彈的效果：通過監控footer布局的margin bottom來確定松手的時候是否需要開始刷新，如果margin bottom大於某個值得時候就修改footer布局的狀態從normal變成ready，在ready狀態下松手就開始刷新操作，回彈也像header布局一樣通過一個timerTask每隔十幾毫秒修改margin的大小來實現回彈效果

注意事項：

1、為了實現頭部和底部的代碼分離，頭部用的是onTouchListener，底部用的是onScrollListener

2、本recyclerVIew裡面已經內置了一個layoutManager,所以不要給recyclerView再設置layoutManager,否則會出現頭部不出來，下拉報空指針的情況，底部出現但是滑動沒有效果

3、這個recyclerView內置了一個抽象類作為adapter，請繼承這個內置的AlxDragRecyclerViewAdapter使用，或者按照這裡面的邏輯重新寫adapter

有其他的問題歡迎問我

4、一些常用的功能，比如設置該控件是否能夠支持下拉加載和上拉刷新，等等api接口，請直接參考XListView的用法即可

使用方法：

繼承AlxDragRecyclerViewAdapter寫一個adapter，然後寫兩個類分別實現OnRefreshListener和LoadMoreListener，把具體的刷新邏輯寫在裡面，在准備好顯示數據後調用adapter的notifyDataSetChanged（）方法或notifyItemInserted（）方法，並執行該recyclerView的stopLoadmore（）方法和stopRefresh（）方法。

下面是代碼，這個控件有很多的內部類，包括頭部，底部的布局控件（CustomDragHeaderView，CustomDragFooterView），adapter，layoutmanager都已經以內部類的方式集成在裡面，減少遷移時候的復雜度

import android.content.Context;
import android.graphics.Color;
import android.os.Handler;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.view.animation.Animation;
import android.view.animation.RotateAnimation;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
import com.xxx.app.R;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;
/**
 * Created by Alex on 2016/1/27.
 */
public class AlxRefreshLoadMoreRecyclerView extends RecyclerView {
 private int footerHeight = -1;
 LinearLayoutManager layoutManager;
 // -- footer view
 private CustomDragRecyclerFooterView mFooterView;
 private boolean mEnablePullLoad;
 private boolean mPullLoading;
 private boolean isBottom;
 private boolean mIsFooterReady = false;
 private LoadMoreListener loadMoreListener;
 // -- header view
 private CustomDragHeaderView mHeaderView;
 private boolean mEnablePullRefresh = true;
 private boolean mIsRefreshing;
 private boolean isHeader;
 private boolean mIsHeaderReady = false;
 private Timer timer;
 private float oldY;
 Handler handler = new Handler();
 private OnRefreshListener refreshListener;
 private AlxDragRecyclerViewAdapter adapter;
 private int maxPullHeight = 50;//最多下拉高度的px值
 private static final int HEADER_HEIGHT = 68;//頭部高度68dp
 private static final int MAX_PULL_LENGTH = 150;//最多下拉150dp
 private OnClickListener footerClickListener;
 public AlxRefreshLoadMoreRecyclerView(Context context) {
  super(context);
  initView(context);
 }
 public AlxRefreshLoadMoreRecyclerView(Context context, AttributeSet attrs) {
  super(context, attrs);
  initView(context);
 }
 public AlxRefreshLoadMoreRecyclerView(Context context, AttributeSet attrs, int defStyle) {
  super(context, attrs, defStyle);
  initView(context);
 }
 public void setAdapter(AlxDragRecyclerViewAdapter adapter){
  super.setAdapter(adapter);
  this.adapter = adapter;
 }
 public boolean ismPullLoading() {
  return mPullLoading;
 }
 public boolean ismIsRefreshing() {
  return mIsRefreshing;
 }
 private void updateFooterHeight(float delta) {
  if(mFooterView==null)return;
  int bottomMargin = mFooterView.getBottomMargin();
//  Log.i("Alex3","初始delta是"+delta);
  if(delta>50)delta = delta/6;
  if(delta>0) {//越往下滑越難滑
   if(bottomMargin>maxPullHeight)delta = delta*0.65f;
   else if(bottomMargin>maxPullHeight * 0.83333f)delta = delta*0.7f;
   else if(bottomMargin>maxPullHeight * 0.66667f)delta = delta*0.75f;
   else if(bottomMargin>maxPullHeight >> 1)delta = delta*0.8f;
   else if(bottomMargin>maxPullHeight * 0.33333f)delta = delta*0.85f;
   else if(bottomMargin>maxPullHeight * 0.16667F && delta > 20)delta = delta*0.2f;//如果是因為慣性向下迅速的俯沖
   else if(bottomMargin>maxPullHeight * 0.16667F)delta = delta*0.9f;
//   Log.i("Alex3","bottomMargin是"+mFooterView.getBottomMargin()+" delta是"+delta);
  }
  int height = mFooterView.getBottomMargin() + (int) (delta+0.5);
  if (mEnablePullLoad && !mPullLoading) {
   if (height > 150){//必須拉超過一定距離才加載更多
//   if (height > 1){//立即刷新
    mFooterView.setState(CustomDragRecyclerFooterView.STATE_READY);
    mIsFooterReady = true;
//    Log.i("Alex2", "ready");
   } else {
    mFooterView.setState(CustomDragRecyclerFooterView.STATE_NORMAL);
    mIsFooterReady = false;
//    Log.i("Alex2", "nomal");
   }
  }
  mFooterView.setBottomMargin(height);
 }
 private void resetFooterHeight() {
  int bottomMargin = mFooterView.getBottomMargin();
  if (bottomMargin > 20) {
   Log.i("Alex2", "准備重置高度,margin是" + bottomMargin + "自高是" + footerHeight);
   this.smoothScrollBy(0,-bottomMargin);
   //一松手就立即開始加載
   if(mIsFooterReady){
    startLoadMore();
   }
  }
 }
 public void setLoadMoreListener(LoadMoreListener listener){
  this.loadMoreListener = listener;
 }
 public void initView(Context context){
  layoutManager = new LinearLayoutManager(context);//自帶layoutManager，請勿設置
  layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
  WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
  int height = wm.getDefaultDisplay().getHeight();
  layoutManager.offsetChildrenVertical(height*2);//預加載2/3的卡片
  this.setLayoutManager(layoutManager);
//  Log.i("Alex", "屏幕密度為" + getContext().getResources().getDisplayMetrics().density);
  maxPullHeight = dp2px(getContext().getResources().getDisplayMetrics().density,MAX_PULL_LENGTH);//最多下拉150dp
  this.footerClickListener = new footerViewClickListener();
  this.addOnScrollListener(new RecyclerView.OnScrollListener() {
   @Override
   public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
    super.onScrollStateChanged(recyclerView, newState);
    switch (newState){
     case RecyclerView.SCROLL_STATE_IDLE:
//      Log.i("Alex2", "停下了||放手了");
      if(isBottom)resetFooterHeight();
      break;
     case RecyclerView.SCROLL_STATE_DRAGGING:
//      Log.i("Alex2", "開始拖了,現在margin是" + (mFooterView == null ? "" : mFooterView.getBottomMargin()));
      break;
     case RecyclerView.SCROLL_STATE_SETTLING:
//      Log.i("Alex2", "開始慣性移動");
      break;
    }
   }
   @Override
   public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
    super.onScrolled(recyclerView, dx, dy);
    int lastItemPosition = layoutManager.findLastVisibleItemPosition();
//    Log.i("Alex2","mEnable是"+mEnablePullLoad+"lastitemPosition是"+lastItemPosition+" itemcount是"+layoutManager.getItemCount());
    if(lastItemPosition == layoutManager.getItemCount()-1 && mEnablePullLoad) {//如果到了最後一個
     isBottom = true;
     mFooterView = (CustomDragRecyclerFooterView)layoutManager.findViewByPosition(layoutManager.findLastVisibleItemPosition());//一開始還不能hide，因為hide得到最後一個可見的就不是footerview了
//     Log.i("Alex2","到底啦！！"+"mfooterView是"+mFooterView);
     if(mFooterView!=null) mFooterView.setOnClickListener(footerClickListener);
     if(footerHeight==-1 && mFooterView!=null){
      mFooterView.show();
      mFooterView.setState(CustomDragRecyclerFooterView.STATE_NORMAL);
      footerHeight = mFooterView.getMeasuredHeight();//這裡的測量一般不會出問題
//      Log.i("Alex2", "底部高度為" + footerHeight);
     }
     updateFooterHeight(dy);
    }else if(lastItemPosition == layoutManager.getItemCount()-1 && mEnablePullLoad){//如果到了倒數第二個
     startLoadMore();//開始加載更多
    }
    else {
     isBottom = false;
    }
   }
  });
 }
 /**
  * 設置是否開啟上拉加載更多的功能
  *
  * @param enable
  */
 public void setPullLoadEnable(boolean enable) {
  mPullLoading = false;
  mEnablePullLoad = enable;
  if(adapter!=null)adapter.setPullLoadMoreEnable(enable);//adapter和recyclerView要同時設置
  if(mFooterView==null)return;
  if (!mEnablePullLoad) {
//   this.smoothScrollBy(0,-footerHeight);
   mFooterView.hide();
   mFooterView.setOnClickListener(null);
   mFooterView.setBottomMargin(0);
   //make sure "pull up" don't show a line in bottom when listview with one page
  } else {
   mFooterView.show();
   mFooterView.setState(CustomDragRecyclerFooterView.STATE_NORMAL);
   mFooterView.setVisibility(VISIBLE);
   //make sure "pull up" don't show a line in bottom when listview with one page
   // both "pull up" and "click" will invoke load more.
   mFooterView.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View v) {
     startLoadMore();
    }
   });
  }
 }
 /**
  * 停止loadmore
  */
 public void stopLoadMore() {
  if (mPullLoading == true) {
   mPullLoading = false;
   if(mFooterView==null)return;
   mFooterView.show();
   mFooterView.setState(CustomDragRecyclerFooterView.STATE_ERROR);
  }
 }
 private void startLoadMore() {
  if(mPullLoading)return;
  mPullLoading = true;
  if(mFooterView!=null)mFooterView.setState(CustomDragRecyclerFooterView.STATE_LOADING);
  Log.i("Alex2", "現在開始加載");
  mIsFooterReady = false;
  if (loadMoreListener != null) {
   loadMoreListener.onLoadMore();
  }
 }
 /**
  * 在刷新時要執行的方法
  */
 public interface LoadMoreListener{
  public void onLoadMore();
 }
 /**
  * 點擊loadMore後要執行的事件
  */
 class footerViewClickListener implements OnClickListener {
  @Override
  public void onClick(View v) {
   startLoadMore();
  }
 }
 private void updateHeaderHeight(float delta) {
  mHeaderView = (CustomDragHeaderView) layoutManager.findViewByPosition(0);
//  Log.i("Alex2", "現在在頭部！！！！ header自高是" + mHeaderView.getHeight() + " margin 是" + mHeaderView.getTopMargin());//自高一般不會算錯
//  Log.i("Alex2", "正在設置margin" + mHeaderView.getTopMargin() +"delta是"+delta);
  if(delta>0){//如果是往下拉
   int topMargin = mHeaderView.getTopMargin();
   if(topMargin>maxPullHeight * 0.33333f)delta = delta*0.5f;
   else if(topMargin>maxPullHeight * 0.16667F)delta = delta*0.55f;
   else if(topMargin>0)delta = delta*0.6f;
   else if(topMargin<0)delta = delta*0.6f;//如果沒有被完全拖出來
   mHeaderView.setTopMargin(mHeaderView.getTopMargin() + (int)delta);
  } else{//如果是推回去
   if(!mIsRefreshing || mHeaderView.getTopMargin()>0) {//在刷新的時候不把margin設為負值以在慣性滑動的時候能滑回去
    this.scrollBy(0, (int) delta);//禁止既滾動，又同時減少觸摸
//    Log.i("Alex2", "正在往回推" + delta);
    mHeaderView.setTopMargin(mHeaderView.getTopMargin() + (int) delta);
   }
  }
  if(mHeaderView.getTopMargin()>0 && !mIsRefreshing){
   mIsHeaderReady = true;
   mHeaderView.setState(CustomDragHeaderView.STATE_READY);
  }//設置為ready狀態
  else if(!mIsRefreshing){
   mIsHeaderReady = false;
   mHeaderView.setState(CustomDragHeaderView.STATE_NORMAL);
  }//設置為普通狀態並且縮回去
 }
 @Override
 public void smoothScrollToPosition(final int position) {
  super.smoothScrollToPosition(position);
  final Timer scrollTimer = new Timer();
  TimerTask timerTask = new TimerTask() {
   @Override
   public void run() {
    int bottomCardPosition = layoutManager.findLastVisibleItemPosition();
    if(bottomCardPosition<position+1){//如果要向下滾
     handler.post(new Runnable() {
      @Override
      public void run() {
       smoothScrollBy(0,50);
      }
     });
    }else if(bottomCardPosition>position){//如果要向上滾
     handler.post(new Runnable() {
      @Override
      public void run() {
       smoothScrollBy(0,-50);
      }
     });
    }else {
     if(scrollTimer!=null)scrollTimer.cancel();
    }
   }
  };
  scrollTimer.schedule(timerTask,0,20);
 }
 /**
  * 在用戶非手動強制刷新的時候，通過一個動畫把頭部一點點冒出來
  */
 private void smoothShowHeader(){
  if(mHeaderView==null)return;
//  if(layoutManager.findFirstVisibleItemPosition()!=0){//如果刷新完畢的時候用戶沒有注視header
//   mHeaderView.setTopMargin(0);
//   return;
//  }
  if(timer!=null)timer.cancel();
  final TimerTask timerTask = new TimerTask() {
   @Override
   public void run() {
    if(mHeaderView==null){
     if(timer!=null)timer.cancel();
     return;
    }
//    Log.i("Alex2","topMargin是"+mHeaderView.getTopMargin()+" height是"+mHeaderView.getHeight());
    if(mHeaderView.getTopMargin()<0){
     handler.post(new Runnable() {
      @Override
      public void run() {
       if (mIsRefreshing) {//如果目前是ready狀態或者正在刷新狀態
        mHeaderView.setTopMargin(mHeaderView.getTopMargin() +2);
       }
      }
     });
    } else if(timer!=null){//如果已經完全縮回去了，但是動畫還沒有結束，就結束掉動畫
     timer.cancel();
    }
   }
  };
  timer = new Timer();
  timer.scheduleAtFixedRate(timerTask,0,16);
 }
 /**
  * 在用戶松手的時候讓頭部自動收縮回去
  */
 private void resetHeaderHeight() {
  if(mHeaderView==null)mHeaderView = (CustomDragHeaderView) layoutManager.findViewByPosition(0);
  if(layoutManager.findFirstVisibleItemPosition()!=0){//如果刷新完畢的時候用戶沒有注視header
   mHeaderView.setTopMargin(-mHeaderView.getRealHeight());
   return;
  }
  if(timer!=null)timer.cancel();
  final TimerTask timerTask = new TimerTask() {
   @Override
   public void run() {
    if(mHeaderView==null)return;
//    Log.i("Alex2","topMargin是"+mHeaderView.getTopMargin()+" height是"+mHeaderView.getHeight());
    if(mHeaderView.getTopMargin()>-mHeaderView.getRealHeight()){//如果header沒有完全縮回去
     handler.post(new Runnable() {
      @Override
      public void run() {
       if (mIsHeaderReady || mIsRefreshing) {//如果目前是ready狀態或者正在刷新狀態
//        Log.i("Alex2", "現在是ready狀態");
        int delta = mHeaderView.getTopMargin() / 9;
        if (delta < 5) delta = 5;
        if (mHeaderView.getTopMargin() > 0)
         mHeaderView.setTopMargin(mHeaderView.getTopMargin() - delta);
       } else {//如果是普通狀態
//        Log.i("Alex2", "現在是普通狀態");
        mHeaderView.setTopMargin(mHeaderView.getTopMargin() - 5);
       }
      }
     });
    } else if(timer!=null){//如果已經完全縮回去了，但是動畫還沒有結束，就結束掉動畫
     timer.cancel();
     handler.post(new Runnable() {
      @Override
      public void run() {
       mHeaderView.setState(mHeaderView.STATE_FINISH);
      }
     });
    }
   }
  };
  timer = new Timer();
  timer.scheduleAtFixedRate(timerTask,0,10);
 }
 /**
  * 頭部是通過onTouchEvent控制的
  * @param event
  * @return
  */
 @Override
 public boolean onTouchEvent(MotionEvent event) {
  switch (event.getAction()) {
   case MotionEvent.ACTION_MOVE:
    int delta = (int)(event.getY()-oldY);
    oldY = event.getY();
    if (layoutManager.findViewByPosition(0) instanceof CustomDragHeaderView) {
     isHeader = true;
     updateHeaderHeight(delta);//更新margin高度
    }else{
     isHeader = false;
     if(mHeaderView!=null && !mIsRefreshing)mHeaderView.setTopMargin(-mHeaderView.getRealHeight());
    }
    break;
//   case MotionEvent.ACTION_DOWN:
//    Log.i("Alex", "touch down");
//    oldY = event.getY();
//    if(timer!=null)timer.cancel();
//    break;
   case MotionEvent.ACTION_UP:
//    Log.i("Alex", "抬手啦！！！！ touch up ");
    if(mIsHeaderReady && !mIsRefreshing)startRefresh();
    if(isHeader)resetHeaderHeight();//抬手之後恢復高度
    break;
   case MotionEvent.ACTION_CANCEL:
//    Log.i("Alex", "touch cancel");
    break;
  }
  return super.onTouchEvent(event);
 }
 /**
  * 因為設置了子元素的onclickListener之後，ontouch方法的down失效，所以要在分發前獲取手指的位置
  * @param ev
  * @return
  */
 @Override
 public boolean dispatchTouchEvent(MotionEvent ev) {
  // TODO Auto-generated method stub
  switch (ev.getAction()) {
   case MotionEvent.ACTION_DOWN:
//    Log.i("Alex", "touch down分發前");
    oldY = ev.getY();
    if (timer != null) timer.cancel();
    break;
  }
  return super.dispatchTouchEvent(ev);
 }
 public void setOnRefreshListener(OnRefreshListener listener){
  this.refreshListener = listener;
 }
 /**
  * 設置是否支持下啦刷新的功能
  *
  * @param enable
  */
 public void setPullRefreshEnable(boolean enable) {
  mIsRefreshing = false;
  mEnablePullRefresh = enable;
  if(mHeaderView==null)return;
  if (!mEnablePullRefresh) {
   mHeaderView.setOnClickListener(null);
  } else {
   mHeaderView.setState(CustomDragFooterView.STATE_NORMAL);
   mHeaderView.setVisibility(VISIBLE);
  }
 }
 /**
  * 停止下拉刷新，並且通過動畫讓頭部自己縮回去
  */
 public void stopRefresh() {
  if (mIsRefreshing == true) {
   mIsRefreshing = false;
   mIsHeaderReady = false;
   if(mHeaderView==null)return;
   mHeaderView.setState(CustomDragFooterView.STATE_NORMAL);
   resetHeaderHeight();
  }
 }
 /**
  * 在用戶沒有用手控制的情況下，通過動畫把頭部露出來並且執行刷新
  */
 public void forceRefresh(){
  if(mHeaderView==null)mHeaderView = (CustomDragHeaderView) layoutManager.findViewByPosition(0);
  if(mHeaderView!=null)mHeaderView.setState(CustomDragHeaderView.STATE_REFRESHING);
  mIsRefreshing = true;
  Log.i("Alex2", "現在開始強制刷新");
  mIsHeaderReady = false;
  smoothShowHeader();
  if (refreshListener != null)refreshListener.onRefresh();
 }
 private void startRefresh() {
  mIsRefreshing = true;
  mHeaderView.setState(CustomDragHeaderView.STATE_REFRESHING);
  Log.i("Alex2", "現在開始加載");
  mIsHeaderReady = false;
  if (refreshListener != null) refreshListener.onRefresh();
 }
 public interface OnRefreshListener{
  public void onRefresh();
 }
 /**
  * 適用於本recycler的頭部下拉刷新view
  */
 public static class CustomDragHeaderView extends LinearLayout {
  public final static int STATE_NORMAL = 0;
  public final static int STATE_READY = 1;
  public final static int STATE_REFRESHING = 2;
  public final static int STATE_FINISH = 3;
  public float screenDensity;
  private final int ROTATE_ANIM_DURATION = 180;
  private Context mContext;
  private View mContentView;
  private View mProgressBar;
  private ImageView mArrowImageView;
  private TextView mHintTextView;
  private Animation mRotateUpAnim;
  private Animation mRotateDownAnim;
  public CustomDragHeaderView(Context context) {
   super(context);
   initView(context);
  }
  public CustomDragHeaderView(Context context, AttributeSet attrs) {
   super(context, attrs);
   initView(context);
  }
  private int mState;
  public void setState(int state) {
   if (state == mState)
    return;
   if (state == STATE_REFRESHING) { // 顯示進度
    mArrowImageView.clearAnimation();
    mArrowImageView.setVisibility(View.INVISIBLE);
    mProgressBar.setVisibility(View.VISIBLE);
   } else { // 顯示箭頭圖片
    mArrowImageView.setVisibility(View.VISIBLE);
    mProgressBar.setVisibility(View.INVISIBLE);
   }
   switch (state) {
    case STATE_NORMAL:
     if (mState == STATE_READY) {
      mArrowImageView.startAnimation(mRotateDownAnim);
      mHintTextView.setText(R.string.xlistview_header_hint_normal);
     }
     else if (mState == STATE_REFRESHING) {//如果是從刷新狀態過來
//      mArrowImageView.clearAnimation();
      mArrowImageView.setVisibility(INVISIBLE);
      mHintTextView.setText("load completed");
     }
     break;
    case STATE_READY:
     if (mState != STATE_READY) {
      mArrowImageView.clearAnimation();
      mArrowImageView.startAnimation(mRotateUpAnim);
     }
      mHintTextView.setText(R.string.xlistview_header_hint_ready);
     break;
    case STATE_REFRESHING:
      mHintTextView.setText(R.string.xlistview_header_hint_loading);
     break;
    case STATE_FINISH:
     mArrowImageView.setVisibility(View.VISIBLE);
     mHintTextView.setText(R.string.xlistview_header_hint_normal);
     break;
    default:
   }
   mState = state;
  }
  public void setTopMargin(int height) {
   if (mContentView==null) return ;
   LayoutParams lp = (LayoutParams)mContentView.getLayoutParams();
   lp.topMargin = height;
   mContentView.setLayoutParams(lp);
  }
  //
  public int getTopMargin() {
   LayoutParams lp = (LayoutParams)mContentView.getLayoutParams();
   return lp.topMargin;
  }
  public void setHeight(int height){
   if (mContentView==null) return ;
   LayoutParams lp = (LayoutParams)mContentView.getLayoutParams();
   lp.height = height;
   mContentView.setLayoutParams(lp);
  }
  private int realHeight;
  /**
   * 得到這個headerView真實的高度，而且這個高度是自己定的
   * @return
   */
  public int getRealHeight(){
   return realHeight;
  }
  private void initView(Context context) {
   mContext = context;
   this.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));//recyclerView裡不加這句話的話寬度就會比較窄
   LinearLayout moreView = (LinearLayout) LayoutInflater.from(mContext).inflate(R.layout.xlistview_header, null);
   addView(moreView);
   moreView.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
   mContentView = moreView.findViewById(R.id.xlistview_header_content);
   LayoutParams lp = (LayoutParams)mContentView.getLayoutParams();
   Log.i("Alex", "初始height是" + mContentView.getHeight());
   lp.height = 150;//手動設置高度,如果要手動加載更多的時候才設置
   screenDensity = getContext().getResources().getDisplayMetrics().density;//設置屏幕密度，用來px向dp轉化
   lp.height = dp2px(screenDensity,HEADER_HEIGHT);//頭部高度75dp
   realHeight = lp.height;
   lp.topMargin = -lp.height;
   mContentView.setLayoutParams(lp);
   mArrowImageView = (ImageView) findViewById(R.id.xlistview_header_arrow);
   mHintTextView = (TextView) findViewById(R.id.xlistview_header_hint_textview);
   mHintTextView.setPadding(0,dp2px(screenDensity,3),0,0);//不知道為什麼這個文字總會向上偏一下，所以要補回來
   mProgressBar = findViewById(R.id.xlistview_header_progressbar);
   mRotateUpAnim = new RotateAnimation(0.0f, -180.0f, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);
   mRotateUpAnim.setDuration(ROTATE_ANIM_DURATION);
   mRotateUpAnim.setFillAfter(true);
   mRotateDownAnim = new RotateAnimation(-180.0f, 0.0f, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);
   mRotateDownAnim.setDuration(ROTATE_ANIM_DURATION);
   mRotateDownAnim.setFillAfter(true);
  }
 }
 public static int dp2px(float density, int dp) {
  if (dp == 0) {
   return 0;
  }
  return (int) (dp * density + 0.5f);
 }
 public static class CustomDragRecyclerFooterView extends LinearLayout {
  public final static int STATE_NORMAL = 0;
  public final static int STATE_READY = 1;
  public final static int STATE_LOADING = 2;
  public final static int STATE_ERROR = 3;
  private Context mContext;
  private View mContentView;
  private View mProgressBar;
  private TextView mHintView;
  public CustomDragRecyclerFooterView(Context context) {
   super(context);
   initView(context);
  }
  public CustomDragRecyclerFooterView(Context context, AttributeSet attrs) {
   super(context, attrs);
   initView(context);
  }
  public void setState(int state) {
   mProgressBar.setVisibility(View.INVISIBLE);
//   mHintView.setVisibility(View.INVISIBLE);
   if (state == STATE_READY) {
    mHintView.setVisibility(View.VISIBLE);
    mHintView.setText("松手加載更多");
   } else if (state == STATE_LOADING) {
    mProgressBar.setVisibility(View.VISIBLE);
    mHintView.setVisibility(INVISIBLE);
   } else if(state == STATE_ERROR){
    mProgressBar.setVisibility(GONE);
    mHintView.setVisibility(VISIBLE);
    mHintView.setText(R.string.xlistview_footer_hint_ready);
   }
   else {
    mHintView.setVisibility(View.VISIBLE);
    mHintView.setText(R.string.xlistview_footer_hint_normal);
    mHintView.setText("Load more");
   }
  }
  public void setBottomMargin(int height) {
   if (height < 0) return ;
   LayoutParams lp = (LayoutParams)mContentView.getLayoutParams();
   lp.bottomMargin = height;
   mContentView.setLayoutParams(lp);
  }
  public int getBottomMargin() {
   LayoutParams lp = (LayoutParams)mContentView.getLayoutParams();
   return lp.bottomMargin;
  }
  /**
   * normal status
   */
  public void normal() {
   mHintView.setVisibility(View.VISIBLE);
   mProgressBar.setVisibility(View.GONE);
  }
  /**
   * loading status
   */
  public void loading() {
   mHintView.setVisibility(View.GONE);
   mProgressBar.setVisibility(View.VISIBLE);
  }
  /**
   * hide footer when disable pull load more
   */
  public void hide() {
   LayoutParams lp = (LayoutParams)mContentView.getLayoutParams();
   lp.height = 1;//這裡如果設為0那麼layoutManger就會抓不到
   mContentView.setLayoutParams(lp);
   mContentView.setBackgroundColor(Color.BLACK);//這裡的顏色要和自己的背景色一致
  }
  /**
   * show footer
   */
  public void show() {
   LayoutParams lp = (LayoutParams)mContentView.getLayoutParams();
   lp.height = LayoutParams.WRAP_CONTENT;
   lp.width = LayoutParams.MATCH_PARENT;
   mContentView.setLayoutParams(lp);
   mContentView.setBackgroundColor(Color.WHITE);//這裡的顏色要和自己的背景色一致
  }
  private void initView(Context context) {
   mContext = context;
   this.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
   LinearLayout moreView = (LinearLayout) LayoutInflater.from(mContext).inflate(R.layout.layout_customdragfooterview, null);
   addView(moreView);
   moreView.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
   mContentView = moreView.findViewById(R.id.rlContentView);
   mProgressBar = moreView.findViewById(R.id.pbContentView);
   mHintView = (TextView)moreView.findViewById(R.id.ctvContentView);
   mHintView.setText("load more");
//   mProgressBar.setVisibility(VISIBLE);//一直會顯示轉圈，自動加載更多時使用
  }
 }
 /**
  * 為了防止代碼上的混亂，使用這個recyclerView自己內置的一個adapter
  * @param <T>
  */
 public static abstract class AlxDragRecyclerViewAdapter<T> extends RecyclerView.Adapter<RecyclerView.ViewHolder>{
  protected static final int TYPE_HEADER = 436874;
  protected static final int TYPE_ITEM = 256478;
  protected static final int TYPE_FOOTER = 9621147;
  private int ITEM;
  private ViewHolder vhItem;
  protected boolean loadMore;
  private List<T> dataList;
  public List<T> getDataList() {
   return dataList;
  }
  public void setDataList(List<T> dataList) {
   this.dataList = dataList;
  }
  public AlxDragRecyclerViewAdapter(List<T> dataList,int itemLayout,boolean pullEnable){
   this.dataList = dataList;
   this.ITEM = itemLayout;
   this.loadMore = pullEnable;
  }
  public abstract ViewHolder setItemViewHolder(View itemView);
  private T getObject(int position){
   if(dataList!=null && dataList.size()>=position)return dataList.get(position-1);//如果有header
   return null;
  }
  @Override
  public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
   if (viewType == TYPE_ITEM) {
    //inflate your layout and pass it to view holder
    View itemView = LayoutInflater.from(parent.getContext()).inflate(ITEM,null);
    Log.i("Alex","itemView是"+itemView);
    this.vhItem = setItemViewHolder(itemView);
    Log.i("Alex","vhItem是"+vhItem);
    return vhItem;
   } else if (viewType == TYPE_HEADER) {
    //inflate your layout and pass it to view holder
    View headerView = new CustomDragHeaderView(parent.getContext());
    return new VHHeader(headerView);
   } else if(viewType==TYPE_FOOTER){
    CustomDragRecyclerFooterView footerView = new CustomDragRecyclerFooterView(parent.getContext());
    return new VHFooter(footerView);
   }
   throw new RuntimeException("there is no type that matches the type " + viewType + " + make sure your using types correctly");
  }
  public void setPullLoadMoreEnable(boolean enable){
   this.loadMore = enable;
  }
  public boolean getPullLoadMoreEnable(){return loadMore;}
  @Override
  public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {//相當於getView
   Log.i("Alex","正在綁定"+position+" "+holder.getClass());
   if (vhItem!=null && holder.getClass() == vhItem.getClass()) {
    //cast holder to VHItem and set data
    initItemView(holder,position,getObject(position));
   }else if (holder instanceof AlxDragRecyclerViewAdapter.VHHeader) {
    //cast holder to VHHeader and set data for header.
   }else if(holder instanceof AlxDragRecyclerViewAdapter.VHFooter){
    if(!loadMore)((VHFooter)holder).footerView.hide();//第一次初始化顯示的時候要不要顯示footerView
   }
  }
  @Override
  public int getItemCount() {
   return (dataList==null ||dataList.size()==0)?1:dataList.size() + 2;//如果有header,若list不存在或大小為0就沒有footView，反之則有
  }//這裡要考慮到頭尾部，多以要加2
  /**
   * 根據位置判斷這裡該用哪個ViewHolder
   * @param position
   * @return
   */
  @Override
  public int getItemViewType(int position) {
   if (position == 0)return TYPE_HEADER;
   else if(isPositonFooter(position))return TYPE_FOOTER;
   return TYPE_ITEM;
  }
  protected boolean isPositonFooter(int position){//這裡的position從0算起
    if (dataList == null && position == 1) return true;//如果沒有item
    return position == dataList.size() + 1;//如果有item(也許為0)
  }
//  class VHItem extends RecyclerView.ViewHolder {
//   public VHItem(View itemView) {
//    super(itemView);
//   }
//   public View getItemView(){return itemView;}
//  }
//
  protected class VHHeader extends RecyclerView.ViewHolder {
   public VHHeader(View headerView) {
    super(headerView);
   }
  }
  protected class VHFooter extends RecyclerView.ViewHolder {
   public CustomDragRecyclerFooterView footerView;
   public VHFooter(View itemView) {
    super(itemView);
    footerView = (CustomDragRecyclerFooterView)itemView;
   }
  }
  public abstract void initItemView(ViewHolder itemHolder,int posion,T entity);
 }
}