ListView 下拉刷新，上拉加载更多的原理：

（1）主要是onScroll()方法和onTouchEvent()方法，先是onTouchEvent()的ACTION_DOWN,然后是 ACTION_MOVE和onScroll()方法同时进行，最后是onTouchEvent()的ACTION_UP。
（2）刷新的4种状态：CLICK_TO_REFRESH(点击刷新状态，初始状态)、DROP_DOWN_TO_REFRESH(当刷新layout高 度低于一定范围时，为此状态)、RELEASE_TO_REFRESH(当刷新layout高度高于一定范围时，为此状态)、REFRESHING(刷新 中)
（3）onTouchEvent函数：
             ACTION_DOWN时：记录此时touch的点的y坐标，在下面调整高度时使用
             ACTION_MOVE时：此时不断调整header的高度
             ACTION_UP时：根据当前状态决定是进行刷新还是放弃刷新
（4）onScrollStateChanged函数：
              SCROLL_STATE_TOUCH_SCROLL：表示listview正在滚动中，并且手指没有离开屏幕
              SCROLL_STATE_FLING：listview正在滚动中，且手指已经离开屏幕
              SCROLL_STATE_IDLE:停止滚动
（5）onScroll函数：根据listView的当前滚动状态即currentScrollState和当前刷新的状态不断修改header内容显示和刷新状态，如下：
               ListView为SCROLL_STATE_TOUCH_SCROLL且刷新状态不为REFRESHING：
               （a）刷新对应的item可见时，若刷新layout高度超出范围，则置刷新状态为RELEASE_TO_REFRESH；若刷新layout高度低于高度范围，则置刷新状态为DROP_DOWN_TO_REFRESH。

                 （b） 刷新对应的item不可见，重置header

 (6) ListView为SCROLL_STATE_FLING状态(松手滚动中)

　　　　　　　　（a） 若刷新对应的item可见并且刷新状态不为REFRESHING，设置position为1的(即第二个)item可见

　　　　　　　　（b） 若反弹回来，设置position为1的(即第二个)item可见

import java.text.SimpleDateFormat;import java.util.Date;import android.content.Context;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.animation.LinearInterpolator;import android.view.animation.RotateAnimation;import android.widget.AbsListView;import android.widget.AbsListView.OnScrollListener;import android.widget.ImageView;import android.widget.ListView;import android.widget.ProgressBar;import android.widget.TextView;/** * @author kchang * @E-mail:kchang244@163.com */public class PullListView extends ListView implements OnScrollListener {    private static final String TAG = PullListView.class.getSimpleName();    //hear view 的四种状态    /**静止的状态*/    private final static int NONE = 0;    /**下拉刷新的状态，文字信息提示下拉刷新，箭头朝下*/    private final static int PULL = 1;    /**下拉刷新的状态，文字提示松开后刷新，箭头朝上*/    private final static int RELEASE = 2;    /**正在刷新数据，提示正在刷新数据，没有箭头，显示圆形进度条*/    private final static int REFRESHING = 3;        //区分当前操作是刷新还是加载    /**刷新*/    private final static int REFERSH = 0;    /**加载数据*/    private final static int LOAD = 1;        //区分pull和release的距离的大小    private final static int SPACE = 20;        //状态    private int state ;        private LayoutInflater layoutInflater;    private View headView;//listview头部view    private View footView;//listView底部view    private TextView  tipTv;//显示提示信息    private TextView lastUpdateTv;//显示最后加载的时间    private ImageView arrow;    private ProgressBar progressBar;//圆形进度条提示状态        private TextView loadFullTv;//数据加载失败    private TextView noDataTv;///没有数据    private TextView moreTv;//加载更多数据    private ProgressBar loadPb;//显示加载数据的状态         private RotateAnimation animation;    private RotateAnimation reverseAnimation;        private int startY;//按下的Y轴位置        private int firstVisibleItem;    private int scrollState;//滚动的状态    private int headerContentInitialHeight;// 头部view初始化高度    private int headerContentHeight;//头部内容的高度        /***只有在listview第一个item显示的时候才进行下来刷新，否则此时的下拉只是滚动listview*/    private boolean isRecodered;    //判断是否正在加载    private boolean isLoading;    //开启或者关闭加载更多功能    private boolean isLoadEnable = true;    private boolean isLoadFull;    /**分页加载一次加载的数据大小*/    private int pageSize = 10;        private onl oadListener onl oadListener;        private OnRefershListener onRefershListener;         public PullListView(Context context, AttributeSet attrs) {        super(context, attrs);        initView(context);    }    public PullListView(Context context, AttributeSet attrs,int defStyle) {        super(context, attrs,defStyle);        initView(context);    }    public PullListView (Context context) {        super(context);        initView(context);            }      // 设置下拉刷新监听      public void setOnRefreshListener(OnRefershListener onRefreshListener) {          this.onRefershListener = onRefreshListener;      }        // 设置加载更多监听      public void setOnLoadListener(OnLoadListener onl oadListener) {          this.isLoadEnable = true;          this.onLoadListener = onl oadListener;      }      @Override    public void onScrollStateChanged(AbsListView view, int scrollState) {        //SCROLL_STATE_TOUCH_SCROLL 1表示listview正在滚动中，并且手指没有离开屏幕        //SCROLL_STATE_FLING 2：listview正在滚动中，且手指已经离开屏幕        //SCROLL_STATE_IDLE 0:停止滚动        this.scrollState = scrollState;        ifNeedLoad(view, scrollState);        Log.d(TAG, "onScrollStateChanged");    }         // 根据listview滑动的状态判断是否需要加载更多      private void ifNeedLoad(AbsListView view, int scrollState) {          if (!isLoadEnable) {              return;          }          try {              if (scrollState == OnScrollListener.SCROLL_STATE_IDLE                      && !isLoading                      && view.getLastVisiblePosition() == view                              .getPositionForView(footView) && !isLoadFull) {                  onl oadData();                  isLoading = true;              }          } catch (Exception e) {              e.printStackTrace();        }      }          @Override    public void onScroll(AbsListView view, int firstVisibleItem,            int visibleItemCount, int totalItemCount) {        this.firstVisibleItem = firstVisibleItem;        Log.d(TAG, "onScroll");    }    /***     * 是否开启加载更多     * @return     *         true表示开启，false表示不加载     */    public boolean isLoadEnable() {          return isLoadEnable;      }       // 这里的开启或者关闭加载更多，并不支持动态调整      public void setLoadEnable(boolean loadEnable) {          this.isLoadEnable = loadEnable;          this.removeFooterView(footView);      }      public int getPageSize() {          return pageSize;      }        public void setPageSize(int pageSize) {          this.pageSize = pageSize;      }      // 初始化组件      private void initView(Context context) {            // 设置箭头特效          animation = new RotateAnimation(0, -180,                  RotateAnimation.RELATIVE_TO_SELF, 0.5f,                  RotateAnimation.RELATIVE_TO_SELF, 0.5f);          animation.setInterpolator(new LinearInterpolator());          animation.setDuration(100);          animation.setFillAfter(true);            reverseAnimation = new RotateAnimation(-180, 0,                  RotateAnimation.RELATIVE_TO_SELF, 0.5f,                  RotateAnimation.RELATIVE_TO_SELF, 0.5f);          reverseAnimation.setInterpolator(new LinearInterpolator());          reverseAnimation.setDuration(100);          reverseAnimation.setFillAfter(true);            layoutInflater = LayoutInflater.from(context);          footView = layoutInflater.inflate(R.layout.listview_footer, null);          loadFullTv = (TextView) footView.findViewById(R.id.loadFull);          noDataTv = (TextView) footView.findViewById(R.id.noData);          moreTv = (TextView) footView.findViewById(R.id.more);          loadPb = (ProgressBar) footView.findViewById(R.id.loading);            headView = layoutInflater.inflate(R.layout.pull_to_refresh_header, null);          arrow = (ImageView) headView.findViewById(R.id.arrow);          tipTv = (TextView) headView.findViewById(R.id.tip);          lastUpdateTv = (TextView) headView.findViewById(R.id.lastUpdate);          progressBar = (ProgressBar) headView.findViewById(R.id.refreshing);            // 为listview添加头部和尾部，并进行初始化          headerContentInitialHeight = headView.getPaddingTop();          measureView(headView);                  headerContentHeight = headView.getMeasuredHeight();          topPadding(-headerContentHeight);                  this.addHeaderView(headView);          this.addFooterView(footView);          this.setOnScrollListener(this);      }      // 调整header的大小。其实调整的只是距离顶部的高度。      private void topPadding(int topPadding) {          headView.setPadding(headView.getPaddingLeft(), topPadding,                  headView.getPaddingRight(), headView.getPaddingBottom());          headView.invalidate();      }         @Override    public boolean onTouchEvent(MotionEvent ev) {        switch (ev.getAction()) {        case MotionEvent.ACTION_DOWN:            if (firstVisibleItem == 0) {                isRecodered = true;                startY =  (int)ev.getY();            }            break;        case MotionEvent.ACTION_MOVE:            //下拉刷新重点            whenMove(ev);            break;        case MotionEvent.ACTION_UP:            if (state == PULL) {                  Log.d(TAG, "ACTION_UP PULL");                state = NONE;                refreshHeaderViewByState();            } else if (state == RELEASE) {//提示用户松开手后刷新数据                Log.d(TAG, "ACTION_UP RELEASE");                state = REFRESHING;                refreshHeaderViewByState();                onRefersh();            }            break;        case MotionEvent.ACTION_CANCEL:            break;        default:            break;        }        return super.onTouchEvent(ev);    }    // 解读手势，刷新header状态      private void whenMove(MotionEvent ev) {          if (!isRecodered) {              return;          }                  int tmpY = (int) ev.getY();          int space = tmpY - startY;          int topPadding = space - headerContentHeight;          switch (state) {          case NONE:              if (space > 0) {                  state = PULL;                  refreshHeaderViewByState();              }              Log.d(TAG, "whenMove NONE");            break;          case PULL:              Log.d(TAG, "whenMove PULL");            topPadding(topPadding);              if (scrollState == SCROLL_STATE_TOUCH_SCROLL                      && space > headerContentHeight + SPACE) {                  state = RELEASE;                  refreshHeaderViewByState();              }              break;          case RELEASE:                 Log.d(TAG, "whenMove RELEASE");            topPadding(topPadding);              if (space > 0 && space < headerContentHeight + SPACE) {                  state = PULL;                  refreshHeaderViewByState();              } else if (space <= 0) {                  state = NONE;                  refreshHeaderViewByState();              }              break;          }        }      /**      * 这个方法是根据结果的大小来决定footer显示的。      * <p>      * 这里假定每次请求的条数为10。如果请求到了10条。则认为还有数据。如过结果不足10条，则认为数据已经全部加载，这时footer显示已经全部加载      * </p>      *       * @param resultSize      */      public void setResultSize(int resultSize) {          if (resultSize == 0) {              isLoadFull = true;              loadFullTv.setVisibility(View.GONE);              loadPb.setVisibility(View.GONE);              moreTv.setVisibility(View.GONE);              noDataTv.setVisibility(View.VISIBLE);          } else if (resultSize > 0 && resultSize < pageSize) {              isLoadFull = true;              loadFullTv.setVisibility(View.VISIBLE);              loadPb.setVisibility(View.GONE);              moreTv.setVisibility(View.GONE);              noDataTv.setVisibility(View.GONE);          } else if (resultSize == pageSize) {              isLoadFull = false;              loadFullTv.setVisibility(View.GONE);              loadPb.setVisibility(View.VISIBLE);              moreTv.setVisibility(View.VISIBLE);              noDataTv.setVisibility(View.GONE);          }        }       // 用来计算header大小的。    private void measureView(View child) {          ViewGroup.LayoutParams p = child.getLayoutParams();          if (p == null) {              p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,                      ViewGroup.LayoutParams.WRAP_CONTENT);          }          int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0, p.width);          int lpHeight = p.height;          int childHeightSpec;          if (lpHeight > 0) {              childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight,                      MeasureSpec.EXACTLY);          } else {              childHeightSpec = MeasureSpec.makeMeasureSpec(0,                      MeasureSpec.UNSPECIFIED);          }          child.measure(childWidthSpec, childHeightSpec);      }        /***       * 执行刷新数据的方法       */    public void onRefersh() {        if (null != onRefershListener) {            onRefershListener.onRefersh();        }    }    /**     * 执行加载数据的方法     */    public void onl oadData() {        if (null != onl oadListener) {            onl oadListener.onLoad();        }    }    // 用于加载更多结束后的回调      public void onl oadComplete() {          isLoading = false;      }      /**     * 刷新完以后的方法     * @param updateTime     *             当前是时间     */    public void onRefershComplete(String updateTime) {        lastUpdateTv.setText(getResources().getString(R.string.lastUpdateTime, updateTime));        state = NONE;        refreshHeaderViewByState();    }     /**     * 刷新数据完毕     */    public void onRefershComlete() {        String currentTiem = getCurrentTime();        onRefershComplete(currentTiem);    }    /**     * 获取当前的时间     * @return     */    private String getCurrentTime() {        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");        return dateFormat.format(new Date());    }    /***     *  根据当前状态，调整header     * */      private void refreshHeaderViewByState() {          switch (state) {          case NONE:  //原始状态            Log.d(TAG, "refreshHeaderViewByState NONE");            topPadding(-headerContentHeight);              tipTv.setText(R.string.pull_to_refresh);              progressBar.setVisibility(View.GONE);              arrow.clearAnimation();              arrow.setImageResource(R.drawable.pull_to_refresh_arrow);              break;          case PULL:  //箭头朝下            Log.d(TAG, "refreshHeaderViewByState PULL");            arrow.setVisibility(View.VISIBLE);              tipTv.setVisibility(View.VISIBLE);              lastUpdateTv.setVisibility(View.VISIBLE);              progressBar.setVisibility(View.GONE);              tipTv.setText(R.string.pull_to_refresh);              arrow.clearAnimation();              arrow.setAnimation(reverseAnimation);              break;          case RELEASE:  //箭头朝上            Log.d(TAG, "refreshHeaderViewByState RELEASE");            arrow.setVisibility(View.VISIBLE);              tipTv.setVisibility(View.VISIBLE);              lastUpdateTv.setVisibility(View.VISIBLE);              progressBar.setVisibility(View.GONE);              tipTv.setText(R.string.pull_to_refresh);              tipTv.setText(R.string.release_to_refresh);              arrow.clearAnimation();              arrow.setAnimation(animation);              break;          case REFRESHING:  //显示数据加载的圆形进度条            Log.d(TAG, "refreshHeaderViewByState REFRESHING");            topPadding(headerContentInitialHeight);              progressBar.setVisibility(View.VISIBLE);              arrow.clearAnimation();              arrow.setVisibility(View.GONE);              tipTv.setVisibility(View.GONE);              lastUpdateTv.setVisibility(View.GONE);              break;          }      }      /**     * 下拉刷新的接口     *     */    public interface OnRefershListener {        void onRefersh();    }    /**     * 定义加载更多的接口     */    public interface onl oadListener {        void onl oad();    }}