重写ListView实现下拉刷新上拉加载

Android本身的ListView没有刷新功能，要想实现这一功能，就得继承ListView并重写它的方法。同时也要实现其OnScrollListener这一接口。

下拉刷新，需要在原本的ListView上部添加一个Head，ListView本身提供了addHeadView（）这一方法，但是没有实现刷新的功能，我们可以自定义Head的内容，并加上刷新的功能。

上拉加载更多数据与下拉刷新类似，是在ListView的下部添加一个Footer。具体实现代码如下：

import java.text.SimpleDateFormat;  import java.util.Date;  import android.content.Context;  import android.util.AttributeSet;  import android.view.LayoutInflater;  import android.view.MotionEvent;  import android.view.View;  import android.view.ViewGroup;  import android.view.animation.RotateAnimation;  import android.widget.AbsListView;  import android.widget.ImageView;  import android.widget.ListView;  import android.widget.AbsListView.OnScrollListener;  import android.widget.ProgressBar;  import android.widget.TextView;     public class ReFlashListView extends ListView implements OnScrollListener {      View header;      View footer;      int headerHeight;      int firstVisibleItem; // 当前第一个可见Item的位置      boolean isRemark; // 标记第一个出现的Item      int startY; // 按下时的Y值      int state; // 当前的状态      int scrollState; // 滚动状态      final int NONE = 0; // 正常状态      final int PULL = 1; // 下拉刷新状态      final int RELESE = 2; // 松开释放状态      final int REFLASHING = 3; // 正在刷新状态      IReflashListener iReflashListener;      int totalItemCount;      int lastVisibleItem;      boolean isLoading;  //正在加载       private TextView txtViewLoading = null;      private ProgressBar prgBarLoading = null;         public ReFlashListView(Context context) {          super(context);          initView(context);          // TODO Auto-generated constructor stub      }         public ReFlashListView(Context context, AttributeSet attrs) {          super(context, attrs);          initView(context);          // TODO Auto-generated constructor stub      }         public ReFlashListView(Context context, AttributeSet attrs, int defStyle) {          super(context, attrs, defStyle);          initView(context);          // TODO Auto-generated constructor stub      }         // 初始化界面，添加顶部布局至ListView      public void initView(Context context) {          LayoutInflater inflater = LayoutInflater.from(context);          header = inflater.inflate(R.layout.header_layout, null);          footer=inflater.inflate(R.layout.footer_layout, null);          footer.findViewById(R.id.load_layout).setVisibility(View.GONE);          measureView(header);          headerHeight = header.getMeasuredHeight();          topPadding(-headerHeight);          this.addHeaderView(header);          this.addFooterView(footer);          this.setOnScrollListener(this);                     txtViewLoading = (TextView)footer.findViewById(R.id.text_loading);          prgBarLoading = (ProgressBar)footer.findViewById(R.id.loading_progress);      }         // 设置header布局的上边距      private void topPadding(int topPadding) {          header.setPadding(header.getPaddingLeft(), topPadding,                  header.getPaddingRight(), header.getPaddingBottom());          header.invalidate();      }         // 通知父布局占用的宽，高      private void measureView(View view) {          ViewGroup.LayoutParams p = view.getLayoutParams();          if (p == null) {              p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,                      ViewGroup.LayoutParams.WRAP_CONTENT);          }          int width = ViewGroup.getChildMeasureSpec(0, 0, p.width);          int height;          int tempHeight = p.height;          if (tempHeight > 0) {              height = MeasureSpec.makeMeasureSpec(tempHeight,                      MeasureSpec.EXACTLY);          } else {              height = MeasureSpec.makeMeasureSpec(tempHeight,                      MeasureSpec.UNSPECIFIED);          }          view.measure(width, height);      }         @Override      public void onScroll(AbsListView view, int firstVisibleItem,              int visibleItemCount, int totalItemCount) {          this.firstVisibleItem = firstVisibleItem;          this.totalItemCount=totalItemCount;          this.lastVisibleItem=firstVisibleItem+visibleItemCount;         }         @Override      public void onScrollStateChanged(AbsListView view, int scrollState) {          this.scrollState = scrollState;          if(totalItemCount==lastVisibleItem && scrollState == SCROLL_STATE_IDLE){              if(!isLoading){                  isLoading=true;              footer.findViewById(R.id.load_layout).setVisibility(View.VISIBLE);              iReflashListener.onLoad();          }          }         }         @Override      public boolean onTouchEvent(MotionEvent ev) {          switch (ev.getAction()) {          case MotionEvent.ACTION_DOWN:              if (firstVisibleItem == 0) {                  isRemark = true;                  startY = (int) ev.getY();              }              break;          case MotionEvent.ACTION_MOVE:              onMove(ev);              break;          case MotionEvent.ACTION_UP:              if (state == RELESE) {                  state = REFLASHING;                  //刷新数据                  iReflashListener.onReflash();                  reflashViewByState();              } else if (state == PULL) {                  state = NONE;                  isRemark = false;                  reflashViewByState();              }              break;          }          return super.onTouchEvent(ev);      }         /*       * 判断移动过程中的操作       */      private void onMove(MotionEvent e) {          int tempY = (int) e.getY();          int space = tempY - startY;          int topPadding = space - headerHeight;          if (!isRemark) {              return;          }          switch (state) {          case NONE:              if (space > 0) {                  state = PULL;                  reflashViewByState();              }              break;          case PULL:              topPadding(topPadding);              if (space > headerHeight + 30                      && scrollState == SCROLL_STATE_TOUCH_SCROLL) {                  state = RELESE;                  reflashViewByState();              }              break;          case RELESE:              topPadding(topPadding);              if (space < headerHeight + 30) {                  state = PULL;                  reflashViewByState();              } else if (space <= 0) {                  state = NONE;                  isRemark = false;                  reflashViewByState();              }              break;          }      }         /*       * 根据当前状态，改变界面显示       */      private void reflashViewByState() {          TextView tip = (TextView) header.findViewById(R.id.tip);          ImageView arrow = (ImageView) header.findViewById(R.id.arrow);          ProgressBar progress = (ProgressBar) header.findViewById(R.id.progress);          RotateAnimation anim = new RotateAnimation(0, 180,                  RotateAnimation.RELATIVE_TO_SELF, 0.5f,                  RotateAnimation.RELATIVE_TO_SELF, 0.5f);          anim.setDuration(500);          anim.setFillAfter(true);          RotateAnimation anim1 = new RotateAnimation(180, 0,                  RotateAnimation.RELATIVE_TO_SELF, 0.5f,                  RotateAnimation.RELATIVE_TO_SELF, 0.5f);          anim1.setDuration(500);          anim1.setFillAfter(true);          switch (state) {          case NONE:              topPadding(-headerHeight);              arrow.clearAnimation();              break;          case PULL:              arrow.setVisibility(View.VISIBLE);              progress.setVisibility(View.GONE);              tip.setText("下拉可以刷新");              arrow.clearAnimation();              arrow.setAnimation(anim1);              break;          case RELESE:              arrow.setVisibility(View.VISIBLE);              progress.setVisibility(View.GONE);              tip.setText("松开可以刷新");              arrow.clearAnimation();              arrow.setAnimation(anim);              break;          case REFLASHING:              topPadding(50);              arrow.setVisibility(View.GONE);              progress.setVisibility(View.VISIBLE);              arrow.clearAnimation();              tip.setText("正在刷新...");              break;          }      }         public void reflashComplete(){          state=NONE;          reflashViewByState();          isRemark=false;          TextView lastupdatetime=(TextView)header.findViewById(R.id.last_update_time);          SimpleDateFormat format=new SimpleDateFormat("yyyy年MM月dd日 hh:mm:ss");          Date date=new Date(System.currentTimeMillis());          String time=format.format(date);          lastupdatetime.setText(time);      }             public void loadingComplete(){          isLoading=false;          footer.findViewById(R.id.load_layout).setVisibility(View.GONE);      }             public void allDataLoadingComplete(){          isLoading=false;          txtViewLoading.setText("全部数据已经加载完成");          prgBarLoading.setVisibility(View.GONE);      }      public void setInterfacs(IReflashListener iReflashListener){          this.iReflashListener=iReflashListener;      }             public interface IReflashListener{          public void onReflash();          public void onLoad();      }  }