android编程之下拉刷新实现方法分析

本文实例讲述了android编程之下拉刷新实现方法。分享给大家供大家参考，具体如下：

现在android应用里面下拉刷新比较多 ，今天自己研究一下相关的资料

public class mylistview extends listview implements onscrolllistener {
 private static final string tag = "listview";
 private final static int release_to_refresh = 0;
 private final static int pull_to_refresh = 1;
 private final static int refreshing = 2;
 private final static int done = 3;
 private final static int loading = 4;
 // 实际的padding的距离与界面上偏移距离的比例
 private final static int ratio = 3;
 private layoutinflater inflater;
 private linearlayout headview;
 private textview tipstextview;
 private textview lastupdatedtextview;
 private imageview arrowimageview;
 private progressbar progressbar;
 private rotateanimation animation;
 private rotateanimation reverseanimation;
 // 用于保证starty的值在一个完整的touch事件中只被记录一次
 private boolean isrecored;
 private int headcontentwidth;
 private int headcontentheight;
 private int starty;
 private int firstitemindex;
 private int state;
 private boolean isback;
 private onrefreshlistener refreshlistener;
 private boolean isrefreshable;
 public mylistview(context context) {
  super(context);
  init(context);
 }
 public mylistview(context context, attributeset attrs) {
  super(context, attrs);
  init(context);
 }
 private void init(context context) {
  setcachecolorhint(context.getresources().getcolor(r.color.transparent));
  inflater = layoutinflater.from(context);
  headview = (linearlayout) inflater.inflate(r.layout.head, null);
  arrowimageview = (imageview) headview
    .findviewbyid(r.id.head_arrowimageview);
  arrowimageview.setminimumwidth(70);
  arrowimageview.setminimumheight(50);
  progressbar = (progressbar) headview
    .findviewbyid(r.id.head_progressbar);
  tipstextview = (textview) headview.findviewbyid(r.id.head_tipstextview);
  lastupdatedtextview = (textview) headview
    .findviewbyid(r.id.head_lastupdatedtextview);
  measureview(headview);
  headcontentheight = headview.getmeasuredheight();
  headcontentwidth = headview.getmeasuredwidth();
  headview.setpadding(0, -1 * headcontentheight, 0, 0);
  headview.invalidate();
  log.v("size", "width:" + headcontentwidth + " height:"
    + headcontentheight);
  addheaderview(headview, null, false);
  setonscrolllistener(this);
  animation = new rotateanimation(0, -180,
    rotateanimation.relative_to_self, 0.5f,
    rotateanimation.relative_to_self, 0.5f);
  animation.setinterpolator(new linearinterpolator());
  animation.setduration(250);
  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(200);
  reverseanimation.setfillafter(true);
  state = done;
  isrefreshable = false;
 }
 public void onscroll(abslistview arg0, int firstvisiableitem, int arg2,
   int arg3) {
  firstitemindex = firstvisiableitem;
 }
 public void onscrollstatechanged(abslistview arg0, int arg1) {
 }
 public boolean ontouchevent(motionevent event) {
  if (isrefreshable) {
   switch (event.getaction()) {
   case motionevent.action_down:
    if (firstitemindex == 0 && !isrecored) {
     isrecored = true;
     starty = (int) event.gety();
     log.v(tag, "在down时候记录当前位置‘");
    }
    break;
   case motionevent.action_up:
    if (state != refreshing && state != loading) {
     if (state == done) {
      // 什么都不做
     }
     if (state == pull_to_refresh) {
      state = done;
      changeheaderviewbystate();
      log.v(tag, "由下拉刷新状态，到done状态");
     }
     if (state == release_to_refresh) {
      state = refreshing;
      changeheaderviewbystate();
      onrefresh();
      log.v(tag, "由松开刷新状态，到done状态");
     }
    }
    isrecored = false;
    isback = false;
    break;
   case motionevent.action_move:
    int tempy = (int) event.gety();
    if (!isrecored && firstitemindex == 0) {
     log.v(tag, "在move时候记录下位置");
     isrecored = true;
     starty = tempy;
    }
    if (state != refreshing && isrecored && state != loading) {
     // 保证在设置padding的过程中，当前的位置一直是在head，否则如果当列表超出屏幕的话，当在上推的时候，列表会同时进行滚动
     // 可以松手去刷新了
     if (state == release_to_refresh) {
      setselection(0);
      // 往上推了，推到了屏幕足够掩盖head的程度，但是还没有推到全部掩盖的地步
      if (((tempy - starty) / ratio < headcontentheight)
        && (tempy - starty) > 0) {
       state = pull_to_refresh;
       changeheaderviewbystate();
       log.v(tag, "由松开刷新状态转变到下拉刷新状态");
      }
      // 一下子推到顶了
      else if (tempy - starty <= 0) {
       state = done;
       changeheaderviewbystate();
       log.v(tag, "由松开刷新状态转变到done状态");
      }
      // 往下拉了，或者还没有上推到屏幕顶部掩盖head的地步
      else {
       // 不用进行特别的操作，只用更新paddingtop的值就行了
      }
     }
     // 还没有到达显示松开刷新的时候,done或者是pull_to_refresh状态
     if (state == pull_to_refresh) {
      setselection(0);
      // 下拉到可以进入release_to_refresh的状态
      if ((tempy - starty) / ratio >= headcontentheight) {
       state = release_to_refresh;
       isback = true;
       changeheaderviewbystate();
       log.v(tag, "由done或者下拉刷新状态转变到松开刷新");
      }
      // 上推到顶了
      else if (tempy - starty <= 0) {
       state = done;
       changeheaderviewbystate();
       log.v(tag, "由done或者下拉刷新状态转变到done状态");
      }
     }
     // done状态下
     if (state == done) {
      if (tempy - starty > 0) {
       state = pull_to_refresh;
       changeheaderviewbystate();
      }
     }
     // 更新headview的size
     if (state == pull_to_refresh) {
      headview.setpadding(0, -1 * headcontentheight
        + (tempy - starty) / ratio, 0, 0);
     }
     // 更新headview的paddingtop
     if (state == release_to_refresh) {
      headview.setpadding(0, (tempy - starty) / ratio
        - headcontentheight, 0, 0);
     }
    }
    break;
   }
  }
  return super.ontouchevent(event);
 }
 // 当状态改变时候，调用该方法，以更新界面
 private void changeheaderviewbystate() {
  switch (state) {
  case release_to_refresh:
   arrowimageview.setvisibility(view.visible);
   progressbar.setvisibility(view.gone);
   tipstextview.setvisibility(view.visible);
   lastupdatedtextview.setvisibility(view.visible);
   arrowimageview.clearanimation();
   arrowimageview.startanimation(animation);
   tipstextview.settext("松开刷新");
   log.v(tag, "当前状态，松开刷新");
   break;
  case pull_to_refresh:
   progressbar.setvisibility(view.gone);
   tipstextview.setvisibility(view.visible);
   lastupdatedtextview.setvisibility(view.visible);
   arrowimageview.clearanimation();
   arrowimageview.setvisibility(view.visible);
   // 是由release_to_refresh状态转变来的
   if (isback) {
    isback = false;
    arrowimageview.clearanimation();
    arrowimageview.startanimation(reverseanimation);
    tipstextview.settext("下拉刷新");
   } else {
    tipstextview.settext("下拉刷新");
   }
   log.v(tag, "当前状态，下拉刷新");
   break;
  case refreshing:
   headview.setpadding(0, 0, 0, 0);
   progressbar.setvisibility(view.visible);
   arrowimageview.clearanimation();
   arrowimageview.setvisibility(view.gone);
   tipstextview.settext("正在刷新...");
   lastupdatedtextview.setvisibility(view.visible);
   log.v(tag, "当前状态,正在刷新...");
   break;
  case done:
   headview.setpadding(0, -1 * headcontentheight, 0, 0);
   progressbar.setvisibility(view.gone);
   arrowimageview.clearanimation();
   arrowimageview.setimageresource(r.drawable.arrow);
   tipstextview.settext("下拉刷新");
   lastupdatedtextview.setvisibility(view.visible);
   log.v(tag, "当前状态，done");
   break;
  }
 }
 public void setonrefreshlistener(onrefreshlistener refreshlistener) {
  this.refreshlistener = refreshlistener;
  isrefreshable = true;
 }
 public interface onrefreshlistener {
  public void onrefresh();
 }
 public void onrefreshcomplete() {
  state = done;
  lastupdatedtextview.settext("最近更新:" + new date().tolocalestring());
  changeheaderviewbystate();
 }
 private void onrefresh() {
  if (refreshlistener != null) {
   refreshlistener.onrefresh();
  }
 }
 // 此方法直接照搬自网络上的一个下拉刷新的demo，此处是“估计”headview的width以及height
 private void measureview(view child) {
  viewgroup.layoutparams p = child.getlayoutparams();
  if (p == null) {
   p = new viewgroup.layoutparams(viewgroup.layoutparams.fill_parent,
     viewgroup.layoutparams.wrap_content);
  }
  int childwidthspec = viewgroup.getchildmeasurespec(0, 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);
 }
 public void setadapter(baseadapter adapter) {
  lastupdatedtextview.settext("最近更新:" + new date().tolocalestring());
  super.setadapter(adapter);
 }
}

希望本文所述对大家android程序设计有所帮助。