android 下拉刷新

现在android应用里面下拉刷新比较多     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);      }    }