Android中ListView下拉刷新的实现代码

package net.loonggg.listview;  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.LinearInterpolator; import android.view.animation.RotateAnimation; import android.widget.AbsListView; import android.widget.AbsListView.OnScrollListener; import android.widget.ImageView; import android.widget.LinearLayout; import android.widget.ListView; import android.widget.ProgressBar; import android.widget.TextView;  public class MyListView extends ListView implements OnScrollListener {    private final static int RELEASE_To_REFRESH = 0;// 下拉过程的状态值   private final static int PULL_To_REFRESH = 1; // 从下拉返回到不刷新的状态值   private final static int REFRESHING = 2;// 正在刷新的状态值   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;    // ListView头部下拉刷新的布局   private LinearLayout headerView;   private TextView lvHeaderTipsTv;   private TextView lvHeaderLastUpdatedTv;   private ImageView lvHeaderArrowIv;   private ProgressBar lvHeaderProgressBar;    // 定义头部下拉刷新的布局的高度   private int headerContentHeight;    private RotateAnimation animation;   private RotateAnimation reverseAnimation;    private int startY;   private int state;   private boolean isBack;    // 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 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);     headerView = (LinearLayout) inflater.inflate(R.layout.lv_header, null);     lvHeaderTipsTv = (TextView) headerView         .findViewById(R.id.lvHeaderTipsTv);     lvHeaderLastUpdatedTv = (TextView) headerView         .findViewById(R.id.lvHeaderLastUpdatedTv);      lvHeaderArrowIv = (ImageView) headerView         .findViewById(R.id.lvHeaderArrowIv);     // 设置下拉刷新图标的最小高度和宽度     lvHeaderArrowIv.setMinimumWidth(70);     lvHeaderArrowIv.setMinimumHeight(50);      lvHeaderProgressBar = (ProgressBar) headerView         .findViewById(R.id.lvHeaderProgressBar);     measureView(headerView);     headerContentHeight = headerView.getMeasuredHeight();     // 设置内边距，正好距离顶部为一个负的整个布局的高度，正好把头部隐藏     headerView.setPadding(0, -1 * headerContentHeight, 0, 0);     // 重绘一下     headerView.invalidate();     // 将下拉刷新的布局加入ListView的顶部     addHeaderView(headerView, null, false);     // 设置滚动监听事件     setOnScrollListener(this);      // 设置旋转动画事件     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);      // 一开始的状态就是下拉刷新完的状态，所以为DONE     state = DONE;     // 是否正在刷新     isRefreshable = false;   }    @Override   public void onScrollStateChanged(AbsListView view, int scrollState) {    }    @Override   public void onScroll(AbsListView view, int firstVisibleItem,       int visibleItemCount, int totalItemCount) {         if (firstVisibleItem == 0) {           isRefreshable = true;          } else {           isRefreshable = false;          }       }    @Override   public boolean onTouchEvent(MotionEvent ev) {     if (isRefreshable) {       switch (ev.getAction()) {       case MotionEvent.ACTION_DOWN:         if (!isRecored) {           isRecored = true;           startY = (int) ev.getY();// 手指按下时记录当前位置         }         break;       case MotionEvent.ACTION_UP:         if (state != REFRESHING && state != LOADING) {           if (state == PULL_To_REFRESH) {             state = DONE;             changeHeaderViewByState();           }           if (state == RELEASE_To_REFRESH) {             state = REFRESHING;             changeHeaderViewByState();             onLvRefresh();           }         }         isRecored = false;         isBack = false;          break;        case MotionEvent.ACTION_MOVE:         int tempY = (int) ev.getY();         if (!isRecored) {           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 < headerContentHeight)// 由松开刷新状态转变到下拉刷新状态                 && (tempY - startY) > 0) {               state = PULL_To_REFRESH;               changeHeaderViewByState();             }             // 一下子推到顶了             else if (tempY - startY <= 0) {// 由松开刷新状态转变到done状态               state = DONE;               changeHeaderViewByState();             }           }           // 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 >= headerContentHeight) {// 由done或者下拉刷新状态转变到松开刷新               state = RELEASE_To_REFRESH;               isBack = true;               changeHeaderViewByState();             }             // 上推到顶了             else if (tempY - startY <= 0) {// 由DOne或者下拉刷新状态转变到done状态               state = DONE;               changeHeaderViewByState();             }           }           // 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) {             headerView.setPadding(0, -1 * headerContentHeight                 + (tempY - startY) / RATIO, 0, 0);            }           // 更新headView的paddingTop           if (state == RELEASE_To_REFRESH) {             headerView.setPadding(0, (tempY - startY) / RATIO                 - headerContentHeight, 0, 0);           }          }         break;        default:         break;       }     }     return super.onTouchEvent(ev);   }    // 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:       lvHeaderArrowIv.setVisibility(View.VISIBLE);       lvHeaderProgressBar.setVisibility(View.GONE);       lvHeaderTipsTv.setVisibility(View.VISIBLE);       lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);        lvHeaderArrowIv.clearAnimation();// 清除动画       lvHeaderArrowIv.startAnimation(animation);// 开始动画效果        lvHeaderTipsTv.setText("松开刷新");       break;     case PULL_To_REFRESH:       lvHeaderProgressBar.setVisibility(View.GONE);       lvHeaderTipsTv.setVisibility(View.VISIBLE);       lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);       lvHeaderArrowIv.clearAnimation();       lvHeaderArrowIv.setVisibility(View.VISIBLE);       // 是由RELEASE_To_REFRESH状态转变来的       if (isBack) {         isBack = false;         lvHeaderArrowIv.clearAnimation();         lvHeaderArrowIv.startAnimation(reverseAnimation);          lvHeaderTipsTv.setText("下拉刷新");       } else {         lvHeaderTipsTv.setText("下拉刷新");       }       break;      case REFRESHING:        headerView.setPadding(0, 0, 0, 0);        lvHeaderProgressBar.setVisibility(View.VISIBLE);       lvHeaderArrowIv.clearAnimation();       lvHeaderArrowIv.setVisibility(View.GONE);       lvHeaderTipsTv.setText("正在刷新...");       lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);       break;     case DONE:       headerView.setPadding(0, -1 * headerContentHeight, 0, 0);        lvHeaderProgressBar.setVisibility(View.GONE);       lvHeaderArrowIv.clearAnimation();       lvHeaderArrowIv.setImageResource(R.drawable.arrow);       lvHeaderTipsTv.setText("下拉刷新");       lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);       break;     }   }    // 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 params = child.getLayoutParams();     if (params == null) {       params = new ViewGroup.LayoutParams(           ViewGroup.LayoutParams.FILL_PARENT,           ViewGroup.LayoutParams.WRAP_CONTENT);     }     int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0,         params.width);     int lpHeight = params.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 setonRefreshListener(OnRefreshListener refreshListener) {     this.refreshListener = refreshListener;     isRefreshable = true;   }    public interface OnRefreshListener {     public void onRefresh();   }    public void onRefreshComplete() {     state = DONE;     lvHeaderLastUpdatedTv.setText("最近更新:" + new Date().toLocaleString());     changeHeaderViewByState();   }    private void onLvRefresh() {     if (refreshListener != null) {       refreshListener.onRefresh();     }   }    public void setAdapter(LvAdapter adapter) {     lvHeaderLastUpdatedTv.setText("最近更新:" + new Date().toLocaleString());     super.setAdapter(adapter);   }  }