下拉刷新

下拉刷新

一：下拉刷新

          自定义控件：继承listview 在头部添加headerview 在底部添加footview

       原理：下拉刷新就是继承listview 在头部添加headerview  本质是先将头布局隐藏 随着用户的动作将头布局显示出来并且改变头布局的状态。

                 用户移动时：首先判断必须是向下拉并且显示的第一条数据的索引为0

                                       状态改变：当由下拉刷新状态改变为释放刷新状态  再变回下拉刷新状态

                 用户松开时：分两种情况：一种是在下拉刷新状态直接松开-------将头布局隐藏

                                                            一种是在释放刷新状态下松开----------将状态改变为正在刷新状态等

二：Android知识的学会标准

              一个过程：了解----熟悉----熟练-----掌握

             在我看来：应该是这样你顺着看书看的懂，学得会，你逆着不用看书查资料也会用=======表示你已经掌握这个知识了

                                                 

三：下拉刷新部分代码：

            

public class RefreshedListView extends ListView implements OnScrollListener {private View headerView;private int downY;private int headerViewHeight;private final int PULL_REFRESH=0;private final int RELEASE_REFRESH=1;private final int REFRESHING=2;private int headerViewCurrentState=PULL_REFRESH;private ImageView iv_picture;private ProgressBar pb;private TextView tv_title;private TextView tv_refreshtime;private int firstVisibleItemPosition;private RotateAnimation downAnimation;private RotateAnimation upAnimation;public RefreshedListView(Context context, AttributeSet attrs) {super(context, attrs);// TODO Auto-generated constructor stubinitHeader();//设置滚动监听器this.setOnScrollListener(this);}private void initHeader() {//创建headerviewheaderView = View.inflate(getContext(), R.layout.headerlayout, null);//获取控件iv_picture = (ImageView) headerView.findViewById(R.id.iv_picture);pb = (ProgressBar) headerView.findViewById(R.id.pb_progressbar);tv_title = (TextView) headerView.findViewById(R.id.tv_title);tv_refreshtime = (TextView) headerView.findViewById(R.id.tv_refreshtime);//让框架帮我们去测量头布局的宽和高headerView.measure(0, 0);headerViewHeight = headerView.getMeasuredHeight();//设置位置headerView.setPadding(0, -headerViewHeight, 0, 0);this.addHeaderView(headerView);initAnimation();}/** * 旋转动画 */private void initAnimation() {downAnimation = new RotateAnimation(0, -180, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);downAnimation.setDuration(500);downAnimation.setFillAfter(true);upAnimation = new RotateAnimation(-180, -360, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);upAnimation.setDuration(500);upAnimation.setFillAfter(true);}@Overridepublic boolean onTouchEvent(MotionEvent ev) {// TODO Auto-generated method stubswitch(ev.getAction()){case MotionEvent.ACTION_DOWN://获取按下时y轴的值downY = (int) ev.getY();break;case MotionEvent.ACTION_MOVE://获取移动时y轴的位置int moveY=(int) ev.getY();//判断移动的距离int diff=moveY-downY;//diff>0  确认是向下拉   firstVisibleItemPosition==0  确认第一个显示的是位置0if(diff>0&&firstVisibleItemPosition==0&&headerViewCurrentState!=REFRESHING){//获取移动后headerview的paddingtopint paddingtop=-headerViewHeight+diff;//判断现headerview的状态和headerview完全显示并要改变状态if(headerViewCurrentState==PULL_REFRESH&&paddingtop>0){//进入释放刷新状态headerViewCurrentState=RELEASE_REFRESH;//更新headerviewrefreshTopLayout();}else if(paddingtop<0&&headerViewCurrentState==RELEASE_REFRESH){//进入下拉刷新状态headerViewCurrentState=PULL_REFRESH;refreshTopLayout();}//移动时headerview显示headerView.setPadding(0, paddingtop, 0, 0);return true;}break;case MotionEvent.ACTION_UP://松开时-----判断是那种状态下松开的if(headerViewCurrentState==PULL_REFRESH){//下拉刷新状态下松开--------将头布局隐藏headerView.setPadding(0, -headerViewHeight, 0, 0);}else if(headerViewCurrentState==RELEASE_REFRESH){//正在更新状态下------------headerViewCurrentState=REFRESHING;refreshTopLayout();headerView.setPadding(0, 0, 0, 0);}break;}return super.onTouchEvent(ev);}private void refreshTopLayout() {// TODO Auto-generated method stubswitch(headerViewCurrentState){case PULL_REFRESH://iv_picture.setAnimation(upAnimation);tv_title.setText("下拉刷新");break;case RELEASE_REFRESH://转变成松开刷新状态下做的动作iv_picture.startAnimation(downAnimation);tv_title.setText("松开刷新");break;case REFRESHING://转变成正在更新状态下做的动作iv_picture.setVisibility(View.INVISIBLE);iv_picture.clearAnimation();pb.setVisibility(View.VISIBLE);tv_title.setText("释放刷新");break;}}@Overridepublic void onScrollStateChanged(AbsListView view, int scrollState) {// TODO Auto-generated method stub}@Overridepublic void onScroll(AbsListView view, int firstVisibleItem,int visibleItemCount, int totalItemCount) {firstVisibleItemPosition = firstVisibleItem;}

四：全部代码：

public class RefreshedListView extends ListView implements OnScrollListener {private View headerView;private int downY;private int headerViewHeight;private OnRefreshListener listener;private final int PULL_REFRESH=0;private final int RELEASE_REFRESH=1;private final int REFRESHING=2;private int headerViewCurrentState=PULL_REFRESH;private ImageView iv_picture;private ProgressBar pb;private TextView tv_title;private TextView tv_refreshtime;private int firstVisibleItemPosition;private RotateAnimation downAnimation;private RotateAnimation upAnimation;private View footerView;private int footerViewHeight;private int lastVisibleItemPosition;private boolean isScrollBottom=false;private boolean isLoadMore=false;public RefreshedListView(Context context, AttributeSet attrs) {super(context, attrs);// TODO Auto-generated constructor stubinitHeader();//设置滚动监听器this.setOnScrollListener(this);initFooter();}private void initFooter() {footerView = View.inflate(getContext(), R.layout.footlayout, null);footerView.measure(0, 0);footerViewHeight = footerView.getMeasuredHeight();footerView.setPadding(0, -footerViewHeight, 0, 0);this.addFooterView(footerView);}private void initHeader() {//创建headerviewheaderView = View.inflate(getContext(), R.layout.headerlayout, null);//获取控件iv_picture = (ImageView) headerView.findViewById(R.id.iv_picture);pb = (ProgressBar) headerView.findViewById(R.id.pb_progressbar);tv_title = (TextView) headerView.findViewById(R.id.tv_title);tv_refreshtime = (TextView) headerView.findViewById(R.id.tv_refreshtime);tv_refreshtime.setText(ChangeSimpleDateFormat());//让框架帮我们去测量头布局的宽和高headerView.measure(0, 0);headerViewHeight = headerView.getMeasuredHeight();//设置位置headerView.setPadding(0, -headerViewHeight, 0, 0);this.addHeaderView(headerView);initAnimation();}/** * 旋转动画 */private void initAnimation() {downAnimation = new RotateAnimation(0, -180, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);downAnimation.setDuration(500);downAnimation.setFillAfter(true);upAnimation = new RotateAnimation(-180, -360, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);upAnimation.setDuration(500);upAnimation.setFillAfter(true);}@Overridepublic boolean onTouchEvent(MotionEvent ev) {// TODO Auto-generated method stubswitch(ev.getAction()){case MotionEvent.ACTION_DOWN://获取按下时y轴的值downY = (int) ev.getY();break;case MotionEvent.ACTION_MOVE://获取移动时y轴的位置int moveY=(int) ev.getY();//判断移动的距离int diff=moveY-downY;//diff>0  确认是向下拉   firstVisibleItemPosition==0  确认第一个显示的是位置0if(diff>0&&firstVisibleItemPosition==0&&headerViewCurrentState!=REFRESHING){//获取移动后headerview的paddingtopint paddingtop=-headerViewHeight+diff;//判断现headerview的状态和headerview完全显示并要改变状态if(headerViewCurrentState==PULL_REFRESH&&paddingtop>0){//进入释放刷新状态headerViewCurrentState=RELEASE_REFRESH;//更新headerviewrefreshTopLayout();}else if(paddingtop<0&&headerViewCurrentState==RELEASE_REFRESH){//进入下拉刷新状态headerViewCurrentState=PULL_REFRESH;refreshTopLayout();}//移动时headerview显示headerView.setPadding(0, paddingtop, 0, 0);return true;}break;case MotionEvent.ACTION_UP://松开时-----判断是那种状态下松开的if(headerViewCurrentState==PULL_REFRESH){//下拉刷新状态下松开--------将头布局隐藏headerView.setPadding(0, -headerViewHeight, 0, 0);}else if(headerViewCurrentState==RELEASE_REFRESH){//正在更新状态下------------headerViewCurrentState=REFRESHING;refreshTopLayout();headerView.setPadding(0, 0, 0, 0);if(listener!=null){listener.onDownPullRefresh();}}break;}return super.onTouchEvent(ev);}private void refreshTopLayout() {// TODO Auto-generated method stubswitch(headerViewCurrentState){case PULL_REFRESH://iv_picture.setAnimation(upAnimation);tv_title.setText("下拉刷新");break;case RELEASE_REFRESH://转变成松开刷新状态下做的动作iv_picture.startAnimation(downAnimation);tv_title.setText("释放刷新");break;case REFRESHING://转变成正在更新状态下做的动作iv_picture.setVisibility(View.INVISIBLE);iv_picture.clearAnimation();pb.setVisibility(View.VISIBLE);tv_title.setText("正在刷新");break;}}@Overridepublic void onScrollStateChanged(AbsListView view, int scrollState) {// TODO Auto-generated method stubif(scrollState==SCROLL_STATE_IDLE||scrollState==SCROLL_STATE_FLING){if(isScrollBottom&&!isLoadMore){isLoadMore = true;footerView.setPadding(0, 0, 0, 0);setSelection(getCount());if(listener!=null){listener.onLoadMore();}}}}public void hideFooterView(){footerView.setPadding(0, -footerViewHeight, 0, 0);isLoadMore=false;}@Overridepublic void onScroll(AbsListView view, int firstVisibleItem,int visibleItemCount, int totalItemCount) {firstVisibleItemPosition = firstVisibleItem;lastVisibleItemPosition = getLastVisiblePosition();if(lastVisibleItemPosition==getCount()-1){isScrollBottom = true;}else{isScrollBottom=false;}}public void setOnRefreshListener(OnRefreshListener listener){this.listener=listener;}public void hideheaderView(){this.setPadding(0, -headerViewHeight, 0, 0);headerViewCurrentState=PULL_REFRESH;iv_picture.setVisibility(View.VISIBLE);pb.setVisibility(View.INVISIBLE);tv_title.setText("下拉刷新");tv_refreshtime.setText(ChangeSimpleDateFormat());}public String ChangeSimpleDateFormat(){SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");return sdf.format(new Date());}