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android UI进阶之实现listview的上拉加载

热度：82   发布时间：2016-05-01 20:21:38.0
android UI进阶之实现listview的下拉加载

关于listview的操作五花八门，有下拉刷新，分级显示，分页列表，逐页加载等，以后会陆续和大家分享这些技术，今天讲下下拉加载这个功能的实现。

最初的下拉加载应该是ios上的效果，现在很多应用如新浪微博等都加入了这个操作。即下拉listview刷新列表，这无疑是一个非常友好的操作。今天就和大家分享下这个操作的实现。

先看下运行效果：

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代码参考国外朋友Johan Nilsson的实现，http://johannilsson.com/2011/03/13/android-pull-to-refresh-update.html。

主要原理为监听触摸和滑动操作，在listview头部加载一个视图。那要做的其实很简单：1.写好加载到listview头部的view 2.重写listview，实现onTouchEvent方法和onScroll方法，监听滑动状态。计算headview全部显示出来即可实行加载动作，加载完成即刷新列表。重新隐藏headview。

首先写下headview的xml代码：

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[html]?view plaincopy
  1. <RelativeLayout?xmlns:android="http://schemas.android.com/apk/res/android"??
  2. ????android:layout_width="fill_parent"??
  3. ????android:layout_height="fill_parent"??
  4. ????android:paddingTop="10dip"??
  5. ????android:paddingBottom="15dip"??
  6. ????android:gravity="center"??
  7. ????????android:id="@+id/pull_to_refresh_header"??
  8. ????>??
  9. ????<ProgressBar???
  10. ????????android:id="@+id/pull_to_refresh_progress"??
  11. ????????android:indeterminate="true"??
  12. ????????android:layout_width="wrap_content"??
  13. ????????android:layout_height="wrap_content"??
  14. ????????android:layout_marginLeft="30dip"??
  15. ????????android:layout_marginRight="20dip"??
  16. ????????android:layout_marginTop="10dip"??
  17. ????????android:visibility="gone"??
  18. ????????android:layout_centerVertical="true"??
  19. ????????style="?android:attr/progressBarStyleSmall"??
  20. ????????/>??
  21. ????<ImageView??
  22. ????????android:id="@+id/pull_to_refresh_image"??
  23. ????????android:layout_width="wrap_content"??
  24. ????????android:layout_height="wrap_content"??
  25. ????????android:layout_marginLeft="30dip"??
  26. ????????android:layout_marginRight="20dip"??
  27. ????????android:visibility="gone"??
  28. ????????android:layout_gravity="center"??
  29. ????????android:gravity="center"??
  30. ????????android:src="@drawable/ic_pulltorefresh_arrow"??
  31. ????????/>??
  32. ????<TextView??
  33. ????????android:id="@+id/pull_to_refresh_text"??
  34. ????????android:textAppearance="?android:attr/textAppearanceMedium"??
  35. ????????android:textStyle="bold"??
  36. ????????android:paddingTop="5dip"??
  37. ????????android:layout_width="fill_parent"??
  38. ????????android:layout_height="wrap_content"??
  39. ????????android:layout_gravity="center"??
  40. ????????android:gravity="center"??
  41. ????????/>??
  42. ????<TextView??
  43. ????????android:id="@+id/pull_to_refresh_updated_at"??
  44. ????????android:layout_below="@+id/pull_to_refresh_text"??
  45. ????????android:visibility="gone"??
  46. ????????android:textAppearance="?android:attr/textAppearanceSmall"??
  47. ????????android:layout_width="fill_parent"??
  48. ????????android:layout_height="wrap_content"??
  49. ????????android:layout_gravity="center"??
  50. ????????android:gravity="center"??
  51. ????????/>??
  52. </RelativeLayout>??

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代码比较简单，即headview包括一个进度条一个箭头和两段文字（一个显示加载状态，另一个显示最后刷新时间，本例就不设置了）。

而后重写listview，代码如下：

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[java]?view plaincopy
  1. package?com.notice.pullrefresh;??
  2. ??
  3. ??
  4. import?android.content.Context;??
  5. import?android.util.AttributeSet;??
  6. import?android.view.LayoutInflater;??
  7. import?android.view.MotionEvent;??
  8. import?android.view.View;??
  9. import?android.view.ViewGroup;??
  10. import?android.view.animation.LinearInterpolator;??
  11. import?android.view.animation.RotateAnimation;??
  12. import?android.widget.AbsListView;??
  13. import?android.widget.AbsListView.OnScrollListener;??
  14. import?android.widget.ImageView;??
  15. import?android.widget.ListAdapter;??
  16. import?android.widget.ListView;??
  17. import?android.widget.ProgressBar;??
  18. import?android.widget.RelativeLayout;??
  19. import?android.widget.TextView;??
  20. ??
  21. ???
  22. ??
  23. public?class?PullToRefreshListView?extends?ListView?implements?OnScrollListener?{??
  24. ??
  25. ????//?状态??
  26. ????private?static?final?int?TAP_TO_REFRESH?=?1;??
  27. ????private?static?final?int?PULL_TO_REFRESH?=?2;??
  28. ????private?static?final?int?RELEASE_TO_REFRESH?=?3;??
  29. ????private?static?final?int?REFRESHING?=?4;??
  30. ??
  31. ??
  32. ????private?OnRefreshListener?mOnRefreshListener;??
  33. ??
  34. ??
  35. ????//?监听对listview的滑动动作??
  36. ????private?OnScrollListener?mOnScrollListener;??
  37. ????private?LayoutInflater?mInflater;??
  38. ??
  39. ????//顶部刷新时出现的控件??
  40. ????private?RelativeLayout?mRefreshView;??
  41. ????private?TextView?mRefreshViewText;??
  42. ????private?ImageView?mRefreshViewImage;??
  43. ????private?ProgressBar?mRefreshViewProgress;??
  44. ????private?TextView?mRefreshViewLastUpdated;??
  45. ??
  46. ????//?当前滑动状态??
  47. ????private?int?mCurrentScrollState;??
  48. ????//?当前刷新状态??
  49. ????private?int?mRefreshState;??
  50. ??????
  51. ????//?箭头动画效果??
  52. ????private?RotateAnimation?mFlipAnimation;??
  53. ????private?RotateAnimation?mReverseFlipAnimation;??
  54. ??
  55. ????private?int?mRefreshViewHeight;??
  56. ????private?int?mRefreshOriginalTopPadding;??
  57. ????private?int?mLastMotionY;??
  58. ??
  59. ????private?boolean?mBounceHack;??
  60. ??
  61. ????public?PullToRefreshListView(Context?context)?{??
  62. ????????super(context);??
  63. ????????init(context);??
  64. ????}??
  65. ??
  66. ????public?PullToRefreshListView(Context?context,?AttributeSet?attrs)?{??
  67. ????????super(context,?attrs);??
  68. ????????init(context);??
  69. ????}??
  70. ??
  71. ????public?PullToRefreshListView(Context?context,?AttributeSet?attrs,?int?defStyle)?{??
  72. ????????super(context,?attrs,?defStyle);??
  73. ????????init(context);??
  74. ????}??
  75. ??
  76. ????/**?
  77. ?????*?初始化控件和箭头动画（这里直接在代码中初始化动画而不是通过xml）?
  78. ?????*/??
  79. ????private?void?init(Context?context)?{??
  80. ????????mFlipAnimation?=?new?RotateAnimation(0,?-180,??
  81. ????????????????RotateAnimation.RELATIVE_TO_SELF,?0.5f,??
  82. ????????????????RotateAnimation.RELATIVE_TO_SELF,?0.5f);??
  83. ????????mFlipAnimation.setInterpolator(new?LinearInterpolator());??
  84. ????????mFlipAnimation.setDuration(250);??
  85. ????????mFlipAnimation.setFillAfter(true);??
  86. ????????mReverseFlipAnimation?=?new?RotateAnimation(-180,?0,??
  87. ????????????????RotateAnimation.RELATIVE_TO_SELF,?0.5f,??
  88. ????????????????RotateAnimation.RELATIVE_TO_SELF,?0.5f);??
  89. ????????mReverseFlipAnimation.setInterpolator(new?LinearInterpolator());??
  90. ????????mReverseFlipAnimation.setDuration(250);??
  91. ????????mReverseFlipAnimation.setFillAfter(true);??
  92. ??
  93. ????????mInflater?=?(LayoutInflater)?context.getSystemService(??
  94. ????????????????Context.LAYOUT_INFLATER_SERVICE);??
  95. ??
  96. ????????mRefreshView?=?(RelativeLayout)?mInflater.inflate(??
  97. ????????????????R.layout.pull_to_refresh_header,?this,?false);??
  98. ????????mRefreshViewText?=??
  99. ????????????(TextView)?mRefreshView.findViewById(R.id.pull_to_refresh_text);??
  100. ????????mRefreshViewImage?=??
  101. ????????????(ImageView)?mRefreshView.findViewById(R.id.pull_to_refresh_image);??
  102. ????????mRefreshViewProgress?=??
  103. ????????????(ProgressBar)?mRefreshView.findViewById(R.id.pull_to_refresh_progress);??
  104. ????????mRefreshViewLastUpdated?=??
  105. ????????????(TextView)?mRefreshView.findViewById(R.id.pull_to_refresh_updated_at);??
  106. ??
  107. ????????mRefreshViewImage.setMinimumHeight(50);??
  108. ????????mRefreshOriginalTopPadding?=?mRefreshView.getPaddingTop();??
  109. ??
  110. ????????mRefreshState?=?TAP_TO_REFRESH;??
  111. ??????????
  112. ????????//为listview头部增加一个view??
  113. ????????addHeaderView(mRefreshView);??
  114. ??
  115. ????????super.setOnScrollListener(this);??
  116. ??
  117. ????????measureView(mRefreshView);??
  118. ????????mRefreshViewHeight?=?mRefreshView.getMeasuredHeight();??
  119. ????}??
  120. ??
  121. ????@Override??
  122. ????protected?void?onAttachedToWindow()?{??
  123. ????????setSelection(1);??
  124. ????}??
  125. ??
  126. ????@Override??
  127. ????public?void?setAdapter(ListAdapter?adapter)?{??
  128. ????????super.setAdapter(adapter);??
  129. ??
  130. ????????setSelection(1);??
  131. ????}??
  132. ??
  133. ????/**?
  134. ?????*?设置滑动监听器?
  135. ?????*??
  136. ?????*/??
  137. ????@Override??
  138. ????public?void?setOnScrollListener(AbsListView.OnScrollListener?l)?{??
  139. ????????mOnScrollListener?=?l;??
  140. ????}??
  141. ??
  142. ????/**?
  143. ?????*?注册一个list需要刷新时的回调接口?
  144. ?????*??
  145. ?????*/??
  146. ????public?void?setOnRefreshListener(OnRefreshListener?onRefreshListener)?{??
  147. ????????mOnRefreshListener?=?onRefreshListener;??
  148. ????}??
  149. ??
  150. ????/**?
  151. ?????*?设置标签显示何时最后被刷新?
  152. ?????*??
  153. [email protected]?
  154. ?????*????????????Last?updated?at.?
  155. ?????*/??
  156. ????public?void?setLastUpdated(CharSequence?lastUpdated)?{??
  157. ????????if?(lastUpdated?!=?null)?{??
  158. ????????????mRefreshViewLastUpdated.setVisibility(View.VISIBLE);??
  159. ????????????mRefreshViewLastUpdated.setText(lastUpdated);??
  160. ????????}?else?{??
  161. ????????????mRefreshViewLastUpdated.setVisibility(View.GONE);??
  162. ????????}??
  163. ????}??
  164. ??
  165. ????//?实现该方法处理触摸??
  166. ????@Override??
  167. ????public?boolean?onTouchEvent(MotionEvent?event)?{??
  168. ????????final?int?y?=?(int)?event.getY();??
  169. ????????mBounceHack?=?false;??
  170. ??
  171. ????????switch?(event.getAction())?{??
  172. ??
  173. ????????????case?MotionEvent.ACTION_UP:??
  174. ????????????????if?(!isVerticalScrollBarEnabled())?{??
  175. ????????????????????setVerticalScrollBarEnabled(true);??
  176. ????????????????}??
  177. ????????????????if?(getFirstVisiblePosition()?==?0?&&?mRefreshState?!=?REFRESHING)?{??
  178. ????????????????//?拖动距离达到刷新需要??
  179. ????????????????????if?((mRefreshView.getBottom()?>=?mRefreshViewHeight??
  180. ????????????????????????????||?mRefreshView.getTop()?>=?0)??
  181. ????????????????????????????&&?mRefreshState?==?RELEASE_TO_REFRESH)?{??
  182. ????????????????????//?把状态设置为正在刷新??
  183. ????????????????????????mRefreshState?=?REFRESHING;??
  184. ????????????????????//?准备刷新??
  185. ????????????????????????prepareForRefresh();??
  186. ????????????????????//?刷新??
  187. ????????????????????????onRefresh();??
  188. ????????????????????}?else?if?(mRefreshView.getBottom()?<?mRefreshViewHeight??
  189. ????????????????????????????||?mRefreshView.getTop()?<=?0)?{??
  190. ????????????????????//?中止刷新??
  191. ????????????????????????resetHeader();??
  192. ????????????????????????setSelection(1);??
  193. ????????????????????}??
  194. ????????????????}??
  195. ????????????????break;??
  196. ????????????case?MotionEvent.ACTION_DOWN:??
  197. ????????????//?获得按下y轴位置??
  198. ????????????????mLastMotionY?=?y;??
  199. ????????????????break;??
  200. ????????????case?MotionEvent.ACTION_MOVE:??
  201. ????????????//?计算边距??
  202. ????????????????applyHeaderPadding(event);??
  203. ????????????????break;??
  204. ????????}??
  205. ????????return?super.onTouchEvent(event);??
  206. ????}??
  207. ??
  208. ????//?获得header的边距??
  209. ????private?void?applyHeaderPadding(MotionEvent?ev)?{??
  210. ??
  211. ????????int?pointerCount?=?ev.getHistorySize();??
  212. ??
  213. ????????for?(int?p?=?0;?p?<?pointerCount;?p++)?{??
  214. ????????????if?(mRefreshState?==?RELEASE_TO_REFRESH)?{??
  215. ????????????????if?(isVerticalFadingEdgeEnabled())?{??
  216. ????????????????????setVerticalScrollBarEnabled(false);??
  217. ????????????????}??
  218. ??
  219. ????????????????int?historicalY?=?(int)?ev.getHistoricalY(p);??
  220. ??
  221. ????????????????//?计算申请的边距，除以1.7使得拉动效果更好??
  222. ????????????????int?topPadding?=?(int)?(((historicalY?-?mLastMotionY)??
  223. ????????????????????????-?mRefreshViewHeight)?/?1.7);??
  224. ??
  225. ????????????????mRefreshView.setPadding(??
  226. ????????????????????????mRefreshView.getPaddingLeft(),??
  227. ????????????????????????topPadding,??
  228. ????????????????????????mRefreshView.getPaddingRight(),??
  229. ????????????????????????mRefreshView.getPaddingBottom());??
  230. ????????????}??
  231. ????????}??
  232. ????}??
  233. ??
  234. ????/**?
  235. ?????*?将head的边距重置为初始的数值?
  236. ?????*/??
  237. ????private?void?resetHeaderPadding()?{??
  238. ????????mRefreshView.setPadding(??
  239. ????????????????mRefreshView.getPaddingLeft(),??
  240. ????????????????mRefreshOriginalTopPadding,??
  241. ????????????????mRefreshView.getPaddingRight(),??
  242. ????????????????mRefreshView.getPaddingBottom());??
  243. ????}??
  244. ??
  245. ????/**?
  246. ?????*?重置header为之前的状态?
  247. ?????*/??
  248. ????private?void?resetHeader()?{??
  249. ????????if?(mRefreshState?!=?TAP_TO_REFRESH)?{??
  250. ????????????mRefreshState?=?TAP_TO_REFRESH;??
  251. ??
  252. ????????????resetHeaderPadding();??
  253. ??
  254. ????????????//?将刷新图标换成箭头??
  255. ????????????mRefreshViewImage.setImageResource(R.drawable.ic_pulltorefresh_arrow);??
  256. ????????????//?清除动画??
  257. ????????????mRefreshViewImage.clearAnimation();??
  258. ????????????//?隐藏图标和进度条??
  259. ????????????mRefreshViewImage.setVisibility(View.GONE);??
  260. ????????????mRefreshViewProgress.setVisibility(View.GONE);??
  261. ????????}??
  262. ????}??
  263. ??
  264. ????//?估算headview的width和height??
  265. ????private?void?measureView(View?child)?{??
  266. ????????ViewGroup.LayoutParams?p?=?child.getLayoutParams();??
  267. ????????if?(p?==?null)?{??
  268. ????????????p?=?new?ViewGroup.LayoutParams(??
  269. ????????????????????ViewGroup.LayoutParams.FILL_PARENT,??
  270. ????????????????????ViewGroup.LayoutParams.WRAP_CONTENT);??
  271. ????????}??
  272. ??
  273. ????????int?childWidthSpec?=?ViewGroup.getChildMeasureSpec(0,??
  274. ????????????????0?+?0,?p.width);??
  275. ????????int?lpHeight?=?p.height;??
  276. ????????int?childHeightSpec;??
  277. ????????if?(lpHeight?>?0)?{??
  278. ????????????childHeightSpec?=?MeasureSpec.makeMeasureSpec(lpHeight,?MeasureSpec.EXACTLY);??
  279. ????????}?else?{??
  280. ????????????childHeightSpec?=?MeasureSpec.makeMeasureSpec(0,?MeasureSpec.UNSPECIFIED);??
  281. ????????}??
  282. ????????child.measure(childWidthSpec,?childHeightSpec);??
  283. ????}??
  284. ??
  285. ????@Override??
  286. ????public?void?onScroll(AbsListView?view,?int?firstVisibleItem,??
  287. ????????????int?visibleItemCount,?int?totalItemCount)?{??
  288. ??
  289. ????????//?在refreshview完全可见时，设置文字为松开刷新，同时翻转箭头??
  290. ????????if?(mCurrentScrollState?==?SCROLL_STATE_TOUCH_SCROLL??
  291. ????????????????&&?mRefreshState?!=?REFRESHING)?{??
  292. ????????????if?(firstVisibleItem?==?0)?{??
  293. ????????????????mRefreshViewImage.setVisibility(View.VISIBLE);??
  294. ????????????????if?((mRefreshView.getBottom()?>=?mRefreshViewHeight?+?20??
  295. ????????????????????????||?mRefreshView.getTop()?>=?0)??
  296. ????????????????????????&&?mRefreshState?!=?RELEASE_TO_REFRESH)?{??
  297. ????????????????????mRefreshViewText.setText("松开加载...");??
  298. ????????????????????mRefreshViewImage.clearAnimation();??
  299. ????????????????????mRefreshViewImage.startAnimation(mFlipAnimation);??
  300. ????????????????????mRefreshState?=?RELEASE_TO_REFRESH;??
  301. ????????????????}?else?if?(mRefreshView.getBottom()?<?mRefreshViewHeight?+?20??
  302. ????????????????????????&&?mRefreshState?!=?PULL_TO_REFRESH)?{??
  303. ????????????????????mRefreshViewText.setText("下拉刷新...");??
  304. ????????????????????if?(mRefreshState?!=?TAP_TO_REFRESH)?{??
  305. ????????????????????????mRefreshViewImage.clearAnimation();??
  306. ????????????????????????mRefreshViewImage.startAnimation(mReverseFlipAnimation);??
  307. ????????????????????}??
  308. ????????????????????mRefreshState?=?PULL_TO_REFRESH;??
  309. ????????????????}??
  310. ????????????}?else?{??
  311. ????????????????mRefreshViewImage.setVisibility(View.GONE);??
  312. ????????????????resetHeader();??
  313. ????????????}??
  314. ????????}?else?if?(mCurrentScrollState?==?SCROLL_STATE_FLING??
  315. ????????????????&&?firstVisibleItem?==?0??
  316. ????????????????&&?mRefreshState?!=?REFRESHING)?{??
  317. ????????????setSelection(1);??
  318. ????????????mBounceHack?=?true;??
  319. ????????}?else?if?(mBounceHack?&&?mCurrentScrollState?==?SCROLL_STATE_FLING)?{??
  320. ????????????setSelection(1);??
  321. ????????}??
  322. ??
  323. ????????if?(mOnScrollListener?!=?null)?{??
  324. ????????????mOnScrollListener.onScroll(view,?firstVisibleItem,??
  325. ????????????????????visibleItemCount,?totalItemCount);??
  326. ????????}??
  327. ????}??
  328. ??
  329. ????@Override??
  330. ????public?void?onScrollStateChanged(AbsListView?view,?int?scrollState)?{??
  331. ????????mCurrentScrollState?=?scrollState;??
  332. ??
  333. ????????if?(mCurrentScrollState?==?SCROLL_STATE_IDLE)?{??
  334. ????????????mBounceHack?=?false;??
  335. ????????}??
  336. ??
  337. ????????if?(mOnScrollListener?!=?null)?{??
  338. ????????????mOnScrollListener.onScrollStateChanged(view,?scrollState);??
  339. ????????}??
  340. ????}??
  341. ??
  342. ????public?void?prepareForRefresh()?{??
  343. ????????resetHeaderPadding();//?恢复header的边距??
  344. ??
  345. ????????mRefreshViewImage.setVisibility(View.GONE);??
  346. ????????//?注意加上，否则仍然显示之前的图片??
  347. ????????mRefreshViewImage.setImageDrawable(null);??
  348. ????????mRefreshViewProgress.setVisibility(View.VISIBLE);??
  349. ??
  350. ????????//?设置文字??
  351. ????????mRefreshViewText.setText("加载中...");??
  352. ??
  353. ????????mRefreshState?=?REFRESHING;??
  354. ????}??
  355. ??
  356. ????public?void?onRefresh()?{??
  357. ??
  358. ????????if?(mOnRefreshListener?!=?null)?{??
  359. ????????????mOnRefreshListener.onRefresh();??
  360. ????????}??
  361. ????}??
  362. ??
  363. ????/**?
  364. ?????*?重置listview为普通的listview，该方法设置最后更新时间?
  365. ?????*??
  366. [email protected]?
  367. ?????*????????????Last?updated?at.?
  368. ?????*/??
  369. ????public?void?onRefreshComplete(CharSequence?lastUpdated)?{??
  370. ????????setLastUpdated(lastUpdated);??
  371. ????????onRefreshComplete();??
  372. ????}??
  373. ??
  374. ????/**?
  375. ?????*?重置listview为普通的listview，不设置最后更新时间?
  376. ?????*/??
  377. ????public?void?onRefreshComplete()?{??????????
  378. ??
  379. ????????resetHeader();??
  380. ??
  381. ????????//?如果refreshview在加载结束后可见，下滑到下一个条目??
  382. ????????if?(mRefreshView.getBottom()?>?0)?{??
  383. ????????????invalidateViews();??
  384. ????????????setSelection(1);??
  385. ????????}??
  386. ????}??
  387. ??
  388. ??
  389. ??
  390. ????/**?
  391. ?????*?刷新监听器接口?
  392. ?????*/??
  393. ????public?interface?OnRefreshListener?{??
  394. ????????/**?
  395. ?????????*?list需要被刷新时调用?
  396. ?????????*/??
  397. ????????public?void?onRefresh();??
  398. ????}??
  399. }??

?

相信我注释已经写的比较详细了，主要注意onTouchEvent和onScroll方法，在这里面计算头部边距，从而通过用户的手势实现“下拉刷新”到“松开加载”以及“加载”三个状态的切换。其中还有一系列和header有关的方法，用来设置header的显示以及取得header的边距。于此同时，代码留出了接口以供调用。

那么现在写一个测试Activity来试验下效果：

?

[java]?view plaincopy
  1. package?com.notice.pullrefresh;??
  2. ??
  3. import?java.util.Arrays;??
  4. import?java.util.LinkedList;??
  5. ??
  6. import?android.app.ListActivity;??
  7. import?android.os.AsyncTask;??
  8. import?android.os.Bundle;??
  9. import?android.widget.ArrayAdapter;??
  10. ??
  11. import?com.notice.pullrefresh.PullToRefreshListView.OnRefreshListener;??
  12. ??
  13. ??
  14. public?class?PullrefreshActivity?extends?ListActivity?{??
  15. ????private?LinkedList<String>?mListItems;??
  16. ????ArrayAdapter<String>?adapter;??
  17. ??
  18. ????/**?Called?when?the?activity?is?first?created.?*/??
  19. ????@Override??
  20. ????public?void?onCreate(Bundle?savedInstanceState)?{??
  21. ????????super.onCreate(savedInstanceState);??
  22. ????????setContentView(R.layout.pull_to_refresh);??
  23. ??
  24. ????????//?list需要刷新时调用??
  25. ????????((PullToRefreshListView)?getListView())??
  26. ????????????????.setOnRefreshListener(new?OnRefreshListener()?{??
  27. ????????????????????@Override??
  28. ????????????????????public?void?onRefresh()?{??
  29. ????????????????????????//?在这执行后台工作??
  30. ????????????????????????new?GetDataTask().execute();??
  31. ????????????????????}??
  32. ????????????????});??
  33. ??
  34. ??
  35. ??
  36. ????????mListItems?=?new?LinkedList<String>();??
  37. ????????mListItems.addAll(Arrays.asList(mStrings));??
  38. ??
  39. ????????adapter?=?new?ArrayAdapter<String>(this,??
  40. ????????????????android.R.layout.simple_list_item_1,?mListItems);??
  41. ??
  42. ????????setListAdapter(adapter);??
  43. ????}??
  44. ??
  45. ??
  46. ????private?class?GetDataTask?extends?AsyncTask<Void,?Void,?String[]>?{??
  47. ??
  48. ????????@Override??
  49. ????????protected?String[]?doInBackground(Void...?params)?{??
  50. ????????????//?在这里可以做一些后台工作??
  51. ????????????try?{??
  52. ????????????????Thread.sleep(2000);??
  53. ????????????}?catch?(InterruptedException?e)?{??
  54. ????????????????e.printStackTrace();??
  55. ????????????}??
  56. ????????????return?mStrings;??
  57. ????????}??
  58. ??
  59. ????????@Override??
  60. ????????protected?void?onPostExecute(String[]?result)?{??
  61. ????????????//?下拉后增加的内容??
  62. ????????????mListItems.addFirst("Added?after?refresh...");??
  63. ??
  64. ????????????//?刷新完成调用该方法复位??
  65. ????????????((PullToRefreshListView)?getListView()).onRefreshComplete();??
  66. ??
  67. ????????????super.onPostExecute(result);??
  68. ????????}??
  69. ????}??
  70. ??
  71. ????private?String[]?mStrings?=?{?"normal?data1",?"normal?data2",??
  72. ????????????"nomal?data3",?"normal?data4",?"norma?data5",?"normal?data6"?};??
  73. }??

?

代码通过asyncTask实现一个异步操作，并通过设置onRefreshListener监听器调用onRefresh方法实现下拉时刷新，并在刷新完成后调用onRefreshComplete做复位处理。

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