android ListView结合xutils3仿微信实现下拉加载更多

public class MyOnScrollListener implements OnScrollListener { private int totalItemCount;  //ListView最后的item项  private int lastItem;  //listview第一项  private int firstItem;  //用于判断当前是否在加载  private boolean isLoading;  //底部加载更多布局  private View footer;  //接口回调的实例  private OnloadDataListener listener;    //数据  private List<MsgBean> data;  Handler handler = new Handler();      public MyOnScrollListener(View footer, List<MsgBean> data) {  this.footer = footer;  this.data = data;  }  //设置接口回调的实例  public void setOnLoadDataListener(OnloadDataListener listener) {  this.listener = listener;  }  /**  * 滑动状态变化  *  * @param view  * @param scrollState 1 SCROLL_STATE_TOUCH_SCROLL是拖动 2 SCROLL_STATE_FLING是惯性滑动 0SCROLL_STATE_IDLE是停止 , 只有当在不同状态间切换的时候才会执行  */  @Override  public void onScrollStateChanged(AbsListView view, int scrollState) {  //如果数据没有加载，并且滑动状态是停止的,并且滚到了第一个item,可在此做下拉更新或者上拉更新的判断  if (!isLoading && firstItem == 0 && scrollState == SCROLL_STATE_IDLE) {   //显示加载更多   footer.setVisibility(View.VISIBLE);     //模拟一个延迟两秒的刷新功能   handler.postDelayed(new Runnable() {   @Override   public void run() {    if (listener != null) {    //开始加载更多数据    loadMoreData();    //回调设置ListView的数据    listener.onLoadData(data);     //加载完成后操作什么    loadComplete();    }   }   }, 2000);  }  }  /**  * 当加载数据完成后，设置加载标志为false表示没有加载数据了  * 并且设置底部加载更多为隐藏  */  private void loadComplete() {  isLoading = false;  footer.setVisibility(View.GONE);    }  /**  * 开始加载更多新数据，这里每次只更新三条数据  */  private void loadMoreData() {  isLoading = true;  MsgBean msg = null;  for (int i = 0; i < 3; i++) {   msg = new MsgBean();   msg .setRemark("Liming"+i);   msg .setMsgID(i);   data.add(stu);  }  }  /**  * 监听可见界面的情况  *  * @param view  ListView  * @param firstVisibleItem 第一个可见的 item 的索引  * @param visibleItemCount 可以显示的 item的条数  * @param totalItemCount 总共有多少个 item  */  @Override  public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {  //实现下拉加载  lastItem = firstVisibleItem + visibleItemCount;   //实现上拉加载  firstItem = firstVisibleItem;   //总listView的item个数  this.totalItemCount = totalItemCount;  }  //回调接口  public interface OnloadDataListener {  void onLoadData(List<MsgBean> data);  }  }

public class ListPageActivity extends Activity implements MyOnScrollListener.OnloadDataListener { @Override  protected void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);  setContentView(R.layout.activity_list_page);   //显示到ListView上  showListView(data); //自定义的滚动监听事件  MyOnScrollListener onScrollListener = new MyOnScrollListener(header, data);  //设置接口回调  onScrollListener.setOnLoadDataListener(this);  //设置ListView的滚动监听事件  mListView.setOnScrollListener(onScrollListener); @Override  public void onLoadData(List<MsgBean> data) {  //加载数据完成后，展示数据到ListView  showListView(data);  }}

/** * 当前屏幕显示的消息数量 */private int MAX_MSG_NUMBER = 20;

private List<MsgBean> getDataFromDb() {  List<?> dbSize = db.selector(MsgBean.class).where(WhereBuilder.b("id", "=", 400)).findAll();//记得捕获null指针和DbException异常//如果数据库比我们显示的页数小,则不偏移,否则,偏移到我们需要显示的位置  if (dbSize.size() < MAX_MSG_NUMBER) {   indexOffset = 0;  } else {   indexOffset = dbSize.size() - MAX_MSG_NUMBER;  }    List<MsgBean> datas = db.selector(MsgBean.class).where(WhereBuilder.b("id", "=", 400)).limit(MAX_MSG_NUMBER)     .offset(indexOffset).findAll();  return datas; }

MAX_MSG_NUMBER += MAX_MSG_NUMBER;getDataFromDb();

/** * 数据库 xutils用法 * @author 青楼爱小生 */public class DbUtil { private static final String TAG = DbUtil.class.getName(); private static DbUtil dbUtil; private DbManager db; private DbUtil(){  db = x.getDb(MyApplication.getInstance().daoConfig); } public static DbUtil getInstance(){  if(dbUtil == null){   synchronized (DbUtil.class) {    if(dbUtil == null){     dbUtil = new DbUtil();    }   }  }  return dbUtil; } /**  * 增加数据  * @param list  * @throws DbException   */ public void addMsgList(List<MsgBean> list) {  try {   db.saveOrUpdate(list);  } catch (DbException e) {   e.printStackTrace();   LogHelper.e(TAG, e.getMessage());  } } /**  * 增加一条数据  * @param node  * @throws DbException  */ public void addMsgToDb(MsgBean node) {  try {   db.saveOrUpdate(node);  } catch (DbException e) {   e.printStackTrace();   LogHelper.e(TAG, e.getMessage());  } } /**  * 删除表中所有数据  * @param cls 创建的表的映射  * @throws DbException   */ public void deleteAll(Class cls) {  try {   db.delete(cls);  } catch (DbException e) {   LogHelper.e(TAG, e.getMessage());   e.printStackTrace();  } } /**  * 删除第一条数据  * @param cls  */ @SuppressWarnings("unchecked") public void deleteFirst(Class cls){  try {   db.delete(db.findFirst(cls));  } catch (DbException e) {   // TODO Auto-generated catch block   e.printStackTrace();  } } /**  * 查询表中所有数据  * @throws DbException   */ @SuppressWarnings("unchecked") public List<?> findAll(Class cls) {  try {   return db.findAll(cls) == null ? Collections.emptyList() : db.findAll(cls);  } catch (DbException e) {  e.printStackTrace();   LogHelper.e(TAG, e.getMessage());   return Collections.emptyList();  } } /**  * //添加查询条件进行查询  List<ChildInfo> all = db.selector(ChildInfo.class).where("id",">",2).and("id","<",4).findAll();  * @return 搜索指定条件的数据  */  @SuppressWarnings("unchecked") public List<?> findDataByWhere(Class cls,WhereBuilder format){  try {   return db.selector(cls).where(format).findAll()== null ?     Collections.emptyList() :db.selector(cls).where(format).findAll();  } catch (DbException e) {  LogHelper.e(TAG, e.getMessage());   e.printStackTrace();   return Collections.emptyList();  }  } /**  * 添加查询条件进行查询  * @param cls 表映射  * @param str select语句  * @param format where语句  * @return List<DbModel> DbModel key为数据库列名 value为值  * eg:(Selector.from(Parent.class)          .where("id" ,"<", 54)          .and(WhereBuilder.b("age", ">", 20).or("age", " < ", 30))          .orderBy("id")          .limit(pageSize) .offset(pageSize * pageIndex));   *   *   *   */  @SuppressWarnings("unchecked") public Selector<?> findDataBySelector(Class cls,WhereBuilder format){  try {   return db.selector(cls).where(format);  } catch (DbException e) {  // TODO Auto-generated catch block   e.printStackTrace();  }  return null; }  }