ListView加载更多

主要是对OnScrllListener的使用介绍,有两个方法来监听滑动的状态，onScroll()和onScrollStateChanged()。

new AbsListView.OnScrollListener() {            /**             *正在滚动时回调，回调2-3次，手指没抛则回调2次。scrollState = 2的这次不回调             *回调顺序如下             *第1次：scrollState = SCROLL_STATE_TOUCH_SCROLL(1) 正在滚动             *第2次：scrollState = SCROLL_STATE_FLING(2) 手指做了抛的动作（手指离开屏幕前，用力滑了一下）             *第3次：scrollState = SCROLL_STATE_IDLE(0) 停止滚动             */            @Override            public void onScrollStateChanged(AbsListView view, int scrollState) {                //当停止滚动时                if (scrollState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {                    //do something                }            }            /**             * 滚动时一直回调，直到停止滚动时才停止回调。单击时回调一次。             *firstVisibleItem：当前能看见的第一个列表项ID（从0开始）             *visibleItemCount：当前能看见的列表项个数（小半个也算）             *totalItemCount：列表项共数             */            @Override            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {                //否滚到最后一行                if (firstVisibleItem + visibleItemCount == totalItemCount && totalItemCount > 0) {                    //do something                }            }        };

下面用Listview的加载更多实例来说明。

重写的Listview，实现了滑动监听。

public class LoaderListView extends ListView implements AbsListView.OnScrollListener {    private Context mContext;    private boolean isCanScroll = false;    private List list = new ArrayList();    /**     * 最后可见条目的索引     */    private int lastVisibleIndex = 0;    private View footView;    private MainActivity.CurAdapter adapter;    private Handler loaderHander = new Handler() {        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            loaderMore();        }    };    public LoaderListView(Context context) {        super(context);        this.mContext = context;        init();    }    public LoaderListView(Context context, AttributeSet attrs) {        super(context, attrs);        this.mContext = context;        init();    }    public LoaderListView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        this.mContext = context;        init();    }    private void init() {        footView = LayoutInflater.from(mContext).inflate(R.layout.item_foot, null);        addFooterView(footView);        setOnScrollListener(this);    }    @Override    public void onScrollStateChanged(AbsListView view, int scrollState) {        if (isCanScroll && OnScrollListener.SCROLL_STATE_IDLE == scrollState && lastVisibleIndex < list.size()) {            loaderHander.sendEmptyMessageDelayed(0, 2000);        }    }    @Override    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {        lastVisibleIndex = firstVisibleItem + visibleItemCount - 1;        if (firstVisibleItem + 15 < totalItemCount) {            isCanScroll = false;        } else {            if (lastVisibleIndex == list.size()) {                removeFooterView(footView);            } else {                isCanScroll = true;            }        }    }    /**     * 加载更多     */    private void loaderMore() {        if (lastVisibleIndex + 10 < list.size()) {            lastVisibleIndex += 10;        } else {            lastVisibleIndex = list.size();        }        adapter.setCountLength(lastVisibleIndex);    }    public List getList() {        return list;    }    public void setList(List list) {        this.list = list;    }    public MainActivity.CurAdapter getCurAdapter() {        return adapter;    }    public void setCurAdapter(MainActivity.CurAdapter adapter) {        this.adapter = adapter;    }}

活动中，主要是传入集合和适配器。

public class MainActivity extends Activity {    private MainActivity mContext;    private int lastPress = 0;    private boolean delState = false;    private List<String> curList = new ArrayList<>();    private LoaderListView curListView;    private CurAdapter adapter;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        init();    }    private void init() {        mContext = this;        for (int i = 0; i < 100; i++) {            curList.add("第" + i + ":行数据");        }        curListView = (LoaderListView) findViewById(R.id.lv_contents);        adapter = new CurAdapter();        curListView.setAdapter(adapter);        curListView.setList(curList);        curListView.setCurAdapter(adapter);    }    public class CurAdapter extends BaseAdapter {        private int count = 0;        public CurAdapter() {            if (0 == count) {                if (15 > curList.size()) {                    count = curList.size();                } else {                    count = 15;                }            }        }        public void setCountLength(int count) {            this.count = count;            notifyDataSetChanged();        }        @Override        public int getCount() {            return count;        }        @Override        public Object getItem(int position) {            return position;        }        @Override        public long getItemId(int position) {            return position;        }        @Override        public View getView(int position, View convertView, ViewGroup parent) {            if (null == convertView) {                convertView = LayoutInflater.from(mContext).inflate(R.layout.item_content, null);            }            ((TextView) convertView.findViewById(R.id.tv_content)).setText(curList.get(position));            return convertView;        }    }}

活动布局：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent">    <cn.com.myapplication.LoaderListView        android:id="@+id/lv_contents"        android:layout_width="match_parent"        android:layout_height="match_parent"></cn.com.myapplication.LoaderListView></RelativeLayout>

子项布局：

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:background="#FFFFFF"    android:layout_height="40dp">    <RelativeLayout        android:id="@+id/rela_content"        android:layout_width="match_parent"        android:visibility="visible"        android:layout_height="40dp">        <TextView            android:id="@+id/tv_content"            android:layout_width="match_parent"            android:layout_height="match_parent"            android:text="content"            android:textColor="#001122"            android:gravity="center" />    </RelativeLayout></RelativeLayout>

在适配器中，对子项数量的处理,是针对那种提前就把数据都取完了的情况：

public CurAdapter() {            if (0 == count) {                if (15 > curList.size()) {                    count = curList.size();                } else {                    count = 15;                }            }        }        public void setCountLength(int count) {            this.count = count;            notifyDataSetChanged();        }

如果加载更多的数据需要去网络上请求的话，那么最好是在loaderMore()中，开启去请求，然后发送handler刷新数据。

   /**     * 加载更多     */    private void loaderMore() {        if (lastVisibleIndex + 10 < list.size()) {            lastVisibleIndex += 10;        } else {            lastVisibleIndex = list.size();        }        adapter.setCountLength(lastVisibleIndex);    }