Android利用V4包中的SwipeRefreshLayout实现上拉加载

/**
 * 继承自SwipeRefreshLayout,从而实现滑动到底部时上拉加载更多的功能.
 * 
 * @author mrsimple
 */
public class RefreshLayout extends SwipeRefreshLayout implements OnScrollListener {

    /**
     * 滑动到最下面时的上拉操作
     */

    private int mTouchSlop;
    /**
     * listview实例
     */
    private ListView mListView;

    /**
     * 上拉监听器, 到了最底部的上拉加载操作
     */
    private OnLoadListener mOnLoadListener;

    /**
     * ListView的加载中footer
     */
    private View mListViewFooter;

    /**
     * 按下时的y坐标
     */
    private int mYDown;
    /**
     * 抬起时的y坐标, 与mYDown一起用于滑动到底部时判断是上拉还是下拉
     */
    private int mLastY;
    /**
     * 是否在加载中 ( 上拉加载更多 )
     */
    private boolean isLoading = false;

    /**
     * @param context
     */
    public RefreshLayout(Context context) {
        this(context, null);
    }

    public RefreshLayout(Context context, AttributeSet attrs) {
        super(context, attrs);

        mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();

        mListViewFooter = LayoutInflater.from(context).inflate(R.layout.listview_footer, null,
                false);
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);

        // 初始化ListView对象
        if (mListView == null) {
            getListView();
        }
    }

    /**
     * 获取ListView对象
     */
    private void getListView() {
        int childs = getChildCount();
        if (childs > 0) {
            View childView = getChildAt(0);
            if (childView instanceof ListView) {
                mListView = (ListView) childView;
                // 设置滚动监听器给ListView, 使得滚动的情况下也可以自动加载
                mListView.setOnScrollListener(this);
                Log.d(VIEW_LOG_TAG, "### 找到listview");
            }
        }
    }

    /*
     * (non-Javadoc)
     * @see android.view.ViewGroup#dispatchTouchEvent(android.view.MotionEvent)
     */
    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        final int action = event.getAction();

        switch (action) {
            case MotionEvent.ACTION_DOWN:
                // 按下
                mYDown = (int) event.getRawY();
                break;

            case MotionEvent.ACTION_MOVE:
                // 移动
                mLastY = (int) event.getRawY();
                break;

            case MotionEvent.ACTION_UP:
                // 抬起
                if (canLoad()) {
                    loadData();
                }
                break;
            default:
                break;
        }

        return super.dispatchTouchEvent(event);
    }

    /**
     * 是否可以加载更多, 条件是到了最底部, listview不在加载中, 且为上拉操作.
     * 
     * @return
     */
    private boolean canLoad() {
        return isBottom() && !isLoading && isPullUp();
    }

    /**
     * 判断是否到了最底部
     */
    private boolean isBottom() {

        if (mListView != null && mListView.getAdapter() != null) {
            return mListView.getLastVisiblePosition() == (mListView.getAdapter().getCount() - 1);
        }
        return false;
    }

    /**
     * 是否是上拉操作
     * 
     * @return
     */
    private boolean isPullUp() {
        return (mYDown - mLastY) >= mTouchSlop;
    }

    /**
     * 如果到了最底部,而且是上拉操作.那么执行onLoad方法
     */
    private void loadData() {
        if (mOnLoadListener != null) {
            // 设置状态
            setLoading(true);
            //
            mOnLoadListener.onLoad();
        }
    }

    /**
     * @param loading
     */
    public void setLoading(boolean loading) {
        isLoading = loading;
        if (isLoading) {
            mListView.addFooterView(mListViewFooter);
        } else {
            mListView.removeFooterView(mListViewFooter);
            mYDown = 0;
            mLastY = 0;
        }
    }

    /**
     * @param loadListener
     */
    public void setOnLoadListener(OnLoadListener loadListener) {
        mOnLoadListener = loadListener;
    }

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {

    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount,
            int totalItemCount) {
        // 滚动时到了最底部也可以加载更多
        if (canLoad()) {
            loadData();
        }
    }

    /**
     * 加载更多的监听器
     * 
     * @author mrsimple
     */
    public static interface OnLoadListener {
        public void onLoad();
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:background="@color/umeng_comm_comments_bg"
    android:gravity="center"
    android:paddingBottom="8dip"
    android:paddingTop="5dip" >

    <ProgressBar
        android:id="@+id/pull_to_refresh_load_progress"
        style="@android:style/Widget.ProgressBar.Small.Inverse"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:paddingRight="100dp"
        android:indeterminate="true" />

    <TextView
        android:id="@+id/pull_to_refresh_loadmore_text"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:gravity="center"
        android:paddingTop="5dip"
        android:text="@string/load"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:textColor="@android:color/darker_gray"
        android:textSize="14sp"
        android:textStyle="bold" />

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<myview.RefreshLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/swipe_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </ListView>

</myview.RefreshLayout>

/**
 * @author mrsimple
 */
public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.refresh);

        // 模拟一些数据
        final List<String> datas = new ArrayList<String>();
        for (int i = 0; i < 20; i++) {
            datas.add("item - " + i);
        }

        // 构造适配器
        final BaseAdapter adapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1,
                datas);
        // 获取listview实例
        ListView listView = (ListView) findViewById(R.id.listview);
        listView.setAdapter(adapter);

        // 获取RefreshLayout实例
        final RefreshLayout myRefreshListView = (RefreshLayout)
                findViewById(R.id.swipe_layout);

        // 设置下拉刷新时的颜色值,颜色值需要定义在xml中
        myRefreshListView
                .setColorScheme(R.color.umeng_comm_text_topic_light_color,
                        R.color.umeng_comm_yellow, R.color.umeng_comm_green,
                        R.color.umeng_comm_linked_text);
        // 设置下拉刷新监听器
        myRefreshListView.setOnRefreshListener(new OnRefreshListener() {

            @Override
            public void onRefresh() {

                Toast.makeText(MainActivity.this, "refresh", Toast.LENGTH_SHORT).show();

                myRefreshListView.postDelayed(new Runnable() {

                    @Override
                    public void run() {
                        // 更新数据
                        datas.add(new Date().toGMTString());
                        adapter.notifyDataSetChanged();
                        // 更新完后调用该方法结束刷新
                        myRefreshListView.setRefreshing(false);
                    }
                }, 1000);
            }
        });

        // 加载监听器
        myRefreshListView.setOnLoadListener(new OnLoadListener() {

            @Override
            public void onLoad() {

                Toast.makeText(MainActivity.this, "load", Toast.LENGTH_SHORT).show();

                myRefreshListView.postDelayed(new Runnable() {

                    @Override
                    public void run() {
                        datas.add(new Date().toGMTString());
                        adapter.notifyDataSetChanged();
                        // 加载完后调用该方法
                        myRefreshListView.setLoading(false);
                    }
                }, 1500);

            }
        });
    }

    }