基于Android-Pull-To-Refresh做的当用户下拉到倒数第N个Item时候加载数据的控件

ListView

目录

1.继承自PullToRefreshListView

package com.culiu.purchase.app.view;
import android.content.Context;
import android.util.AttributeSet;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import com.culiu.core.pulltorefresh.library.PullToRefreshListView;
/**
 * 具有倒数第N个Item可见的时候的监听的下拉刷新控件，注意千万别给mRefreshView设置滚动监听，否则这个类就废了
 * 
 * @author wangheng
 * 
 */
public class CountdownPullToRefreshListView extends PullToRefreshListView {
    /** 上一个可见的Item的索引 **/
    private int mPreviousItem = 0;
    /** 监听器，你懂得 **/
    private OnCountdownItemVisibleListener mCountdownListener = null;
    public CountdownPullToRefreshListView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }
    public CountdownPullToRefreshListView(
            Context context,
            com.culiu.core.pulltorefresh.library.PullToRefreshBase.Mode mode,
            com.culiu.core.pulltorefresh.library.PullToRefreshBase.AnimationStyle style) {
        super(context, mode, style);
        init(context);
    }
    public CountdownPullToRefreshListView(Context context,
            com.culiu.core.pulltorefresh.library.PullToRefreshBase.Mode mode) {
        super(context, mode);
        init(context);
    }
    public CountdownPullToRefreshListView(Context context) {
        super(context);
        init(context);
    }
    /**
     * 初始化View
     * 
     * @param context
     */
    private void init(Context context) {
        mRefreshableView.setOnScrollListener(new InternalOnScrollListener());
    }
    /**
     * 
     * @author wangheng
     * 
     */
    private class InternalOnScrollListener implements OnScrollListener {
        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {
            // 回调父类的方法
            CountdownPullToRefreshListView.this.onScrollStateChanged(view,
                    scrollState);
        }
        @Override
        public void onScroll(AbsListView view, int firstVisibleItem,
                int visibleItemCount, int totalItemCount) {
            // 回调父类的方法
            CountdownPullToRefreshListView.this.onScroll(view,
                    firstVisibleItem, visibleItemCount, totalItemCount);
            int lastItem = firstVisibleItem + visibleItemCount;
            if (mCountdownListener != null) {
                int countdown = mCountdownListener.getCountdownNumber();
                // 为什么是大于而不是大于等于？这里取满足条件的的一个临界点，假如有20个Item，倒数第4个的时候调用onVisible，则这个时机在第15个跳转到第16个的一瞬间进行加载
                if (lastItem > mPreviousItem && lastItem == totalItemCount - countdown) {
                    mCountdownListener.onVisible();
                }
            }
            mPreviousItem = lastItem;
        }
    }
    /**
     * 设置倒数第N个元素可见的时候的监听器
     * 
     * @param listener
     */
    public void setOnCountdownItemVisibleListener(OnCountdownItemVisibleListener listener) {
        this.mCountdownListener = listener;
    }
    /**
     * 倒数第几个Item可见的时候刷新舰艇 注意，只有在ListView往上拉的时候，回调方法才会调用
     * 
     * @author wangheng
     * 
     */
    public interface OnCountdownItemVisibleListener {
        /**
         * 倒数第几个Item的时候刷新数据
         * 
         * @return 实现这个接口的对象需要给定倒数第几个数据开始刷新
         */
        int getCountdownNumber();
        /**
         * 第getCountdownNumber()个Item可见的时候的回调，特别注意这个方法会调用多次，自己要在这个方法中做是否正在刷新的判断
         */
        void onVisible();
    }
}

2. 在布局文件中使用

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:culiu="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    <!-- <com.culiu.core.pulltorefresh.library.PullToRefreshListView -->
    <com.culiu.purchase.app.view.CountdownPullToRefreshListView
        android:id="@+id/home99ListView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:listSelector="@color/transparent"
        android:cacheColorHint="@color/transparent"
        android:divider="@color/transparent"
        android:dividerHeight="1px"
        android:fastScrollEnabled="false"
        android:scrollbarStyle="outsideOverlay"
        android:fadingEdge="none"
        culiu:ptrMode="pullFromStart"
        culiu:ptrAnimationStyle="flip"
        culiu:ptrHeaderTextColor="@color/ptr_header_text_color"
        android:layout_marginTop="-1dip"
        />
</LinearLayout>

3. 在代码中使用

/** ListView **/
private CountdownPullToRefreshListView mRefreshView = null;
@Override
protected View onCreateViewExecute(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_home99, container, false);
    mViewFinder = new ViewFinder(view);
    mRefreshView = mViewFinder.find(R.id.home99ListView);
    // 为什么实现OnRefreshListener2而不是OnRefreshListener？为了扩展的需要
    mRefreshView.setOnRefreshListener(Home99Fragment.this);
    mRefreshView.setOnCountdownItemVisibleListener(Home99Fragment.this);
    return view;
}
@Override
public int getCountdownNumber() {
    // 倒数第四个元素执行刷新操作
    return 4;
}
@Override
public void onVisible() {
    DebugLog.e("xinye","==============执行了================");
}