ListView下拉刷新，上拉自动加载更多

下拉刷新，Android中非常普遍的功能。为了方便便重写的ListView来实现下拉刷新，同时添加了上拉自动加载更多的功能。设计最初是参考开源中国的Android客户端源码。先看示例图。

图1 图2

图3 图4

图5 图6

下拉刷新的时动画效果: 图1 ==》图2 ==》图3 ==》图4 ==》图1。

上拉自动加载更多的效果：图5

图6是示例demo的截图

重写后的listview动画效果来源于添加的头部（header）和尾部（footer），listview提供了addHeaderView和 addFooterView方法来添加header和footer。大家也可以通过修改头部、尾部的xml文件来定义自己的动画效果。

实现原理

1.下拉刷新

通过onTouchEvent判断手势，来改变listview的header。header的状态共4种，自己定义为：

NONE（对应图1）：初始状态

PULL（对应图2）：下拉状态，此时松开会还原到状态NONE，并不进行刷新

RELEASE（对应图3）：同样是下拉状态，但此刻松开会执行刷新，进入状态REFRESHING

REFRESHING（对应图4）：正在执行刷新，刷新结束后进入状态NONE。

header在四种状态切换时不仅改变内部组件，同时改变自身的大小。改变内部组件的体现比如，箭头的朝上或者朝下，文字提示的变化，等待圆圈的显示与否。大小的改变其实就是高度的改变，NONE时header高度为0,RELEASE时header的高度由你下拉的程度决定。

2.加载更多

在listview滑动停止后，判断listview的最后一个item是否已经显示，如果显示说明listview已经滑动到了最底部，这时便触发加载更多的方法，方法结束根据结果改变footer。

3.回调方法

在类中定义了两个接口OnRefreshListener和OnLoadListener，用来定义和提供加载数据的方法，具体实现则交给它们的实现类去做。

示例代码

AutoListView.java

package com.example.autolistview.widget;

import com.example.autolistview.R;
import com.example.autolistview.utils.Utils;

import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.LinearInterpolator;
import android.view.animation.RotateAnimation;
import android.widget.AbsListView;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;

/**
 * @author SunnyCoffee
 * @create 2013-10-24
 * @version 1.0
 * @desc 自定义Listview　下拉刷新,上拉加载更多
 */

public class AutoListView extends ListView implements OnScrollListener {

    // 区分当前操作是刷新还是加载
    public static final int REFRESH = 0;
    public static final int LOAD = 1;

    // 区分PULL和RELEASE的距离的大小
    private static final int SPACE = 20;

    // 定义header的四种状态和当前状态
    private static final int NONE = 0;
    private static final int PULL = 1;
    private static final int RELEASE = 2;
    private static final int REFRESHING = 3;
    private int state;

    private LayoutInflater inflater;
    private View header;
    private View footer;
    private TextView tip;
    private TextView lastUpdate;
    private ImageView arrow;
    private ProgressBar refreshing;

    private TextView noData;
    private TextView loadFull;
    private TextView more;
    private ProgressBar loading;

    private RotateAnimation animation;
    private RotateAnimation reverseAnimation;

    private int startY;

    private int firstVisibleItem;
    private int scrollState;
    private int headerContentInitialHeight;
    private int headerContentHeight;

    // 只有在listview第一个item显示的时候（listview滑到了顶部）才进行下拉刷新， 否则此时的下拉只是滑动listview
    private boolean isRecorded;
    private boolean isLoading;// 判断是否正在加载
    private boolean loadEnable = true;// 开启或者关闭加载更多功能
    private boolean isLoadFull;
    private int pageSize = 10;

    private OnRefreshListener onRefreshListener;
    private OnLoadListener onLoadListener;

    public AutoListView(Context context) {
        super(context);
        initView(context);
    }

    public AutoListView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initView(context);
    }

    public AutoListView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        initView(context);
    }

    // 下拉刷新监听
    public void setOnRefreshListener(OnRefreshListener onRefreshListener) {
        this.onRefreshListener = onRefreshListener;
    }

    // 加载更多监听
    public void setOnLoadListener(OnLoadListener onLoadListener) {
        this.loadEnable = true;
        this.onLoadListener = onLoadListener;
    }

    public boolean isLoadEnable() {
        return loadEnable;
    }

    // 这里的开启或者关闭加载更多，并不支持动态调整
    public void setLoadEnable(boolean loadEnable) {
        this.loadEnable = loadEnable;
        this.removeFooterView(footer);
    }

    public int getPageSize() {
        return pageSize;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    // 初始化组件
    private void initView(Context context) {

        // 设置箭头特效
        animation = new RotateAnimation(0, -180,
                RotateAnimation.RELATIVE_TO_SELF, 0.5f,
                RotateAnimation.RELATIVE_TO_SELF, 0.5f);
        animation.setInterpolator(new LinearInterpolator());
        animation.setDuration(100);
        animation.setFillAfter(true);

        reverseAnimation = new RotateAnimation(-180, 0,
                RotateAnimation.RELATIVE_TO_SELF, 0.5f,
                RotateAnimation.RELATIVE_TO_SELF, 0.5f);
        reverseAnimation.setInterpolator(new LinearInterpolator());
        reverseAnimation.setDuration(100);
        reverseAnimation.setFillAfter(true);

        inflater = LayoutInflater.from(context);
        footer = inflater.inflate(R.layout.listview_footer, null);
        loadFull = (TextView) footer.findViewById(R.id.loadFull);
        noData = (TextView) footer.findViewById(R.id.noData);
        more = (TextView) footer.findViewById(R.id.more);
        loading = (ProgressBar) footer.findViewById(R.id.loading);

        header = inflater.inflate(R.layout.pull_to_refresh_header, null);
        arrow = (ImageView) header.findViewById(R.id.arrow);
        tip = (TextView) header.findViewById(R.id.tip);
        lastUpdate = (TextView) header.findViewById(R.id.lastUpdate);
        refreshing = (ProgressBar) header.findViewById(R.id.refreshing);

        // 为listview添加头部和尾部，并进行初始化
        headerContentInitialHeight = header.getPaddingTop();
        measureView(header);
        headerContentHeight = header.getMeasuredHeight();
        topPadding(-headerContentHeight);
        this.addHeaderView(header);
        this.addFooterView(footer);
        this.setOnScrollListener(this);
    }

    public void onRefresh() {
        if (onRefreshListener != null) {
            onRefreshListener.onRefresh();
        }
    }

    public void onLoad() {
        if (onLoadListener != null) {
            onLoadListener.onLoad();
        }
    }

    public void onRefreshComplete(String updateTime) {
        lastUpdate.setText(this.getContext().getString(R.string.lastUpdateTime,
                lastUpdate));
        state = NONE;
        refreshHeaderViewByState();
    }

    // 用于下拉刷新结束后的回调
    public void onRefreshComplete() {
        String currentTime = Utils.getCurrentTime();
        onRefreshComplete(currentTime);
    }

    // 用于加载更多结束后的回调
    public void onLoadComplete() {
        isLoading = false;
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {
        this.firstVisibleItem = firstVisibleItem;
    }

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
        this.scrollState = scrollState;
        ifNeedLoad(view, scrollState);
    }

    // 根据listview滑动的状态判断是否需要加载更多
    private void ifNeedLoad(AbsListView view, int scrollState) {
        if (!loadEnable) {
            return;
        }
        try {
            if (scrollState == OnScrollListener.SCROLL_STATE_IDLE
                    && !isLoading
                    && view.getLastVisiblePosition() == view
                            .getPositionForView(footer) && !isLoadFull) {
                onLoad();
                isLoading = true;
            }
        } catch (Exception e) {
        }
    }

    /**
     * 监听触摸事件，解读手势
     */
    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        switch (ev.getAction()) {
        case MotionEvent.ACTION_DOWN:
            if (firstVisibleItem == 0) {
                isRecorded = true;
                startY = (int) ev.getY();
            }
            break;
        case MotionEvent.ACTION_CANCEL:
        case MotionEvent.ACTION_UP:
            if (state == PULL) {
                state = NONE;
                refreshHeaderViewByState();
            } else if (state == RELEASE) {
                state = REFRESHING;
                refreshHeaderViewByState();
                onRefresh();
            }
            isRecorded = false;
            break;
        case MotionEvent.ACTION_MOVE:
            whenMove(ev);
            break;
        }
        return super.onTouchEvent(ev);
    }

    // 解读手势，刷新header状态
    private void whenMove(MotionEvent ev) {
        if (!isRecorded) {
            return;
        }
        int tmpY = (int) ev.getY();
        int space = tmpY - startY;
        int topPadding = space - headerContentHeight;
        switch (state) {
        case NONE:
            if (space > 0) {
                state = PULL;
                refreshHeaderViewByState();
            }
            break;
        case PULL:
            topPadding(topPadding);
            if (scrollState == SCROLL_STATE_TOUCH_SCROLL
                    && space > headerContentHeight + SPACE) {
                state = RELEASE;
                refreshHeaderViewByState();
            }
            break;
        case RELEASE:
            topPadding(topPadding);
            if (space > 0 && space < headerContentHeight + SPACE) {
                state = PULL;
                refreshHeaderViewByState();
            } else if (space <= 0) {
                state = NONE;
                refreshHeaderViewByState();
            }
            break;
        }

    }

    // 调整header的大小。其实调整的只是距离顶部的高度。
    private void topPadding(int topPadding) {
        header.setPadding(header.getPaddingLeft(), topPadding,
                header.getPaddingRight(), header.getPaddingBottom());
        header.invalidate();
    }

    /**
     * 这个方法是根据结果的大小来决定footer显示的。
     * <p>
     * 这里假定每次请求的条数为10。如果请求到了10条。则认为还有数据。如过结果不足10条，则认为数据已经全部加载，这时footer显示已经全部加载
     * </p>
     * 
     * @param resultSize
     */
    public void setResultSize(int resultSize) {
        if (resultSize == 0) {
            isLoadFull = true;
            loadFull.setVisibility(View.GONE);
            loading.setVisibility(View.GONE);
            more.setVisibility(View.GONE);
            noData.setVisibility(View.VISIBLE);
        } else if (resultSize > 0 && resultSize < pageSize) {
            isLoadFull = true;
            loadFull.setVisibility(View.VISIBLE);
            loading.setVisibility(View.GONE);
            more.setVisibility(View.GONE);
            noData.setVisibility(View.GONE);
        } else if (resultSize == pageSize) {
            isLoadFull = false;
            loadFull.setVisibility(View.GONE);
            loading.setVisibility(View.VISIBLE);
            more.setVisibility(View.VISIBLE);
            noData.setVisibility(View.GONE);
        }

    }

    // 根据当前状态，调整header
    private void refreshHeaderViewByState() {
        switch (state) {
        case NONE:
            topPadding(-headerContentHeight);
            tip.setText(R.string.pull_to_refresh);
            refreshing.setVisibility(View.GONE);
            arrow.clearAnimation();
            arrow.setImageResource(R.drawable.pull_to_refresh_arrow);
            break;
        case PULL:
            arrow.setVisibility(View.VISIBLE);
            tip.setVisibility(View.VISIBLE);
            lastUpdate.setVisibility(View.VISIBLE);
            refreshing.setVisibility(View.GONE);
            tip.setText(R.string.pull_to_refresh);
            arrow.clearAnimation();
            arrow.setAnimation(reverseAnimation);
            break;
        case RELEASE:
            arrow.setVisibility(View.VISIBLE);
            tip.setVisibility(View.VISIBLE);
            lastUpdate.setVisibility(View.VISIBLE);
            refreshing.setVisibility(View.GONE);
            tip.setText(R.string.pull_to_refresh);
            tip.setText(R.string.release_to_refresh);
            arrow.clearAnimation();
            arrow.setAnimation(animation);
            break;
        case REFRESHING:
            topPadding(headerContentInitialHeight);
            refreshing.setVisibility(View.VISIBLE);
            arrow.clearAnimation();
            arrow.setVisibility(View.GONE);
            tip.setVisibility(View.GONE);
            lastUpdate.setVisibility(View.GONE);
            break;
        }
    }

    // 用来计算header大小的。比较隐晦。
    private void measureView(View child) {
        ViewGroup.LayoutParams p = child.getLayoutParams();
        if (p == null) {
            p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                    ViewGroup.LayoutParams.WRAP_CONTENT);
        }
        int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0, p.width);
        int lpHeight = p.height;
        int childHeightSpec;
        if (lpHeight > 0) {
            childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight,
                    MeasureSpec.EXACTLY);
        } else {
            childHeightSpec = MeasureSpec.makeMeasureSpec(0,
                    MeasureSpec.UNSPECIFIED);
        }
        child.measure(childWidthSpec, childHeightSpec);
    }

    /*
     * 定义下拉刷新接口
     */
    public interface OnRefreshListener {
        public void onRefresh();
    }

    /*
     * 定义加载更多接口
     */
    public interface OnLoadListener {
        public void onLoad();
    }

}

这个类的逻辑复杂的地方就是header四种状态的判断和切换。

以下是几种状态的切换情况

NONE ==》 PULL

NONE 《== PULL ==》 RELEASE

PULL 《== RELEASE ==》 REFRESHING

REFRESHING ==》 NONE

代码中对于 RELEASE ==》PULL 状态的切换处理的不太理想，好像是纵坐标的记录方式有问题，如果有谁解决，希望能够留言告知。

为了减少篇幅，其他代码就不在贴了。

注意：定义header的xml最外层必须使用线性布局，不然的话会出错。

测试代码：点击下载（eclipse工程项目，编码UTF-8）。由于代码涉及公司项目，所以提供的demo是自己新写的。如图6所示。

本篇会持续更新。