Android实现ListView下拉刷新和上拉加载更多的思路

import java.text.SimpleDateFormat;
import java.util.Date;

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

/**
 * 自定义ListView，下拉刷新、上拉自动加载更多
 */
public class PullListView extends ListView implements OnScrollListener {

    private final int PULL_DOWN_REFRESH = 0;//下拉状态
    private final int RELEASE_REFRESH = 1;//松开状态
    private final int REFRESHING = 2;//刷新中状态
    private int currentState = PULL_DOWN_REFRESH;
    private int mListViewOnScreenY = -1;//listview的y坐标
    private int downY = -1;//触摸点的y坐标

    private boolean isLoadingMore = false;
    private boolean isEnabledPullDownRefresh = false;
    private boolean isEnabledLoadMore = false;
    private OnPullDownRefresh mOnPullDownRefresh;

    //头布局、脚布局及高度
    private View mFootView;
    private LinearLayout mHeaderView;
    private int mFooterViewHeight;
    private int mPullDownHeaderViewHeight;

    //mHeaderView中组件及动画
    private View mCustomHeaderView;//用户自定义头布局
    private View mPullDownHeader;//下拉刷新头布局
    private RotateAnimation upAnimation,downAnimation;
    private ImageView ivArrow;
    private ProgressBar mProgressBar;
    private TextView tv_statue,tv_time;


    public PullListView(Context context) {
        this(context, null);
    }

    public PullListView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public PullListView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        initPullDownHeaderView();
        initLoadMoreFooterView();
    }

    private void initLoadMoreFooterView() {
        //加载更多的布局文件
        mFootView = View.inflate(getContext(), R.layout.pull_listview_footer,
                null);
        mFootView.measure(0, 0);//测量
        mFooterViewHeight = mFootView.getMeasuredHeight();
        //隐藏脚布局
        mFootView.setPadding(0,-mFooterViewHeight,0,0);
        addFooterView(mFootView);
        setOnScrollListener(this);
    }

    private void initPullDownHeaderView() {
        //下拉刷新的布局文件
        mHeaderView = (LinearLayout) View.inflate(getContext(),
                R.layout.pull_listview_header, null);
        mPullDownHeader = mHeaderView
                .findViewById(R.id.ll_refresh_pull_down_header);
        ivArrow = (ImageView) mHeaderView
                .findViewById(R.id.iv_refresh_header_arrow);
        mProgressBar = (ProgressBar) mHeaderView
                .findViewById(R.id.pb_refresh_header);
        tv_statue = (TextView) mHeaderView
                .findViewById(R.id.tv_refresh_header_status);
        tv_time = (TextView) mHeaderView
                .findViewById(R.id.tv_refresh_header_time);
        mPullDownHeader.measure(0, 0);//测量
        mPullDownHeaderViewHeight = mPullDownHeader.getMeasuredHeight();
        //隐藏头布局
        mPullDownHeader.setPadding(0, -mPullDownHeaderViewHeight, 0, 0);
        addHeaderView(mHeaderView);
        initAnimation();
    }

    /**
     * 添加额外的头布局，比如轮播图
     * @param v 自定义头布局
     */
    public void addListViewCustomHeaderView(View v) {
        mCustomHeaderView = v;
        mHeaderView.addView(mCustomHeaderView);
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                downY = (int) ev.getY();
                break;
            case MotionEvent.ACTION_MOVE:
                if (downY == -1)//-1是初始值
                    downY = (int) ev.getY();
                //是否启用下拉刷新
                if (!isEnabledPullDownRefresh)
                    break;
                if (currentState == REFRESHING)
                    break;
                //解决用户添加header与下拉刷新header的冲突
                if (mCustomHeaderView != null) {
                    int[] location = new int[2];
                    if (mListViewOnScreenY == -1) {
                        this.getLocationOnScreen(location);//获取控件在屏幕的xy坐标 左上角的
                        mListViewOnScreenY = location[1];
                    }
                    mCustomHeaderView.getLocationOnScreen(location);
                    if (location[1] < mListViewOnScreenY) {
                        break;
                    }
                }

                int moveY = (int) ev.getY();
                int diffY = (moveY - downY)/2;//当前的点和上一次的点的距离
                if (diffY > 0 && getFirstVisiblePosition() == 0) {//下拉操作 并且listview第一个item可见
                    int paddingTop = -mPullDownHeaderViewHeight + diffY;//距离顶部的距离
                    if (paddingTop < 0 && currentState != PULL_DOWN_REFRESH) {
                        //当前没有完全显示且当前状态为松开刷新，进入下拉刷新
                        currentState = PULL_DOWN_REFRESH;
                        refreshPullDownState();
                    } else if (paddingTop > 0 && currentState != RELEASE_REFRESH) {
                        //当前完全显示且当前状态为下拉刷新，进入松开刷新
                        currentState = RELEASE_REFRESH;
                        refreshPullDownState();
                    }
                    mPullDownHeader.setPadding(0, paddingTop, 0, 0);
                    return true;
                }else if(diffY < 0 && getLastVisiblePosition() == getCount()-1){//上拉操作 并且最后一个item可见
                    //脚布局可向上滑动
                    mFootView.setPadding(0,0,0,0);
                }
                break;
            case MotionEvent.ACTION_UP:
                downY = -1;
                if (currentState == PULL_DOWN_REFRESH) {
                    //隐藏header
                    mPullDownHeader.setPadding(0, -mPullDownHeaderViewHeight, 0, 0);
                } else if (currentState == RELEASE_REFRESH) {
                    currentState = REFRESHING;
                    refreshPullDownState();
                    mPullDownHeader.setPadding(0, 0, 0, 0);
                    //回调刷新方法
                    if (mOnPullDownRefresh != null) {
                        mOnPullDownRefresh.onPullDownRefresh();
                    }
                }
                break;
        }
        return super.onTouchEvent(ev);
    }

    /**
     * 隐藏头布局或脚布局并重置控件
     */
    public void OnRefreshDataFinish() {
        if (isLoadingMore) {
            isLoadingMore = false;
            mFootView.setPadding(0,-mFooterViewHeight,0,0);
        } else {
            ivArrow.setVisibility(View.VISIBLE);
            mProgressBar.setVisibility(View.INVISIBLE);
            tv_statue.setText("下拉刷新");
            tv_time.setText("最后刷新时间：" + getCurrentTime());
            mPullDownHeader.setPadding(0, -mPullDownHeaderViewHeight, 0, 0);
            currentState = PULL_DOWN_REFRESH;

        }
    }

    private String getCurrentTime() {
        SimpleDateFormat format = new SimpleDateFormat("HH:mm:ss");
        return format.format(new Date());
    }

    private void refreshPullDownState() {
        switch (currentState) {
                case PULL_DOWN_REFRESH:
                    ivArrow.startAnimation(downAnimation);
                    tv_statue.setText("下拉刷新");
                    break;
                case RELEASE_REFRESH:
                    ivArrow.startAnimation(upAnimation);
                    tv_statue.setText("松开刷新");
                    break;
                case REFRESHING:
                    ivArrow.clearAnimation();
                    ivArrow.setVisibility(View.INVISIBLE);
                    mProgressBar.setVisibility(View.VISIBLE);
                    tv_statue.setText("正在刷新");
                    break;
                default:
                break;
        }
    }

    /**
     * 箭头旋转动画
     */
    private void initAnimation() {
        upAnimation = new RotateAnimation(0, -180, Animation.RELATIVE_TO_SELF,
                0.5f, Animation.RELATIVE_TO_SELF, 0.5f);
        upAnimation.setDuration(200);
        upAnimation.setFillAfter(true);

        downAnimation = new RotateAnimation(-180, -360,
                Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF,
                0.5f);
        downAnimation.setDuration(200);
        downAnimation.setFillAfter(true);
    }

    /**
     * 回调方法，用于刷新数据及加载更多
     * @param listener
     */
    public void setOnPullDownRefresh(OnPullDownRefresh listener) {
        this.mOnPullDownRefresh = listener;
    }

    public interface OnPullDownRefresh {
        public void onPullDownRefresh();
        public void onLoadingMore();
    }
    /*
    下拉加载更多通过onScrollStateChanged事件来实现
     */
    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
        if (!isEnabledLoadMore) {
            return;
        }
        //listView停止状态或惯性滑动状态
        if (scrollState == SCROLL_STATE_IDLE
                || scrollState == SCROLL_STATE_FLING) {
            //listView已到达最底部
            if ((getLastVisiblePosition() == getCount() - 1) && !isLoadingMore) {
                isLoadingMore = true;
                //展示脚布局
                mFootView.setPadding(0, 0, 0, 0);
                setSelection(getCount());
                if (mOnPullDownRefresh != null) {
                    mOnPullDownRefresh.onLoadingMore();
                }
            }
        }
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
                         int visibleItemCount, int totalItemCount) {

    }

    /**
     * 是否启用下拉刷新
     * @param isEnable
     */
    public void setEnabledPullDownRefresh(boolean isEnable) {
        isEnabledPullDownRefresh = isEnable;
    }

    /**
     * 是否启用加载更多
     * @param isEnable
     */
    public void setEnabledLoadMore(boolean isEnable) {
        isEnabledLoadMore = isEnable;
    }
}