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2013年6月11日 星期二

*Android App***列表之下拉刷新 *^~!

*Android App**
*列表之下拉刷新 *^~!

*Android的ListView是应用 
最广的一个组件,功能强大,
扩展性灵活(不局限于ListView
本身一个类),前面的文章有
介绍分组,拖拽,3D立体, 
游标,圆角,而今天我们要 
介绍的是另外一个扩展 
ListView:下拉刷新的ListView。
  

  下拉刷新界面最初流行
于iphone应用界面,如图:
    然后在Android中也逐渐被应用,比如微博
,资讯类。
   所以,今天要实现的结果应该也是类似的,

先贴出最终完成效果,如下图,接下来我们一
步一步实现 *
*
*1. 流程分析
    下拉刷新最主要的流程是:
    (1). 下拉,显示提示头部界面(HeaderView),
这个过程提示用户"下拉刷新"
    (2). 下拉到一定程度,超出了刷新最基本的
下拉界限,我们认为达到了刷新的条件,提示
用户可以"松手刷新"了,效果上允许用户继续
下拉 
    (3). 用户松手,可能用户下拉远远不止提示
头部界面,所以这一步,先反弹回仅显示提示
头部界面,然后提示用户"正在加载"。
    (4). 加载完成后,隐藏提示头部界面。
    示意图如下:*
*
->->
2. 实现分析
    当前我们要实现上述流程,是基于
ListView的,所以对应ListView本身的功能
我们来分析一下实现原理:
    (1). 下拉,显示提示头部界面,这个过程
提示用户"下拉刷新"
        a. 下拉的操作,首先是监听滚动,
ListView提供了onScroll()方法
        b. 与下拉类似一个动作向下飞滑,所以
ListView的scrollState有种值:SCROLL_STATE_IDLE, SCROLL_STATE_
TOUCH_SCROLL, SCROLL_STATE_FLING,
意思容易理解,而我们要下拉的触发条件是SCROLL_STATE_TOUCH_SCROLL。
判断当前的下拉操作状态,ListView提供了
public void onScrollStateChanged
(AbsListView view, int scrollState) {}。
    c. 下拉的过程中,我们可能还需要下拉
到多少的边界值处理,重写onTouchEvent
(MotionEvent ev){}方法,可依
据ACTION_DOWN,ACTION_MOVE,
ACTION_UP实现更精细的判断。
    (2). 下拉到一定程度,超出了刷新最基本
的下拉界限,我们认为达到了刷新的条件,
提示用户可以"松手刷新"了,效果上允
许用户继续下拉
        a. 达到下拉刷新界限,一般指达
到header的高度的,所以有两步,第一,
获取header的高度,第二,
当header.getBottom()>=header的高度时,
我们认为就达到了刷新界限值
        b. 继续允许用户下拉,当header完全
下拉后,默认无法继续下拉,但是可以增加
header的PaddingTop实现这种效果  
    (3). 用户松手,可能用户下拉远远不止提示
头部界面,所以这一步,先反弹回仅显示提示
头部界面,然后提示用户"正在加载"。
        a. 松手后反弹,这个不能一下子弹回去
,看上去太突然,需要一步一步柔性的弹回
去,像弹簧一样,我们可以new一个Thread循
环计算减少PaddingTop,直到PaddingTop为0,
反弹结束。
        b. 正在加载,在子线程里处理后台任务
    (4). 加载完成后,隐藏提示头部界面。
        a. 后台任务完成后,我们需要隐
藏header,setSelection(1)即实现了从第2项
开始显示,间接隐藏了header。
上面我们分析了实现过程的轮廓,接下来,
通过细节说明和代码具体实现。*

*
3. 初始化
    一切状态显示都是用HeaderView显示的,
所以我们需要一个HeaderView的layout,
使用addHeaderView方法添加到ListView中。
    同时,默认状态下,HeaderView是不显示的,
只是在下拉后才显示,所以我们需要隐藏HeaderView且---
---不影响后续的下拉显示,用setSelection(1)。
    refresh_list_header.xml布局如下:
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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center">
    <ProgressBar android:id="@+id/refresh_list_header_progressbar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        style="?android:attr/progressBarStyleSmall"
        android:visibility="gone">
    </ProgressBar>
    <ImageView android:id="@+id/refresh_list_header_pull_down"
        android:layout_width="9dip"
        android:layout_height="25dip"
        android:layout_gravity="center"
        android:src="@drawable/refresh_list_pull_down" />
    <ImageView android:id="@+id/refresh_list_header_release_up"
        android:layout_width="9dip"
        android:layout_height="25dip"
        android:layout_gravity="center"
        android:src="@drawable/refresh_list_release_up"
        android:visibility="gone" />
    <RelativeLayout android:layout_width="180dip"
        android:layout_height="wrap_content">
        <TextView android:id="@+id/refresh_list_header_text"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:layout_alignParentTop="true"
            android:textSize="12dip"
            android:textColor="#192F06"
            android:paddingTop="8dip"
            android:text="@string/app_list_header_refresh_down"/>
        <TextView android:id="@+id/refresh_list_header_last_update"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:layout_below="@id/refresh_list_header_text"
            android:textSize="12dip"
            android:textColor="#192F06"
            android:paddingBottom="8dip"
            android:text="@string/app_list_header_refresh_last_update"/>
    </RelativeLayout>
</LinearLayout>
    代码中在构造函数中添加init()方法加载如下:
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private LinearLayout mHeaderLinearLayout = null;
private TextView mHeaderTextView = null;
private TextView mHeaderUpdateText = null;
private ImageView mHeaderPullDownImageView = null;
private ImageView mHeaderReleaseDownImageView = null;
private ProgressBar mHeaderProgressBar = null;
public RefreshListView(Context context) {
    this(context, null);
}
public RefreshListView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init(context);
}
void init(final Context context) {
   mHeaderLinearLayout = (LinearLayout) LayoutInflater.
from(context).inflate(R.layout.refresh_list_header, null);
    addHeaderView(mHeaderLinearLayout);
    mHeaderTextView = (TextView) findViewById(R.id.refresh_
list_header_text);
    mHeaderUpdateText = (TextView) findViewById(R.id.refresh_
list_header_last_update);
    mHeaderPullDownImageView = (ImageView) findViewById(R.id.refresh_list_header_pull_down);
    mHeaderReleaseDownImageView = (ImageView) findViewById(R.id.refresh_list_header_release_up);
    mHeaderProgressBar = (ProgressBar) findViewById(R.id.refresh_
list_header_progressbar);
    setSelection(1);
}
    默认就显示完成了。*

*4. HeaderView的默认高度测量
    因为下拉到HeaderView全部显示出来,
就由提示"下拉刷新"变为"松手刷新",全部显示
的出来的测量标准
就是header.getBottom()>=header的高度。
    所以,首先我们需要测量HeaderView的
默认高度。
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//因为是在构造函数里测量高度,应该先measure一下
private void measureView(View child) {
    ViewGroup.LayoutParams p = child.getLayoutParams();
    if (p == null) {
        p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_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);
}
    然后在init的上述代码后面加上调用measureView后,
使用getMeasureHeight()方法获取header的高度:
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private int mHeaderHeight;
void init(final Context context) {
    ... ...
    measureView(mHeaderLinearLayout);
    mHeaderHeight = mHeaderLinearLayout.getMeasuredHeight();
}
*
*5. scrollState监听记录
    scrollState有3种,使用onScrollStateChanged() 方法监听记录。
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private int mCurrentScrollState;
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {  
    mCurrentScrollState = scrollState;
}
    然后即可使用mCurrentScrollState作为后面
判断的条件了。
6. 刷新状态分析
    因为一些地方需要知道我们处在正常状态
下还是进入下拉刷新状态还是松手反弹状态,
比如,
    (1). 在非正常的状态下,我们不小心飞滑了
一下(松手的瞬间容易出现这种情况),我们不能
setSelection(1)的,否则总是松手后header跳的
一下消失掉了。
    (2). 下拉后要做一个下拉效果的特殊处理,
需要用到OVER_PULL_REFRESH
(松手刷新状态下)
    (3). 松手反弹后要做一个反弹效果的特殊处理
,需要用到OVER_PULL_REFRESH和ENTER_PULL_REFRESH。
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private final static int NONE_PULL_REFRESH = 0;   //正常状态
private final static int ENTER_PULL_REFRESH = 1//进入下拉刷新状态
private final static int OVER_PULL_REFRESH = 2;   //进入松手刷新状态
private final static int EXIT_PULL_REFRESH = 3;     //松手后反弹后加载状态
private int mPullRefreshState = 0;                         //记录刷新状态
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
 int visibleItemCount, int totalItemCount) {
    if (mCurrentScrollState ==SCROLL_STATE_TOUCH_SCROLL
            && firstVisibleItem == 0
            && (mHeaderLinearLayout.getBottom() >=
 0 && mHeaderLinearLayout.getBottom() < mHeaderHeight)) {
        //进入且仅进入下拉刷新状态
        if (mPullRefreshState == NONE_PULL_REFRESH) {
            mPullRefreshState = ENTER_PULL_REFRESH;
        }
    } else if (mCurrentScrollState ==SCROLL_STATE_TOUCH_SCROLL
            && firstVisibleItem == 0
            && (mHeaderLinearLayout.getBottom() >=
 mHeaderHeight)) {
        //下拉达到界限,进入松手刷新状态
        if (mPullRefreshState ==
 ENTER_PULL_REFRESH || mPullRefreshState == NONE_PULL_REFRESH) {
            mPullRefreshState = OVER_PULL_REFRESH;
            //下面是进入松手刷新状态需要做的一个显示改变
            mDownY = mMoveY;//用于后面的下拉特殊效果
            mHeaderTextView.setText("松手刷新");
            mHeaderPullDownImageView.setVisibility(View.GONE);
            mHeaderReleaseDownImageView.setVisibility
(View.VISIBLE);
        }
    } else if (mCurrentScrollState ==SCROLL_STATE_TOUCH_SCROLL
 && firstVisibleItem != 0) {
        //不刷新了
        if (mPullRefreshState == ENTER_PULL_REFRESH) {
            mPullRefreshState = NONE_PULL_REFRESH;
        }
    } else if (mCurrentScrollState == SCROLL_STATE_FLING &&
 firstVisibleItem == 0) {
        //飞滑状态,不能显示出header,也不能影响正常的飞滑
        //只在正常情况下才纠正位置
        if (mPullRefreshState == NONE_PULL_REFRESH) {
            setSelection(1);
        }
    }
}
  
mPullRefreshState将是后面我们处理边界的重要变量。
6. 下拉效果的特殊处理
    所谓的特殊处理,当header完全显示后,
下拉只按下拉1/3的距离下拉,给用户一种艰难下拉,该松手的弹簧感觉。
    这个在onTouchEvent里处理比较方便:
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private float mDownY;
private float mMoveY;
@Override
public boolean onTouchEvent(MotionEvent ev) {
    switch (ev.getAction()) {
        case MotionEvent.ACTION_DOWN:
            //记下按下位置
            //改变
            mDownY = ev.getY();
            break;
        case MotionEvent.ACTION_MOVE:
            //移动时手指的位置
            mMoveY = ev.getY();
            if (mPullRefreshState == OVER_PULL_REFRESH) {
                //注意下面的mDownY在onScroll的第二个else中被改变了
                mHeaderLinearLayout.
setPadding(mHeaderLinearLayout.getPaddingLeft(),
                        (int)((mMoveY - mDownY)/3), //1/3距离折扣
                        mHeaderLinearLayout.getPaddingRight(),
                        mHeaderLinearLayout.getPaddingBottom());
            }
            break;
        case MotionEvent.ACTION_UP:
            ... ...
            break;
    }
    return super.onTouchEvent(ev);
}
//重复贴出下面这段需要注意的代码
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
 int visibleItemCount, int totalItemCount) {
    ... ...
    else if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL
            && firstVisibleItem == 0
            && (mHeaderLinearLayout.getBottom() >=
 mHeaderHeight)) {
        //下拉达到界限,进入松手刷新状态
        if (mPullRefreshState ==
 ENTER_PULL_REFRESH || mPullRefreshState == NONE_PULL_REFRESH) {  
            mPullRefreshState = OVER_PULL_REFRESH;
            mDownY = mMoveY; //为下拉1/3折扣效果记录开始位置
            mHeaderTextView.setText
("松手刷新");//显示松手刷新
            mHeaderPullDownImageView.setVisibility
(View.GONE);//隐藏"下拉刷新"
            mHeaderReleaseDownImageView.setVisibility
  (View.VISIBLE);//显示向上的箭头
        }
    }
    ... ... }
  onScroll里监听到了进入松手刷新状态,
onTouchEvent就开始在ACTION_MOVE中
处理1/3折扣问题。*

*7. 反弹效果的特殊处理
    松手后我们需要一个柔性的反弹效果,
意味着我们弹回去的过程需要分一步步走,
我的解决方案是:
    在子线程里计算PaddingTop,并减少到
原来的3/4,循环通知主线程,
直到PaddingTop小于1(这个值取一个小值,
合适即可)。
    松手后,当然是在onTouchEvent的ACTION_
UP条件下处理比较方便:
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//因为涉及到handler数据处理,为方便我们定义如下常量
private final static int REFRESH_BACKING = 0;      //反弹中
private final static int REFRESH_BACED = 1;        //达到刷新界限,
反弹结束后
private final static int REFRESH_RETURN = 2;       //没有达到刷新
界限,返回
private final static int REFRESH_DONE = 3;         //加载数据结束
@Override
public boolean onTouchEvent(MotionEvent ev) {
    switch (ev.getAction()) {
        ... ...
        case MotionEvent.ACTION_UP:
            //when you action up, it will do these:
            //1. roll back util header topPadding is 0
            //2. hide the header by setSelection(1)
            if (mPullRefreshState == OVER_PULL_REFRESH ||
 mPullRefreshState == ENTER_PULL_REFRESH) {
                new Thread() {
                    public void run() {
                        Message msg;
                        while(mHeaderLinearLayout.getPaddingTop() > 1) {
                            msg = mHandler.obtainMessage();
                            msg.what = REFRESH_BACKING;
                            mHandler.sendMessage(msg);
                            try {
                                sleep(5);//慢一点反弹,
别一下子就弹回去了
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                        msg = mHandler.obtainMessage();
                        if (mPullRefreshState == OVER_PULL_REFRESH) {
                            msg.what = REFRESH_BACED;//
加载数据完成,结束返回
                        } else {
                            msg.what = REFRESH_RETURN;//
未达到刷新界限,直接返回
                        }
                        mHandler.sendMessage(msg);
                    };
                }.start();
            }
            break;
    }
    return super.onTouchEvent(ev);
}
private Handler mHandler = new Handler(){
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
        case REFRESH_BACKING:
            mHeaderLinearLayout.setPadding
(mHeaderLinearLayout.getPaddingLeft(),
                    (int) (mHeaderLinearLayout.
getPaddingTop()*0.75f),
                    mHeaderLinearLayout.getPaddingRight(),
                    mHeaderLinearLayout.getPaddingBottom());
            break;
        case REFRESH_BACED:
            mHeaderTextView.setText("正在加载...");
            mHeaderProgressBar.setVisibility(View.VISIBLE);
            mHeaderPullDownImageView.setVisibility(View.GONE);
            mHeaderReleaseDownImageView.setVisibility(View.GONE);
            mPullRefreshState = EXIT_PULL_REFRESH;
            new Thread() {
                public void run() {
                    sleep(2000);//处理后台加载数据
                    Message msg = mHandler.obtainMessage();
                    msg.what = REFRESH_DONE;
                    //通知主线程加载数据完成
                    mHandler.sendMessage(msg);
                };
            }.start();
            break;
        case REFRESH_RETURN:
            //未达到刷新界限,返回
            mHeaderTextView.setText("下拉刷新");
            mHeaderProgressBar.setVisibility(View.INVISIBLE);
            mHeaderPullDownImageView.setVisibility(View.VISIBLE);
            mHeaderReleaseDownImageView.setVisibility(View.GONE);
            mHeaderLinearLayout.setPadding(mHeaderLinearLayout.
getPaddingLeft(),
                    0,
                    mHeaderLinearLayout.getPaddingRight(),
                    mHeaderLinearLayout.getPaddingBottom());
            mPullRefreshState = NONE_PULL_REFRESH;
            setSelection(1);
            break;
        case REFRESH_DONE:
            //刷新结束后,恢复原始默认状态
            mHeaderTextView.setText("下拉刷新");
            mHeaderProgressBar.setVisibility(View.INVISIBLE);
            mHeaderPullDownImageView.setVisibility(View.VISIBLE);
            mHeaderReleaseDownImageView.setVisibility(View.GONE);
            mHeaderUpdateText.setText(getContext().getString(R.string.app_list_header_refresh_last_update, 
                    mSimpleDateFormat.format(new Date())));
            mHeaderLinearLayout.setPadding
(mHeaderLinearLayout.getPaddingLeft(),
                    0,
                    mHeaderLinearLayout.getPaddingRight(),
                    mHeaderLinearLayout.getPaddingBottom());
            mPullRefreshState = NONE_PULL_REFRESH;
            setSelection(1);
            break;
        default:
            break;
        }
    }
};
   
为了一下子看的明确,我把效果中的数据
处理代码也贴出来了。*

*
8. 切入数据加载过程
    上面数据后台处理我们用sleep(2000)来处理,实际处理中,
作为公共组件,我们也不好把具体代码直接写在这里,
我们需要一个更灵活的分离:
    (1). 定义接口
    (2). 注入接口
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//定义接口
public interface RefreshListener {
    Object refreshing();                //加载数据
    void refreshed(Object obj);    //外部可扩展加载完成后的操作
}
//注入接口
private Object mRefreshObject = null; //传值
private RefreshListener mRefreshListener = null;
public void setOnRefreshListener(RefreshListener refreshListener) {
    this.mRefreshListener = refreshListener;
}
//我们需要重写上面的mHandler如下代码
case REFRESH_BACED:
    ... ...
    new Thread() {
        public void run() {
            if (mRefreshListener != null) {
                mRefreshObject = mRefreshListener.refreshing();
            }
            Message msg = mHandler.obtainMessage();
            msg.what = REFRESH_DONE;
            mHandler.sendMessage(msg);
        };
    }.start();
    break;
case REFRESH_DONE:
    ... ...
    mPullRefreshState = NONE_PULL_REFRESH;
    setSelection(1);
    if (mRefreshListener != null) {
        mRefreshListener.refreshed(mRefreshObject);
    }
    break;
    在其他地方我们就可以不修改这个listview组件的代码,使用如下:
?
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public xxx implements RefreshListener{
  
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //类似如下
        ((RefreshListView) listView).setOnRefreshListener(this);
    }
  
    @Override
    public Object refreshing() {
        String result = null;
        //result = FileUtils.readTextFile(file);
        return result;
    }
  
    @Override
    public void refreshed(Object obj) {
        if (obj != null) {
           //扩展操作
        }
    };
}
  很方便了。*

*9. 扩展"更多"功能
    下拉刷新之外,我们也可以通过相同
方法使用FooterView切入底部"更多"过程,
这里我就不详细说明了
10. 源码
    上面的每段代码都看做是"零部件",需要
组合一下。
    因为我们上面实现了下拉刷新,还增加
了"更多"功能,我们直接命名这个类为
RefreshListView吧:
?
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package com.tianxia.lib.baseworld.widget;
  
import java.text.SimpleDateFormat;
import java.util.Date;
  
import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;
  
import com.tianxia.lib.baseworld.R;
  
/**
 * 下拉刷新,底部更多
 *
 */
public class RefreshListView extends ListView
implements OnScrollListener{
  
    private float mDownY;
    private float mMoveY;
  
    private int mHeaderHeight;
  
    private int mCurrentScrollState;
  
    private final static int NONE_PULL_REFRESH = 0;   
//正常状态
    private final static int ENTER_PULL_REFRESH = 1;  
//进入下拉刷新状态
    private final static int OVER_PULL_REFRESH = 2;   
//进入松手刷新状态
    private final static int EXIT_PULL_REFRESH = 3;   
//松手后反弹和加载状态
    private int mPullRefreshState = 0;                
 //记录刷新状态
  
    private final static int REFRESH_BACKING = 0;     
//反弹中
    private final static int REFRESH_BACED = 1;       
//达到刷新界限,反弹结束后
    private final static int REFRESH_RETURN = 2;      
 //没有达到刷新界限,返回
    private final static int REFRESH_DONE = 3;        
//加载数据结束
  
    private LinearLayout mHeaderLinearLayout = null;
    private LinearLayout mFooterLinearLayout = null;
    private TextView mHeaderTextView = null;
    private TextView mHeaderUpdateText = null;
    private ImageView mHeaderPullDownImageView = null;
    private ImageView mHeaderReleaseDownImageView = null;
    private ProgressBar mHeaderProgressBar = null;
    private TextView mFooterTextView = null;
    private ProgressBar mFooterProgressBar = null;
  
    private SimpleDateFormat mSimpleDateFormat;
  
    private Object mRefreshObject = null;
    private RefreshListener mRefreshListener = null;
    public void setOnRefreshListener
(RefreshListener refreshListener) {
        this.mRefreshListener = refreshListener;
    }
  
    public RefreshListView(Context context) {
        this(context, null);
    }
  
    public RefreshListView(Context context,
 AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }
  
    void init(final Context context) {
        mHeaderLinearLayout = (LinearLayout)
 LayoutInflater.from(context).inflate(R.layout.
refresh_list_header, null);
        addHeaderView(mHeaderLinearLayout);
        mHeaderTextView = (TextView) findViewById
(R.id.refresh_list_header_text);
        mHeaderUpdateText = (TextView) findViewById(R.id.refresh_list_header_last_update);
        mHeaderPullDownImageView = (ImageView) findViewById(R.id.refresh_list_header_pull_down);
        mHeaderReleaseDownImageView = (ImageView) findViewById(R.id.refresh_list_header_release_up);
        mHeaderProgressBar = (ProgressBar) findViewById(R.id.refresh_list_header_progressbar);
  
        mFooterLinearLayout = (LinearLayout)
 LayoutInflater.from(context).inflate(R.layout.
refresh_list_footer, null);
        addFooterView(mFooterLinearLayout);
        mFooterProgressBar = (ProgressBar) findViewById(R.id.refresh_list_footer_progressbar);
        mFooterTextView = (TextView)
 mFooterLinearLayout.findViewById(R.id.refresh_list_footer_text);
        mFooterLinearLayout.setOnClickListener
(new OnClickListener() {
            @Override
            public void onClick(View v) {
                if (context.getString(R.string.
app_list_footer_more).equals(mFooterTextView.getText())) {
                    mFooterTextView.setText
(R.string.app_list_footer_loading);
                    mFooterProgressBar.setVisibility(View.VISIBLE);
                    if (mRefreshListener != null) {
                        mRefreshListener.more();
                    }
                }
            }
        });
  
        setSelection(1);
        setOnScrollListener(this);
        measureView(mHeaderLinearLayout);
        mHeaderHeight = mHeaderLinearLayout.getMeasuredHeight();
  
        mSimpleDateFormat = new SimpleDateFormat
("yyyy-MM-dd hh:mm");
        mHeaderUpdateText.setText(context.getString(R.string.app_list_header_refresh_last_update,
 mSimpleDateFormat.format(new Date())));
    }
  
    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mDownY = ev.getY();
                break;
            case MotionEvent.ACTION_MOVE:
                mMoveY = ev.getY();
                if (mPullRefreshState == OVER_PULL_REFRESH) {
                    mHeaderLinearLayout.setPadding
(mHeaderLinearLayout.getPaddingLeft(),
                            (int)((mMoveY - mDownY)/3),
                            mHeaderLinearLayout.getPaddingRight(),
                            mHeaderLinearLayout.getPaddingBottom());
                }
                break;
            case MotionEvent.ACTION_UP:
                //when you action up, it will do these:
                //1. roll back util header topPadding is 0
                //2. hide the header by setSelection(1)
                if (mPullRefreshState == OVER_PULL_REFRESH ||
 mPullRefreshState == ENTER_PULL_REFRESH) {
                    new Thread() {
                        public void run() {
                            Message msg;
                            while(mHeaderLinearLayout.
getPaddingTop() > 1) {
                                msg = mHandler.obtainMessage();
                                msg.what = REFRESH_BACKING;
                                mHandler.sendMessage(msg);
                                try {
                                    sleep(5);
                                } catch
(InterruptedException e) {
                                    e.printStackTrace();
                                }
                            }
                            msg = mHandler.obtainMessage();
                            if (mPullRefreshState ==
 OVER_PULL_REFRESH) {
                                msg.what = REFRESH_BACED;
                            } else {
                                msg.what = REFRESH_RETURN;
                            }
                            mHandler.sendMessage(msg);
                        };
                    }.start();
                }
                break;
        }
        return super.onTouchEvent(ev);
    }
  
    @Override
    public void onScroll(AbsListView view,
 int firstVisibleItem, int visibleItemCount, int totalItemCount) {
        if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL
                && firstVisibleItem == 0
                && (mHeaderLinearLayout.getBottom() >=
 0 && mHeaderLinearLayout.getBottom() < mHeaderHeight)) {
            //进入且仅进入下拉刷新状态
            if (mPullRefreshState == NONE_PULL_REFRESH) {
                mPullRefreshState = ENTER_PULL_REFRESH;
            }
        } else if (mCurrentScrollState ==
 SCROLL_STATE_TOUCH_SCROLL
                && firstVisibleItem == 0
                && (mHeaderLinearLayout.getBottom() >=
 mHeaderHeight)) {
            //下拉达到界限,进入松手刷新状态
            if (mPullRefreshState ==
 ENTER_PULL_REFRESH || mPullRefreshState == NONE_PULL_REFRESH) {
                mPullRefreshState = OVER_PULL_REFRESH;
                mDownY = mMoveY; //为下拉1/3折扣效果记录开始位置
                mHeaderTextView.setText("松手刷新");//显示松手刷新
                mHeaderPullDownImageView.setVisibility
(View.GONE);//隐藏"下拉刷新"
                mHeaderReleaseDownImageView.setVisibility
(View.VISIBLE);//显示向上的箭头
            }
        } else if (mCurrentScrollState ==
 SCROLL_STATE_TOUCH_SCROLL && firstVisibleItem != 0) {
            //不刷新了
            if (mPullRefreshState == ENTER_PULL_REFRESH) {
                mPullRefreshState = NONE_PULL_REFRESH;
            }
        } else if (mCurrentScrollState ==
 SCROLL_STATE_FLING && firstVisibleItem == 0) {
            //飞滑状态,不能显示出header,也不能影响正常的飞滑
            //只在正常情况下才纠正位置
            if (mPullRefreshState == NONE_PULL_REFRESH) {
                setSelection(1);
            }
        }
    }
  
    @Override
    public void onScrollStateChanged
(AbsListView view, int scrollState) {
        mCurrentScrollState = scrollState;
    }
  
    @Override
    public void setAdapter(ListAdapter adapter) {
        super.setAdapter(adapter);
        setSelection(1);
    }
  
    private void measureView(View child) {
        ViewGroup.LayoutParams p = child.getLayoutParams();
        if (p == null) {
            p = new ViewGroup.LayoutParams
(ViewGroup.LayoutParams.FILL_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);
    }
  
    private Handler mHandler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
            case REFRESH_BACKING:
                mHeaderLinearLayout.setPadding
(mHeaderLinearLayout.getPaddingLeft(),
                        (int) (mHeaderLinearLayout.
getPaddingTop()*0.75f),
                        mHeaderLinearLayout.getPaddingRight(),
                        mHeaderLinearLayout.getPaddingBottom());
                break;
            case REFRESH_BACED:
                mHeaderTextView.setText("正在加载...");
                mHeaderProgressBar.setVisibility(View.VISIBLE);
                mHeaderPullDownImageView.setVisibility(View.GONE);
                mHeaderReleaseDownImageView.setVisibility(View.GONE);
                mPullRefreshState = EXIT_PULL_REFRESH;
                new Thread() {
                    public void run() {
                        if (mRefreshListener != null) {
                            mRefreshObject =
 mRefreshListener.refreshing();
                        }
                        Message msg = mHandler.obtainMessage();
                        msg.what = REFRESH_DONE;
                        mHandler.sendMessage(msg);
                    };
                }.start();
                break;
            case REFRESH_RETURN:
                mHeaderTextView.setText("下拉刷新");
                mHeaderProgressBar.setVisibility(View.INVISIBLE);
                mHeaderPullDownImageView.setVisibility(View.VISIBLE);
                mHeaderReleaseDownImageView.setVisibility(View.GONE);
                mHeaderLinearLayout.setPadding
(mHeaderLinearLayout.getPaddingLeft(),
                        0,
                        mHeaderLinearLayout.getPaddingRight(),
                        mHeaderLinearLayout.getPaddingBottom());
                mPullRefreshState = NONE_PULL_REFRESH;
                setSelection(1);
                break;
            case REFRESH_DONE:
                mHeaderTextView.setText("下拉刷新");
                mHeaderProgressBar.setVisibility(View.INVISIBLE);
                mHeaderPullDownImageView.setVisibility(View.VISIBLE);
                mHeaderReleaseDownImageView.setVisibility(View.GONE);
                mHeaderUpdateText.setText(getContext().getString(R.string.app_list_header_refresh_last_update,
                        mSimpleDateFormat.format(new Date())));
                mHeaderLinearLayout.setPadding
(mHeaderLinearLayout.getPaddingLeft(),
                        0,
                        mHeaderLinearLayout.getPaddingRight(),
                        mHeaderLinearLayout.getPaddingBottom());
                mPullRefreshState = NONE_PULL_REFRESH;
                setSelection(1);
                if (mRefreshListener != null) {
                    mRefreshListener.refreshed(mRefreshObject);
                }
                break;
            default:
                break;
            }
        }
    };
    public interface RefreshListener {
        Object refreshing();
        void refreshed(Object obj);
        void more();
    }
  
    public void finishFootView() {
        mFooterProgressBar.setVisibility(View.GONE);
        mFooterTextView.setText(R.string.app_list_footer_more);
    }
  
    public void addFootView() {
        if (getFooterViewsCount() == 0) {
            addFooterView(mFooterLinearLayout);
        }
    }
  
    public void removeFootView() {
        removeFooterView(mFooterLinearLayout);
    }
}
**
&这个只是一个原型,无论代码风格和逻辑处理&
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&7
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

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