Android筆記之:App列表之下拉刷新的使用

更新時(shí)間：2013年04月28日 10:30:46 作者：

本篇文章介紹了，在Android中App列表之下拉刷新的使用。需要的朋友參考下

Android的ListView是應(yīng)用最廣的一個(gè)組件，功能強(qiáng)大，擴(kuò)展性靈活(不局限于ListView本身一個(gè)類)，前面的文章有介紹分組，拖拽，3D立體，游標(biāo)，圓角，而今天我們要介紹的是另外一個(gè)擴(kuò)展ListView：下拉刷新的ListView。
下拉刷新界面最初流行于iphone應(yīng)用界面，如圖：

然后在Android中也逐漸被應(yīng)用，比如微博，資訊類。
所以，今天要實(shí)現(xiàn)的結(jié)果應(yīng)該也是類似的，先貼出最終完成效果,如下圖，接下來我們一步一步實(shí)現(xiàn)。

1. 流程分析
下拉刷新最主要的流程是：
(1). 下拉，顯示提示頭部界面(HeaderView)，這個(gè)過程提示用戶"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，我們認(rèn)為達(dá)到了刷新的條件，提示用戶可以"松手刷新"了，效果上允許用戶繼續(xù)下拉
(3). 用戶松手，可能用戶下拉遠(yuǎn)遠(yuǎn)不止提示頭部界面，所以這一步，先反彈回僅顯示提示頭部界面，然后提示用戶"正在加載"。
(4). 加載完成后，隱藏提示頭部界面。
示意圖如下：

->->

2. 實(shí)現(xiàn)分析
當(dāng)前我們要實(shí)現(xiàn)上述流程，是基于ListView的，所以對(duì)應(yīng)ListView本身的功能我們來分析一下實(shí)現(xiàn)原理：
(1). 下拉，顯示提示頭部界面，這個(gè)過程提示用戶"下拉刷新"
a. 下拉的操作，首先是監(jiān)聽滾動(dòng)，ListView提供了onScroll()方法
b. 與下拉類似一個(gè)動(dòng)作向下飛滑，所以ListView的scrollState有3種值:SCROLL_STATE_IDLE, SCROLL_STATE_TOUCH_SCROLL, SCROLL_STATE_FLING,意思容易理解，而我們要下拉的觸發(fā)條件是SCROLL_STATE_TOUCH_SCROLL。判斷當(dāng)前的下拉操作狀態(tài)，ListView提供了public void onScrollStateChanged(AbsListView view, int scrollState) {}。
c. 下拉的過程中，我們可能還需要下拉到多少的邊界值處理，重寫onTouchEvent(MotionEvent ev){}方法，可依據(jù)ACTION_DOWN，ACTION_MOVE，ACTION_UP實(shí)現(xiàn)更精細(xì)的判斷。
(2). 下拉到一定程度，超出了刷新最基本的下拉界限，我們認(rèn)為達(dá)到了刷新的條件，提示用戶可以"松手刷新"了，效果上允許用戶繼續(xù)下拉
a. 達(dá)到下拉刷新界限，一般指達(dá)到header的高度的，所以有兩步，第一，獲取header的高度，第二，當(dāng)header.getBottom()>=header的高度時(shí)，我們認(rèn)為就達(dá)到了刷新界限值
b. 繼續(xù)允許用戶下拉，當(dāng)header完全下拉后，默認(rèn)無法繼續(xù)下拉，但是可以增加header的PaddingTop實(shí)現(xiàn)這種效果
(3). 用戶松手，可能用戶下拉遠(yuǎn)遠(yuǎn)不止提示頭部界面，所以這一步，先反彈回僅顯示提示頭部界面，然后提示用戶"正在加載"。
a. 松手后反彈，這個(gè)不能一下子彈回去，看上去太突然，需要一步一步柔性的彈回去，像彈簧一樣，我們可以new一個(gè)Thread循環(huán)計(jì)算減少PaddingTop，直到PaddingTop為0，反彈結(jié)束。
b. 正在加載，在子線程里處理后臺(tái)任務(wù)
(4). 加載完成后，隱藏提示頭部界面。
a. 后臺(tái)任務(wù)完成后，我們需要隱藏header,setSelection(1)即實(shí)現(xiàn)了從第2項(xiàng)開始顯示，間接隱藏了header。
上面我們分析了實(shí)現(xiàn)過程的輪廓，接下來，通過細(xì)節(jié)說明和代碼具體實(shí)現(xiàn)。

3. 初始化
一切狀態(tài)顯示都是用HeaderView顯示的，所以我們需要一個(gè)HeaderView的layout，使用addHeaderView方法添加到ListView中。
同時(shí)，默認(rèn)狀態(tài)下，HeaderView是不顯示的，只是在下拉后才顯示，所以我們需要隱藏HeaderView且不影響后續(xù)的下拉顯示，用setSelection(1)。
refresh_list_header.xml布局如下:

復(fù)制代碼代碼如下:

<?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>    

代碼中在構(gòu)造函數(shù)中添加init()方法加載如下:

復(fù)制代碼代碼如下:

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);
}

默認(rèn)就顯示完成了。

4. HeaderView的默認(rèn)高度測(cè)量
因?yàn)橄吕紿eaderView全部顯示出來，就由提示"下拉刷新"變?yōu)?松手刷新",全部顯示的出來的測(cè)量標(biāo)準(zhǔn)就是header.getBottom()>=header的高度。
所以，首先我們需要測(cè)量HeaderView的默認(rèn)高度。

復(fù)制代碼代碼如下:

//因?yàn)槭窃跇?gòu)造函數(shù)里測(cè)量高度，應(yīng)該先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的上述代碼后面加上調(diào)用measureView后，使用getMeasureHeight()方法獲取header的高度：

復(fù)制代碼代碼如下:

private int mHeaderHeight;
void init(final Context context) {
    ... ...
    measureView(mHeaderLinearLayout);
    mHeaderHeight = mHeaderLinearLayout.getMeasuredHeight();
}

　后面我們就會(huì)用到這個(gè)mHeaderHeight.

5. scrollState監(jiān)聽記錄
scrollState有3種，使用onScrollStateChanged()方法監(jiān)聽記錄。

復(fù)制代碼代碼如下:

private int mCurrentScrollState;
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
    mCurrentScrollState = scrollState;
}

然后即可使用mCurrentScrollState作為后面判斷的條件了。

6. 刷新狀態(tài)分析
    因?yàn)橐恍┑胤叫枰牢覀兲幵谡顟B(tài)下還是進(jìn)入下拉刷新狀態(tài)還是松手反彈狀態(tài)，比如，
    (1). 在非正常的狀態(tài)下，我們不小心飛滑了一下(松手的瞬間容易出現(xiàn)這種情況),我們不能setSelection(1)的，否則總是松手后header跳的一下消失掉了。
    (2). 下拉后要做一個(gè)下拉效果的特殊處理，需要用到OVER_PULL_REFRESH(松手刷新狀態(tài)下)
    (3). 松手反彈后要做一個(gè)反彈效果的特殊處理，需要用到OVER_PULL_REFRESH和ENTER_PULL_REFRESH。

復(fù)制代碼代碼如下:

private final static int NONE_PULL_REFRESH = 0;   //正常狀態(tài)
private final static int ENTER_PULL_REFRESH = 1;  //進(jìn)入下拉刷新狀態(tài)
private final static int OVER_PULL_REFRESH = 2;   //進(jìn)入松手刷新狀態(tài)
private final static int EXIT_PULL_REFRESH = 3;     //松手后反彈后加載狀態(tài)
private int mPullRefreshState = 0;                         //記錄刷新狀態(tài)
@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)) {
        //進(jìn)入且僅進(jìn)入下拉刷新狀態(tài)
        if (mPullRefreshState == NONE_PULL_REFRESH) {
            mPullRefreshState = ENTER_PULL_REFRESH;
        }
    } else if (mCurrentScrollState ==SCROLL_STATE_TOUCH_SCROLL
            && firstVisibleItem == 0
            && (mHeaderLinearLayout.getBottom() >= mHeaderHeight)) {
        //下拉達(dá)到界限，進(jìn)入松手刷新狀態(tài)
        if (mPullRefreshState == ENTER_PULL_REFRESH || mPullRefreshState == NONE_PULL_REFRESH) {
            mPullRefreshState = OVER_PULL_REFRESH;
            //下面是進(jìn)入松手刷新狀態(tài)需要做的一個(gè)顯示改變
            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) {
        //飛滑狀態(tài)，不能顯示出header，也不能影響正常的飛滑
        //只在正常情況下才糾正位置
        if (mPullRefreshState == NONE_PULL_REFRESH) {
            setSelection(1);
        }
    }
}

　　mPullRefreshState將是后面我們處理邊界的重要變量。

6. 下拉效果的特殊處理
所謂的特殊處理，當(dāng)header完全顯示后，下拉只按下拉1/3的距離下拉，給用戶一種艱難下拉，該松手的彈簧感覺。
這個(gè)在onTouchEvent里處理比較方便：

復(fù)制代碼代碼如下:

private float mDownY;
private float mMoveY;
@Override
public boolean onTouchEvent(MotionEvent ev) {
    switch (ev.getAction()) {
        case MotionEvent.ACTION_DOWN:
            //記下按下位置
            //改變
            mDownY = ev.getY();
            break;
        case MotionEvent.ACTION_MOVE:
            //移動(dòng)時(shí)手指的位置
            mMoveY = ev.getY();
            if (mPullRefreshState == OVER_PULL_REFRESH) {
                //注意下面的mDownY在onScroll的第二個(gè)else中被改變了
                mHeaderLinearLayout.setPadding(mHeaderLinearLayout.getPaddingLeft(),
                        (int)((mMoveY - mDownY)/3), //1/3距離折扣
                        mHeaderLinearLayout.getPaddingRight(),
                        mHeaderLinearLayout.getPaddingBottom());
            }
            break;
        case MotionEvent.ACTION_UP:
            ... ...
            break;
    }
    return super.onTouchEvent(ev);
}

//重復(fù)貼出下面這段需要注意的代碼
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
    ... ...
    else if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL
            && firstVisibleItem == 0
            && (mHeaderLinearLayout.getBottom() >= mHeaderHeight)) {
        //下拉達(dá)到界限，進(jìn)入松手刷新狀態(tài)
        if (mPullRefreshState == ENTER_PULL_REFRESH || mPullRefreshState == NONE_PULL_REFRESH) {
            mPullRefreshState = OVER_PULL_REFRESH;
            mDownY = mMoveY; //為下拉1/3折扣效果記錄開始位置
            mHeaderTextView.setText("松手刷新");//顯示松手刷新
            mHeaderPullDownImageView.setVisibility(View.GONE);//隱藏"下拉刷新"
            mHeaderReleaseDownImageView.setVisibility(View.VISIBLE);//顯示向上的箭頭
        }
    }
    ... ...
}

　　onScroll里監(jiān)聽到了進(jìn)入松手刷新狀態(tài)，onTouchEvent就開始在ACTION_MOVE中處理1/3折扣問題。

7. 反彈效果的特殊處理
    松手后我們需要一個(gè)柔性的反彈效果，意味著我們彈回去的過程需要分一步步走,我的解決方案是：
    在子線程里計(jì)算PaddingTop，并減少到原來的3/4，循環(huán)通知主線程，直到PaddingTop小于1(這個(gè)值取一個(gè)小值，合適即可)。
    松手后，當(dāng)然是在onTouchEvent的ACTION_UP條件下處理比較方便：

復(fù)制代碼代碼如下:

//因?yàn)樯婕暗絟andler數(shù)據(jù)處理，為方便我們定義如下常量
private final static int REFRESH_BACKING = 0;      //反彈中
private final static int REFRESH_BACED = 1;        //達(dá)到刷新界限，反彈結(jié)束后
private final static int REFRESH_RETURN = 2;       //沒有達(dá)到刷新界限，返回
private final static int REFRESH_DONE = 3;         //加載數(shù)據(jù)結(jié)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);//慢一點(diǎn)反彈，別一下子就彈回去了
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                        msg = mHandler.obtainMessage();
                        if (mPullRefreshState == OVER_PULL_REFRESH) {
                            msg.what = REFRESH_BACED;//加載數(shù)據(jù)完成，結(jié)束返回
                        } else {
                            msg.what = REFRESH_RETURN;//未達(dá)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("正在加載...");
            mHeaderProgressBar.setVisibility(View.VISIBLE);
            mHeaderPullDownImageView.setVisibility(View.GONE);
            mHeaderReleaseDownImageView.setVisibility(View.GONE);
            mPullRefreshState = EXIT_PULL_REFRESH;
            new Thread() {
                public void run() {
                    sleep(2000);//處理后臺(tái)加載數(shù)據(jù)
                    Message msg = mHandler.obtainMessage();
                    msg.what = REFRESH_DONE;
                    //通知主線程加載數(shù)據(jù)完成
                    mHandler.sendMessage(msg);
                };
            }.start();
            break;
        case REFRESH_RETURN:
            //未達(dá)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:
            //刷新結(jié)束后，恢復(fù)原始默認(rèn)狀態(tài)
            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;
        }
    }
};

為了一下子看的明確，我把效果中的數(shù)據(jù)處理代碼也貼出來了。

8. 切入數(shù)據(jù)加載過程
    上面數(shù)據(jù)后臺(tái)處理我們用sleep(2000)來處理，實(shí)際處理中，作為公共組件，我們也不好把具體代碼直接寫在這里，我們需要一個(gè)更靈活的分離:
    (1). 定義接口
    (2). 注入接口

復(fù)制代碼代碼如下:

//定義接口
public interface RefreshListener {
    Object refreshing();                //加載數(shù)據(jù)
    void refreshed(Object obj);    //外部可擴(kuò)展加載完成后的操作
}

//注入接口
private Object mRefreshObject = null; //傳值
private RefreshListener mRefreshListener = null;
public void setOnRefreshListener(RefreshListener refreshListener) {
    this.mRefreshListener = refreshListener;
}

 
//我們需要重寫上面的mHandler如下代碼
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;

在其他地方我們就可以不修改這個(gè)listview組件的代碼，使用如下：

復(fù)制代碼代碼如下:

public xxx implements RefreshListener{

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //類似如下
        ((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) {
           //擴(kuò)展操作
        }
    };
}

　　很方便了。

9. 擴(kuò)展"更多"功能
下拉刷新之外，我們也可以通過相同方法使用FooterView切入底部"更多"過程，這里我就不詳細(xì)說明了

10. 源碼
上面的每段代碼都看做是"零部件"，需要組合一下。
因?yàn)槲覀兩厦鎸?shí)現(xiàn)了下拉刷新，還增加了"更多"功能，我們直接命名這個(gè)類為RefreshListView吧：

復(fù)制代碼代碼如下:

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;    //正常狀態(tài)
    private final static int ENTER_PULL_REFRESH = 1;   //進(jìn)入下拉刷新狀態(tài)
    private final static int OVER_PULL_REFRESH = 2;    //進(jìn)入松手刷新狀態(tài)
    private final static int EXIT_PULL_REFRESH = 3;    //松手后反彈和加載狀態(tài)
    private int mPullRefreshState = 0;                 //記錄刷新狀態(tài)

    private final static int REFRESH_BACKING = 0;      //反彈中
    private final static int REFRESH_BACED = 1;        //達(dá)到刷新界限，反彈結(jié)束后
    private final static int REFRESH_RETURN = 2;       //沒有達(dá)到刷新界限，返回
    private final static int REFRESH_DONE = 3;         //加載數(shù)據(jù)結(jié)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)) {
            //進(jìn)入且僅進(jìn)入下拉刷新狀態(tài)
            if (mPullRefreshState == NONE_PULL_REFRESH) {
                mPullRefreshState = ENTER_PULL_REFRESH;
            }
        } else if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL
                && firstVisibleItem == 0
                && (mHeaderLinearLayout.getBottom() >= mHeaderHeight)) {
            //下拉達(dá)到界限，進(jìn)入松手刷新狀態(tài)
            if (mPullRefreshState == ENTER_PULL_REFRESH || mPullRefreshState == NONE_PULL_REFRESH) {
                mPullRefreshState = OVER_PULL_REFRESH;
                mDownY = mMoveY; //為下拉1/3折扣效果記錄開始位置
                mHeaderTextView.setText("松手刷新");//顯示松手刷新
                mHeaderPullDownImageView.setVisibility(View.GONE);//隱藏"下拉刷新"
                mHeaderReleaseDownImageView.setVisibility(View.VISIBLE);//顯示向上的箭頭
            }
        } 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) {
            //飛滑狀態(tài)，不能顯示出header，也不能影響正常的飛滑
            //只在正常情況下才糾正位置
            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("正在加載...");
                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);
    }
}