ListView的下拉刷新及上拉加载更多数据是我们开发中通常要实现的功能，开源项目中有很多的上下拉加载刷新的ListView可直接拿来使用，这几天刚好学习了下刷新的实现方式，把学习的资料做个记录：

实现的简单效果图片：这是下拉时显示，文字可能有些不一样。向上返回如图：。此时放开手后，就有一个圆形进度条加载状态，加载完成后HeaderView部分（包括上面的图片，及加载条都是隐藏）。

实现的代码：

/** 
* 自定义可以下拉刷新的ListView 
*  
* @description： 
* 下拉刷新实现方式分析： 
* 1，我们要给ListView添加头部（HeaderView）实现下拉加载的提示效果 
* 2，需要对ListView进行onScrollListener监听，来判断当前是否显示在listview的最顶部 
* 3，ListView的下拉加载等界面是随手势滑动过程不断变化的，所以要监听onTouch事件，来改变当前的状态及界面显示 
* 4，最后就是根据当前的状态来实现加载数据 
* @date 2015-10-27 下午12:16:59 
*/ 
public class PullDownFreshListView extends ListView implements OnScrollListener {
/* 下拉的ListView头部* */ 
private View mHeaderView; 
/* 头部的高度* */ 
private int headerHeight; 
/* 当前每一个可见的item的位置* */ 
private int mFirstVisibleItem; 
/* 当前的滚动状态* */ 
private int mScrollState; 
/* 设置下拉起始的y值* */ 
private int startY; 
/* 是否是在ListView顶端按下的（下拉的）* */ 
private boolean isRemark = false; 
/* 定义当前ListView所处的状态* */ 
private int state; 
/* 定义状态：正常* */ 
private static final int NORMAL = 1; 
/* 定义状态：下拉状态* */ 
private static final int PULL = 2; 
/* 定义状态：下拉释放状态* */ 
private static final int RELEASE = 3; 
/* 定义状态：刷新中状态* */ 
private static final int FRESHING = 4; 
/* 刷新完成回调接口* */ 
private IPullDownFreshListener freshListener; 
public void setFreshListener(IPullDownFreshListener freshListener) { 
this.freshListener = freshListener; 
} 
public PullDownFreshListView(Context context) { 
super(context); 
initHeaderView(context); 
} 
public PullDownFreshListView(Context context, AttributeSet attrs) { 
super(context, attrs); 
initHeaderView(context); 
} 
public PullDownFreshListView(Context context, AttributeSet attrs, int defStyleAttr) { 
super(context, attrs, defStyleAttr); 
initHeaderView(context); 
} 
/** 
* 初始化头部headerView 
* @description： 
* @date 2015-10-27 下午1:03:32 
*/ 
private void initHeaderView(Context context) { 
LayoutInflater mInflater = LayoutInflater.from(context); 
mHeaderView = mInflater.inflate(R.layout.fresh_header, null); 
measureHeaderView(mHeaderView); 
headerHeight = mHeaderView.getMeasuredHeight(); 
topPadding(-headerHeight);// 设置pading为header高度的负责来初始隐藏headerView
this.addHeaderView(mHeaderView); 
} 
/** 
* 设置ListView的padding 
* @description： 
* @date 2015-10-27 下午1:25:45 
*/ 
private void topPadding(int top) { 
setPadding(mHeaderView.getPaddingLeft(), top, mHeaderView.getPaddingRight(), mHeaderView.getPaddingBottom()); 
mHeaderView.invalidate(); 
} 
/** 
* 测量view在父容器中占用的高度 
* @description： 
* @date 2015-10-27 下午1:17:39 
*/ 
private void measureHeaderView(View view) { 
ViewGroup.LayoutParams lp = view.getLayoutParams(); 
if (lp == null) { 
lp = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT); 
} 
int width = ViewGroup.getChildMeasureSpec(0, 0, lp.width); 
int height; 
int tempHeight = lp.height; 
if (tempHeight > 0) { 
height = MeasureSpec.makeMeasureSpec(tempHeight, MeasureSpec.EXACTLY); 
} 
else { 
height = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 
} 
view.measure(width, height); 
} 
@Override 
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { 
this.mFirstVisibleItem = firstVisibleItem;// 获取当前可见item的位置 
} 
@Override 
public void onScrollStateChanged(AbsListView view, int scrollState) { 
this.mScrollState = scrollState; 
} 
@Override 
public boolean onTouchEvent(MotionEvent ev) { 
switch (ev.getAction()) { 
case MotionEvent.ACTION_DOWN: 
if (mFirstVisibleItem == 0) { 
isRemark = true; 
startY = (int) ev.getY();// 按下手指时获取到初始的位置y值 
state = NORMAL; 
} 
break; 
case MotionEvent.ACTION_MOVE: 
onMove(ev); 
break; 
case MotionEvent.ACTION_UP: 
if (state == RELEASE) { 
state = FRESHING; 
// 加载最新数据 
reFreshViewsByState(); 
if (freshListener != null) { 
freshListener.onFresh(); 
} 
} 
else if (state == PULL) { 
state = NORMAL; 
isRemark = false; 
reFreshViewsByState(); 
} 
break; 
} 
return super.onTouchEvent(ev); 
} 
/** 
* 下拉过程中的逻辑处理 
* @description： 
* @date 2015-10-27 下午1:34:13 
*/ 
private void onMove(MotionEvent ev) { 
if (!isRemark) { return; } 
int tempY = (int) ev.getY(); 
int spaceY = tempY - startY;// 获取到滑动（拉动）产生的距离 
int topPadding = tempY - startY; 
switch (state) { 
case NORMAL: 
if (spaceY > 0) { 
state = PULL; 
} 
break; 
case PULL: 
topPadding(topPadding); 
if (spaceY > headerHeight + 30 && mScrollState == SCROLL_STATE_TOUCH_SCROLL) { 
state = RELEASE; 
} 
break; 
case RELEASE: 
if (spaceY < headerHeight + 30) { 
state = PULL; 
} 
else if (spaceY <= 0) { 
state = NORMAL; 
} 
break; 
case FRESHING: 
break; 
} 
} 
/** 
* 刷新结束的处理 
* @description： 
* @date 2015-10-27 下午1:50:53 
*/ 
@SuppressLint("SimpleDateFormat") 
public void freshCompelete() { 
state = NORMAL; 
isRemark = false; 
reFreshViewsByState(); 
TextView freshTimeTv = (TextView) mHeaderView.findViewById(R.id.item_time); 
SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 mm:dd:ss"); 
Date now = new Date(System.currentTimeMillis()); 
freshTimeTv.setText(sdf.format(now));// 设置刷新的时间显示 
} 
/** 
* 根据当前 状态 来显示headerView 
* @description： 
* @date 2015-10-27 下午1:51:45 
*/ 
private void reFreshViewsByState() { 
TextView tip = (TextView) mHeaderView.findViewById(R.id.item_title); 
ImageView freshIv = (ImageView) mHeaderView.findViewById(R.id.item_iv); 
ProgressBar pBar = (ProgressBar) mHeaderView.findViewById(R.id.item_progress); 
// 设置下拉时的图片动画 
RotateAnimation downAnim = new RotateAnimation(0, 180, 0.5f, 0.5f); 
downAnim.setDuration(500); 
downAnim.setFillAfter(true); 
RotateAnimation upAnim = new RotateAnimation(180, 0, 0.5f, 0.5f); 
upAnim.setDuration(500); 
upAnim.setFillAfter(true); 
switch (state) { 
case NORMAL: 
topPadding(-headerHeight); 
break; 
case PULL: 
freshIv.setVisibility(View.VISIBLE); 
pBar.setVisibility(View.GONE); 
tip.setText("下拉可以刷新!"); 
freshIv.clearAnimation(); 
freshIv.setAnimation(downAnim); 
break; 
case RELEASE: 
freshIv.setVisibility(View.VISIBLE); 
pBar.setVisibility(View.GONE); 
tip.setText("松开可以刷新!"); 
freshIv.clearAnimation(); 
freshIv.setAnimation(upAnim); 
break; 
case FRESHING: 
topPadding(50); 
freshIv.setVisibility(View.GONE); 
pBar.setVisibility(View.VISIBLE); 
tip.setText("正在刷新!"); 
freshIv.clearAnimation(); 
break; 
} 
} 
/** 
* 增加一个刷新完成的回调接口 
* @description： 
* @date 2015-10-28 上午9:06:05 
*/ 
public interface IPullDownFreshListener { 
void onFresh();// 刷新方法 
} 
} 

--------------在Activity中使用很方便，同通常的ListView是一样的，在布局文件中引入我们自定义ListView--------------------------------------------------------

public class MainActivity extends Activity { 
private PullDownFreshListView mDownFreshListView; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
setContentView(R.layout.activity_main); 
mDownFreshListView = (PullDownFreshListView) findViewById(R.id.fresh_listview);