我们在做一些Listview的时候为了便于用户操作通常需要这种功能，向下拉动Listview列表时候可以进行对列表的更新操作。
我们知道系统自带的列表功能是非常少的，而为了让我们工程的列表能有我们想要的功能，我们自然而然想对Listview进行自定义
MyListView类：
public class MyListView extends ListView implements OnScrollListener {
private static final String TAG = "listview";
private final static int RELEASE_To_REFRESH = 0;
private final static int PULL_To_REFRESH = 1;
private final static int REFRESHING = 2;
private final static int DONE = 3;
private final static int LOADING = 4;
// 实际的padding的距离与界面上偏移距离的比例
private final static int RATIO = 3;
private LayoutInflater inflater;
private LinearLayout headView;
private TextView tipsTextview;
private TextView lastUpdatedTextView;
private ImageView arrowImageView;
private ProgressBar progressBar;
private RotateAnimation animation;
private RotateAnimation reverseAnimation;
// 用于保证startY的值在一个完整的touch事件中只被记录一次
private boolean isRecored;
private int headContentWidth;
private int headContentHeight;
private int startY;
private int firstItemIndex;
private int state;
private boolean isBack;
private OnRefreshListener refreshListener;
private boolean isRefreshable;
public MyListView(Context context) {
super(context);
init(context);
}
public MyListView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
private void init(Context context) {
setCacheColorHint(context.getResources().getColor(R.color.transparent));
inflater = LayoutInflater.from(context);
headView = (LinearLayout) inflater.inflate(R.layout.head, null);
arrowImageView = (ImageView) headView
.findViewById(R.id.head_arrowImageView);
arrowImageView.setMinimumWidth(70);
arrowImageView.setMinimumHeight(50);
progressBar = (ProgressBar) headView
.findViewById(R.id.head_progressBar);
tipsTextview = (TextView) headView.findViewById(R.id.head_tipsTextView);
lastUpdatedTextView = (TextView) headView
.findViewById(R.id.head_lastUpdatedTextView);
measureView(headView);
headContentHeight = headView.getMeasuredHeight();
headContentWidth = headView.getMeasuredWidth();
headView.setPadding(0, -1 * headContentHeight, 0, 0);
headView.invalidate();
Log.v("size", "width:" + headContentWidth + " height:"
+ headContentHeight);
addHeaderView(headView, null, false);
setOnScrollListener(this);
animation = new RotateAnimation(0, -180,
RotateAnimation.RELATIVE_TO_SELF, 0.5f,
RotateAnimation.RELATIVE_TO_SELF, 0.5f);
animation.setInterpolator(new LinearInterpolator());
animation.setDuration(250);
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(200);
reverseAnimation.setFillAfter(true);
state = DONE;
isRefreshable = false;
}
public void onScroll(AbsListView arg0, int firstVisiableItem, int arg2,
int arg3) {
firstItemIndex = firstVisiableItem;
}
public vo