1.实现原理
在ListView的顶部添加一个header布局，在下拉过程中，然后重新onTouchEvent()，根据滑动过程中y轴的变化，改变header布局的状态，包括hender的提示音和箭头方向。
2.实现步骤
1）创建header布局文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<LinearLayout
android:id="@+id/layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
android:layout_centerInParent="true"
android:gravity="center">
<TextView
android:id="@+id/tv_tip"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="下拉可以刷新"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/tv_lastupdatetime"/>
</LinearLayout>
<ImageView
android:id="@+id/arrow"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toLeftOf="@+id/layout"
android:layout_marginRight="20dp"
android:src="@drawable/pull_to_refresh_arrow"
/>
<ProgressBar
android:id="@+id/progress"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="?android:attr/progressBarStyleSmall"
android:layout_toLeftOf="@+id/layout"
android:layout_marginRight="20dp"
android:visibility="gone"/>
</RelativeLayout>
</LinearLayout>
2)自定义ListView
public class RefreshListView extends ListView implements AbsListView.OnScrollListener{
private static final String TAG = "RefreshListView";
private int headerHeight;//顶部布局文件的高度
//顶部的各种状态
private final static int RELEASE_TO_REFRESH = 0;//松开刷新
private final static int PULL_TO_REFRESH = 1;//下拉刷新
private final static int REFRESHING = 2;//正在刷新
private final static int DONE = 3;//刷新完成
private final static int LOADING = 4;//正在加载
//
private final static int RATIO = 3;
//实际的padding的距离与界面上偏移距离的比例
//头部布局文件的控件
private LinearLayout headView;
private TextView tipsTextview;
private TextView lastUpdatedTextView;
private ImageView arrowImageView;
private ProgressBar progressBar;
//箭头旋转动画
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 firstItemIndex;
//记录初始的Y坐标
private int startY;
//记录当前的状态
private int state;
private boolean isRefreshable;
private boolean isBack;
private onRefreshListener refreshListener;
public RefreshListView(Context context) {
super(context);
initView(context);
}
public RefreshListView(Context context, AttributeSet attrs) {
super(context, attrs);
initView(context);
}
public RefreshListView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initView(context);
}
private void initView(Context context){
LayoutInflater inflater = LayoutInflater.from(context);
headView = (LinearLayout) inflater.inflate(R.layout.header_layout, null);
measureView(headView);
headerHeight = headView.getMeasuredHeight();
//隐藏顶部布局文件
headView.setPadding(headView.getPaddingLeft(), -headerHeight, headView.getPaddingRight(), headView.getPaddingBottom());
headView.invalidate();
this.addHeaderView(headView);
arrowImageView = (ImageView) headView.findViewById(R.id.arrow);
arrowImageView.setMinimumWidth(50);
arrowImageView.setMinimumHeight(70);
progressBar = (ProgressBar) headView.findViewById(R.id.progress);
tipsTextview = (TextView) headView.findViewById(R.id.tv_tip);
lastUpdatedTextView = (TextView) headView.findViewById(R.id.tv_lastupdatetime);
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);
animation.setDuration(200);
animation.setFillAfter(true);
state = DONE;
isRefreshable = false;
}
/**
* 通知父布局，View占用的宽高
* @param view
*/
private void measureView(View view) {
ViewGroup.LayoutParams p = view.getLayoutParams();
if (p == null){
p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
}
int width = ViewGroup.getChildMeasureSpec(0, 0, p.width);
int height;
int tempHeight = p.height;
if (tempHeight > 0) {
height = MeasureSpec.makeMeasureSpec(tempHeight, MeasureSpec.EXACTLY);
} else {
height = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
}
view.measure(width, height);
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
firstItemIndex = firstVisibleItem;
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (isRefreshable) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
if (firstItemIndex == 0 && !isRecored) {
isRecored = true;
startY = (int) ev.getY();
Log.i(TAG, "在down时候记录当前位置");
}
break;
case MotionEvent.ACTION_UP:
Log.i(TAG, "down时候记录当前位置");
if (state != REFRESHING && state != LOADING) {
if (state == DONE) {
}
if (state == PULL_TO_REFRESH) {
state = DONE;
changeHeaderViewByState();
Log.i(TAG, "有下拉刷新状态，到done状态");
}
if (state == RELEASE_TO_REFRESH) {
state = REFRESHING;
changeHeaderViewByState();
onRefresh();
Log.i(TAG, "由松开刷新状态，到done状态");
}
}
isRecored = false;
isBack = false;
break;
case MotionEvent.ACTION_MOVE:
int tempY = (int) ev.getY();
if (!isRecored && firstItemIndex == 0) {
Log.i(TAG, "在move时候记录下位置");
isRecored = true;
startY = tempY;
}
if (state != REFRESHING && isRecored && state != LOADING) {
//保证在设置padding的过程中，当前的位置一直在head
if (state == RELEASE_TO_REFRESH) {
setSelection(0);
//下拉到当前状态后又往上推了，推到了屏幕足够掩盖head的程度
if ((tempY - startY) / RATIO < headerHeight && (tempY - startY) > 0) {
state = PULL_TO_REFRESH;
changeHeaderViewByState();
Log.i(TAG, "松开刷新转为下拉刷新");
} else if (tempY - startY <= 0) {
state = DONE;
changeHeaderViewByState();
Log.i(TAG, "松开刷新转为done");
}
}
if (state == DONE) {
if (tempY - startY > 0) {
state = PULL_TO_REFRESH;
changeHeaderViewByState();
}
}
if (state == PULL_TO_REFRESH) {
setSelection(0);
if ((tempY - startY) / RATIO >= headerHeight) {
state = RELEASE_TO_REFRESH;
isBack = true;
changeHeaderViewByState();
Log.i(TAG, "有下拉刷新转为松开刷新");
}
}
//更新headView的size
if (state == PULL_TO_REFRESH) {
headView.setPadding(0, -1 * headerHeight + (tempY - startY) / RATIO, 0, 0);
}
// 更新headView的paddingTop
if (state == RELEASE_TO_REFRESH) {
headView.setPadding(0, (tempY - startY) / RATIO
- headerHeight, 0, 0);
}
}
break;
}
}
return super.onTouchEvent(ev);
}
// 当状态改变时候，调用该方法，以更新界面
private void changeHeaderViewByState()
{
switch (state)
{
case RELEASE_TO_REFRESH:
arrowImageView.setVisibility(View.VISIBLE);
progressBar.setVisibility(View.GONE);
tipsTextview.setVisibility(View.VISIBLE);
lastUpdatedTextView.setVisibility(View.VISIBLE);
arrowImageView.clearAnimation();
arrowImageView.startAnimation(animation);
tipsTextview.setText("放开以刷新");
Log.v(TAG, "当前状态，松开刷新");
break;
case PULL_TO_REFRESH:
progressBar.setVisibility(View.GONE);
tipsTextview.setVisibility(View.VISIBLE);
lastUpdatedTextView.setVisibility(View.VISIBLE);
arrowImageView.clearAnimation();
arrowImageView.setVisibility(View.VISIBLE);
// 是由RELEASE_To_REFRESH状态转变来的
if (isBack) {
isBack = false;
arrowImageView.clearAnimation();
arrowImageView.startAnimation(reverseAnimation);
tipsTextview.setText("下拉刷新");
} else {
tipsTextview.setText("下拉刷新");
}
Log.v(TAG, "当前状态，下拉刷新");
break;
case REFRESHING:
headView.setPadding(0, 0, 0, 0);
progressBar.setVisibility(View.VISIBLE);
arrowImageView.clearAnimation();
arrowImageView.setVisibility(View.GONE);
tipsTextview.setText("正在刷新...");
lastUpdatedTextView.setVisibility(View.VISIBLE);
Log.v(TAG, "当前状态,正在刷新...");
break;
case DONE:
headView.setPadding(0, -1 * headerHeight, 0, 0);
progressBar.setVisibility(View.GONE);
arrowImageView.clearAnimation();
arrowImageView.setImageResource(R.drawable.pull_to_refresh_arrow);
tipsTextview.setText("下拉刷新");
lastUpdatedTextView.setVisibility(View.VISIBLE);
Log.v(TAG, "当前状态，done");
break;
}
}
public interface onRefreshListener {
public void onRefresh();
}
public void setonRefreshListener(onRefreshListener onRefreshListener) {
this.refreshListener = onRefreshListener;
isRefreshable = true;
}
private void onRefresh() {
if (refreshListener != null) {
refreshListener.onRefresh();
}
}
public void onRefreshComplete() {
state = DONE;
lastUpdatedTextView.setText("最近更新：" + new Date().toLocaleString());
changeHeaderViewByState();
}
}
3）实现接口
@Override
public void onRefresh() {
new AsyncTask<Void, Void, Void>() {
@Override
protected Void doInBackground(Void... params) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
setReflashData();
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
adapter.notifyDataSetChanged();
listview.onRefreshComplete();
}
}.execute();
}
