android 实现下拉刷新

1.布局文件 listview
<com.and.netease.utils.MyListView
android:id="@+id/lv_b" android:layout_width="fill_parent"
android:layout_height="fill_parent" android:layout_marginRight="10dip"
/>
2.刷新的header 布局
<?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:background="#ffffff"
>

<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/head_contentLayout"
android:paddingLeft="30dp"
>

<FrameLayout
android:layout_width="18dip"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_centerVertical="true"
>

<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:src="@drawable/arrow_down"
android:id="@+id/head_arrowImageView"
/>

<ProgressBar
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="?android:attr/progressBarStyleSmall"
android:layout_gravity="center"
android:id="@+id/head_progressBar"
android:visibility="gone"
/>
</FrameLayout>

<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:orientation="vertical"
android:gravity="center_horizontal"
>

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="下拉刷新"
android:textSize="15dp"
android:id="@+id/head_tipsTextView"
/>

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/head_lastUpdatedTextView"
android:text="上次更新"
android:textSize="12dp"
/>
</LinearLayout>
</RelativeLayout>
</LinearLayout>
3.核心代码
package com.and.netease.utils;

import java.text.SimpleDateFormat;
import java.util.Date;

import com.and.netease.R;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.LinearInterpolator;
import android.view.animation.RotateAnimation;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;

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) {
System.out.println("scroll");
//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 void onScrollStateChanged(AbsListView arg0, int arg1) {
}

public boolean onTouchEvent(MotionEvent event) {
if (isRefreshable) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
if (firstItemIndex == 0 && !isRecored) {
isRecored = true;
startY = (int) event.getY();
Log.v(TAG, "在down时候记录当前位置‘");
}
break;
case MotionEvent.ACTION_UP:
if (state != REFRESHING && state != LOADING) {
if (state == DONE) {
// 什么都不做
}
if (state == PULL_To_REFRESH) {
state = DONE;
changeHeaderViewByState();

Log.v(TAG, "由下拉刷新状态，到done状态");
}
if (state == RELEASE_To_REFRESH) {
state = REFRESHING;
changeHeaderViewByState();
onRefresh();

Log.v(TAG, "由松开刷新状态，到done状态");
}
}
isRecored = false;
isBack = false;
break;
case MotionEvent.ACTION_MOVE:
int tempY = (int) event.getY();
if (!isRecored && firstItemIndex == 0) {
Log.v(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，当前的位置一直是在head，否则如果当列表超出屏幕的话，当在上推的时候，列表会同时进行滚动

// 可以松手去刷新了
if (state == RELEASE_To_REFRESH) {
setSelection(0);
// 往上推了，推到了屏幕足够掩盖head的程度，但是还没有推到全部掩盖的地步
if (((tempY - startY) / RATIO < headContentHeight)
&& (tempY - startY) > 0) {
state = PULL_To_REFRESH;
changeHeaderViewByState();
Log.v(TAG, "由松开刷新状态转变到下拉刷新状态");
}
// 一下子推到顶了
else if (tempY - startY <= 0) {
state = DONE;
changeHeaderViewByState();
Log.v(TAG, "由松开刷新状态转变到done状态");
}
// 往下拉了，或者还没有上推到屏幕顶部掩盖head的地步
else {
// 不用进行特别的操作，只用更新paddingTop的值就行了
}
}
// 还没有到达显示松开刷新的时候,DONE或者是PULL_To_REFRESH状态
if (state == PULL_To_REFRESH) {
setSelection(0);
// 下拉到可以进入RELEASE_TO_REFRESH的状态
if ((tempY - startY) / RATIO >= headContentHeight) {
state = RELEASE_To_REFRESH;
isBack = true;
changeHeaderViewByState();
Log.v(TAG, "由done或者下拉刷新状态转变到松开刷新");
}
// 上推到顶了
else if (tempY - startY <= 0) {
state = DONE;
changeHeaderViewByState();
Log.v(TAG, "由DOne或者下拉刷新状态转变到done状态");
}
}

// done状态下
if (state == DONE) {
if (tempY - startY > 0) {
state = PULL_To_REFRESH;
changeHeaderViewByState();
}
}

// 更新headView的size
if (state == PULL_To_REFRESH) {
headView.setPadding(0, -1 * headContentHeight
+ (tempY - startY) / RATIO, 0, 0);

}

// 更新headView的paddingTop
if (state == RELEASE_To_REFRESH) {
headView.setPadding(0, (tempY - startY) / RATIO
- headContentHeight, 0, 0);
}
}
break;
}
}
return super.onTouchEvent(event);
}

// 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("松开刷新");

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 * headContentHeight, 0, 0);

progressBar.setVisibility(View.GONE);
arrowImageView.clearAnimation();
arrowImageView.setImageResource(R.drawable.arrow_down);
tipsTextview.setText("下拉刷新");
lastUpdatedTextView.setVisibility(View.VISIBLE);

Log.v(TAG, "当前状态，done");
break;
}
}

public void setonRefreshListener(OnRefreshListener refreshListener) {
this.refreshListener = refreshListener;
isRefreshable = true;
}

public interface OnRefreshListener {
public void onRefresh();
}

public void onRefreshComplete() {
state = DONE;
SimpleDateFormat format=new SimpleDateFormat("yyyy年MM月dd日 HH:mm");
String date=format.format(new Date());
lastUpdatedTextView.setText("最近更新:" + date);
changeHeaderViewByState();
}

private void onRefresh() {
if (refreshListener != null) {
refreshListener.onRefresh();
}
}

// 此方法直接照搬自网络上的一个下拉刷新的demo，此处是“估计”headView的width以及height
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);
}

public void setAdapter(BaseAdapter adapter) {
SimpleDateFormat format=new SimpleDateFormat("yyyy年MM月dd日 HH:mm");
String date=format.format(new Date());
lastUpdatedTextView.setText("最近更新:" + date);
super.setAdapter(adapter);
}
}
4.activity调用
MyListView listview = (MyListView) findViewById(R.id.lv_b);
listview.setAdapter(adapter);
listview.setonRefreshListener(new MyListView.OnRefreshListener() {
public void onRefresh() {
new AsyncTask<Void, Void, Void>() {
protected Void doInBackground(Void... params) {
try {
Thread.sleep(1000);
} catch (Exception e) {
e.printStackTrace();
}
List<ArticleData> la = new ArrayList<ArticleData>();
ArticleData data = new ArticleData();
data.setTitle("刷新的标题");
data.setContent("刷新的内容");
la.add(data);
articleData.addAll(0,la);
return null;
}
@Override
protected void onPostExecute(Void result) {
adapter.notifyDataSetChanged();
listview.onRefreshComplete();
}
}.execute(null);
}
});

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