Android listview下拉刷新学习

以后的博客都在csdn写吧，原来在网易上写的代码太乱了，不适合写技术博客，今天要学习下拉刷新,虽说轮子造一遍就可以了，但是总得学习一下轮子是怎么造的吧，哎，好难。。

先看看效果：

其listview是自定义的组件

package com.laohuai.appdemo.customui.ui;import java.util.Date;import com.laohuai.appdemo.customui.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.BaseAdapter;import android.widget.ImageView;import android.widget.LinearLayout;import android.widget.ListView;import android.widget.AbsListView.OnScrollListener;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) {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sizeif (state == PULL_To_REFRESH) {headView.setPadding(0, -1 * headContentHeight+ (tempY - startY) / RATIO, 0, 0);}// 更新headView的paddingTopif (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);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;lastUpdatedTextView.setText("最近更新:" + new Date().toLocaleString());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heightprivate 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) {lastUpdatedTextView.setText("最近更新:" + new Date().toLocaleString());super.setAdapter(adapter);}}

主界面的代码：

package com.laohuai.appdemo.customui;import java.util.ArrayList;import java.util.List;import com.laohuai.appdemo.customui.ui.MyListView;import com.laohuai.appdemo.customui.ui.MyListView.OnRefreshListener;import android.app.Activity;import android.os.AsyncTask;import android.os.Bundle;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.TextView;public class MainActivity extends Activity {private List<String> data;private BaseAdapter adapter;public void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);data = new ArrayList<String>();data.add("a");data.add("b");data.add("c");final MyListView listView = (MyListView) findViewById(R.id.listView);adapter = new BaseAdapter() {public View getView(int position, View convertView, ViewGroup parent) {TextView tv = new TextView(getApplicationContext());tv.setText(data.get(position));return tv;}public long getItemId(int position) {return 0;}public Object getItem(int position) {return null;}public int getCount() {return data.size();}};listView.setAdapter(adapter);listView.setonRefreshListener(new OnRefreshListener() {public void onRefresh() {new AsyncTask<Void, Void, Void>() {protected Void doInBackground(Void... params) {try {Thread.sleep(1000);} catch (Exception e) {e.printStackTrace();}data.add("刷新后添加的内容");return null;}@Overrideprotected void onPostExecute(Void result) {adapter.notifyDataSetChanged();listView.onRefreshComplete();}}.execute(null);}});}}

主要是通过listview的 setonRefreshListener方法来设定下拉刷新的监听器 然后 刷新完毕时调用listView.onRefreshComplete()方法即可停止刷新