Android中ListView下拉刷新的实现方法实例分析

package net.loonggg.listview; import java.util.Date; import android.content.Context; import android.util.AttributeSet; 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.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 final static int RELEASE_To_REFRESH = 0;// 下拉过程的状态值  private final static int PULL_To_REFRESH = 1; // 从下拉返回到不刷新的状态值 private final static int REFRESHING = 2;// 正在刷新的状态值  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;  // ListView头部下拉刷新的布局  private LinearLayout headerView;  private TextView lvHeaderTipsTv;  private TextView lvHeaderLastUpdatedTv;  private ImageView lvHeaderArrowIv;  private ProgressBar lvHeaderProgressBar;  // 定义头部下拉刷新的布局的高度  private int headerContentHeight;  private RotateAnimation animation;  private RotateAnimation reverseAnimation;  private int startY;  private int state;  private boolean isBack;  // 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 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);   headerView = (LinearLayout) inflater.inflate(R.layout.lv_header, null);  lvHeaderTipsTv = (TextView) headerView     .findViewById(R.id.lvHeaderTipsTv);   lvHeaderLastUpdatedTv = (TextView) headerView     .findViewById(R.id.lvHeaderLastUpdatedTv);   lvHeaderArrowIv = (ImageView) headerView     .findViewById(R.id.lvHeaderArrowIv);   // 设置下拉刷新图标的最小高度和宽度   lvHeaderArrowIv.setMinimumWidth(70);   lvHeaderArrowIv.setMinimumHeight(50);   lvHeaderProgressBar = (ProgressBar) headerView     .findViewById(R.id.lvHeaderProgressBar);   measureView(headerView);   headerContentHeight = headerView.getMeasuredHeight();   // 设置内边距，正好距离顶部为一个负的整个布局的高度，正好把头部隐藏   headerView.setPadding(0, -1 * headerContentHeight, 0, 0);   // 重绘一下   headerView.invalidate();   // 将下拉刷新的布局加入ListView的顶部   addHeaderView(headerView, null, false);   // 设置滚动监听事件   setOnScrollListener(this);   // 设置旋转动画事件   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);   // 一开始的状态就是下拉刷新完的状态，所以为DONE   state = DONE;   // 是否正在刷新   isRefreshable = false;  }  @Override  public void onScrollStateChanged(AbsListView view, int scrollState) {  }  @Override  public void onScroll(AbsListView view, int firstVisibleItem,    int visibleItemCount, int totalItemCount) {     if (firstVisibleItem == 0) {      isRefreshable = true;      } else {      isRefreshable = false;      }    }  @Override  public boolean onTouchEvent(MotionEvent ev) {   if (isRefreshable) {    switch (ev.getAction()) {    case MotionEvent.ACTION_DOWN:     if (!isRecored) {      isRecored = true;      startY = (int) ev.getY();// 手指按下时记录当前位置     }     break;    case MotionEvent.ACTION_UP:     if (state != REFRESHING && state != LOADING) {      if (state == PULL_To_REFRESH) {       state = DONE;       changeHeaderViewByState();      }      if (state == RELEASE_To_REFRESH) {       state = REFRESHING;       changeHeaderViewByState();       onLvRefresh();      }     }     isRecored = false;     isBack = false;     break;    case MotionEvent.ACTION_MOVE:     int tempY = (int) ev.getY();     if (!isRecored) {      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 < headerContentHeight)// 由松开刷新状态转变到下拉刷新状态         && (tempY - startY) > 0) {        state = PULL_To_REFRESH;        changeHeaderViewByState();       }       // 一下子推到顶了       else if (tempY - startY <= 0) {// 由松开刷新状态转变到done状态        state = DONE;        changeHeaderViewByState();       }      }      // 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 >= headerContentHeight) {// 由done或者下拉刷新状态转变到松开刷新        state = RELEASE_To_REFRESH;        isBack = true;        changeHeaderViewByState();       }       // 上推到顶了       else if (tempY - startY <= 0) {// 由DOne或者下拉刷新状态转变到done状态        state = DONE;        changeHeaderViewByState();       }      }      // 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) {       headerView.setPadding(0, -1 * headerContentHeight         + (tempY - startY) / RATIO, 0, 0);      }      // 更新headView的paddingTop      if (state == RELEASE_To_REFRESH) {       headerView.setPadding(0, (tempY - startY) / RATIO         - headerContentHeight, 0, 0);      }     }     break;    default:     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:    lvHeaderArrowIv.setVisibility(View.VISIBLE);    lvHeaderProgressBar.setVisibility(View.GONE);    lvHeaderTipsTv.setVisibility(View.VISIBLE);    lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);    lvHeaderArrowIv.clearAnimation();// 清除动画    lvHeaderArrowIv.startAnimation(animation);// 开始动画效果    lvHeaderTipsTv.setText("松开刷新");    break;   case PULL_To_REFRESH:    lvHeaderProgressBar.setVisibility(View.GONE);    lvHeaderTipsTv.setVisibility(View.VISIBLE);    lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);    lvHeaderArrowIv.clearAnimation();    lvHeaderArrowIv.setVisibility(View.VISIBLE);    // 是由RELEASE_To_REFRESH状态转变来的    if (isBack) {     isBack = false;     lvHeaderArrowIv.clearAnimation();     lvHeaderArrowIv.startAnimation(reverseAnimation);     lvHeaderTipsTv.setText("下拉刷新");    } else {     lvHeaderTipsTv.setText("下拉刷新");    }    break;   case REFRESHING:    headerView.setPadding(0, 0, 0, 0);    lvHeaderProgressBar.setVisibility(View.VISIBLE);    lvHeaderArrowIv.clearAnimation();    lvHeaderArrowIv.setVisibility(View.GONE);    lvHeaderTipsTv.setText("正在刷新...");    lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);    break;   case DONE:    headerView.setPadding(0, -1 * headerContentHeight, 0, 0);    lvHeaderProgressBar.setVisibility(View.GONE);    lvHeaderArrowIv.clearAnimation();    lvHeaderArrowIv.setImageResource(R.drawable.arrow);    lvHeaderTipsTv.setText("下拉刷新");    lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);    break;   }  }  // 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 params = child.getLayoutParams();   if (params == null) {    params = new ViewGroup.LayoutParams(      ViewGroup.LayoutParams.FILL_PARENT,      ViewGroup.LayoutParams.WRAP_CONTENT);   }   int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0,     params.width);   int lpHeight = params.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 setonRefreshListener(OnRefreshListener refreshListener) {   this.refreshListener = refreshListener;   isRefreshable = true;  }  public interface OnRefreshListener {   public void onRefresh();  }  public void onRefreshComplete() {   state = DONE;   lvHeaderLastUpdatedTv.setText("最近更新:" + new Date().toLocaleString());   changeHeaderViewByState();  }  private void onLvRefresh() {   if (refreshListener != null) {    refreshListener.onRefresh();   }  }  public void setAdapter(LvAdapter adapter) {   lvHeaderLastUpdatedTv.setText("最近更新:" + new Date().toLocaleString());   super.setAdapter(adapter);  } }

<?xml version="1.0" encoding="utf-8"?> <!-- ListView的头部 --> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  android:layout_width="fill_parent"  android:layout_height="wrap_content"  android:background="#000000" >  <!-- 内容 -->  <RelativeLayout   android:id="@+id/head_contentLayout"   android:layout_width="fill_parent"   android:layout_height="wrap_content"   android:paddingLeft="30dp" >   <!-- 箭头图像、进度条 -->   <FrameLayout    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:layout_alignParentLeft="true"    android:layout_centerVertical="true" >    <!-- 箭头 -->    <ImageView     android:id="@+id/lvHeaderArrowIv"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_gravity="center"     android:src="@drawable/arrow" />    <!-- 进度条 -->    <ProgressBar     android:id="@+id/lvHeaderProgressBar"     style="?android:attr/progressBarStyleSmall"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_gravity="center"     android:visibility="gone" />   </FrameLayout>   <!-- 提示、最近更新 -->   <LinearLayout    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:layout_centerHorizontal="true"    android:gravity="center_horizontal"    android:orientation="vertical" >    <!-- 提示 -->    <TextView     android:id="@+id/lvHeaderTipsTv"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="下拉刷新"     android:textColor="@color/white"     android:textSize="20sp" />    <!-- 最近更新 -->    <TextView     android:id="@+id/lvHeaderLastUpdatedTv"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="上次更新"     android:textColor="@color/gold"     android:textSize="10sp" />   </LinearLayout>  </RelativeLayout> </LinearLayout>

<?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="fill_parent"  android:background="#000000"  android:orientation="vertical" >  <net.loonggg.listview.MyListView   android:id="@+id/lv"   android:layout_width="fill_parent"   android:layout_height="fill_parent" /> </LinearLayout>

package net.loonggg.listview; import java.util.ArrayList; import java.util.List; import net.loonggg.listview.MyListView.OnRefreshListener; import android.app.Activity; import android.os.AsyncTask; import android.os.Bundle; import android.view.View; public class MainActivity extends Activity {  private List<String> list;  private MyListView lv;  private LvAdapter adapter;  @Override  protected void onCreate(Bundle savedInstanceState) {   super.onCreate(savedInstanceState);   setContentView(R.layout.activity_main);   lv = (MyListView) findViewById(R.id.lv);   list = new ArrayList<String>();   list.add("loonggg");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   list.add("我们都是开发者");   adapter = new LvAdapter(list, this);   lv.setAdapter(adapter);   lv.setonRefreshListener(new OnRefreshListener() {    @Override    public void onRefresh() {     new AsyncTask<Void, Void, Void>() {      protected Void doInBackground(Void... params) {       try {        Thread.sleep(1000);       } catch (Exception e) {        e.printStackTrace();       }       list.add("刷新后添加的内容");       return null;      }      @Override      protected void onPostExecute(Void result) {       adapter.notifyDataSetChanged();       lv.onRefreshComplete();      }     }.execute(null, null, null);    }   });  }}

package net.loonggg.listview; import java.util.List; import android.content.Context; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.TextView; public class LvAdapter extends BaseAdapter {  private List<String> list;  private Context context;  public LvAdapter(List<String> list, Context context) {   this.list = list;   this.context = context;  }  @Override  public int getCount() {   return list.size();  }  @Override  public Object getItem(int position) {   return list.get(position);  }  @Override  public long getItemId(int position) {   return position;  }  @Override  public View getView(int position, View convertView, ViewGroup parent) {   TextView tv = new TextView(context.getApplicationContext());   tv.setText(list.get(position));   return tv;  } }