Android中ListView下拉刷新的实现方法实例分析

本文实例讲述了Android中ListView下拉刷新的实现方法。分享给大家供大家参考，具体如下：

ListView中的下拉刷新是非常常见的，也是经常使用的，看到有很多同学想要，那我就整理一下，供大家参考。那我就不解释，直接上代码了。

这里需要自己重写一下ListView,重写代码如下:

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);
 }
}

重写完ListView之后，在布局文件中是这么使用的，头部下拉刷新的布局文件lv_header.xml代码如下：

<?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>

在Main.xml中进行设置，代码如下：

<?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>

然后就是在MainActivity中实现，代码如下：

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);
   }
  });
 }
}

这里还需要为ListView设置一下Adapter,自定义的Adapter如下：

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;
 }
}

到这里就完了，代码中的解释非常详细，具体的我就不多说了，也不解释了，自己看看并研究吧！

希望本文所述对大家Android程序设计有所帮助。