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Android中ListView下拉刷新的实现方法 Android中ListView下拉刷新的实现方法实例分析

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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。

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