Android ListView实现下拉加载功能

本文实例为大家分享了ListView下拉加载展示的具体代码，供大家参考，具体内容如下

1、MyListView.Java

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) {
  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);
 } 

}

2、MainActivity.java

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.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);
   }
  });
 }
}

3、LvAdapter
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; 
    } 
 
}

4、lv_header.xml
[html] view plain copy
<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="#fff" 
                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="#333" 
                android:textSize="10sp" /> 
        </LinearLayout> 
    </RelativeLayout> 
 
</LinearLayout>

5、main.xml
[html] view plain copy
<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>

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。