Android刷新加载框架详解

public interface Pullable {

  /**
   * 是否可下拉
   */
  boolean canPullDown();

  /**
   * 是否可上拉
   */
  boolean canPullUp();
}

public class PullToRefreshLayout extends RelativeLayout {

  /**
   * 头
   */
  private View headView;//头视图
  private ImageView headIv;//头图标
  private TextView headTv;//头文字
  private int headHeight;//头高度
  private float headBorder;//头临界
  /**
   * 拉
   */
  private View pullView;//拉视图
  private int pullHeight;//拉高度
  private int pullWidth;//拉宽度

  /**
   * 尾
   */
  private View footView;//尾视图
  private ImageView footIv;//尾图标
  private TextView footTv;//尾文字
  private int footHeight;//尾高度
  private float footBorder;//尾临界

  /**
   * 状态
   */
  public static final int INIT = 0;//初始
  public static final int RELEASE_TO_REFRESH = 1;//释放刷新
  public static final int REFRESHING = 2;//正在刷新
  public static final int RELEASE_TO_LOAD = 3;//释放加载
  public static final int LOADING = 4;//正在加载
  public static final int DONE = 5;//完成
  private int state = INIT;

  /**
   * 接口
   */
  private OnRefreshListener mListener;

  private float downY;//按下时Y坐标
  private float lastY;//上一个Y坐标
  private float pullDownY = 0;//下拉偏移量
  private float pullUpY = 0;//上拉偏移量
  private int offset;//偏移量

  /**
   * 动画
   */
  private RotateAnimation rotateAnimation;

  /**
   * 线程
   */
  private Handler handler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
      super.handleMessage(msg);
      if (msg != null) {
        switch (msg.what) {
          case 1:
            headIv.clearAnimation();
            break;
          case 2:
            footIv.clearAnimation();
            break;
          default:
            break;
        }
        pullDownY = 0;
        pullUpY = 0;
        requestLayout();
        state = INIT;
        refreshViewByState();
        isTouch = true;
      }
    }
  };

  /**
   * 第一次执行布局
   */
  private boolean isLayout = false;
  /**
   * 在刷新过程中滑动操作
   */
  private boolean isTouch = false;
  /**
   * 手指滑动距离与下拉头的滑动距离比，中间会随正切函数变化
   */
  private float radio = 2;
  /**
   * 过滤多点触碰
   */
  private int mEvents;
  /**
   * 这两个变量用来控制pull的方向，如果不加控制，当情况满足可上拉又可下拉时没法下拉
   */
  private boolean canPullDown = true;
  private boolean canPullUp = true;

  public void setOnRefreshListener(OnRefreshListener listener) {
    mListener = listener;
  }

  public PullToRefreshLayout(Context context) {
    super(context);
    initView(context);
  }

  public PullToRefreshLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
    initView(context);
  }

  public PullToRefreshLayout(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    initView(context);
  }

  private void initView(Context context) {
    rotateAnimation = (RotateAnimation) AnimationUtils.loadAnimation(context, R.anim.rotating);
  }

  private void refreshViewByState() {
    switch (state) {
      case INIT:
        // 下拉布局初始状态
        headIv.setImageResource("下拉刷新显示的图片");
        headTv.setText("下拉刷新");
        // 上拉布局初始状态
        footIv.setImageResource("上拉加载显示的图片");
        footTv.setText("上拉加载");
        break;
      case RELEASE_TO_REFRESH:
        // 释放刷新状态
        headIv.setImageResource("释放刷新显示的图片");
        headTv.setText("释放刷新");
        break;
      case REFRESHING:
        // 正在刷新状态
        headIv.setImageResource("正在刷新显示的图片");
        headTv.setText("正在刷新");
        break;
      case RELEASE_TO_LOAD:
        // 释放加载状态
        footIv.setImageResource("释放加载显示的图片");
        footTv.setText("释放加载");
        break;
      case LOADING:
        // 正在加载状态
        footIv.setImageResource("正在加载显示的图片");
        footTv.setText("正在加载");
        break;
      case DONE:
        // 刷新或加载完毕，啥都不做
        break;
    }
  }

  /**
   * 不限制上拉或下拉
   */
  private void releasePull() {
    canPullDown = true;
    canPullUp = true;
  }
  
  @Override
  public boolean dispatchTouchEvent(MotionEvent ev) {
    switch (ev.getActionMasked()) {
      case MotionEvent.ACTION_DOWN:
        downY = ev.getY();
        lastY = downY;
        mEvents = 0;
        releasePull();
        if (state != REFRESHING && state != LOADING) {
          isTouch = true;
        }
        break;
      case MotionEvent.ACTION_POINTER_DOWN:
      case MotionEvent.ACTION_POINTER_UP:
        // 过滤多点触碰
        mEvents = -1;
        break;
      case MotionEvent.ACTION_MOVE:
        if (mEvents == 0) {
          if (pullDownY > 0 || (((Pullable) pullView).canPullDown()
              && canPullDown && state != LOADING && state != REFRESHING)) {
            // 可以下拉，正在加载时不能下拉
            // 对实际滑动距离做缩小，造成用力拉的感觉
            pullDownY = pullDownY + (ev.getY() - lastY) / radio;
            if (pullDownY < 0) {
              pullDownY = 0;
              canPullDown = false;
              canPullUp = true;
            }
            if (pullDownY > getMeasuredHeight()) {
              pullDownY = getMeasuredHeight();
            }
            if (state == REFRESHING) {
              // 正在刷新的时候触摸移动
              isTouch = false;
            }
          } else if (pullUpY < 0
              || (((Pullable) pullView).canPullUp() && canPullUp && state != REFRESHING && state != LOADING)) {
            // 可以上拉，正在刷新时不能上拉
            pullUpY = pullUpY + (ev.getY() - lastY) / radio;

            if (pullUpY > 0) {
              pullUpY = 0;
              canPullDown = true;
              canPullUp = false;
            }
            if (pullUpY < -getMeasuredHeight()) {
              pullUpY = -getMeasuredHeight();
            }
            if (state == LOADING) {
              // 正在加载的时候触摸移动
              isTouch = false;
            }
          }
        }
        if (isTouch) {
          lastY = ev.getY();
          if (pullDownY > 0 || pullUpY < 0) {
            requestLayout();
          }
          if (pullDownY > 0) {
            if (pullDownY <= headBorder && (state == RELEASE_TO_REFRESH || state == DONE)) {
              // 如果下拉距离没达到刷新的距离且当前状态是释放刷新，改变状态为下拉刷新
              state = INIT;
              refreshViewByState();
            }
            if (pullDownY >= headBorder && state == INIT) {
              // 如果下拉距离达到刷新的距离且当前状态是初始状态刷新，改变状态为释放刷新
              state = RELEASE_TO_REFRESH;
              refreshViewByState();
            }
          } else if (pullUpY < 0) {
            // 下面是判断上拉加载的，同上，注意pullUpY是负值
            if (-pullUpY <= footBorder && (state == RELEASE_TO_LOAD || state == DONE)) {
              state = INIT;
              refreshViewByState();
            }
            // 上拉操作
            if (-pullUpY >= footBorder && state == INIT) {
              state = RELEASE_TO_LOAD;
              refreshViewByState();
            }
          }
          // 因为刷新和加载操作不能同时进行，所以pullDownY和pullUpY不会同时不为0，因此这里用(pullDownY +
          // Math.abs(pullUpY))就可以不对当前状态作区分了
          if ((pullDownY + Math.abs(pullUpY)) > 8) {
            // 防止下拉过程中误触发长按事件和点击事件
            ev.setAction(MotionEvent.ACTION_CANCEL);
          }
        }
        break;
      case MotionEvent.ACTION_UP:
        if (pullDownY > headBorder || -pullUpY > footBorder) {
          // 正在刷新时往下拉（正在加载时往上拉），释放后下拉头（上拉头）不隐藏
          isTouch = false;
        }
        if (state == RELEASE_TO_REFRESH) {
          state = REFRESHING;
          refreshViewByState();
          // 刷新操作
          if (mListener != null) {
            canPullDown = false;
            pullDownY = headBorder;
            pullUpY = 0;
            requestLayout();
            headIv.startAnimation(rotateAnimation);
            mListener.onRefresh(this);
          }
        } else if (state == RELEASE_TO_LOAD) {
          state = LOADING;
          refreshViewByState();
          // 加载操作
          if (mListener != null) {
            canPullUp = false;
            pullDownY = 0;
            pullUpY = -footBorder;
            requestLayout();
            footIv.startAnimation(rotateAnimation);
            mListener.onLoadMore(this);
          }
        } else {
          pullDownY = 0;
          pullUpY = 0;
          requestLayout();
        }
      default:
        break;
    }
    // 事件分发交给父类
    super.dispatchTouchEvent(ev);
    return true;
  }

  public void hideHeadView() {
    handler.sendEmptyMessage(1);
  }

  public void hideFootView() {
    handler.sendEmptyMessage(2);
  }

  private void initView() {
    // 初始化下拉布局
    headIv = (ImageView) headView.findViewById(R.id.iv_head);
    headTv = (TextView) headView.findViewById(R.id.tv_head);
    //初始化上拉布局
    footIv = (ImageView) footView.findViewById(R.id.iv_foot);
    footTv = (TextView) footView.findViewById(R.id.tv_foot);
    refreshViewByState();
  }

  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
    if (!isLayout) {
      // 这里是第一次进来的时候做一些初始化
      headView = getChildAt(0);
      pullView = getChildAt(1);
      footView = getChildAt(2);
      headBorder = ((ViewGroup) headView).getChildAt(0).getMeasuredHeight();
      footBorder = ((ViewGroup) footView).getChildAt(0).getMeasuredHeight();
      headHeight = headView.getMeasuredHeight();
      pullHeight = pullView.getMeasuredHeight();
      footHeight = footView.getMeasuredHeight();
      pullWidth = pullView.getMeasuredWidth();
      initView();
      isLayout = true;
    }
    // 改变子控件的布局，这里直接用(pullDownY + pullUpY)作为偏移量，这样就可以不对当前状态作区分
    offset = (int) (pullDownY + pullUpY);
    headView.layout(0, -headHeight + offset, pullWidth, offset);
    pullView.layout(0, offset, pullWidth, pullHeight + offset);
    footView.layout(0, pullHeight + offset, pullWidth, pullHeight + footHeight + offset);
  }

  public interface OnRefreshListener {
    void onRefresh(PullToRefreshLayout pullToRefreshLayout);

    void onLoadMore(PullToRefreshLayout pullToRefreshLayout);
  }

}

public class PullableListView extends ListView implements Pullable {

  public PullableListView(Context context) {
    super(context);
  }

  public PullableListView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  public PullableListView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }

  @Override
  public boolean canPullDown() {
    if (getCount() == 0) {
      // 没有item的时候也可以下拉刷新
      return false;
    } else if (getFirstVisiblePosition() == 0 && getChildAt(0).getTop() >= 0) {
      // 滑到ListView的顶部了
      return true;
    } else
      return false;
  }

  @Override
  public boolean canPullUp() {
    if (getCount() == 0) {
      // 没有item的时候也可以上拉加载
      return false;
    } else if (getLastVisiblePosition() == (getCount() - 1)) {
      // 滑到底部了
      if (getChildAt(getLastVisiblePosition() - getFirstVisiblePosition()) != null
          && getChildAt(getLastVisiblePosition() - getFirstVisiblePosition())
          .getBottom() <= getMeasuredHeight())
        return true;
    }
    return false;
  }
}

public class PullableGridView extends GridView implements Pullable {

  public PullableGridView(Context context) {
    super(context);
  }

  public PullableGridView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  public PullableGridView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }

  @Override
  public boolean canPullDown() {
    if (getCount() == 0) {
      // 没有item的时候也可以下拉刷新
      return false;
    } else if (getFirstVisiblePosition() == 0
        && getChildAt(0).getTop() >= 0) {
      // 滑到顶部了
      return true;
    } else
      return false;
  }

  @Override
  public boolean canPullUp() {
    if (getCount() == 0) {
      // 没有item的时候也可以上拉加载
      return false;
    } else if (getLastVisiblePosition() == (getCount() - 1)) {
      // 滑到底部了
      if (getChildAt(getLastVisiblePosition() - getFirstVisiblePosition()) != null
          && getChildAt(
          getLastVisiblePosition()
              - getFirstVisiblePosition()).getBottom() <= getMeasuredHeight())
        return true;
    }
    return false;
  }

}

public class PullableRecyclerView extends RecyclerView implements Pullable {

  public PullableRecyclerView(Context context) {
    super(context);
  }

  public PullableRecyclerView(Context context, @Nullable AttributeSet attrs) {
    super(context, attrs);
  }

  public PullableRecyclerView(Context context, @Nullable AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }

  @Override
  public boolean canPullDown() {
    RecyclerView.LayoutManager layoutManager = getLayoutManager();
    if (layoutManager instanceof LinearLayoutManager) {
      LinearLayoutManager linearLayoutManager = (LinearLayoutManager) layoutManager;
      if (linearLayoutManager.getItemCount() == 0) {
        return false;
      } else if (linearLayoutManager.findFirstVisibleItemPosition() == 0 && linearLayoutManager.getChildAt(0).getTop() >= 0) {
        return true;
      } else {
        return false;
      }
    } else if (layoutManager instanceof StaggeredGridLayoutManager) {
      StaggeredGridLayoutManager staggeredGridLayoutManager = (StaggeredGridLayoutManager) layoutManager;
      if (staggeredGridLayoutManager.getItemCount() == 0) {
        return false;
      } else {
        int[] firstVisibleItems = null;
        firstVisibleItems = staggeredGridLayoutManager.findFirstVisibleItemPositions(firstVisibleItems);
        if (firstVisibleItems != null && firstVisibleItems.length > 0) {
          if (staggeredGridLayoutManager.getChildCount() + firstVisibleItems[0] == staggeredGridLayoutManager.getItemCount()) {
            return true;
          }
        }
      }
    }
    return false;
  }

  @Override
  public boolean canPullUp() {
    RecyclerView.LayoutManager layoutManager = getLayoutManager();
    if (layoutManager instanceof LinearLayoutManager) {
      LinearLayoutManager linearLayoutManager = (LinearLayoutManager) layoutManager;
      if (linearLayoutManager.getItemCount() == 0) {
        return false;
      } else if (linearLayoutManager.findLastVisibleItemPosition() == (linearLayoutManager.getItemCount() - 1)) {
        if (linearLayoutManager.getChildAt(linearLayoutManager.findLastVisibleItemPosition() - linearLayoutManager.findFirstVisibleItemPosition()) != null
            && linearLayoutManager.getChildAt(linearLayoutManager.findLastVisibleItemPosition() - linearLayoutManager.findFirstVisibleItemPosition()).getBottom() <= getMeasuredHeight()) {
          return true;
        }
      }
    } else if (layoutManager instanceof StaggeredGridLayoutManager) {
      StaggeredGridLayoutManager staggeredGridLayoutManager = (StaggeredGridLayoutManager) layoutManager;
      if (staggeredGridLayoutManager.getItemCount() == 0) {
        return false;
      } else {
        int[] lastPositions = new int[staggeredGridLayoutManager.getSpanCount()];
        lastPositions = staggeredGridLayoutManager.findLastVisibleItemPositions(lastPositions);
        if (findMax(lastPositions) >= staggeredGridLayoutManager.getItemCount() - 1) {
          return true;
        }
      }
    }
    return false;
  }

  private int findMax(int[] lastPositions) {
    int max = lastPositions[0];
    for (int value : lastPositions) {
      if (value > max) {
        max = value;
      }
    }
    return max;
  }
}

public class PullableExpandableListView extends ExpandableListView implements
    Pullable {

  public PullableExpandableListView(Context context) {
    super(context);
  }

  public PullableExpandableListView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  public PullableExpandableListView(Context context, AttributeSet attrs,
                   int defStyle) {
    super(context, attrs, defStyle);
  }

  @Override
  public boolean canPullDown() {
    if (getCount() == 0) {
      // 没有item的时候也可以下拉刷新
      return false;
    } else if (getFirstVisiblePosition() == 0
        && getChildAt(0).getTop() >= 0) {
      // 滑到顶部了
      return true;
    } else
      return false;
  }

  @Override
  public boolean canPullUp() {
    if (getCount() == 0) {
      // 没有item的时候也可以上拉加载
      return false;
    } else if (getLastVisiblePosition() == (getCount() - 1)) {
      // 滑到底部了
      if (getChildAt(getLastVisiblePosition() - getFirstVisiblePosition()) != null
          && getChildAt(
          getLastVisiblePosition()
              - getFirstVisiblePosition()).getBottom() <= getMeasuredHeight())
        return true;
    }
    return false;
  }

}

public class PullableScrollView extends ScrollView implements Pullable {

  public PullableScrollView(Context context) {
    super(context);
  }

  public PullableScrollView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  public PullableScrollView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }

  @Override
  public boolean canPullDown() {
    if (getScrollY() == 0)
      return true;
    else
      return false;
  }

  @Override
  public boolean canPullUp() {
    if (getScrollY() >= (getChildAt(0).getHeight() - getMeasuredHeight()))
      return true;
    else
      return false;
  }

}

 public class PullableWebView extends WebView implements Pullable {

  public PullableWebView(Context context) {
    super(context);
  }

  public PullableWebView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  public PullableWebView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }

  @Override
  public boolean canPullDown() {
    if (getScrollY() == 0)
      return true;
    else
      return false;
  }

  @Override
  public boolean canPullUp() {
    if (getScrollY() >= getContentHeight() * getScale()
        - getMeasuredHeight())
      return true;
    else
      return false;
  }
}

public class PullableImageView extends ImageView implements Pullable
{

  public PullableImageView(Context context)
  {
    super(context);
  }

  public PullableImageView(Context context, AttributeSet attrs)
  {
    super(context, attrs);
  }

  public PullableImageView(Context context, AttributeSet attrs, int defStyle)
  {
    super(context, attrs, defStyle);
  }

  @Override
  public boolean canPullDown()
  {
    return true;
  }

  @Override
  public boolean canPullUp()
  {
    return true;
  }

}

public class PullableTextView extends TextView implements Pullable {

  public PullableTextView(Context context) {
    super(context);
  }

  public PullableTextView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  public PullableTextView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }

  @Override
  public boolean canPullDown() {
    return true;
  }

  @Override
  public boolean canPullUp() {
    return true;
  }

}

<view.PullToRefreshLayout
  android:id="@+id/ptrl"
  android:layout_width="match_parent"
  android:layout_height="match_parent">

  <include layout="@layout/head" />

  <view.PullableListView
    android:id="@+id/plv"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

  <include layout="@layout/foot" />
  
</view.PullToRefreshLayout>

<?xml version="1.0" encoding="UTF-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/head_view"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:background="@android:color/darker_gray">

  <RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:paddingBottom="20dp"
    android:paddingTop="20dp">

    <RelativeLayout
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true">

      <ImageView
        android:id="@+id/iv_head"
        android:layout_width="20dp"
        android:layout_height="20dp"
        android:layout_centerVertical="true"
        android:layout_marginLeft="60dp"
        android:scaleType="fitXY" />

      <TextView
        android:id="@+id/tv_head"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:textColor="@android:color/white"
        android:textSize="16sp" />
      
    </RelativeLayout>
    
  </RelativeLayout>
  
</RelativeLayout>

<?xml version="1.0" encoding="UTF-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/loadmore_view"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:background="@android:color/darker_gray">

  <RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:paddingBottom="20dp"
    android:paddingTop="20dp">

    <RelativeLayout
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true">

      <ImageView
        android:id="@+id/iv_foot"
        android:layout_width="20dp"
        android:layout_height="20dp"
        android:layout_centerVertical="true"
        android:layout_marginLeft="60dp"
        android:scaleType="fitXY" />

      <TextView
        android:id="@+id/tv_foot"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:textColor="@android:color/white"
        android:textSize="16sp" />
    </RelativeLayout>
    
  </RelativeLayout>
  
</RelativeLayout>