android教你打造独一无二的上拉下拉刷新加载框架

其实早在去年七月，群里小伙伴就有让我共享这个。但我当时绝的技术不纯熟。代码有bug什么的。没有写出来。现在感觉整理的差不多了。就写出来让大家看看，有问题一起讨论解决。

说到刷新加载，我们第一个想到啥，对了就是swiperefreshlayout，还有什么SuperSwiperefreshlayout，XRecyclerView等等。反正老多了，我还是之前那句话，不管用什么，我们需要知道他的原理。

打造框架开始

对于刷新加载的实现，你们第一个想到的是什么？是用swiperefresh然后在recyclerview底部加一个不同type？还是用事件拦截呢？那必须是事件拦截啊，虽然现在swiperefreshlayout很火，基本很多app都能看到他。但是遇到那种坑比公司说刷新要用自己公司logo你也没辙。对把。。好了，感觉得罪了好多公司，不管他，我们继续。

我们先看下我们的效果图：

老铁，没毛病。下面我介绍如何实现的。

下拉刷新

首先我们给出如下几个参数，后面要用：

  private NestedScrollingParentHelper helper = null;
  private boolean IsRefresh = true;
  private boolean IsLoad = true;
  //滑动的总距离
  private int totalY = 0;
  private LinearLayout headerLayout = null;
  private MyRecyclerView myRecyclerView = null;
  private LinearLayout footerLayout = null;

既然是刷新，我们的滚动肯定是在父view之前的。所以我们需要在onNestedPreScroll这个方法里面写上我们所需要改动的x，y值。

我们需要用父view去拦截它。

我们需要判断dy的值是否大于0，因为大于0是刷新操作，小于0是加载操作。然后我们需要判断recyclerview是否是纵向的而不是横向的。

public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
    if (IsRefresh) {
      if (dy > 0) {
        if (myRecyclerView.isOrientation(0)) {
          totalY += dy;
          if ((totalY / 2) <= 0) {
            scrollTo(0, totalY / 2);
            consumed[1] = dy;
          } else {
            scrollTo(0, 0);
            consumed[1] = 0;
          }
        }
        return;
      }
    }

上拉加载

上面我也说了onNestedPreScroll这个方法中判断dy<0才是加载操作。所以综上所述，代码变成了这样：

 public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
    if (totalY < 0 && myRecyclerView.isOrientation(0) || totalY > 0 && myRecyclerView.isOrientation(1)) {
      isfling = true;
    }
    if (IsRefresh) {
      if (dy > 0) {
        if (myRecyclerView.isOrientation(0)) {
          totalY += dy;
          if ((totalY / 2) <= 0) {
            scrollTo(0, totalY / 2);
            consumed[1] = dy;
          } else {
            scrollTo(0, 0);
            consumed[1] = 0;
          }
        }
        return;
      }
    }
    if (IsLoad) {
      if (dy < 0) {
        if (myRecyclerView.isOrientation(1)) {
          totalY += dy;
          if ((totalY / 2) >= 0) {
            scrollTo(0, totalY / 2);
            consumed[1] = dy;
          } else {
            scrollTo(0, 0);
            consumed[1] = 0;
          }
        }
        return;
      }
    }
  }

最后我们需要在子view滑动结束后，实行如下操作：

 //子view滑动结束调用
  //dyUnconsumed < 0 向下滚
  //dyUnconsumed > 0 向上滚
  public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
    if (dyUnconsumed != 0) {
      totalY += dyUnconsumed;
      scrollTo(0, totalY / 2);
    }
  }

其实最主要的两个方法已经解决了，其他到没什么了，这边，我把nestedscrolling的8个接口的功能和自定义recyclerview放出来。已变大家参考。希望大家都能实现自己的刷新加载。告别swiperefreshlayout。

添加header和footer

这里我们参考listview自带的addheaderview和addfooterview。代码如下：

 public void addHeaderView(View headerView, int headerHeight) {
    this.headerLayout.removeAllViews();
    this.headerLayout.addView(headerView);
    LayoutParams layoutParams = new LayoutParams(LayoutParams.MATCH_PARENT, headerHeight);
    layoutParams.topMargin = -headerHeight;
    this.headerLayout.setLayoutParams(layoutParams);
  }
  public void addFooterView(View footerView, int footerHeight) {
    this.footerLayout.removeAllViews();
    this.footerLayout.addView(footerView);
    this.footerLayout.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, footerHeight));
  }

几个接口的实现

 public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
    return true;
  }
  public void onNestedScrollAccepted(View child, View target, int axes) {
    helper.onNestedScrollAccepted(child, target, axes);
  }
  //父view拦截子view的滚动
  public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
    if (totalY < 0 && myRecyclerView.isOrientation(0) || totalY > 0 && myRecyclerView.isOrientation(1)) {
      isfling = true;
    }
    if (IsRefresh) {
      if (dy > 0) {
        if (myRecyclerView.isOrientation(0)) {
          totalY += dy;
          if ((totalY / 2) <= 0) {
            scrollTo(0, totalY / 2);
            consumed[1] = dy;
          } else {
            scrollTo(0, 0);
            consumed[1] = 0;
          }
        }
        return;
      }
    }
    if (IsLoad) {
      if (dy < 0) {
        if (myRecyclerView.isOrientation(1)) {
          totalY += dy;
          if ((totalY / 2) >= 0) {
            scrollTo(0, totalY / 2);
            consumed[1] = dy;
          } else {
            scrollTo(0, 0);
            consumed[1] = 0;
          }
        }
        return;
      }
    }
  }
  //子view滑动结束调用
  //dyUnconsumed < 0 向下滚
  //dyUnconsumed > 0 向上滚
  public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
    if (dyUnconsumed != 0) {
      totalY += dyUnconsumed;
      scrollTo(0, totalY / 2);
    }
  }
  public void onStopNestedScroll(View child) {
    helper.onStopNestedScroll(child);
    if (onTouchUpListener != null) {
      isfling = false;
      onTouchUpListener.touchUp();
    }
  }
  public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {
    return isfling;
  }
  public boolean onNestedPreFling(View target, float velocityX, float velocityY) {
    return isfling;
  }
  public int getNestedScrollAxes() {
    return helper.getNestedScrollAxes();
  }

自定义recyclerview

既然是自己写的刷新加载框架，总不能还有自定义layout中在放个recyclerview。多麻烦，自定义一个，直接放在里面，然后分别放个header和footer 就没必要每次有页面用到刷新都要写一个布局。3个布局解决整个项目的刷新和加载。话不多说，代码如下：

  private class MyRecyclerView extends RecyclerView {
    private StaggeredGridLayoutManager staggeredGridLayoutManager = null;
    private LinearLayoutManager linearLayoutManager = null;
    private GridLayoutManager gridLayoutManager = null;
    private boolean isScrollLoad = false;
    private boolean isScrollRefresh = false;
    public MyRecyclerView(Context context) {
      super(context);
      setVerticalFadingEdgeEnabled(false);
      setHorizontalFadingEdgeEnabled(false);
      setVerticalScrollBarEnabled(false);
      setHorizontalScrollBarEnabled(false);
      setOverScrollMode(OVER_SCROLL_NEVER);
      setItemAnimator(new DefaultItemAnimator());
    }
    private void setMyLayoutManager(LayoutManager layoutManager) {
      if (layoutManager instanceof StaggeredGridLayoutManager) {
        staggeredGridLayoutManager = (StaggeredGridLayoutManager) layoutManager;
      } else if (layoutManager instanceof GridLayoutManager) {
        gridLayoutManager = (GridLayoutManager) layoutManager;
      } else if (layoutManager instanceof LinearLayoutManager) {
        linearLayoutManager = (LinearLayoutManager) layoutManager;
      }
      setLayoutManager(layoutManager);
      if (!isVertical()) {
        throw new NullPointerException("vertical!");
      }
    }
    private boolean isOrientation(int orientation) {//orientation,0代表向下，1代表向上
      if (orientation == 0)
        return isCanPullDown();
      else if (orientation == 1)
        return isCanPullUp();
      return false;
    }
    private boolean isCanPullDown() {
      return !canScrollVertically(-1);
    }
    private boolean isCanPullUp() {
      return !canScrollVertically(1);
    }
//    private int scrollLoad() {
//      int lastItem = 0;
//      int itemCount = 0;
//      int spanCount = 1;
//      if (staggeredGridLayoutManager != null) {
//        lastItem = staggeredGridLayoutManager.findLastVisibleItemPositions(null)[0];
//        itemCount = staggeredGridLayoutManager.getItemCount();
//        spanCount = staggeredGridLayoutManager.getSpanCount();
//      } else if (linearLayoutManager != null) {
//        lastItem = linearLayoutManager.findLastVisibleItemPosition();
//        itemCount = linearLayoutManager.getItemCount();
//        spanCount = 1;
//      } else if (gridLayoutManager != null) {
//        lastItem = gridLayoutManager.findLastVisibleItemPosition();
//        itemCount = gridLayoutManager.getItemCount();
//        spanCount = gridLayoutManager.getSpanCount();
//      }
//      return ((itemCount - 1) / spanCount + 1) - (lastItem / spanCount + 1);
//    }
    private boolean isVertical() {
      if (staggeredGridLayoutManager != null)
        return staggeredGridLayoutManager.getOrientation() == StaggeredGridLayoutManager.VERTICAL;
      else if (linearLayoutManager != null)
        return linearLayoutManager.getOrientation() == LinearLayoutManager.VERTICAL;
      else if (gridLayoutManager != null)
        return gridLayoutManager.getOrientation() == GridLayoutManager.VERTICAL;
      return false;
    }
//    public void onScrolled(int dx, int dy) {
//      if (dy > 0 && !isScrollLoad) {
//        if (oLior != null) {
//          onScrollListener.scrollLoad(sc````````
`
``
llLoad());//传递滚动到倒数第几行
//        }
//      }
//    }
  }

这样我们变实现了自己的刷新加载框架，代码我已上传：SWPullRecyclerLayout_jb51.rar

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