安卓爬坑指南之Recylerview

本文主要针对两个问题进行说明：

• 横向rv和viewpager滚动冲突
• rv滚动到底部监听

首先我们写一个自定义的rv

public class DefRecylerView extends RecyclerView {
    
    public DefRecylerView(Context context) {
        super(context);
    }

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

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

1. rv、viewpager滚动冲突

当遇到外层viewpager里面有一个横向滚动的rv，为防止rv滚动到最右侧时触发viewpager的滚动我们需要这样做:

    private ViewPager viewPager = null;

    public void setViewPager(ViewPager viewPager) {
        this.viewPager = viewPager;
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        if (viewPager != null) {
            getParent().requestDisallowInterceptTouchEvent(true);
        }
        return super.dispatchTouchEvent(ev);
    }

我们在自定义的rv中重写dispatchTouchEvent方法，最为核心的一句代码为:
getParent().requestDisallowInterceptTouchEvent(true);
意思是当外层view是viewpager时，我们取消viewpager对滚动事件的拦截，让滚动事件继续往下传递到rv，从而实现了横向rv滚动到最右侧时不触发viewpager的滚动。

2. rv滚动到底部监听

自定义rv中重写onScroll方法,定义一个回调接口，当rv滚动到底部时回调通知，适用于列表数据加载更多操作。

回调接口：

public interface OnSlideBottomListener {
    /**
     * 滚动到底部
     */
    void onSlideBottom();
}

重写onScroll：

    private OnSlideBottomListener onSlideBottomListener = null;

    public void setOnSlideBottomListener(OnSlideBottomListener onSlideBottomListener) {
        this.onSlideBottomListener = onSlideBottomListener;
    }
    
    @Override
    public void onScrolled(int dx, int dy) {
        if (isSlideToBottom()) {
            if (onSlideBottomListener != null) {
                onSlideBottomListener.onSlideBottom();
            }
        }
    }

    /**
     * 是否滑动到底部
     */
    public boolean isSlideToBottom() {
        if (this.getLayoutManager() instanceof LinearLayoutManager) {
            LinearLayoutManager layoutManager = (LinearLayoutManager) this.getLayoutManager();
            if (layoutManager.getOrientation() == LinearLayoutManager.VERTICAL) {
                return this != null
                        && this.computeVerticalScrollExtent() + this.computeVerticalScrollOffset()
                        >= this.computeVerticalScrollRange();
            } else {
                return this != null
                        && this.computeHorizontalScrollExtent() + this.computeHorizontalScrollOffset()
                        >= this.computeHorizontalScrollRange();
            }
        } else if(this.getLayoutManager() instanceof StaggeredGridLayoutManager){
            StaggeredGridLayoutManager layoutManager = (StaggeredGridLayoutManager) this.getLayoutManager();
            if (layoutManager.getOrientation() == StaggeredGridLayoutManager.VERTICAL) {
                return this != null
                        && this.computeVerticalScrollExtent() + this.computeVerticalScrollOffset()
                        >= this.computeVerticalScrollRange();
            } else {
                return this != null
                        && this.computeHorizontalScrollExtent() + this.computeHorizontalScrollOffset()
                        >= this.computeHorizontalScrollRange();
            }
        }

        return false;
    }