如何检测用户何时滚动到RecyclerView中的最高项目

问题描述

我尝试编写以下代码

@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
  super.onScrolled(recyclerView, dx, dy);
  if(dy > 0){
    //scrolling up
  } else {
    //scrolling down
    int pastVisibleItems = linearLayoutManager.findFirstVisibleItemPosition();
    if (pastVisibleItems  == 0) {
      Toast.makeText(getContext(),"Top most item",Toast.LENGTH_SHORT).show();
    }
  }
}

但是它不起作用.我也尝试过使用android的SwipeRefreshLayout来执行此操作，因为它可以执行我想要的操作，能够在用户滚动到最顶部的项目时进行检测.我决定不使用它，因为我似乎无法阻止加载指示器弹出(我根本不希望看到加载指示器出来).

but it doesn't work. I have also tried using the android's SwipeRefreshLayout to do this since it does what I want which is able to detect when user has scroll to the topmost item. I decided to not use it because I can't seem to prevent the loading indicator from popping out (I don't want to see the loading indicator come out at all).

所以，基本上我想做的是:

So, basically what I want to do is:

1. 检查用户滚动
2. 它已经是最高的商品了吗?
3. 如果是，执行一些操作，如果否，则什么都不做

任何想法如何实现这一目标?

Any idea how to accomplish this?

谢谢.

推荐答案

我自己解决了我的问题.我改用下面的代码

I have solved my question by myself. I used the code below instead

private boolean isUserScrolling = false;
private boolean isListGoingUp = true;

然后在RecyclerView OnScrollListener中

Then in the RecyclerView OnScrollListener

@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
    super.onScrollStateChanged(recyclerView, newState);
    //detect is the topmost item visible and is user scrolling? if true then only execute
    if(newState ==  RecyclerView.SCROLL_STATE_DRAGGING){
        isUserScrolling = true;
        if(isListGoingUp){
            //my recycler view is actually inverted so I have to write this condition instead
            if(linearLayoutManager.findLastCompletelyVisibleItemPosition() + 1 == list.size()){
                Handler handler = new Handler();
                handler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        if(isListGoingUp) {
                            if (linearLayoutManager.findLastCompletelyVisibleItemPosition() + 1 == list.size()) {
                                Toast.makeText(getContext(),"exeute something", Toast.LENGTH_SHORT).show();
                            }
                        }
                    }
                },50);
                //waiting for 50ms because when scrolling down from top, the variable isListGoingUp is still true until the onScrolled method is executed
            }
        }
    }
}

@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
    super.onScrolled(recyclerView, dx, dy);
    if(isUserScrolling){
        if(dy > 0){
            //means user finger is moving up but the list is going down
            isListGoingUp = false;
        }
        else{
            //means user finger is moving down but the list is going up
            isListGoingUp = true;
        }
    }
}

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