Question

是否可以检查RecyclerView的第一项或第二项在用户的屏幕上是否可见？

例如，当用户向下滚动时：

  if (first item not visible to user)  { 
      // do something
  }
  else if ( first item is visible){
      // do something
  }

我目前要做的是在回收站中添加一个侦听器，以便当用户向下滚动时，它可以执行某些操作并向上滚动。

recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {

    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);
        if (dy > 0) {
            mAccountLayout.setVisibility(View.GONE);
            mDateLayout.setVisibility(View.GONE);
            Log.d("SCROLLINGDOWN","SCROLL");
        } else {
            mAccountLayout.setVisibility(View.VISIBLE);
            mDateLayout.setVisibility(View.VISIBLE);
            Log.d("SCROLLINGUP","SCROLL");
        }
    }
});

但是我需要检查第一项是否可见。

Answer 1

int firstVisiblePosition = layoutManager.findFirstVisibleItemPosition();
if (firstVisiblePosition  == 0) { do your thing )

Answer 2

您可以在RecyclerView.LayoutManager中找到一些帮助方法，例如，如果您使用LinearLayoutManager，请检查以下方法：

int findFirstCompletelyVisibleItemPosition() // Returns the adapter position of the first fully visible view.
int findFirstVisibleItemPosition() // Returns the adapter position of the first visible view.
int findLastCompletelyVisibleItemPosition() // Returns the adapter position of the last fully visible view.
int findLastVisibleItemPosition() // Returns the adapter position of the last visible view.

查看完整的文档here。

在您的代码中：

recyclerView.setAdapter(adapter);
final LinearLayoutManager layoutManager = new LinearLayoutManager(context);
recyclerView.setLayoutManager(layoutManager);

recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {

    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        if (layoutManager.findFirstVisibleItemPosition() > 0) {
            mAccountLayout.setVisibility(View.GONE);
            mDateLayout.setVisibility(View.GONE);
            Log.d("SCROLLINGDOWN","SCROLL");
        } else {
            mAccountLayout.setVisibility(View.VISIBLE);
            mDateLayout.setVisibility(View.VISIBLE);
            Log.d("SCROLLINGUP","SCROLL");
        }
    }
});

Answer 3

   declare globally LinearLayoutManager layoutManager;

and in oncreate use

     layoutManager = new LinearLayoutManager(this);

use this layoutmanager in recyclerview
   recyclerview.setLayoutManager(layoutManager);

        recyclerview.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);

                //Tocheck if  recycler is on top
                if (layoutManager.findFirstCompletelyVisibleItemPosition() == 0) {
//Its at top ..
                    //ie first item is visible
                } else {
             //not visible`enter code here`
                }
            }
        });

Answer 4

尝试一下。

    private LinearLayoutManager linearLayoutManager;// this two line define as global level.
protected int pastVisibleItems, visibleItemCount, totalItemCount;
protected void addScrollListener() {
    rvData.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            if (dy > 0) //check for scroll down
            {
                visibleItemCount = linearLayoutManager.getChildCount();
                totalItemCount = linearLayoutManager.getItemCount();
                pastVisibleItems = linearLayoutManager.findFirstVisibleItemPosition();

                if (!isPullingMoreResults) {
                    if ((visibleItemCount + pastVisibleItems) >= totalItemCount) {
                        if (mHasMoreResultsToPull && !isPullingMoreResults) {
                            isPullingMoreResults = true;
                            pageNumber++;
                            getMessage();
                        }
                    }
                }
            }
        }
    });
}

如何检查RecyclerView的第一项在屏幕上是否可见

4 个答案: