How to check if first item of RecyclerView is visible on the screen

问题

Is it possible to check if the first or second item of the RecyclerView is visible on the screen of the user?

For example when the user scrolls down:

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

What I currently do is I add a listener to my recycler so that when the user scrolls down, it will do something and scroll up.

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");
        }
    }
});

But what I need is to check if the first item is visible or not.

回答1:

You can find some helper methods in RecyclerView.LayoutManager, for example, if you use a LinearLayoutManager, check these methods:

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.

See the full docs here.

In your code:

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");
        }
    }
});

回答2:

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

回答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`
                }
            }
        });

回答4:

Try this things..

    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();
                        }
                    }
                }
            }
        }
    });
}

来源：https://stackoverflow.com/questions/50983472/how-to-check-if-first-item-of-recyclerview-is-visible-on-the-screen