Question

我在我的应用程序中使用了 recyclerView ，并希望在其中添加向上滚动到顶部按钮，我在其中添加了按钮但无法当我点击按钮时，将我的recyclerView滚动到顶部，同时我还颠倒我的RecyclerView，以便我在其中添加的新帖子位于顶部而不是底部。请帮助我，非常感谢提前。我也使用了getPosition方法，但这对我没用。

我正在使用Android Studio

滚动操作类文件代码：

public class HomePage extends AppCompatActivity {

private FirebaseAuth mAuth;
private RecyclerViewPager mrecyclerView;
private DatabaseReference mDatabaseReference;
private Button rollUp;
public static int recyclerPos = 0;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home_page);
    mDatabaseReference = FirebaseDatabase.getInstance().getReference().child("post");
    mrecyclerView = (RecyclerViewPager) findViewById(R.id.list);
    final LinearLayoutManager layout = new LinearLayoutManager(HomePage.this, LinearLayoutManager.VERTICAL, false);
    layout.setReverseLayout(true);//<---- to get new posted data on top of list
    layout.setStackFromEnd(true);//<-----
    mrecyclerView.setLayoutManager(layout);
    rollUp = (Button) findViewById(R.id.roll_up);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    mAuth = FirebaseAuth.getInstance();

    this.mrecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        int mLastFirstVisibleItem = 0;

        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
        }

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);
            final int currentFirstVisibleItem = layout.findFirstVisibleItemPosition();

            if (currentFirstVisibleItem < this.mLastFirstVisibleItem) {
                HomePage.this.getSupportActionBar().hide();
            } else if (currentFirstVisibleItem > this.mLastFirstVisibleItem) {
                HomePage.this.getSupportActionBar().show();
            }
            this.mLastFirstVisibleItem = currentFirstVisibleItem;
        }
    });

}

    private void sentToStart() {
    Intent intent = new Intent(HomePage.this, LoginPage.class);
    startActivity(intent);
    finish();
}
@Override
    public boolean onCreateOptionsMenu(Menu menu) {
    super.onCreateOptionsMenu(menu);
    getMenuInflater().inflate(R.menu.menu_home_page, menu);
    return true;
}
@Override
    public boolean onOptionsItemSelected(MenuItem item) {
    super.onOptionsItemSelected(item);
    int id = item.getItemId();

    if (id == R.id.action_settings){
        Intent intentSettings = new Intent(HomePage.this,settings.class);
        startActivity(intentSettings);
        LinearLayoutManager layoutManager = ((LinearLayoutManager) mrecyclerView.getLayoutManager());
        recyclerPos = layoutManager.findFirstVisibleItemPosition();
    }
    if (id == R.id.roll_up){
        LinearLayoutManager layoutManagerroll = ((LinearLayoutManager) mrecyclerView.getLayoutManager());
        recyclerPos = layoutManagerroll.findFirstVisibleItemPosition();
        layoutManagerroll.scrollToPositionWithOffset(0,0);

    }
    return super.onOptionsItemSelected(item);
}

Answer 1

问题是您的位置错误，因为您要滚动到顶部，即0位置的元素，您必须执行此操作 mRecyclerView.smoothScrollToPosition(0); 不是这个 mrecyclerView.smoothScrollToPosition(recyclerPos.getItemCount()-1); 因为你滚动到最后只有一个元素。位置错误

另外，要在特定位置添加元素，请使用此 addItemAtPosition() and don't callnotifyDataSetChanged()，无需像您提到的那样反转整个列表。

使用按钮滚动到Android中的recyclerView顶部

1 个答案: