滾動到recyclerView在Android的頂部用一個按鈕

我用recyclerView在我的應用程序，並希望在添加向上滾動到頂部的按鈕，我已經在裏面添加的按鈕，但也不能當我點擊按鈕滾動我的recyclerView時，我也有顛倒我的RecyclerView，以便我添加的新帖子出現在頂部而不是底部。請提前幫助我，非常感謝。我也使用getPosition方法，但這並不適合我。滾動到recyclerView在Android的頂部用一個按鈕

我使用過Android Studio

滾動操作類文件代碼：

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); 
}

來源

2017-10-15 rohit b

此問題以前已被詢問過很多次。 –

@ H.Brooks你可以參考一些，我已經嘗試了很多，但他們沒有爲我工作，我無法得到正確的答案 –

https://stackoverflow.com/q/32159724/5550161 –

的問題是，你的立場是錯誤的，因爲要滾動到頂部這是元素在0的位置，你必須這樣做mRecyclerView.smoothScrollToPosition(0); 不是這個mrecyclerView.smoothScrollToPosition(recyclerPos.getItemCount()-1);。
當你滾動到最後只有一個元素。所在的方位不對

而且到在特定位置使用添加元素這個addItemAtPosition() and don't callnotifyDataSetChanged()無需逆整個列表像你提到的。

來源

2017-10-16 00:45:26

滾動到recyclerView在Android的頂部用一個按鈕

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