Android中的smoothScrollToPosition兒童內部ViewPager中的片段

Question

我在ViewPager中設置了光滑滾動Fragments，嵌套在另一個Fragment中，它充當它們的父項。

我成立這個方法：

public void scrollToTop() 
    { 
     this.recyclerView.smoothScrollToPosition(0); 
    } 

對於Fragments不是在ViewPager，但我不知道怎麼弄的Fragments一個ViewPager內部參考。

我做

BottomLobiFragment activeLobi = (BottomLobiFragment)getSupportFragmentManager().findFragmentByTag(utilities.lobbyTag); 

獲取父Fragment。

代碼爲ViewPager（其餘的幾乎相同，差別只在項目數量和構造函數）

public class LobbyPagerAdapter extends FragmentStatePagerAdapter { 

     public LobbyPagerAdapter (FragmentManager fm) { 
      super(fm); 
     } 

     @Override 
     public Fragment getItem(int pos) { 
      switch(pos) { 
       case 0: return Friends.newInstance("Friends, Instance 1"); 
//    case 1: return Photo.newInstance("Photo, Instance 1"); 
//    case 2: return Activities.newInstance("Activities, Instance 1"); 
       default: return Friends.newInstance("Friends, Default"); 
      } 
     } 

     @Override 
     public CharSequence getPageTitle(int position) { 
      return CONTENT[position % CONTENT.length]; 
     } 

     @Override 
     public int getCount() { 
      //return 3; 
      return CONTENT.length; 
     } 

     private class setAdapterTask extends AsyncTask<Void,Void,Void> { 
      protected Void doInBackground(Void... params) { 
       return null; 
      } 

      @Override 
      protected void onPostExecute(Void result) { 
      } 
     } 
    } 

注：每個適配器位於父裏面Fragment

Answer 1

首先修改適配器到這個

public class LobbyPagerAdapter extends FragmentStatePagerAdapter { 

     private ArrayList<Fragment> mFragments = new ArrayList<>(); 

     public LobbyPagerAdapter (FragmentManager fm) { 
      super(fm); 
      mFragments.add(Friends.newInstance("Friends, Instance 1")); 
      mFragments.add(Photo.newInstance("Photo, Instance 1")); 
      mFragments.add(Activities.newInstance("Activities, Instance 1")); 
     } 

     @Override 
     public Fragment getItem(int pos) { 
      return mFragments.get(pos); 
     } 

     @Override 
     public CharSequence getPageTitle(int position) { 
      return CONTENT[position % CONTENT.length]; 
     } 

     @Override 
     public int getCount() { 
      //return 3; 
      return CONTENT.length; 
     } 

     private class setAdapterTask extends AsyncTask<Void,Void,Void> { 
      protected Void doInBackground(Void... params) { 
       return null; 
      } 

      @Override 
      protected void onPostExecute(Void result) { 
      } 
     } 
    } 

現在在你的片段或活動是拿着ViewPager &適配器實例，你可以簡單地做如adapter.getItem（1）;例如：

//Suppose your LobbyPagerAdapter instance looks like this in your code 

LobbyPagerAdapter adapter = new LobbyPagerAdapter(getFragmentManager()); 

// And now you want to get the fragment at second position in your tab 

Photo photoFragmentObject = (Photo)adapter.getItem(1); 

// And now you want to get the fragment at first position in your tab 

Friends friendsFragmentObject = (Friends)adapter.getItem(0);