获取Infinite RecyclerView的中心可见项目值

1

By using center indicator(textview) in the layout and addOnScrollListner we can achieve this 
please refer the following example

在XML：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" 
android:layout_height="match_parent" 
> 
<TextView 
    android:layout_width="wrap_content" 
    android:text="↓" 
    android:id="@+id/centerIndicator" 
    android:textSize="24sp" 
    android:textStyle="bold" 
    android:visibility="visible" 
    android:textColor="@color/theme_yellow" 
    android:layout_centerHorizontal="true" 
    android:layout_height="wrap_content" 
    android:layout_marginTop="27dp" 
    android:background="@android:color/transparent" 
    /> 
<android.support.v7.widget.RecyclerView 
    android:layout_width="match_parent" 
    android:id="@+id/list" 
    android:clipToPadding="false" 
    android:divider="@android:color/transparent" 
    android:layout_height="wrap_content"/> 

</RelativeLayout>

在活动/片段：

public class Sample extends Fragment { 
    RecyclerView listView; 
    ArrayList<String>mWeekDaysList=new ArrayList<>(); 
    LinearLayoutManager mlinearLayoutManagerForDateList; 
    DateAdapter mDateAdapter; 
    TimeListAdapter mtimeAdapter; 
    private int mCenterPivot; 
    private boolean mAutoSet = true; 
    Activity mactivity; 
    public NigaichiNiralFrag() { 
     // Required empty public constructor 
    } 
    @Override 
    public View onCreateView(final LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     // Inflate the layout for this fragment 
     View view= inflater.inflate(R.layout.fragment_nigaichi_niral, container, false); 
mactivity=getActivity(); 
     mWeekDaysList.add("Sunday"); 
     mWeekDaysList.add("Monday"); 
     mWeekDaysList.add("Tuesday"); 
     mWeekDaysList.add("Wednesday"); 
     mWeekDaysList.add("Thursday"); 
     mWeekDaysList.add("Friday"); 
     mWeekDaysList.add("Saturday"); 

     listView = (RecyclerView) view.findViewById(R.id.list); 
     mlinearLayoutManagerForDateList = new LinearLayoutManager(mactivity); 
mlinearLayoutManagerForDateList.setOrientation(LinearLayoutManager.HORIZONTAL); 
     listView.setLayoutManager(mlinearLayoutManagerForDateList); 
     final TextView mCenterIndicator = (TextView) view.findViewById(R.id.centerIndicator); 
     final int itemWidth = (int) getResources().getDimension(R.dimen.flexible_space_image_height) ; 
     mlinearLayoutManagerForDateList.scrollToPosition(Integer.MAX_VALUE/2);   
     mDateAdapter=new DateAdapter(mWeekDaysList); 
     listView.setAdapter(mDateAdapter); 
     mCenterIndicator.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() { 
      @Override 
      public void onGlobalLayout() { 

       int center = (mCenterIndicator.getLeft() + mCenterIndicator.getRight())/2 ; 
       int padding = center - itemWidth/2; //Assuming both left and right padding needed are the same 
       listView.setPadding(5,0,5,0); 
       mCenterPivot = center; 
       listView.addOnScrollListener(new RecyclerView.OnScrollListener() { 
        @Override 
        public void onScrollStateChanged(RecyclerView recyclerView, int newState) { 
         super.onScrollStateChanged(recyclerView, newState); 
         LinearLayoutManager lm = (LinearLayoutManager) recyclerView.getLayoutManager(); 
         if(mCenterPivot == 0) { 

          // Default pivot , Its a bit inaccurate . 
          // Better pass the center pivot as your Center Indicator view's 
          // calculated center on it OnGlobalLayoutListener event 
          mCenterPivot = lm.getOrientation() == LinearLayoutManager.HORIZONTAL ? (recyclerView.getLeft() + recyclerView.getRight()) : (recyclerView.getTop() + recyclerView.getBottom()); 
         } 
         if(!mAutoSet) { 

          if(newState == RecyclerView.SCROLL_STATE_IDLE) { 
           //ScrollStoppped 

           View view = findCenterView(lm);//get the view nearest to center 
           //view.setBackgroundColor(Color.RED); 

           int position = recyclerView.getChildAdapterPosition(view) % mWeekDaysList.size(); 
           Log.d("isideScroll",mWeekDaysList.get(position)); 
           mDateAdapter.setSelecteditem(position); 
           int viewCenter = lm.getOrientation() == LinearLayoutManager.HORIZONTAL ? (view.getLeft() + view.getRight())/2 :(view.getTop() + view.getBottom())/2; 
           //compute scroll from center 
           int scrollNeeded = viewCenter - mCenterPivot; // Add or subtract any offsets you need here 

           if(lm.getOrientation() == LinearLayoutManager.HORIZONTAL) { 

            recyclerView.smoothScrollBy(scrollNeeded, 0); 
           } 
           else 
           { 
            recyclerView.smoothScrollBy(0, (int) (scrollNeeded)); 

           } 
           mAutoSet =true; 
          } 
         } 
         if(newState == RecyclerView.SCROLL_STATE_DRAGGING || newState == RecyclerView.SCROLL_STATE_SETTLING){ 

          mAutoSet =false; 
         } 
        } 

        @Override 
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) { 
         super.onScrolled(recyclerView, dx, dy); 
        } 
       }); 

      } 
     }); 
     return returnView; 
    } 
    private void scrollToCenter(View v) { 
     int itemToScroll = listView.getChildAdapterPosition(v); 
     int centerOfScreen = listView.getWidth()/2 - v.getWidth()/2; 
     //v.setBackgroundColor(Color.RED); 
     mlinearLayoutManagerForDateList.scrollToPositionWithOffset(itemToScroll, centerOfScreen); 
    } 
    private View findCenterView(LinearLayoutManager lm) { 

    int minDistance = 0; 
    View view = null; 
    View returnView = null; 
    boolean notFound = true; 

    for(int i = lm.findFirstVisibleItemPosition(); i <= lm.findLastVisibleItemPosition() && notFound ; i++) { 

     view=lm.findViewByPosition(i); 

     int center = lm.getOrientation() == LinearLayoutManager.HORIZONTAL ? (view.getLeft() + view.getRight())/ 2 : (view.getTop() + view.getBottom())/ 2; 
     int leastDifference = Math.abs(mCenterPivot - center); 

     if(leastDifference <= minDistance || i == lm.findFirstVisibleItemPosition()) 
     { 
      minDistance = leastDifference; 
      returnView=view; 
     } 
     else 
     { 
      notFound=false; 

     } 
    } 
    return returnView; 
} 
}

适配器：

public class DateAdapter extends RecyclerView.Adapter<DateAdapter.ReviewHolder> { 
    ArrayList<String> mData; 
    private int selectedItem = -1; 
    int pos=0; 
    public DateAdapter(ArrayList<String> data){ 
     mData=data; 
    } 

    @Override 
    public ReviewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
     Context context = parent.getContext(); 
     View v= LayoutInflater.from(context).inflate(R.layout.item_horz,parent,false); 
     return new DateAdapter.ReviewHolder(v); 
    } 

    @Override 
    public void onBindViewHolder(ReviewHolder holder, int position) { 
     pos=position; 
     position = position % mData.size(); 
     holder.tvName.setText(mData.get(position)); 
     holder.tvName.setGravity(Gravity.CENTER); 

     if (position == selectedItem) { 
      Log.d("CenterPosition", "center" + position); 
      holder.tvName.setTextColor(Color.RED); 
      holder.tvName.setTextSize(20); 
      holder.tvName.setBackgroundColor(Color.parseColor("#fccd00")); 

     } else { 
      holder.tvName.setTextColor(Color.WHITE); 
      holder.tvName.setTextSize(16); 
      holder.tvName.setBackgroundColor(Color.BLACK); 
     } 
    } 

    @Override 
    public int getItemCount() { 
     // return mData.size(); 
     return Integer.MAX_VALUE; 
    } 

    public class ReviewHolder extends RecyclerView.ViewHolder { 

     protected TextView tvName; 
     View container; 

     public ReviewHolder(View itemView) { 
      super(itemView); 
      container=itemView; 
      tvName= (TextView) itemView.findViewById(R.id.text); 
     } 
    } 
    public void setSelecteditem(int selecteditem) { 
     Log.d("POSITION",String.valueOf(selecteditem)); 
     this.selectedItem = selecteditem; 
     notifyDataSetChanged(); 
    } 

}

item_horz.xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 

     android:layout_width="151dp" 
     android:id="@+id/wrapper" 
     android:background="@color/white" 
    android:orientation="horizontal" 
     android:layout_height="50dp"> 
    <LinearLayout 
     android:layout_width="150dp" 
     android:layout_height="50dp" 
     android:background="@color/black"> 
     <TextView 
      android:layout_width="match_parent" 
      android:layout_height="match_parent" 
      android:textSize="20sp" 
      android:id="@+id/text" 
      android:textColor="@color/white" 
      android:text="21" 
      android:gravity="center" 
      /> 
    </LinearLayout> 
    </LinearLayout>

希望这会帮助你们..

来源

2017-07-24 12:59:25

+0

哇！它为我的情况正确工作。谢谢很多！ – Darsy

0

在BindView中，您可以检查适配器的中间位置，并为该特定支架应用图像的逻辑。

onBindViewHolder(View holder, int postion){ 
if(position == getItemCount()/2) 
{ //Write image logic for holder 
}}

来源

2017-07-19 12:32:11

+0

它不工作，因为适配器的大小是无限的..它会给IndexOutOfboundexception – Darsy

1

如果您想使用horizontalscrollview（动态创建项目）而不是recyclerview。

创建父布局

<HorizontalScrollView 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:layout_alignParentBottom="true"> 

      <LinearLayout 
       android:layout_alignParentBottom="true" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:orientation="horizontal"/> 

     </HorizontalScrollView>

膨胀您的孩子的物品父布局。

 LayoutInflater inflater = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE); 

       for (int i = 0; i < list.size(); i++) { 
      // inflate child element 
      final LinearLayout titleRow = (LinearLayout) inflater.inflate(R.layout.item_gallery, fragmentGalleryScrollLl, false); 
        final CircleImageView shapeImageView = (CircleImageView) titleRow.findViewById(R.id.item_gallery_iv); 

        shapeImageView.setOnClickListener(new View.OnClickListener() { 
         @Override 
         public void onClick(View v) { 

          scrollItem(titleRow); 


         } 
        }); 
        fragmentGalleryScrollLl.addView(titleRow); 

       }

当您单击项目时使用此方法。

private void scrollItem(LinearLayout titleRow) { 
     int scrollX = (titleRow.getLeft() - (fragmentGalleryScrollSv.getWidth()/2)) + (titleRow.getWidth()/2); 
     fragmentGalleryScrollSv.smoothScrollTo(scrollX, 0); 
    }

来源

2017-07-19 12:52:24 6155031

获取Infinite RecyclerView的中心可见项目值

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