如何创建具有多种视图类型的 RecyclerView?

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {

    private String[] mDataset;

    public MyAdapter(String[] myDataset) {
        mDataset = myDataset;
    }

    public static class ViewHolder extends RecyclerView.ViewHolder {
        public TextView mTextView;
        public ViewHolder(TextView v) {
            super(v);
            mTextView = v;
        }
    }

    @Override
    public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.some_layout, parent, false);

        //findViewById...

        ViewHolder vh = new ViewHolder(v);
        return vh;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        holder.mTextView.setText(mDataset[position]);
    }

    @Override
    public int getItemCount() {
        return mDataset.length;
    }
}

答案

是的,有可能。只需实现getItemViewType() ,并在onCreateViewHolder()中处理viewType参数即可。

因此,您可以执行以下操作:

public class MyAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    class ViewHolder0 extends RecyclerView.ViewHolder {
        ...
        public ViewHolder0(View itemView){
        ...
        }
    }

    class ViewHolder2 extends RecyclerView.ViewHolder {
        ...
        public ViewHolder2(View itemView){
        ...
    }

    @Override
    public int getItemViewType(int position) {
        // Just as an example, return 0 or 2 depending on position
        // Note that unlike in ListView adapters, types don't have to be contiguous
        return position % 2 * 2;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
         switch (viewType) {
             case 0: return new ViewHolder0(...);
             case 2: return new ViewHolder2(...);
             ...
         }
    }

    @Override
    public void onBindViewHolder(final RecyclerView.ViewHolder holder, final int position) {
        switch (holder.getItemViewType()) {
            case 0:
                ViewHolder0 viewHolder0 = (ViewHolder0)holder;
                ...
                break;

            case 2:
                ViewHolder2 viewHolder2 = (ViewHolder2)holder;
                ...
                break;
        }
    }
}

如果视图类型的布局很少,并且绑定逻辑很简单,请遵循 Anton 的解决方案。
但是,如果您需要管理复杂的布局和绑定逻辑,则代码将很混乱。

我相信以下解决方案对于需要处理复杂视图类型的人很有用。

基础 DataBinder 类

abstract public class DataBinder<T extends RecyclerView.ViewHolder> {

    private DataBindAdapter mDataBindAdapter;

    public DataBinder(DataBindAdapter dataBindAdapter) {
        mDataBindAdapter = dataBindAdapter;
    }

    abstract public T newViewHolder(ViewGroup parent);

    abstract public void bindViewHolder(T holder, int position);

    abstract public int getItemCount();

......

}

创建单个视图类型时,在此类中定义的功能与适配器类几乎相同。
对于每种视图类型,通过扩展此 DataBinder 创建类。

示例 DataBinder 类

public class Sample1Binder extends DataBinder<Sample1Binder.ViewHolder> {

    private List<String> mDataSet = new ArrayList();

    public Sample1Binder(DataBindAdapter dataBindAdapter) {
        super(dataBindAdapter);
    }

    @Override
    public ViewHolder newViewHolder(ViewGroup parent) {
        View view = LayoutInflater.from(parent.getContext()).inflate(
            R.layout.layout_sample1, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void bindViewHolder(ViewHolder holder, int position) {
        String title = mDataSet.get(position);
        holder.mTitleText.setText(title);
    }

    @Override
    public int getItemCount() {
        return mDataSet.size();
    }

    public void setDataSet(List<String> dataSet) {
        mDataSet.addAll(dataSet);
    }

    static class ViewHolder extends RecyclerView.ViewHolder {

        TextView mTitleText;

        public ViewHolder(View view) {
            super(view);
            mTitleText = (TextView) view.findViewById(R.id.title_type1);
        }
    }
}

为了管理 DataBinder 类,请创建适配器类。

基础 DataBindAdapter 类

abstract public class DataBindAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return getDataBinder(viewType).newViewHolder(parent);
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) {
        int binderPosition = getBinderPosition(position);
        getDataBinder(viewHolder.getItemViewType()).bindViewHolder(viewHolder, binderPosition);
    }

    @Override
    public abstract int getItemCount();

    @Override
    public abstract int getItemViewType(int position);

    public abstract <T extends DataBinder> T getDataBinder(int viewType);

    public abstract int getPosition(DataBinder binder, int binderPosition);

    public abstract int getBinderPosition(int position);

......

}

通过扩展此基类来创建该类,然后实例化 DataBinder 类并重写抽象方法

  1. getItemCount
    返回 DataBinder 的总项目数

  2. getItemViewType
    定义适配器位置和视图类型之间的映射逻辑。

  3. getDataBinder
    根据视图类型返回 DataBinder 实例

  4. getPosition
    从指定 DataBinder 中的位置定义转换逻辑到适配器位置

  5. getBinderPosition
    从适配器位置定义转换逻辑到 DataBinder 中的位置

希望此解决方案会有所帮助。
我在 GitHub 上留下了更多详细的解决方案和示例,因此如果需要,请参考以下链接。
https://github.com/yqritc/RecyclerView-MultipleViewTypesAdapter

以下不是伪代码,我已经对其进行了测试,并且对我有用。

我想在我的 recyclerview 中创建一个 headerview,然后在用户可以单击的 header 下显示一个图片列表。

我在代码中使用了一些开关,不知道这是否是最有效的方法,所以请随意发表评论:

public class ViewHolder extends RecyclerView.ViewHolder{

        //These are the general elements in the RecyclerView
        public TextView place;
        public ImageView pics;

        //This is the Header on the Recycler (viewType = 0)
        public TextView name, description;

        //This constructor would switch what to findViewBy according to the type of viewType
        public ViewHolder(View v, int viewType) {
            super(v);
            if (viewType == 0) {
                name = (TextView) v.findViewById(R.id.name);
                decsription = (TextView) v.findViewById(R.id.description);
            } else if (viewType == 1) {
                place = (TextView) v.findViewById(R.id.place);
                pics = (ImageView) v.findViewById(R.id.pics);
            }
        }
    }


    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent,
                                         int viewType)
    {
        View v;
        ViewHolder vh;
        // create a new view
        switch (viewType) {
            case 0: //This would be the header view in my Recycler
                v = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.recyclerview_welcome, parent, false);
                vh = new ViewHolder(v,viewType);
                return  vh;
            default: //This would be the normal list with the pictures of the places in the world
                v = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.recyclerview_picture, parent, false);
                vh = new ViewHolder(v, viewType);
                v.setOnClickListener(new View.OnClickListener(){

                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent(mContext, nextActivity.class);
                        intent.putExtra("ListNo",mRecyclerView.getChildPosition(v));
                        mContext.startActivity(intent);
                    }
                });
                return vh;
        }
    }

    //Overriden so that I can display custom rows in the recyclerview
    @Override
    public int getItemViewType(int position) {
        int viewType = 1; //Default is 1
        if (position == 0) viewType = 0; //if zero, it will be a header view
        return viewType;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        //position == 0 means its the info header view on the Recycler
        if (position == 0) {
            holder.name.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Toast.makeText(mContext,"name clicked", Toast.LENGTH_SHORT).show();
                }
            });
            holder.description.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Toast.makeText(mContext,"description clicked", Toast.LENGTH_SHORT).show();
                }
            });
            //this means it is beyond the headerview now as it is no longer 0. For testing purposes, I'm alternating between two pics for now
        } else if (position > 0) {
           holder.place.setText(mDataset[position]);
            if (position % 2 == 0) {
               holder.pics.setImageDrawable(mContext.getResources().getDrawable(R.drawable.pic1));
            }
            if (position % 2 == 1) {
                holder.pics.setImageDrawable(mContext.getResources().getDrawable(R.drawable.pic2));
            }

        }
    }

对的,这是可能的。

编写一个通用视图持有人:

public abstract class GenericViewHolder extends RecyclerView.ViewHolder
{
    public GenericViewHolder(View itemView) {
        super(itemView);
    }

    public abstract  void setDataOnView(int position);
}

然后创建您的视图持有人,并让他们扩展 GenericViewHolder。例如,这一个:

public class SectionViewHolder extends GenericViewHolder{
    public final View mView;
    public final TextView dividerTxtV;

    public SectionViewHolder(View itemView) {
        super(itemView);
        mView = itemView;
        dividerTxtV = (TextView) mView.findViewById(R.id.dividerTxtV);
    }

    @Override
    public void setDataOnView(int position) {
        try {
            String title= sections.get(position);
            if(title!= null)
                this.dividerTxtV.setText(title);
        }catch (Exception e){
            new CustomError("Error!"+e.getMessage(), null, false, null, e);
        }
    }
}

那么 RecyclerView.Adapter 类将如下所示:

public class MyClassRecyclerViewAdapter extends RecyclerView.Adapter<MyClassRecyclerViewAdapter.GenericViewHolder> {

@Override
public int getItemViewType(int position) {
     // depends on your problem
     switch (position) {
         case : return VIEW_TYPE1;
         case : return VIEW_TYPE2;
         ...
     }
}

    @Override
   public GenericViewHolder onCreateViewHolder(ViewGroup parent, int viewType)  {
    View view;
    if(viewType == VIEW_TYPE1){
        view = LayoutInflater.from(parent.getContext()).inflate(R.layout.layout1, parent, false);
        return new SectionViewHolder(view);
    }else if( viewType == VIEW_TYPE2){
        view = LayoutInflater.from(parent.getContext()).inflate(R.layout.layout2, parent, false);
        return new OtherViewHolder(view);
    }
    // Cont. other view holders ...
    return null;
   }

@Override
public void onBindViewHolder(GenericViewHolder holder, int position) {
    holder.setDataOnView(position);
}

为不同的布局创建不同的 ViewHolder

在此处输入图片说明
RecyclerView 可以具有任意数量的所需的 Viewholder,但是为了提高可读性,让我们看看如何使用两个 ViewHolder 创建一个 Viewholder。

只需三个简单步骤即可完成

  1. 重写public int getItemViewType(int position)
  2. 根据onCreateViewHolder()方法中的 ViewType 返回不同的 ViewHolders
  3. 根据onBindViewHolder()方法中的onBindViewHolder()填充视图

这是一个小代码段

public class YourListAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

   private static final int LAYOUT_ONE= 0;
   private static final int LAYOUT_TWO= 1;

   @Override
   public int getItemViewType(int position)
   {
      if(position==0)
        return LAYOUT_ONE;
      else
        return LAYOUT_TWO;
   }

   @Override
   public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

      View view =null;
      RecyclerView.ViewHolder viewHolder = null;

      if(viewType==LAYOUT_ONE)
      {
          view = LayoutInflater.from(parent.getContext()).inflate(R.layout.one,parent,false);
          viewHolder = new ViewHolderOne(view);
      }
      else
      {
          view = LayoutInflater.from(parent.getContext()).inflate(R.layout.two,parent,false);
          viewHolder= new ViewHolderTwo(view);
      }

      return viewHolder;
   }

   @Override
   public void onBindViewHolder(RecyclerView.ViewHolder holder, final int position) {

      if(holder.getItemViewType()== LAYOUT_ONE)
      {
            // Typecast Viewholder 
            // Set Viewholder properties 
            // Add any click listener if any 
      }
      else {

        ViewHolderOne vaultItemHolder = (ViewHolderOne) holder;
        vaultItemHolder.name.setText(displayText);
        vaultItemHolder.name.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
            .......
           }
         });

       }

   }

  //****************  VIEW HOLDER 1 ******************//

   public class ViewHolderOne extends RecyclerView.ViewHolder {

      public TextView name;

      public ViewHolderOne(View itemView) {
         super(itemView);
         name = (TextView)itemView.findViewById(R.id.displayName);
     }
   }


   //****************  VIEW HOLDER 2 ******************//

   public class ViewHolderTwo extends RecyclerView.ViewHolder{

      public ViewHolderTwo(View itemView) {
         super(itemView);

        ..... Do something
      }
   }
}

getItemViewType(int position)是关键

我认为,创建这种 recyclerView 的出发点是该方法的知识。由于此方法是可选的,因此默认情况下它在 RecylerView 类中不可见,从而使许多开发人员(包括我在内)想知道从哪里开始。一旦知道该方法存在,创建这样的 RecyclerView 就是一件容易的事。

让我们看一个例子来证明我的观点。如果要在备用位置显示两个布局,请执行此操作

@Override
public int getItemViewType(int position)
{
   if(position%2==0)       // Even position 
     return LAYOUT_ONE;
   else                   // Odd position 
     return LAYOUT_TWO;
}

相关链接:

查看我已在其中实施此项目的项目

对的,这是可能的。在您的适配器中,getItemViewType 布局如下所示。

public class MultiViewTypeAdapter extends RecyclerView.Adapter {

        private ArrayList<Model>dataSet;
        Context mContext;
        int total_types;
        MediaPlayer mPlayer;
        private boolean fabStateVolume = false;

        public static class TextTypeViewHolder extends RecyclerView.ViewHolder {

            TextView txtType;
            CardView cardView;

            public TextTypeViewHolder(View itemView) {
                super(itemView);

                this.txtType = (TextView) itemView.findViewById(R.id.type);
                this.cardView = (CardView) itemView.findViewById(R.id.card_view);
            }
        }

        public static class ImageTypeViewHolder extends RecyclerView.ViewHolder {

            TextView txtType;
            ImageView image;

            public ImageTypeViewHolder(View itemView) {
                super(itemView);

                this.txtType = (TextView) itemView.findViewById(R.id.type);
                this.image = (ImageView) itemView.findViewById(R.id.background);
            }
        }

        public static class AudioTypeViewHolder extends RecyclerView.ViewHolder {

            TextView txtType;
            FloatingActionButton fab;

            public AudioTypeViewHolder(View itemView) {
                super(itemView);

                this.txtType = (TextView) itemView.findViewById(R.id.type);
                this.fab = (FloatingActionButton) itemView.findViewById(R.id.fab);
            }
        }

        public MultiViewTypeAdapter(ArrayList<Model>data, Context context) {
            this.dataSet = data;
            this.mContext = context;
            total_types = dataSet.size();
        }

        @Override
        public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

            View view;
            switch (viewType) {
                case Model.TEXT_TYPE:
                    view = LayoutInflater.from(parent.getContext()).inflate(R.layout.text_type, parent, false);
                    return new TextTypeViewHolder(view);
                case Model.IMAGE_TYPE:
                    view = LayoutInflater.from(parent.getContext()).inflate(R.layout.image_type, parent, false);
                    return new ImageTypeViewHolder(view);
                case Model.AUDIO_TYPE:
                    view = LayoutInflater.from(parent.getContext()).inflate(R.layout.audio_type, parent, false);
                    return new AudioTypeViewHolder(view);
            }
            return null;
        }

        @Override
        public int getItemViewType(int position) {

            switch (dataSet.get(position).type) {
                case 0:
                    return Model.TEXT_TYPE;
                case 1:
                    return Model.IMAGE_TYPE;
                case 2:
                    return Model.AUDIO_TYPE;
                default:
                    return -1;
            }
        }

        @Override
        public void onBindViewHolder(final RecyclerView.ViewHolder holder, final int listPosition) {

            Model object = dataSet.get(listPosition);
            if (object != null) {
                switch (object.type) {
                    case Model.TEXT_TYPE:
                        ((TextTypeViewHolder) holder).txtType.setText(object.text);

                        break;
                    case Model.IMAGE_TYPE:
                        ((ImageTypeViewHolder) holder).txtType.setText(object.text);
                        ((ImageTypeViewHolder) holder).image.setImageResource(object.data);
                        break;
                    case Model.AUDIO_TYPE:

                        ((AudioTypeViewHolder) holder).txtType.setText(object.text);

                }
            }
        }

        @Override
        public int getItemCount() {
            return dataSet.size();
        }
    }

参考链接: https : //www.journaldev.com/12372/android-recyclerview-example

遵循安东的解决方案,提出了此ViewHolder ,用于保存 / 处理 / 委托不同类型的布局。但是不确定当回收视图的ViewHolder不是数据类型时,替换新布局是否会起作用。

因此,基本上,仅当需要新的视图布局时才调用onCreateViewHolder(ViewGroup parent, int viewType)

getItemViewType(int position)将被称为为viewType ;

回收视图时(总是引入新数据并尝试使用该ViewHolder进行显示onBindViewHolder(ViewHolder holder, int position) ,总是会调用onBindViewHolder(ViewHolder holder, int position) )。

因此,在onBindViewHolder时,需要放入正确的视图布局并更新ViewHolder

是为要引入的ViewHolder替换视图布局的正确方法,还是有任何问题?感谢任何评论!

public int getItemViewType(int position) {
    TypedData data = mDataSource.get(position);
    return data.type;
}

public ViewHolder onCreateViewHolder(ViewGroup parent, 
    int viewType) {
    return ViewHolder.makeViewHolder(parent, viewType);
}

public void onBindViewHolder(ViewHolder holder, 
    int position) {
    TypedData data = mDataSource.get(position);
    holder.updateData(data);
}

///
public static class ViewHolder extends 
    RecyclerView.ViewHolder {

    ViewGroup mParentViewGroup;
    View mCurrentViewThisViewHolderIsFor;
    int mDataType;

    public TypeOneViewHolder mTypeOneViewHolder;
    public TypeTwoViewHolder mTypeTwoViewHolder;

    static ViewHolder makeViewHolder(ViewGroup vwGrp, 
        int dataType) {
        View v = getLayoutView(vwGrp, dataType);
        return new ViewHolder(vwGrp, v, viewType);
    }

    static View getLayoutView(ViewGroup vwGrp, 
        int dataType) {
        int layoutId = getLayoutId(dataType);
        return LayoutInflater.from(vwGrp.getContext())
                             .inflate(layoutId, null);
    }

    static int getLayoutId(int dataType) {
        if (dataType == TYPE_ONE) {
            return R.layout.type_one_layout;
        } else if (dataType == TYPE_TWO) {
            return R.layout.type_two_layout;
        }
    }

    public ViewHolder(ViewGroup vwGrp, View v, 
        int dataType) {
        super(v);
        mDataType = dataType;
        mParentViewGroup = vwGrp;
        mCurrentViewThisViewHolderIsFor = v;

        if (data.type == TYPE_ONE) {
            mTypeOneViewHolder = new TypeOneViewHolder(v);
        } else if (data.type == TYPE_TWO) {
            mTypeTwoViewHolder = new TypeTwoViewHolder(v);
        }
    }

    public void updateData(TypeData data) {
        mDataType = data.type;
        if (data.type == TYPE_ONE) {
            mTypeTwoViewHolder = null;
            if (mTypeOneViewHolder == null) {
                View newView = getLayoutView(mParentViewGroup,
                               data.type);

                /**
                 *  how to replace new view with 
                    the view in the parent 
                    view container ???
                 */
                replaceView(mCurrentViewThisViewHolderIsFor, 
                            newView);
                mCurrentViewThisViewHolderIsFor = newView;

                mTypeOneViewHolder = 
                    new TypeOneViewHolder(newView);
            }
            mTypeOneViewHolder.updateDataTypeOne(data);

        } else if (data.type == TYPE_TWO){
            mTypeOneViewHolder = null;
            if (mTypeTwoViewHolder == null) {
                View newView = getLayoutView(mParentViewGroup, 
                               data.type);

                /**
                 *  how to replace new view with 
                    the view in the parent view 
                    container ???
                 */
                replaceView(mCurrentViewThisViewHolderIsFor, 
                            newView);
                mCurrentViewThisViewHolderIsFor = newView;

                mTypeTwoViewHolder = 
                    new TypeTwoViewHolder(newView);
            }
            mTypeTwoViewHolder.updateDataTypeOne(data);
        }
    }
}

public static void replaceView(View currentView, 
    View newView) {
    ViewGroup parent = (ViewGroup)currentView.getParent();
    if(parent == null) {
        return;
    }
    final int index = parent.indexOfChild(currentView);
    parent.removeView(currentView);
    parent.addView(newView, index);
}

编辑: ViewHolder 有成员 mItemViewType 来保存视图

编辑:看起来像在 onBindViewHolder(ViewHolderholder,int position)中,通过查看 getItemViewType(int position)来拾取(或创建)传入的 ViewHolder 以确保它是匹配的,因此可能不必担心 ViewHolder 的类型与 data [position] 的类型不匹配。有谁知道如何在 onBindViewHolder()中获取 ViewHolder?

编辑:看起来回收ViewHolder是按类型选择的,所以那里没有战士。

编辑: http : //wiresareobsolete.com/2014/09/building-a-recyclerview-layoutmanager-part-1/回答了这个问题。

它得到如下的回收ViewHolder

holder = getRecycledViewPool().getRecycledView(mAdapter.getItemViewType(offsetPosition));

或创建一个新的,如果找不到正确类型的回收ViewHolder

public ViewHolder getRecycledView(int viewType) {
        final ArrayList<ViewHolder> scrapHeap = mScrap.get(viewType);
        if (scrapHeap != null && !scrapHeap.isEmpty()) {
            final int index = scrapHeap.size() - 1;
            final ViewHolder scrap = scrapHeap.get(index);
            scrapHeap.remove(index);
            return scrap;
        }
        return null;
    }

View getViewForPosition(int position, boolean dryRun) {
    ......

    if (holder == null) {
            final int offsetPosition = mAdapterHelper.findPositionOffset(position);
            if (offsetPosition < 0 || offsetPosition >= mAdapter.getItemCount()) {
                throw new IndexOutOfBoundsException("Inconsistency detected. Invalid item "
                        + "position " + position + "(offset:" + offsetPosition + ")."
                        + "state:" + mState.getItemCount());
            }

            final int type = mAdapter.getItemViewType(offsetPosition);
            // 2) Find from scrap via stable ids, if exists
            if (mAdapter.hasStableIds()) {
                holder = getScrapViewForId(mAdapter.getItemId(offsetPosition), type, dryRun);
                if (holder != null) {
                    // update position
                    holder.mPosition = offsetPosition;
                    fromScrap = true;
                }
            }
            if (holder == null && mViewCacheExtension != null) {
                // We are NOT sending the offsetPosition because LayoutManager does not
                // know it.
                final View view = mViewCacheExtension
                        .getViewForPositionAndType(this, position, type);
                if (view != null) {
                    holder = getChildViewHolder(view);
                    if (holder == null) {
                        throw new IllegalArgumentException("getViewForPositionAndType returned"
                                + " a view which does not have a ViewHolder");
                    } else if (holder.shouldIgnore()) {
                        throw new IllegalArgumentException("getViewForPositionAndType returned"
                                + " a view that is ignored. You must call stopIgnoring before"
                                + " returning this view.");
                    }
                }
            }
            if (holder == null) { // fallback to recycler
                // try recycler.
                // Head to the shared pool.
                if (DEBUG) {
                    Log.d(TAG, "getViewForPosition(" + position + ") fetching from shared "
                            + "pool");
                }
                holder = getRecycledViewPool()
                        .getRecycledView(mAdapter.getItemViewType(offsetPosition));
                if (holder != null) {
                    holder.resetInternal();
                    if (FORCE_INVALIDATE_DISPLAY_LIST) {
                        invalidateDisplayListInt(holder);
                    }
                }
            }
            if (holder == null) {
                holder = mAdapter.createViewHolder(RecyclerView.this,
                        mAdapter.getItemViewType(offsetPosition));
                if (DEBUG) {
                    Log.d(TAG, "getViewForPosition created new ViewHolder");
                }
            }
        }
        boolean bound = false;
        if (mState.isPreLayout() && holder.isBound()) {
            // do not update unless we absolutely have to.
            holder.mPreLayoutPosition = position;
        } else if (!holder.isBound() || holder.needsUpdate() || holder.isInvalid()) {
            if (DEBUG && holder.isRemoved()) {
                throw new IllegalStateException("Removed holder should be bound and it should"
                        + " come here only in pre-layout. Holder: " + holder);
            }
            final int offsetPosition = mAdapterHelper.findPositionOffset(position);
            mAdapter.bindViewHolder(holder, offsetPosition);
            attachAccessibilityDelegate(holder.itemView);
            bound = true;
            if (mState.isPreLayout()) {
                holder.mPreLayoutPosition = position;
            }
        }

        final ViewGroup.LayoutParams lp = holder.itemView.getLayoutParams();
        final LayoutParams rvLayoutParams;
        if (lp == null) {
            rvLayoutParams = (LayoutParams) generateDefaultLayoutParams();
            holder.itemView.setLayoutParams(rvLayoutParams);
        } else if (!checkLayoutParams(lp)) {
            rvLayoutParams = (LayoutParams) generateLayoutParams(lp);
            holder.itemView.setLayoutParams(rvLayoutParams);
        } else {
            rvLayoutParams = (LayoutParams) lp;
        }
        rvLayoutParams.mViewHolder = holder;
        rvLayoutParams.mPendingInvalidate = fromScrap && bound;
        return holder.itemView;
}

我有一个更好的解决方案,它允许以声明性和类型安全的方式创建多个视图类型。它是用 Kotlin 写的,顺便说一句,真的很棒。

适用于所有必需视图类型的简单视图持有人

class ViewHolderMedium(itemView: View) : RecyclerView.ViewHolder(itemView) {
    val icon: ImageView = itemView.findViewById(R.id.icon) as ImageView
    val label: TextView = itemView.findViewById(R.id.label) as TextView
}

适配器数据项有一个抽象。请注意,视图类型由特定视图持有者类(在 Kotlin 中为 KClass)的 hashCode 表示。

trait AdapterItem {
   val viewType: Int
   fun bindViewHolder(viewHolder: RecyclerView.ViewHolder)
}

abstract class AdapterItemBase<T>(val viewHolderClass: KClass<T>) : AdapterItem {
   override val viewType: Int = viewHolderClass.hashCode()  
   abstract fun bindViewHolder(viewHolder: T)
   override fun bindViewHolder(viewHolder: RecyclerView.ViewHolder) {
       bindViewHolder(viewHolder as T)
   }
}

在具体的适配器项目类中仅需要覆盖bindViewHolder (类型安全的方式)

class AdapterItemMedium(val icon: Drawable, val label: String, val onClick: () -> Unit) : AdapterItemBase<ViewHolderMedium>(ViewHolderMedium::class) {
    override fun bindViewHolder(viewHolder: ViewHolderMedium) {
        viewHolder.icon.setImageDrawable(icon)
        viewHolder.label.setText(label)
        viewHolder.itemView.setOnClickListener { onClick() }
    }
}

此类AdapterItemMedium对象的列表是适配器的数据源,该适配器实际接受List<AdapterItem>参见下文。

该解决方案的重要部分是视图持有者工厂,它将提供特定 ViewHolder 的新实例。

class ViewHolderProvider {
    private val viewHolderFactories = hashMapOf<Int, Pair<Int, Any>>()

    fun provideViewHolder(viewGroup: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
        val (layoutId: Int, f: Any) = viewHolderFactories.get(viewType)
        val viewHolderFactory = f as (View) -> RecyclerView.ViewHolder
        val view = LayoutInflater.from(viewGroup.getContext()).inflate(layoutId, viewGroup, false)
        return viewHolderFactory(view)
    }

    fun registerViewHolderFactory<T>(key: KClass<T>, layoutId: Int, viewHolderFactory: (View) -> T) {
        viewHolderFactories.put(key.hashCode(), Pair(layoutId, viewHolderFactory))
    }
}

和简单的适配器类看起来像这样

public class MultitypeAdapter(val items: List<AdapterItem>) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {

   val viewHolderProvider = ViewHolderProvider() // inject ex Dagger2

   init {
        viewHolderProvider!!.registerViewHolderFactory(ViewHolderMedium::class, R.layout.item_medium, { itemView ->
            ViewHolderMedium(itemView)
        })
   }

   override fun getItemViewType(position: Int): Int {
        return items[position].viewType
    }

    override fun getItemCount(): Int {
        return items.size()
    }

    override fun onCreateViewHolder(viewGroup: ViewGroup, viewType: Int): RecyclerView.ViewHolder? {
        return viewHolderProvider!!.provideViewHolder(viewGroup, viewType)
    }

    override fun onBindViewHolder(viewHolder: RecyclerView.ViewHolder, position: Int) {
        items[position].bindViewHolder(viewHolder)     
    }
}

只需 3 个步骤即可创建新的视图类型:

  1. 创建一个视图持有者类
  2. 创建一个适配器项类(从 AdapterItemBase 扩展)
  3. ViewHolderProvider注册视图持有者类

这是这个概念的一个例子: android-drawer-template它甚至更进一步 - 充当微调器组件的视图类型,可选的适配器项。

这非常简单直接。

只需在适配器中重写getItemViewType()方法即可。根据数据返回不同的 itemViewType 值。例如,考虑具有成员 isMale 的 Person 类型的对象,如果 isMale 为 true,则返回 1,isMale 为 false,在getItemViewType()方法中返回 2。

现在谈到createViewHolder(ViewGroup 父类,int viewType) ,基于不同的 viewType yon 可以膨胀不同的布局文件。像下面

if (viewType ==1){
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.male,parent,false);
    return new AdapterMaleViewHolder(view);
}
else{
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.female,parent,false);
    return new AdapterFemaleViewHolder(view);
}

onBindViewHolder(VH 支架,int 位置)中 ,通过instanceof检查 holder 是AdapterFemaleViewHolderAdapterMaleViewHolderinstanceof并相应地分配值。

ViewHolder 可能会像这样

class AdapterMaleViewHolder extends RecyclerView.ViewHolder {
            ...
            public AdapterMaleViewHolder(View itemView){
            ...
            }
        }

    class AdapterFemaleViewHolder extends RecyclerView.ViewHolder {
         ...
         public AdapterFemaleViewHolder(View itemView){
            ...
         }
    }

我推荐 Hannes Dorfmann 的这个库。它将与特定视图类型相关的所有逻辑封装在称为 “AdapterDelegate” 的单独对象中。 https://github.com/sockeqwe/AdapterDelegates

public class CatAdapterDelegate extends AdapterDelegate<List<Animal>> {

  private LayoutInflater inflater;

  public CatAdapterDelegate(Activity activity) {
    inflater = activity.getLayoutInflater();
  }

  @Override public boolean isForViewType(@NonNull List<Animal> items, int position) {
    return items.get(position) instanceof Cat;
  }

  @NonNull @Override public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent) {
    return new CatViewHolder(inflater.inflate(R.layout.item_cat, parent, false));
  }

  @Override public void onBindViewHolder(@NonNull List<Animal> items, int position,
      @NonNull RecyclerView.ViewHolder holder, @Nullable List<Object> payloads) {

    CatViewHolder vh = (CatViewHolder) holder;
    Cat cat = (Cat) items.get(position);

    vh.name.setText(cat.getName());
  }

  static class CatViewHolder extends RecyclerView.ViewHolder {

    public TextView name;

    public CatViewHolder(View itemView) {
      super(itemView);
      name = (TextView) itemView.findViewById(R.id.name);
    }
  }
}

public class AnimalAdapter extends ListDelegationAdapter<List<Animal>> {

  public AnimalAdapter(Activity activity, List<Animal> items) {

    // DelegatesManager is a protected Field in ListDelegationAdapter
    delegatesManager.addDelegate(new CatAdapterDelegate(activity))
                    .addDelegate(new DogAdapterDelegate(activity))
                    .addDelegate(new GeckoAdapterDelegate(activity))
                    .addDelegate(23, new SnakeAdapterDelegate(activity));

    // Set the items from super class.
    setItems(items);
  }
}