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超级简单RecycleViewAdapter的封装-支持多视图,

2016-08-09  本文已影响2214人  laogui

其实RecycleView已经出来很长时间了,对RecycleView的用法网上也有很多教程了。本篇文章不讲解RecycleView的用法,不讲解LayoutManager的用法也不讲解ItemDecoration的用法,我们只关注Adapter的用法以及如何封装成一个通用的Adapter

Adapter的正常使用方法

其实很简单,只需要继承RecyclerView.Adapter<VH extends ViewHolder>传入范型类型为ViewHolder的子类就可以,代码演示如下:
MainActivity.java

public class MainActivity extends AppCompatActivity {
    ...
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...
        List<String> datas = new ArrayList<>();
        for (int i = 0; i < 20; ++i) {
            datas.add("item:" + (i + 1));
        }
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        MyAdapter myAdapter = new MyAdapter(datas);
        myAdapter.setItemClickListener(new MyAdapter.ItemClickListener() {
            @Override
            public void onItemClicked(View view, int position) {
                Log.d(TAG,"root clicked..." + position);
            }
        });
        recyclerView.setAdapter(myAdapter);
    }

    private static class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder>{

        private List<String> dataList;

        private ItemClickListener itemClickListener;

        public MyAdapter(List<String> dataList){
            this.dataList = dataList;
        }

        public interface ItemClickListener {
            void onItemClicked(View view,int position);
        }

        //设置点击回调接口
        public void setItemClickListener(ItemClickListener itemClickListener) {
            this.itemClickListener = itemClickListener;
        }

        //生成ViewHolder
        @Override
        public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_view_main1, parent, false);
            return new ViewHolder(itemView);
        }

        private String getItem(int position){
            return dataList.get(position);
        }

        //更新列表Item视图(根据需要绑定click事件)
        @Override
        public void onBindViewHolder(ViewHolder holder, final int position) {
            String str = getItem(position);
//            holder.icon.setImageDrawable(xxx);
            holder.name.setText(str);
            holder.root.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if(itemClickListener != null)
                        itemClickListener.onItemClicked(v,position);
                }
            });
        }

        @Override
        public int getItemCount() {
            return dataList.size();
        }
        //ViewHolder保存每个item视图
        public class ViewHolder extends RecyclerView.ViewHolder{
            private ImageView icon;
            private TextView name;
            private View root;
            public ViewHolder(View itemView) {
                super(itemView);
                icon = (ImageView)itemView.findViewById(R.id.icon);
                name = (TextView)itemView.findViewById(R.id.id_text);
                root = itemView.findViewById(R.id.root);
            }
        }
    }
}

通过以上代码演示,我们可以得出结论:构造一个比较完整的Adapter至少需要完成以下三件事情

  1. onCreateViewHolder通过视图Id加载不同Item视图并生成ViewHolder用来保存每个列表Item视图
  2. onBindViewHolder更新列表Item视图(填充model数据)
  3. 新建ViewHolder类来存储Item视图及其子视图

如果需要实现点击事件,需要在onBindViewHolder中适当绑定点击事件,比如在以上代码中绑定了点击列表视图中的Item根视图的点击事件如下:

holder.root.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        if(itemClickListener != null)
            itemClickListener.onItemClicked(v,position);
    }
});

在需要实现具体的点击事件时调用如下代码:

myAdapter.setItemClickListener(new MyAdapter.ItemClickListener() {
    @Override
    public void onItemClicked(View view, int position) {
        Log.d(TAG,"root clicked..." + position);
    }
});

问题

  1. 如果需要实现在同一个Item视图中点击不同view要实现不同功能
    比如以上代码中处理了点击Item跟视图的点击事件,如果需要点击根视图中的icon子视图如何实现?
    是不是继续写setOnXXXListener,麻烦也不太现实
  2. 如果要实现列表中多视图展示如何实现?正常如果需要支持多视图咱们是在onCreateViewHolder方法中根据不同的ViewType来加载不同的Item视图代码演示如下:
//重写getItemViewType函数,更具需要返回不同的viewType
@Override
public int getItemViewType(int position) {
    String model = getItem();
    if(...){
        return 1;
    }else if(...){
        return 2;
    }
    return super.getItemViewType(position);
}

//生成ViewHolder
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    int itemViewId = -1;
    if(viewType == 1){
        itemViewId = R.layout.item_view_main1;
    }else if(viewType == 2){
        itemViewId = R.layout.item_view_main2;
    }
    View itemView = LayoutInflater.from(parent.getContext()).inflate(itemViewId, parent, false);
    return new ViewHolder(itemView);
}

以上方案纯属针对某种列表来实现的,如果换了一个列表视图咱们就需要重现创建adapter并分别在onCreateViewHolder,onBindViewHolder方法中实现不同逻辑并重新创建xxxViewHolder继承ViewHolder来保存不同的Item视图

解决方案

基于以上问题,给出如下方案
LGViewHolder.java用来设计通用的ViewHolder

public class LGViewHolder extends RecyclerView.ViewHolder {
    private SparseArray<View> mViews;
    private View mConvertView;//缓存itemView内部的子View

    public LGViewHolder(View itemView) {
        super(itemView);
        mConvertView = itemView;
        mViews = new SparseArray<>();
    }

    /**
     * 加载layoutId视图并用LGViewHolder保存
     * @param parent
     * @param layoutId
     * @return
     */
    protected static LGViewHolder getViewHolder(ViewGroup parent, int layoutId) {
        View itemView = LayoutInflater.from(parent.getContext()).inflate(layoutId, parent, false);
        return new LGViewHolder(itemView);
    }

    /**
     * 根据ItemView的id获取子视图View
     * @param viewId
     * @return
     */
    public View getView(int viewId) {
        View view = mViews.get(viewId);
        if (view == null) {
            view = mConvertView.findViewById(viewId);
            mViews.put(viewId, view);
        }
        return view;
    }
}

LGRecycleViewAdapter.java

public abstract class LGRecycleViewAdapter<T> extends RecyclerView.Adapter<LGViewHolder> {
    private final String TAG = "LGRecycleViewAdapter";
    //存储监听回调
    private SparseArray<ItemClickListener> onClickListeners;

    private List<T> dataList;

    public interface ItemClickListener {
        void onItemClicked(View view,int position);
    }

    public LGRecycleViewAdapter(List<T> dataList) {
        this.dataList = dataList;
        onClickListeners = new SparseArray<>();
    }

    /**
     * 存储viewId对应的回调监听实例listener
     * @param viewId
     * @param listener
     */
    public void setOnItemClickListener(int viewId,ItemClickListener listener) {
        ItemClickListener listener_ = onClickListeners.get(viewId);
        if(listener_ == null){
            onClickListeners.put(viewId,listener);
        }
    }

    /**
     * 获取列表控件的视图id(由子类负责完成)
     * @param viewType
     * @return
     */
    public abstract int getLayoutId(int viewType);

    //更新itemView视图(由子类负责完成)
    public abstract void convert(LGViewHolder holder, T t, int position);

    public T getItem(final int position){
        if(dataList == null)
            return null;
        return dataList.get(position);
    }

    @Override
    public LGViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        int layoutId = getLayoutId(viewType);
        LGViewHolder viewHolder = LGViewHolder.getViewHolder(parent, layoutId);
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(LGViewHolder holder, final int position) {
        T itemModel = dataList.get(position);
        convert(holder, itemModel, position);//更新itemView视图
        //设置点击监听
        for (int i = 0; i < onClickListeners.size(); ++i){
            int id = onClickListeners.keyAt(i);
            View view = holder.getView(id);
            if(view == null)
                continue;
            final ItemClickListener listener = onClickListeners.get(id);
            view.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if(listener != null){
                        listener.onItemClicked(v,position);
                    }
                }
            });
        }
    }

    @Override
    public int getItemCount() {
        if (dataList == null)
            return 0;
        return dataList.size();
    }

    public void destroyAdapter(){
        if(onClickListeners != null)
            onClickListeners.clear();
        onClickListeners = null;

        if(dataList != null)
            dataList.clear();
        dataList = null;
    }
}

使用方法如下:
单视图方式:
定义adapter

private static class MainAdapter extends LGRecycleViewAdapter<String> {
    ...

    @Override
    public int getLayoutId(int viewType) {
        return R.layout.item_view_main1;
    }

    @Override
    public void convert(LGViewHolder holder, String s, final int position) {
        TextView textView = (TextView) holder.getView(R.id.id_text);
        textView.setText(s);
    }
}

在需要时使用:

mainAdapter = new MainAdapter(datas);
mainAdapter.setOnItemClickListener(R.id.root, new LGRecycleViewAdapter.ItemClickListener() {
    @Override
    public void onItemClicked(View view, int position) {
        Log.d(TAG,"root clicked..." + position);
    }
});
mainAdapter.setOnItemClickListener(R.id.icon, new LGRecycleViewAdapter.ItemClickListener() {
    @Override
    public void onItemClicked(View view, int position) {
        Log.d(TAG,"icon clicked..." + position);
    }
});
recyclerView.setAdapter(mainAdapter);

可以看出我们轻松的实现了同一Item视图不同子视图的点击监听,并且在MainAdapter子类中只需通过getLayoutId告诉父类Item视图对应的视图id,并在convert方法中只更新视图即可
如果需要支持多视图模式则只需在子类中重现getViewType即可,代码如下:
MainAdapter.java

@Override
public int getLayoutId(int viewType) {
    if(viewType == 1)
        return R.layout.item_view_main1;
    return R.layout.item_view_main2;
}

//支持不同viewType视图
@Override
public int getItemViewType(int position) {
    String model = getItem(position);//实际开发中可以通过model的属性来决定返回viewType类型
    if(position % 2 == 0)
        return  1;
    return  2;
}

写在最后

为了简单起见,本篇文章设计的adapter适合没有header和footer视图的RecycleView,至于这方面的功能打算在github上更新
完整的代码及案例可以到我的github下载
demo开源github地址如下:
LGRecycleViewAdapter
欢迎大家访问并star,如果有任何问题可以在评论中加以提问,谢谢~~

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