Android通用的Adapter，或许你用我这一个就够了

一、概述

相信Android开发，特别是电商项目开发，使用RecyclerView、ListView、GridView是正常不过的了。一个项目下来，基本就是一直在写Adapter。刚开始写Adapter觉得没什么，无非就是ListView的继承BaseAdapter复写几个方法，getView里面使用ViewHolder模式；RecyclerView的就继承 RecyclerView.Adapter，复写onCreateViewHolder、onBindViewHolder然后实现便完事。但当我写到10遍、100遍甚至更多的时候，我就不想写了，反正都是这种写法，也没什么新的套路。于是我就想写一个RecyclerView、ListView、GridView通用的Adapter。

二、常见ListView、RecyclerView Adapter写法的例子

代码没什么难度可以随便看看就好。

public class ListViewAdapter extends BaseAdapter  
{  
    private LayoutInflater mInflater;  
    private Context mContext;  
    private List<String> mDatas;  
    private int mLayoutId;
  
    public ListViewAdapter(Context context, List<String> mDatas,int layoutId)  
    {  
        mInflater = LayoutInflater.from(context);  
        this.mContext = context;  
        this.mDatas = mDatas;  
        this.mLayoutId = layoutId;
    }  
  
    @Override  
    public int getCount()  
    {  
        return mDatas.size();  
    }  
  
    @Override  
    public Object getItem(int position)  
    {  
        return mDatas.get(position);  
    }  
  
    @Override  
    public long getItemId(int position)  
    {  
        return position;  
    }  
  
    @Override  
    public View getView(int position, View convertView, ViewGroup parent)  
    {  
        ViewHolder viewHolder = null;  
        if (convertView == null)  
        {  
            convertView = mInflater.inflate(R.mLayoutId, parent, false);  
            viewHolder = new ViewHolder();  
            viewHolder.mTextView = (TextView) convertView  
                    .findViewById(R.id.id_tv);  
            convertView.setTag(viewHolder);  
        } else  
        {  
            viewHolder = (ViewHolder) convertView.getTag();  
        }  
        viewHolder.mTextView.setText(mDatas.get(position));  
        return convertView;  
    }  
  
    private final class ViewHolder  
    {  
        TextView mTextView;  
    }  
  
}  

private class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.Holder> {

    private LayoutInflater mInflater;
    private Context mContext;
    private List<String> mData;
    private int mLayoutId;

    public RecyclerAdapter(Context context, List<String> data, int layoutId) {
        mInflater = LayoutInflater.from(context);
        this.mContext = context;
        this.mData = data;
        this.mLayoutId = layoutId;
    }

    @Override
    public Holder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = mInflater.inflate(mLayoutId, parent, false);
        return new Holder(view);
    }

    @Override
    public void onBindViewHolder(Holder holder, int position) {
        holder.tv.setText(mData.get(position));
    }

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

    class Holder extends RecyclerView.ViewHolder {
        public TextView tv;

        public Holder(View itemView) {
            super(itemView);
            tv = itemView.findViewById(R.id.tv);
        }
    }
}

三、ListView、RecyclerView Adapter一些共性分析

1. 要显示的条目个数
2. 要显示和条目对应的类型
3. ListView、RecyclerView中，总共有多少个条目类型
4. 根据不同的条目类型加载不同的View
5. ListView复用条目convertView，RecyclerView自带ViewHoler复用

四、抽取RecyclerView、ListView、GridView适配器的基类

由于要通用RecyclerView、ListView、GridView只能将RecyclerView.Adapter和ListAdapter，SpinnerAdapter
这些都给实现了。里面也没多少个方法，其实也是很简单。至于一些方法的实现我考贝BaseAdapter的实现，
大家可以去看看BaseAdapter的源码。

public class BaseAdapter extends RecyclerView.Adapter implements ListAdapter, SpinnerAdapter {
    private final DataSetObservable mDataSetObservable = new DataSetObservable();

    // RecyclerView========================================================================
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return null;
    }

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

    }

    // RecyclerView
    @Override
    public int getItemCount() {
        return 0;
    }
    // RecyclerView========================================================================

    // ListView========================================================================
    @Override
    public boolean areAllItemsEnabled() {
        return true;
    }

    @Override
    public boolean isEnabled(int position) {
        return true;
    }

    @Override
    public void registerDataSetObserver(DataSetObserver observer) {
        mDataSetObservable.registerObserver(observer);
    }

    @Override
    public void unregisterDataSetObserver(DataSetObserver observer) {
        mDataSetObservable.unregisterObserver(observer);
    }

    public void notifyListDataSetChanged() {
        mDataSetObservable.notifyChanged();
    }


    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        return null;
    }

    @Override
    public int getViewTypeCount() {
        return 1;
    }

    @Override
    public int getItemViewType(int position) {
        return 0;
    }

    @Override
    public int getCount() {
        return 0;
    }
    
    @Override
    public boolean isEmpty() {
        return getCount() == 0;
    }

    @Override
    public View getDropDownView(int position, View convertView, ViewGroup parent) {
        return getView(position, convertView, parent);
    }
}

五、抽取支持ListView、 GridView、 RecyclerView多条目的共性

public interface QuickMultiSupport<T> {
    /**
     * 获取多条目View类型的数量
     */
    int getViewTypeCount();

    /**
     * 根据数据，获取多条目布局ID
     */
    int getLayoutId(T data);

    /**
     * 根据数据，获取多条目的ItemViewType
     */
    int getItemViewType(T data);


    /**
     * 是否合并条目-->>使用RecyclerView时，如果无效，请用原生的RecyclerView
     */
    boolean isSpan(T data);

六、打造RecyclerView、ListView、GridView通用的适配器

由于要同时适配RecyclerView、ListView、GridView，也就等于把两个Adapter的实现放在一个类里面
所以代码有点多，但代码我已分开，很容易看。
还有数据都复制出来的，条目的增删改查都在Adapter里面。

/**
 * RecyclerView、ListView、GridView通用的适配器
 */
public abstract class QuickAdapter<T> extends BaseAdapter {
    private Context mContext;
    private List<T> mData;
    private int mLayoutId;
    private QuickMultiSupport<T> mSupport;
    private boolean isRecycler;
    private int mPosition;

    public QuickAdapter(Context context, List<T> data, int layoutId) {
        this.mContext = context;
        this.mData = data == null ? new ArrayList<T>() : new ArrayList<T>(data);
        this.mLayoutId = layoutId;
    }

    public QuickAdapter(Context context, List<T> data, QuickMultiSupport<T> support) {
        this(context, data, 0);
        this.mSupport = support;
    }

    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public T getItem(int position) {
        return mData.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        QuickViewHolder holder;
        if (convertView == null) {
            int layoutId = mLayoutId;
            // 多条目的
            if (mSupport != null) {
                layoutId = mSupport.getLayoutId(mData.get(position));
            }
            // 创建ViewHolder
            holder = createListHolder(parent, layoutId);
        } else {
            holder = (QuickViewHolder) convertView.getTag();
            // 防止失误，还要判断
            if (mSupport != null) {
                int layoutId = mSupport.getLayoutId(mData.get(position));
                // 如果布局ID不一样，又重新创建
                if (layoutId != holder.getLayoutId()) {
                    // 创建ViewHolder
                    holder = createListHolder(parent, layoutId);
                }
            }

        }
        // 绑定View的数据
        convert(holder, mData.get(position), position);
        return holder.itemView;
    }

    /**
     * 创建ListView的Holer
     */
    @NonNull
    private QuickViewHolder createListHolder(ViewGroup parent, int layoutId) {
        QuickViewHolder holder;
        View itemView = LayoutInflater.from(mContext).inflate(layoutId, parent, false);
        holder = new QuickViewHolder(itemView, layoutId);
        itemView.setTag(holder);
        return holder;
    }

    /**
     * ViewType的数量
     */
    @Override
    public int getViewTypeCount() {
        // 多条目的
        if (mSupport != null) {
            return mSupport.getViewTypeCount() + super.getViewTypeCount();
        }
        return super.getViewTypeCount();
    }

    /**
     * 这个方法是共用的
     */
    @Override
    public int getItemViewType(int position) {
        mPosition = position;
        // 多条目的
        if (mSupport != null) {
            return mSupport.getItemViewType(mData.get(position));
        }
        return super.getItemViewType(position);
    }


    // RecyclerView=================================================================================
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        isRecycler = true;
        // 如果是多条目，viewType就是布局ID
        View view;
        if (mSupport != null) {
            int layoutId = mSupport.getLayoutId(mData.get(mPosition));
            view = LayoutInflater.from(mContext).inflate(layoutId, parent, false);
        } else {
            view = LayoutInflater.from(mContext).inflate(mLayoutId, parent, false);
        }

        QuickViewHolder holder = new QuickViewHolder(view);
        return holder;
    }


    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (holder instanceof QuickViewHolder) {
            convert((QuickViewHolder) holder, mData.get(position), position);
        }

    }

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

    @Override
    public void onAttachedToRecyclerView(RecyclerView recyclerView) {
        if (mSupport == null || recyclerView == null) {
            return;
        }
        RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager) {
            final GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;
            final GridLayoutManager.SpanSizeLookup spanSizeLookup = gridLayoutManager.getSpanSizeLookup();
            // 如果设置合并单元格就占用SpanCount那个多个位置
            gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
                @Override
                public int getSpanSize(int position) {
                    if (mSupport.isSpan(mData.get(position))) {
                        return gridLayoutManager.getSpanCount();
                    } else if (spanSizeLookup != null) {
                        return spanSizeLookup.getSpanSize(position);
                    }
                    return 1;
                }
            });
            gridLayoutManager.setSpanCount(gridLayoutManager.getSpanCount());
        }
    }

    @Override
    public void onViewAttachedToWindow(RecyclerView.ViewHolder holder) {
        if (mSupport == null) {
            return;
        }
        int position = holder.getLayoutPosition();
        // 如果设置合并单元格
        if (mSupport.isSpan(mData.get(position))) {
            ViewGroup.LayoutParams lp = holder.itemView.getLayoutParams();
            if (lp != null && lp instanceof StaggeredGridLayoutManager.LayoutParams) {
                StaggeredGridLayoutManager.LayoutParams p = (StaggeredGridLayoutManager.LayoutParams) lp;
                p.setFullSpan(true);
            }
        }
    }

    // RecyclerView=================================================================================


    /**
     * 绑定View的数据
     */
    protected abstract void convert(QuickViewHolder holder, T item, int position);


    //==========================================数据相关================================================
    public void add(T elem) {
        mData.add(elem);
        notifyData();

    }
    public void addAll(List<T> data) {
        mData.addAll(data);
        notifyData();
    }
    
    public void addFirst(T elem) {
        mData.add(0, elem);
        notifyData();
    }
    
    public void set(T oldElem, T newElem) {
        set(mData.indexOf(oldElem), newElem);
        notifyData();
    }
    
    public void set(int index, T elem) {
        mData.set(index, elem);
        notify();
    }

    public void remove(T elem) {
        mData.remove(elem);
        notifyData();
    }

    public void remove(int index) {
        mData.remove(index);
        notifyData();
    }

    public void replaceAll(List<T> elem) {
        mData.clear();
        mData.addAll(elem);
        notifyData();
    }

    /**
     * 清除
     */
    public void clear() {
        mData.clear();
        notifyData();
    }

    private void notifyData() {
        if (isRecycler) {
            notifyDataSetChanged();
        } else {
            notifyListDataSetChanged();
        }
    }

    public List<T> getData() {
        return mData;
    }
}

七、通用ViewHolder的抽取

ViewHolder最主要就是实现平时常用的方法，比如：点击事件、长按事件、给TextView设置内容等等
如果不够，实际开发可以自己添加。

public class QuickViewHolder extends RecyclerView.ViewHolder {
    private SparseArray<WeakReference<View>> mViews;
    private int mLayoutId;

    public QuickViewHolder(View itemView) {
        this(itemView, -1);
    }

    public QuickViewHolder(View itemView, int layoutId) {
        super(itemView);
        mViews = new SparseArray<>();
        this.mLayoutId = layoutId;

    }

    public int getLayoutId() {
        return mLayoutId;
    }

    /**
     * 设置条目的点击事件
     */
    public QuickViewHolder setOnClickListener(View.OnClickListener listener) {
        itemView.setOnClickListener(listener);
        return this;
    }

    /**
     * 设置条目的长按事件
     */
    public QuickViewHolder setOnLongClickListener(View.OnLongClickListener listener) {
        itemView.setOnLongClickListener(listener);
        return this;
    }

    /**
     * 设置View的点击事件
     *
     * @return
     */
    public QuickViewHolder setOnClickListener(int viewId, View.OnClickListener listener) {
        View view = getView(viewId);
        if (view != null) {
            view.setOnClickListener(listener);
        }
        return this;
    }

    /**
     * 获取条目的View
     */
    public View getView() {
        return itemView;
    }

    /**
     * 根据ID获取条目里面的View
     */
    public <T extends View> T getView(int viewId) {
        WeakReference<View> viewWeakReference = mViews.get(viewId);
        View view = null;
        if (viewWeakReference == null) {
            view = itemView.findViewById(viewId);
            if (view != null) {
                mViews.put(viewId, new WeakReference<>(view));
            }
        } else {
            view = viewWeakReference.get();
        }
        return (T) view;
    }

    public QuickViewHolder setText(int viewId, CharSequence text) {
        TextView tv = getView(viewId);
        if (tv != null && !TextUtils.isEmpty(text)) {
            tv.setText(text);
        }
        return this;
    }

    /**
     * 设置图片背景颜色
     */
    public QuickViewHolder setTextColor(int viewId, int color) {
        TextView view = getView(viewId);
        if (view != null) {
            view.setTextColor(color);
        }
        return this;
    }

    /**
     * 设置控件是否可见
     */
    public QuickViewHolder setVisible(int viewId, int visible) {
        View view = getView(viewId);
        view.setVisibility(visible);
        return this;
    }

    /**
     * 设置控件选中
     */
    public QuickViewHolder setChecked(int viewId, boolean checked) {
        Checkable view = getView(viewId);
        view.setChecked(checked);
        return this;
    }

    /**
     * 设置控件背景
     */
    public QuickViewHolder setBackgroundRes(int viewId, int backgroundRes) {
        View view = getView(viewId);
        view.setBackgroundResource(backgroundRes);
        return this;
    }

    /**
     * 设置图片
     */
    public QuickViewHolder setImageResource(int viewId, int imageResId) {
        ImageView imageView = getView(viewId);
        imageView.setImageResource(imageResId);
        return this;
    }

    /**
     * 设置图片
     */
    public QuickViewHolder setImageBitmap(int viewId, Bitmap bitmap) {
        ImageView imageView = getView(viewId);
        imageView.setImageBitmap(bitmap);
        return this;
    }


}

八、项目实际使用

我只写了多条目的测试使用，对于一种类型的写法更为简单，我就不写了。

public class MainActivity extends AppCompatActivity {

    private List<IViewType> mData = new ArrayList<>();
    private QuickMultiSupport<IViewType> mQuickSupport;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initData();
        initViews();
    }

    /**
     * 多条目的ViewType
     */

    public interface IViewType {
        int getItemViewType();
    }

    private void initData() {
        for (int i = 0; i < 199; i++) {
            if (i % 10 == 0) {
                MultiBean bean = new MultiBean();
                bean.name = "mData--------" + i;
                mData.add(bean);
            } else {
                MultiBean1 bean = new MultiBean1();
                bean.name = "mData--------" + i;
                mData.add(bean);
            }
        }
        // 多条目支持
        mQuickSupport = new QuickMultiSupport<IViewType>() {
            // 条目总共两种类型
            @Override
            public int getViewTypeCount() {
                return 2;
            }

            // 根据不用的JavaBean返回不同的布局
            @Override
            public int getLayoutId(IViewType data) {
                if (data instanceof MultiBean) {
                    return R.layout.item_list1;
                }
                return R.layout.item_list;
            }

            @Override
            public int getItemViewType(IViewType data) {
                return data.getItemViewType();
            }

            @Override
            public boolean isSpan(IViewType data) {
                // 是否占用一个条目，针对RecyclerView
                if (data instanceof MultiBean) {
                    return true;
                }
                return false;
            }
        };
    }

    private void initViews() {
        ListView listView = findViewById(R.id.list_view);
        RecyclerView recyclerView = findViewById(R.id.recycler_view);
        // ListView设置Adapter
        listView.setAdapter(new CommAdapter(this, mData, mQuickSupport));
        // RecyclerView设置Adapter
        recyclerView.setLayoutManager(new StaggeredGridLayoutManager(2, StaggeredGridLayoutManager.VERTICAL));
        recyclerView.setAdapter(new CommAdapter(this, mData, mQuickSupport));
    }

    class CommAdapter extends QuickAdapter<IViewType> {
        public CommAdapter(Context context, List<IViewType> data, int layoutId) {
            super(context, data, layoutId);
        }

        public CommAdapter(Context context, List<IViewType> data, QuickMultiSupport<IViewType> support) {
            super(context, data, support);
        }

        @Override
        protected void convert(QuickViewHolder holder, IViewType item, final int position) {
            holder.setText(R.id.tv, item.toString());
            holder.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    // 点击移除当前条目
                    remove(position);
                }
            });
        }
    }
}

至此无论是RecyclerView还是ListView终于只用一个Adapter，是不是很开心
项目运行的实际效果：左边是ListView，右边是RecyclerView。

实际效果.jpg

九、感谢

鸿洋大神的
1.Android 快速开发系列 打造万能的ListView GridView 适配器
2.为RecyclerView打造通用Adapter 让RecyclerView更加好用