前一段时间，因为项目需要使用了RecyclerView，为了方便使用还进行封装了，详细参见此处：RecyclerView中Adapter和ViewHolder的封装 - DevWiki。
那样的封装有几个问题：
1. ViewHolder的setData(M data)虽然方便设置数据，但是ViewHolder需要知晓数据类型。ViewHolder应该只用作View的缓存，而不应该知晓填充View的数据。
2. BaseAdapter无法添加Header和Footer。
3. 点击事件耦合性较高。
基于以上几点，对BaseHolder和BaseAdapter进行修改优化。
BaseHolder的优化
相对于旧版的BaseHolder：
1. 新版的去除的数据类型的注入，使ViewHolder只用来缓存View。
2. 添加SparseArray，使之来缓存View。
3. 添加BaseHolder(View view)构造器，外部更方便控制View。
4. 保留getContext()方法，方便获取Context对象。
新版的BaseHolder代码如下：
[代码]java代码：
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public class BaseHolder extends RecyclerView.ViewHolder {
private SparseArray
public BaseHolder(ViewGroup parent, @LayoutRes int resId) { super(LayoutInflater.from(parent.getContext()).inflate(resId, parent, false)); viewArray = new SparseArray(); }
public BaseHolder(View view) { super(view); viewArray = new SparseArray(); }
protected View view = viewArray.get(viewId); if (view == null) { view = itemView.findViewById(viewId); viewArray.put(viewId, view); } return (T) view; }
protected Context getContext() { return itemView.getContext(); } } |
Adapter部分的优化
Adapter拆分为两个抽象类：AbsAdapter与BaseAdapter，其中：
AbsAdapter：封装了和ViewHolder和HeaderView，FooterView相关的方法。
BaseAdapter：继承AbsAdapter,封装了数据相关的方法。
各自聚焦于不同的方面，方面日后扩展。
AbsAdapter的代码如下：
[代码]java代码：
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public abstract class AbsAdapter
private static final String TAG = "AbsAdapter";
public static final int VIEW_TYPE_HEADER = 1024; public static final int VIEW_TYPE_FOOTER = 1025;
protected View headerView; protected View footerView;
protected Context context;
public AbsAdapter(Context context) { this.context = context; }
@Override public final BaseHolder onCreateViewHolder(ViewGroup parent, int viewType) { if (viewType == VIEW_TYPE_HEADER) { return new BaseHolder(headerView); } else if (viewType == VIEW_TYPE_FOOTER) { return new BaseHolder(footerView); } else { return createCustomViewHolder(parent, viewType); } }
public abstract VH createCustomViewHolder(ViewGroup parent, int viewType);
@Override public final void onBindViewHolder(BaseHolder holder, int position) { switch (holder.getItemViewType()) { case VIEW_TYPE_HEADER: case VIEW_TYPE_FOOTER: break; default: bindCustomViewHolder((VH) holder, position); break; } }
public abstract void bindCustomViewHolder(VH holder, int position);
public void addHeaderView(View headerView) { if (headerView == null) { Log.w(TAG, "add the header view is null"); return ; } this.headerView = headerView; notifyDataSetChanged(); }
public void removeHeaderView() { if (headerView != null) { headerView = null; notifyDataSetChanged(); } }
public void addFooterView(View footerView) { if (footerView == null) { Log.w(TAG, "add the footer view is null"); return; } this.footerView = footerView; notifyDataSetChanged(); }
public void removeFooterView() { if (footerView != null) { footerView = null; notifyDataSetChanged(); } }
public int getExtraViewCount() { int extraViewCount = 0; if (headerView != null) { extraViewCount++; } if (footerView != null) { extraViewCount++; } return extraViewCount; }
public int getHeaderExtraViewCount() { return headerView == null ? 0 : 1; }
public int getFooterExtraViewCount() { return footerView == null ? 0 : 1; }
@Override public abstract long getItemId(int position); },> |
BaseAdapter的代码如下：
[代码]java代码：
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public abstract class BaseAdapter
private List
public BaseAdapter(Context context) { super(context); this.dataList = new ArrayList(); }
public BaseAdapter(Context context, List super(context); this.dataList = new ArrayList(); this.dataList.addAll(list); }
public boolean fillList(List dataList.clear(); boolean result = dataList.addAll(list); if (result) { notifyDataSetChanged(); } return result; }
public boolean appendItem(M data) { boolean result = dataList.add(data); if (result) { if (getHeaderExtraViewCount() == 0) { notifyItemInserted(dataList.size() - 1); } else { notifyItemInserted(dataList.size()); } } return result; }
public boolean appendList(List boolean result = dataList.addAll(list); if (result) { notifyDataSetChanged(); } return result; }
public void proposeItem(M data) { dataList.add(0, data); if (getHeaderExtraViewCount() == 0) { notifyItemInserted(0); } else { notifyItemInserted(getHeaderExtraViewCount()); } }
public void proposeList(List dataList.addAll(0, list); notifyDataSetChanged(); }
@Override public long getItemId(int position) { return position; }
@Override public final int getItemViewType(int position) { if (headerView != null && position == 0) { return VIEW_TYPE_HEADER; } else if (footerView != null && position == dataList.size() + getHeaderExtraViewCount()) { return VIEW_TYPE_FOOTER; } else { return getCustomViewType(position); } }
public abstract int getCustomViewType(int position);
@Override public int getItemCount() { return dataList.size() + getExtraViewCount(); }
public M getItem(int position) { if (headerView != null && position == 0 || position >= dataList.size() + getHeaderExtraViewCount()) { return null; } return headerView == null ? dataList.get(position) : dataList.get(position - 1); }
public M getItem(VH holder) { return getItem(holder.getAdapterPosition()); }
public void updateItem(M data) { int index = dataList.indexOf(data); if (index return; } dataList.set(index, data); if (headerView == null) { notifyItemChanged(index); } else { notifyItemChanged(index + 1); } }
public void removeItem(int position) { if (headerView == null) { dataList.remove(position); } else { dataList.remove(position - 1); } notifyItemRemoved(position); }
public void removeItem(M data) { int index = dataList.indexOf(data); if (index return; } dataList.remove(index); if (headerView == null) { notifyItemRemoved(index); } else { notifyItemRemoved(index + 1); } } },>,> |
点击事件的优化
为了降低点击事件的耦合性，将点击事件从Adapter中移除，使用另外一种方式来实现。使用代码如下：
[代码]java代码：
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recyclerView.addOnItemTouchListener(new RecyclerItemClickListener(recyclerView, new RecyclerItemClickListener.OnItemClickListener() { @Override public void onItemClick(View view, int position) { Person person = singleAdapter.getItem(position); Toast.makeText(SingleActivity.this, "click:" + person, Toast.LENGTH_SHORT).show(); }
@Override public void onItemLongClick(View view, int position) { Person person = singleAdapter.getItem(position); Toast.makeText(SingleActivity.this, "Long Click:" + person, Toast.LENGTH_SHORT).show(); } })); |
使用RecyclerView的自带的方法addOnItemTouchListener()实现点击和长点击事件。实现代码如下：
[代码]java代码：
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public class RecyclerItemClickListener implements RecyclerView.OnItemTouchListener {
private OnItemClickListener clickListener; private GestureDetector gestureDetector;
public interface OnItemClickListener {
void onItemClick(View view, int position);
void onItemLongClick(View view, int position); }
public RecyclerItemClickListener(final RecyclerView recyclerView, OnItemClickListener listener) { this.clickListener = listener; gestureDetector = new GestureDetector(recyclerView.getContext(), new GestureDetector.SimpleOnGestureListener() { @Override public boolean onSingleTapUp(MotionEvent e) { return true; }
@Override public void onLongPress(MotionEvent e) { View childView = recyclerView.findChildViewUnder(e.getX(), e.getY()); if (childView != null && clickListener != null) { clickListener.onItemLongClick(childView, recyclerView.getChildAdapterPosition(childView)); } } }); }
@Override public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) { View childView = rv.findChildViewUnder(e.getX(), e.getY()); if (childView != null && clickListener != null && gestureDetector.onTouchEvent(e)) { clickListener.onItemClick(childView, rv.getChildAdapterPosition(childView)); return true; } return false; }
@Override public void onTouchEvent(RecyclerView rv, MotionEvent e) {
}
@Override public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
} } |
分割线的优化
RecyclerView的分割线不像ListView那样方便，但是RecyclerView也提供了``方法来添加分割线。
分割线代码使用的是SDK中的Sample的代码，在其中添加了``方法，方便设置分割线的形式。
具体的代码参见此处：DividerDecoration.java
优化后的使用
优化后使用方式有所改变，具体使用方式如下：
[代码]java代码：
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recyclerView = (RecyclerView) findViewById(R.id.single_rv); layoutManager = new LinearLayoutManager(this); recyclerView.setLayoutManager(layoutManager); DividerDecoration decoration = new DividerDecoration(this, DividerDecoration.VERTICAL_LIST); Drawable drawable = getResources().getDrawable(R.drawable.divider_single); decoration.setDivider(drawable); recyclerView.addItemDecoration(decoration); recyclerView.setAdapter(singleAdapter);
View view = LayoutInflater.from(this).inflate(R.layout.item_single_header, null, false); singleAdapter.addHeaderView(view);
recyclerView.addOnItemTouchListener(new RecyclerItemClickListener(recyclerView, new RecyclerItemClickListener.OnItemClickListener() { @Override public void onItemClick(View view, int position) { Person person = singleAdapter.getItem(position); Toast.makeText(SingleActivity.this, "click:" + person, Toast.LENGTH_SHORT).show(); }
@Override public void onItemLongClick(View view, int position) { Person person = singleAdapter.getItem(position); Toast.makeText(SingleActivity.this, "Long Click:" + person, Toast.LENGTH_SHORT).show(); } })); |
以上所有的代码均在GitHub上，具体地址在此：Dev-Wiki/RecyclerView
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/2508/viewspace-2814823/ ，如需转载，请注明出处，否则将追究法律责任。
