不管是android还是iOS，列表视图应该是最复杂的控件了。android中的listview从命名能够看出是个一维数组，而iOS中的tableview则是二维数组。但事实上须要注意的地方是差点儿相同的。都是重用机制。这是考量你对listview是否能掌握的最好的方法。
常见的listview的初始化以及设置适配器的代码例如以下：
ListView listView;MyAdapter listAdapter;ArrayList当中setAdapter是主要用来设置数据的。我们不防看一下ListView（）的setAdapter源代码listString;listView = (ListView)this.findViewById(R.id.listview);listString = new ArrayList ();for(int i = 0 ; i < 100 ; i++){listString.add(Integer.toString(i));}listAdapter = new MyAdapter(this);listView.setAdapter(listAdapter);}class MyAdapter extends BaseAdapter{Context mContext;LinearLayout linearLayout = null;LayoutInflater inflater;public MyAdapter(Context context) {// TODO Auto-generated constructor stubmContext = context;inflater = LayoutInflater.from(mContext);}@Overridepublic int getCount() {// TODO Auto-generated method stubreturn listString.size();}@Overridepublic Object getItem(int arg0) {// TODO Auto-generated method stubreturn listString.get(arg0);}@Overridepublic long getItemId(int position) {// TODO Auto-generated method stubreturn position;}public final class ViewHolder{ public ImageView img; public TextView title; public TextView info; public Button viewBtn; } public class MyAdapter extends BaseAdapter{ private LayoutInflater mInflater; public MyAdapter(Context context){ this.mInflater = LayoutInflater.from(context); } @Override public int getCount() { // TODO Auto-generated method stub return mData.size(); } @Override public Object getItem(int arg0) { // TODO Auto-generated method stub return null; } @Override public long getItemId(int arg0) { // TODO Auto-generated method stub return 0; } @Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder holder = null; if (convertView == null) { holder=new ViewHolder(); convertView = mInflater.inflate(R.layout.vlist2, null); holder.img = (ImageView)convertView.findViewById(R.id.img); holder.title = (TextView)convertView.findViewById(R.id.title); holder.info = (TextView)convertView.findViewById(R.id.info); holder.viewBtn = (Button)convertView.findViewById(R.id.view_btn); convertView.setTag(holder); }else { holder = (ViewHolder)convertView.getTag(); } holder.img.setBackgroundResource((Integer)mData.get(position).get("img")); holder.title.setText((String)mData.get(position).get("title")); holder.info.setText((String)mData.get(position).get("info")); holder.viewBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { showInfo(); } }); return convertView; } }
@Override public void setAdapter(ListAdapter adapter) { if (null != mAdapter) { mAdapter.unregisterDataSetObserver(mDataSetObserver); } resetList(); mRecycler.clear(); if (mHeaderViewInfos.size() > 0|| mFooterViewInfos.size() > 0) { mAdapter = new HeaderViewListAdapter(mHeaderViewInfos, mFooterViewInfos, adapter); } else { mAdapter = adapter; } mOldSelectedPosition = INVALID_POSITION; mOldSelectedRowId = INVALID_ROW_ID; if (mAdapter != null) { mAreAllItemsSelectable = mAdapter.areAllItemsEnabled(); mOldItemCount = mItemCount; mItemCount = mAdapter.getCount(); checkFocus(); mDataSetObserver = new AdapterDataSetObserver(); mAdapter.registerDataSetObserver(mDataSetObserver); mRecycler.setViewTypeCount(mAdapter.getViewTypeCount()); int position; if (mStackFromBottom) { position = lookForSelectablePosition(mItemCount - 1, false); } else { position = lookForSelectablePosition(0, true); } setSelectedPositionInt(position); setNextSelectedPositionInt(position); if (mItemCount == 0) { // Nothing selected checkSelectionChanged(); } } else { mAreAllItemsSelectable = true; checkFocus(); // Nothing selected checkSelectionChanged(); } if (mCheckStates != null) { mCheckStates.clear(); } requestLayout(); } 从以上代码能够看出其分为两步，第一步是当前adapter不为空的话。先清空本地adapter数据。然后是设置新的数据到listview。 当中里面有个重要的类
AdapterDataSetObserver
是用来存储数据的，我们看一下里面的代码,有个成员变量
mDataSetObserver
就是这个对象申明在listview的父类AbsListView（源代码在此）中 那么这个AdapterDataSetObserver到底是个什么东西呢，我们还是到AbsListView的父类AdapterView（）中一探到底吧。
class AdapterDataSetObserver extends DataSetObserver { private Parcelable mInstanceState = null; @Override public void onChanged() { mDataChanged = true; mOldItemCount = mItemCount; mItemCount = getAdapter().getCount(); // Detect the case where a cursor that was previously invalidated has // been repopulated with new data. if (AdapterView.this.getAdapter().hasStableIds() && mInstanceState != null && mOldItemCount == 0 && mItemCount > 0) { AdapterView.this.onRestoreInstanceState(mInstanceState); mInstanceState = null; } else { rememberSyncState(); } checkFocus(); requestLayout(); } @Override public void onInvalidated() { mDataChanged = true; if (AdapterView.this.getAdapter().hasStableIds()) { // Remember the current state for the case where our hosting activity is being // stopped and later restarted mInstanceState = AdapterView.this.onSaveInstanceState(); } // Data is invalid so we should reset our state mOldItemCount = mItemCount; mItemCount = 0; mSelectedPosition = INVALID_POSITION; mSelectedRowId = INVALID_ROW_ID; mNextSelectedPosition = INVALID_POSITION; mNextSelectedRowId = INVALID_ROW_ID; mNeedSync = false; checkSelectionChanged(); checkFocus(); requestLayout(); } public void clearSavedState() { mInstanceState = null; } } 从以上代码能够看出，这个类事实上是继承自DataSetObserver( )。 使用的是观察者模式，用于listview的数据处理。
这是一个抽象类，不多说了。
未完待续。
。。