BaseAdapter&GridView

Adapter是串連後端資料和最上層顯示的適配器介面，是資料和UI（View）之間一個重要的紐帶。在常見的View(ListView,GridView)等地方都需要用到Adapter。如直觀的表達了Data、Adapter、View三者的關係：

BaseAdapter是一個abstrace class要使用時必須重寫他的方法，注意這些方法都是抽象方法，分別生命在Adapter abstrace class中。分別是：

public int getCount()返回該Adapter中裝載的資源的數量

public Object getItem(int position)從data set中取出指定poistion處的資料

public long getItemId(int position)return position處的item所在的row id

public View getView(int position, View convertView, ViewGroup parent)

position:data set 中position處的資料，this data we want to view.

convertView:使用之前用convertView ? null判斷，if can't covert to a view來裝載資料然後顯示的話，就需要建立一個新的view了；了；來裝載資料.

parent: as the convertView's parent view and must attached to parent.

after call this function will return the view with data in the position  of  the adapter. 

點擊時候的響應函數：

public abstract void onItemClick
(AdapterView<?> parent,

View view, int position, long id)

parent	The AdapterView where the click happened.發生click事件的那個AdapterView
view	The view within the AdapterView that was clicked (this will be a view provided by the adapter)
position	The position of the view in the adapter.
id	The row id of the item that was clicked.

ImageSwitcher: