最近看到有人在问这三个参数的含义，其实帮助已经很详细的介绍了这三个参数，看来还是要好好学学英语了，不然连解释都看不懂。
/**
* Get a View that displays the data at the specified position in the data set. You can either
* create a View manually or inflate it from an XML layout file. When the View is inflated, the
* parent View (GridView, ListView...) will apply default layout parameters unless you use
* {@link android.view.LayoutInflater#inflate(int, android.view.ViewGroup, boolean)}
* to specify a root view and to prevent attachment to the root.
*
* @param position The position of the item within the adapter's data set of the item whose view
* we want.
* @param convertView The old view to reuse, if possible. Note: You should check that this view
* is non-null and of an appropriate type before using. If it is not possible to convert
* this view to display the correct data, this method can create a new view.
* @param parent The parent that this view will eventually be attached to
* @return A View corresponding to the data at the specified position.
*/