viewPager-viewAdapter的使用

viewPager:

1. public method:

• setCurrentItem(int item)/setCurrentItem(int item,boolean smoothScroll) : 设置选择的页面

set the currently selected page.

• setAdapter(PagerAdapter adapter):设置提供views的adapter

set a PagerAdapter that will supply views for this pager as needed.

• addOnPageChangeListener(OnPageChangeListener):设置动作监听器
• OnPageChangeListener:
  • onPageScrollStateChanged(int state):页面完全停止或空闲时,发生滑动状态时调用.用于发现用户滑动的时刻
  • onPageScrolled(int position, float positionOffset, int positionOffsetPixels):当前页面被滑动时调用.不管是程序引起的还是用户触发的.
  • onPageSelected(int position):一个新的页面被选中时调用.动画不一定完成.

pageAdapter:

• 实现一个pageAdapter时,必须重载以下方法:

1. instantiateItem(ViewGroup,int):在给定位置创建view.可以把view添加此处给出的容器中.

Create the page for the given position. The adapter is responsible for adding the view to the container given here, although it only must ensure this is done by the time it returns from finishUpdate(ViewGroup).

2. destroyItem(ViewGroup, int, Object):把page从给定位置移出.

Remove a page for the given position. The adapter is responsible for removing the view from its container, although it only must ensure this is done by the time it returns from finishUpdate(ViewGroup)

3. getCount():返回可用的view数

Return the number of views available.

4. isViewFromObject(view, Object):判断view是否和一个关键object绑定起来

Determines whether a page View is associated with a specific key object as returned by instantiateItem(ViewGroup, int)

• 还有两个子类可以实现:
  • FragmentPagerAdapter
  • FragmentStatePagerAdapter
• notifyDataSetChanged():但view改变时,应该调用此函数!

This method should be called by the application if the data backing this adapter has changed and associated views should update.