dynamically add and remove view to viewpager

原文地址：dynamically
add and remove view to viewpager

动态增加、删除 ViewPager

国人的代码质量确实差，加油～我当前的应用场景：由于业务的树状关系，让界面层级很多，就用ViewPager来做，类似视图栈的管理。转来一篇stackoverflow的解决方案，如下：

class MainPagerAdapter extends PagerAdapter
{
// This holds all the currently displayable views, in order from left to right.
private ArrayList<View> views = new ArrayList<View>();

//-----------------------------------------------------------------------------
// Used by ViewPager.  "Object" represents the page; tell the ViewPager where the
// page should be displayed, from left-to-right.  If the page no longer exists,
// return POSITION_NONE.
@Override
public int getItemPosition (Object object)
{
int index = views.indexOf (object);
if (index == -1)
return POSITION_NONE;
else
return index;
}

//-----------------------------------------------------------------------------
// Used by ViewPager.  Called when ViewPager needs a page to display; it is our job
// to add the page to the container, which is normally the ViewPager itself.  Since
// all our pages are persistent, we simply retrieve it from our "views" ArrayList.
@Override
public Object instantiateItem (ViewGroup container, int position)
{
View v = views.get (position);
container.addView (v);
return v;
}

//-----------------------------------------------------------------------------
// Used by ViewPager.  Called when ViewPager no longer needs a page to display; it
// is our job to remove the page from the container, which is normally the
// ViewPager itself.  Since all our pages are persistent, we do nothing to the
// contents of our "views" ArrayList.
@Override
public void destroyItem (ViewGroup container, int position, Object object)
{
container.removeView (views.get (position));
}

//-----------------------------------------------------------------------------
// Used by ViewPager; can be used by app as well.
// Returns the total number of pages that the ViewPage can display.  This must
// never be 0.
@Override
public int getCount ()
{
return views.size();
}

//-----------------------------------------------------------------------------
// Used by ViewPager.
@Override
public boolean isViewFromObject (View view, Object object)
{
return view == object;
}

//-----------------------------------------------------------------------------
// Add "view" to right end of "views".
// Returns the position of the new view.
// The app should call this to add pages; not used by ViewPager.
public int addView (View v)
{
return addView (v, views.size());
}

//-----------------------------------------------------------------------------
// Add "view" at "position" to "views".
// Returns position of new view.
// The app should call this to add pages; not used by ViewPager.
public int addView (View v, int position)
{
views.add (position, v);
return position;
}

//-----------------------------------------------------------------------------
// Removes "view" from "views".
// Retuns position of removed view.
// The app should call this to remove pages; not used by ViewPager.
public int removeView (ViewPager pager, View v)
{
return removeView (pager, views.indexOf (v));
}

//-----------------------------------------------------------------------------
// Removes the "view" at "position" from "views".
// Retuns position of removed view.
// The app should call this to remove pages; not used by ViewPager.
public int removeView (ViewPager pager, int position)
{
// ViewPager doesn't have a delete method; the closest is to set the adapter
// again.  When doing so, it deletes all its views.  Then we can delete the view
// from from the adapter and finally set the adapter to the pager again.  Note
// that we set the adapter to null before removing the view from "views" - that's
// because while ViewPager deletes all its views, it will call destroyItem which
// will in turn cause a null pointer ref.
pager.setAdapter (null);
views.remove (position);
pager.setAdapter (this);

return position;
}

//-----------------------------------------------------------------------------
// Returns the "view" at "position".
// The app should call this to retrieve a view; not used by ViewPager.
public View getView (int position)
{
return views.get (position);
}

// Other relevant methods:

// finishUpdate - called by the ViewPager - we don't care about what pages the
// pager is displaying so we don't use this method.
}

class MainActivity extends Activity
{
private ViewPager pager = null;
private MainPagerAdapter pagerAdapter = null;

//-----------------------------------------------------------------------------
@Override
public void onCreate (Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView (R.layout.main_activity);

... do other initialization, such as create an ActionBar ...

pagerAdapter = new MainPagerAdapter();
pager = (ViewPager) findViewById (R.id.view_pager);
pager.setAdapter (pagerAdapter);

// Create an initial view to display; must be a subclass of FrameLayout.
FrameLayout v0 = (FrameLayout) inflater.inflate (R.layout.one_of_my_page_layouts, null);
pagerAdapter.addView (v0, 0);
}

//-----------------------------------------------------------------------------
// Here's what the app should do to add a view to the ViewPager.
public void addView (View newPage)
{
int pageIndex = pagerAdapter.addView (newPage);
// You might want to make "newPage" the currently displayed page:
pager.setCurrentItem (pageIndex, true);
}

//-----------------------------------------------------------------------------
// Here's what the app should do to remove a view from the ViewPager.
public void removeView (View defunctPage)
{
int pageIndex = pagerAdapter.removeView (pager, defunctPage);
// You might want to choose what page to display, if the current page was "defunctPage".
if (pageIndex == pagerAdapter.getCount())
pageIndex--;
pager.setCurrentItem (pageIndex);
}

//-----------------------------------------------------------------------------
// Here's what the app should do to get the currently displayed page.
public View getCurrentPage ()
{
return pagerAdapter.getView (pager.getCurrentItem());
}

//-----------------------------------------------------------------------------
// Here's what the app should do to set the currently displayed page.  "pageToShow" must
// currently be in the adapter, or this will crash.
public void setCurrentPage (View pageToShow)
{
pager.setCurrentItem (pagerAdapter.getItemPosition (pageToShow), true);
}
}

最后，这边在addview、removeview会报出error，加上PagerAdapter 的NotifyDataChanged就行，应该是状态检查的Exception。

另外，如果用Pager的地方多，也可以写个代理：PagerHelper(ViewPager, XXPagerAdapter)，在这里面来实现各种方便的操作～