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～