由网友(国民男神゛)分享简介：（我想出了一个解决方案 - 请参阅我下面的回答部分后） 在我的应用程序，用户将开始他的数据的单一视图。我想补充一个ViewPager，并允许根据需要用户添加更多的意见。我该怎么做呢？ （我不'要使用的FragmentPagerAdapter。）In my app, the user will start with...
（我想出了一个解决方案 - 请参阅我下面的回答部分后）
在我的应用程序，用户将开始他的数据的单一视图。我想补充一个ViewPager，并允许根据需要用户添加更多的意见。我该怎么做呢？ （我不'要使用的FragmentPagerAdapter。）
In my app, the user will start with a single view of his data. I'd like to add a ViewPager and allow the user to add more views as desired. How do I do this? (I dont' want to use the FragmentPagerAdapter.)
我看过无数的文章和概述，但是我仍然失去了一些东西。这就是我想我明白了：
I've read countless posts and overviews but am still missing something. Here's what I think I understand:
MainActivity创建ViewPager和PagerAdapter：
MainActivity creates a ViewPager and PagerAdapter:
ViewPager pager = null;
MainPagerAdapter adapter = null;
public void onCreate (Bundle savedInstanceState)
{
super.onCreate (savedInstanceState);
pager = new ViewPager (this);
setContentView (pager);
adapter = new MainPagerAdapter();
pager.setAdapter (adapter);
View v0 = code_to_create_initial_view();
adapter.add (v0, 0);
}
使用一个PagerAdapter提供的视图集。对于这一点，看来我需要的方法来添加和删除的意见，像这样的东西;显然更需要的是告诉ViewPager的东西已经改变，以及如何显示更改：
Use a PagerAdapter to provide the sets of view. For this it seems I need methods to add and remove views, something like this; obviously more is needed to tell the ViewPager stuff has changed and how to show the change:
class MainPagerAdapter extends PagerAdapter
{
// This holds all the currently displayable views, in order from left to right.
private ArrayList<View> views = new ArrayList<View>();
public void addView (View v, int position)
{
views.add (position, v);
}
public void removeView (int position)
{
views.remove (position);
}
}
另外，我需要实现以下vitual方法。我迷失在这里 - 什么叫他们，什么是他们应该做的（好吧，getCount将是显而易见的）？
In addition, I need to implement the following vitual methods. I'm lost here - what calls them and what are they supposed to do (ok, getCount is obvious)?
public object instantiateItem (ViewGroup pager, int position);
public void destroyItem (ViewGroup, int, Object);
public int getCount ();
public boolean isViewFromObject (View, Object);
什么的ViewGroup PARAMS的 - 不包含组ViewPager本身？ 在什么isViewFromObject办？ - 如何对象获得与摆在首位的视图相关 我应该打电话startUpdate和finishUdate当我添加或删除的看法？
感谢。
推荐答案
搞清楚哪些ViewPager方法是通过ViewPager调用，这是出于其他目的后，我想出了一个解决方案。我present在这里，因为我看到很多人都在努力与这一点，我没有看到任何其他相关的答案。
After figuring out which ViewPager methods are called by ViewPager and which are for other purposes, I came up with a solution. I present it here since I see a lot of people have struggled with this and I didn't see any other relevant answers.
首先，这里是我的适配器;内code有望评论就足够了：
First, here's my adapter; hopefully comments within the code are sufficient:
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.
}
和这里的code一些剪展示了如何使用适配器。
And here's some snips of code showing how to use the adapter.
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.
LayoutInflater inflater = context.getLayoutInflater();
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，你可以使用下面为您 activity_main.xml 布局：
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/view_pager"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</android.support.v4.view.ViewPager>
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