blocks|key|1942591|text|也许这能帮助你理解这种行为。如果您签出FragmentManagerImpl.java，您将发现以下内容：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1942592|首先通过调用onCreateView()+(第845行)创建视图，然后用另一个视图包装已创建的视图，该视图将成为视图的父视图(第848-849行)。这意味着我们的视图不是真正容器的子视图，而是包装器视图的子视图。当视图从容器中移除时，重用问题就会发生(第998行)。FragmentManager从容器中移除包装器视图，但是我们的实际视图仍然被添加到父包装视图中。这就是你所经历的问题的原因。|style|CODE|1942593|因此，如果从其父视图中删除视图，则它可以工作。即使知道了这一点，我也不会建议重用片段中的视图，因为视图比片段活得更长，因为它们可以用于“消失”的动画，即使片段被销毁了。如果您当时试图从其父视图中删除这样的视图，那么动画可能会中断。|1942594|另一个不缓存视图的理由是，Android不支持按设计在片段中回收视图。还记得ListAdapter允许重用视图吗？Android负责缓存和正确重用这些视图。然而，碎片的情况并非如此。|1942595|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/grantland/android-support-v4/blob/master/src/java/android/support/v4/app/FragmentManager.java#L377^0|J|O|0|0|6|E|0|0|12|B|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|D|3|E|5|6|7|X|8|@$A|Y|B|Z|F|G]]|9|@]|C|$]]|$1|H|3|I|5|6|7|10|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|11|8|@$A|12|B|13|F|G]]|9|@]|C|$]]|$1|L|3|-4|5|6|7|14|8|@]|9|@]|C|$]]]|M|$N|$5|O|P|Q|C|$R|S]]]]

Maybe this can help to understand the behavior. If you check out <a href="https://github.com/grantland/android-support-v4/blob/master/src/java/android/support/v4/app/FragmentManager.java#L377" rel="noreferrer">FragmentManagerImpl.java</a> you will find the following:

First we create a view by calling <code>onCreateView()</code> (line 845) and then we wrap created view with another view, which becomes a parent of our view (lines 848-849). This means our view does not become a child of real container, but it's a child of a wrapper view now. The problem with reuse happens, when view gets removed from the container (line 998). FragmentManager removes wrapper view from the container, but our real view stays added to the parent wrapper view. This is what causes the issue you experience.

Thus, if you remove the view from its parent, it can work. Even knowing this, I would not recommend reusing views in the fragment also because views can live a bit longer than fragments, because they can be used in "disappearing" animations even after the fragment is been destroyed. If you try to remove such a view from its parent at that time, then the animation might be broken.

Another argument to not cache the view is that Android doesn't support view recycling in fragments by design. Remember <code>ListAdapter</code> allowing to reuse the views? Android takes care for caching and proper reusing those views. This is not the case with fragment though.

blocks|key|866796|text|我目前正在重用视图，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|866797|if(view+==+null){
++++view+=+(ViewGroup)+inflater.inflate(R.layout.news_list,+container,+false);
}+else+{
++++((ViewGroup)+view.getParent()).removeView(view);
}
return+view;|code-block|syntax|javascript|866798|我不知道这种方法是否正确，但它似乎对我有用。|866799|注意:我使用这个aproach是因为我在片段中有一个listview，当用户点击一个项目时，它会加载一个新的片段(片段管理器替换当前的列表片段)。然后，当用户单击same按钮时，由于我正在重用片段的相同旧视图(在使用FM删除时未被销毁)，则用户将继续在打开详细片段视图之前的位置查看列表。|866800|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I'm currently reusing the view with something like this:

<pre><code>if(view == null){
 view = (ViewGroup) inflater.inflate(R.layout.news_list, container, false);
} else {
 ((ViewGroup) view.getParent()).removeView(view);
}
return view;
</code></pre>

I don't know if this way is correct, but it seems to work for me..

NOTE: I'm using this aproach because I have a listview in a fragment, and when user tap on an item it loads a new fragment (fragment manager replace current list fragment using). Then, when user hit backbutton, as I'm reusing the same old view of the fragment (that is not destroyed when removed with FM) then the user continues viewing the list in the position it was before opening detail fragment view.

blocks|key|1942645|text|我知道这是个老问题。但是在使用了几个月的片段之后，我发现在以这种方式使用缓存时需要提到的一件事是:如果您当前的缓存布局还有另一个片段标记，这种缓存策略将导致嵌入片段丢失一些生命周期回调。我会详细讲一下：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1942646|第一次调用当前片段onCreateView。通过像上面这样的缓存，我们将膨胀目标布局(这个布局包括一个片段标记)。|ordered-list-item|offset|length|style|CODE|1942647|通过inflater.inflate，这将使嵌入片段正确地添加到布局中，onCreateView将被调用。|1942648|当需要销毁当前片段时，将正确调用嵌入片段onDestroyView。|1942649|当当前片段onCreateView再次调用时，我们返回缓存的视图，而不调用inflater.inflate。您将发现嵌入片段onCreateView和onDestroyView或其他生命周期方法不会被调用。|1942650|我只想提这些。|1942651|entityMap^0|0|9|C|0|2|G|10|C|0|K|D|0|5|C|11|G|1Q|C|23|D|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@$E|U|F|V|G|H]]|9|@]|A|$]]|$1|I|3|J|5|D|7|W|8|@$E|X|F|Y|G|H]|$E|Z|F|10|G|H]]|9|@]|A|$]]|$1|K|3|L|5|D|7|11|8|@$E|12|F|13|G|H]]|9|@]|A|$]]|$1|M|3|N|5|D|7|14|8|@$E|15|F|16|G|H]|$E|17|F|18|G|H]|$E|19|F|1A|G|H]|$E|1B|F|1C|G|H]]|9|@]|A|$]]|$1|O|3|P|5|6|7|1D|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]]|R|$]]

I know it's a old question. But after working with fragments for months, I found one thing need to mention when using cache this way is that: if your current cached layout still has another fragment tag, this cache strategy will lead to the embed fragment loss some life-cycle callback. I'll talk it in detail:
<ol>
<li>The current fragment <code>onCreateView</code> was called first time. By caching like above, we will inflate the target layout(this layout including a fragment tag).</li>
<li>By <code>inflater.inflate</code> this will make the embed fragment added to the layout correctly, the <code>onCreateView</code> will be called.</li>
<li>When current fragment needs to be destroy, the embed fragment <code>onDestroyView</code> will be called correctly.</li>
<li>When current fragment <code>onCreateView</code> called again, we return a cached view, without calling <code>inflater.inflate</code>. You will find the embed fragment <code>onCreateView</code> and <code>onDestroyView</code> or other life-cycle methods won't be called.</li>
</ol>
That's all what I want to mention.

Actually, I always reused my view in my fragments like the following:

<pre><code>private View mView = null;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
 if (mView == null)
 mView = inflater.inflate(R.layout.view);
 return mView;
}
</code></pre>

That worked, with viewpager and so on. Now I started using my fragments in simple activities as well and if, and only if, I add the fragment to the backstack, this will fail because of <code>java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.</code>

So my questions are:

<ul>
<li>Is it ok, if I check the the views parent, remove it and add it to the new parent?</li>
<li>Or should I always recreate the view and never reuse it? If yes, why?</li>
<li>Are there other points, where reusing the view will fail?</li>
</ul>

Fragment - should I reuse view in onCreateView and how should I do that?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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实际上，我总是在我的片段中重用我的视图，如下所示：private View mView = null;@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){  ...

问片段-我应该在onCreateView中重用视图吗?我应该如何做到这一点？
EN

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问片段-我应该在onCreateView中重用视图吗?我应该如何做到这一点？EN