Android 从返回堆栈恢复片段时的savedInstanceState
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原文地址: http://stackoverflow.com/questions/11111649/
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savedInstanceState when restoring fragment from back stack
提问by heero
Can I use savedInstanceState()to save the state when removing a fragment, then restore the state when I pop the fragment off the back stack? When I restore the fragment from the back stack, savedInstanceState bundle is always null.
我可以savedInstanceState()在删除片段时使用保存状态，然后在从返回堆栈中弹出片段时恢复状态吗？当我从返回堆栈中恢复片段时，savedInstanceState 包始终为空。
Right now, the app flow is: fragment created -> fragment removed (added to back stack) -> fragment restored from back stack (savedInstanceState bundle is null).
现在，应用流程是：创建片段 -> 删除片段（添加到后台堆栈）-> 从后台堆栈恢复片段（savedInstanceState 包为空）。
Here is the relevant code:
这是相关的代码：
public void onActivityCreated(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Bundle bundle = getArguments();
Long playlistId = bundle.getLong(Constants.PLAYLIST_ID);
int playlistItemId = bundle.getInt(Constants.PLAYLISTITEM_ID);
if (savedInstanceState == null) {
selectedVideoNumber = playlistItemId;
} else {
selectedVideoNumber = savedInstanceState.getInt("SELECTED_VIDEO");
}
}
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt(Constants.SELECTED_VIDEO, selectedVideoNumber);
}
I think the problem is that onSavedInstanceState()is never called when being removed and being added to back stack. If I cant use onsavedInstanceState(), is there another way to fix this?
我认为问题在于它onSavedInstanceState()在被删除并被添加到后台堆栈时永远不会被调用。如果我不能使用 onsavedInstanceState()，还有其他方法可以解决这个问题吗？
回答by Eric
onSaveInstanceState is (unfortunately) not called in normal back-stack re-creation of a fragment. Check out http://developer.android.com/guide/components/fragments.html#Creatingand the answer on How can I maintain fragment state when added to the back stack?
onSaveInstanceState（不幸的是）在片段的正常后台堆栈重新创建中没有被调用。查看http://developer.android.com/guide/components/fragments.html#Creating和有关如何在添加到后台堆栈时保持片段状态的答案？
回答by AllDayAmazing
I like to store the View I return in onCreateView as a global variable and then when I return I simply check this:
我喜欢将我在 onCreateView 中返回的视图存储为全局变量，然后当我返回时，我只需检查一下：
if(mBaseView != null) {
// Remove the view from the parent
((ViewGroup)mBaseView.getParent()).removeView(mBaseView);
// Return it
return mBaseView;
}
回答by bcorso
The problem is that the fragment needs to have an Idor Tagassociated with it in order for the FragmentManagerto keep track of it.
问题是片段需要有一个Id或Tag与之关联，以便FragmentManager跟踪它。
There are at least 3 ways to do this:
至少有 3 种方法可以做到这一点：
In xml layout declare an
Idfor your fragment:android:id=@+id/<Id>If your fragments container
Viewhas anId, use FragmentTransaction:FragmentTransaction add (int containerViewId, Fragment fragment)If your fragment is not associated with any
View(e.g. headless fragment), give it aTag:FragmentTransaction add (Fragment fragment, String tag)
在 xml 布局中
Id为您的片段声明一个：android:id=@+id/<Id>如果您的片段容器
View有Id，请使用FragmentTransaction：FragmentTransaction add (int containerViewId, Fragment fragment)如果您的片段不与任何
View（例如无头片段）相关联，请给它一个Tag：FragmentTransaction add (Fragment fragment, String tag)
回答by kenyee
FWIW, I hit this as well, but in my case onSaveInstanceState was called properly and I pushed in my state data when a new activity fragment was brought up on the smartphone. Same as you, the onActivityCreated was called w/ savedInstanceState always null. IMHO, I think it's a bug.
FWIW，我也打了这个，但在我的情况下，onSaveInstanceState 被正确调用，当智能手机上出现一个新的活动片段时，我推送了我的状态数据。与您一样， onActivityCreated 被调用 w/savedInstanceState 始终为空。恕我直言，我认为这是一个错误。
I worked around it by creating a static MyApplication state and putting the data there for the equivalent of "global variables"...
我通过创建一个静态的 MyApplication 状态并将数据放在那里来解决它，相当于“全局变量”......
