在setRetainInstance文档说:
the docs on setRetainInstance say :
这只能用于与碎片不会在背面叠层
This can only be used with fragments not in the back stack.
所以我就开始摆弄它。
我有一个活性的增加先断枝A
I have one Activity with adds first frag A
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.content, new PackageFragment());
ft.commit
然后再从这个断枝我运行父活动的方法,其增加的frag B至backstack
then from this frag I run a method from parent Activity which adds frag B to backstack
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.content, new OrderFragment());
ft.addToBackStack(null);
ft.commit();
然后我从创建日志味精的onCreate,的onDestroy,的onSaveInstanceState,onActivityCreated ...等
then I create log msg from onCreate,onDestroy,onSaveInstanceState,onActivityCreated...etc
我尝试两个版本的过程。旋转设备的每个片段上。
I try two versions of this process. Rotating the device on each fragment.
默认一切都如预期。的onCreate,对的onDestroy火片段
Everything is as expected. onCreate, onDestroy on fragments fire
setRetainInstance(真)一切都如预期?的onCreate,对的onDestroy碎片不火
Everything is as expected?. onCreate, onDestroy on fragments dont fire
和一切似乎工作,而片段在backstack ..所以,为什么文档说我不应该使用它吗? 是什么,我可能会遇到麻烦的情况下?
and all seems to work while fragments are in the backstack.. so why the docs say I shouldnt use it? What are the scenarios where I might get in trouble?
感谢
推荐答案
更新答案:
什么是在那里我会遇到麻烦的情况下?
What are the scenarios where I might get in trouble?
在添加片段
到后面堆和片段传递
从捆绑
的onSaveInstanceState()
到 onCreateView()
的配置变化。呼叫 setRetainInstance(真)
将设置捆绑
来对配置更改为空。
When adding a Fragment
to the back stack and passing a Bundle
in the Fragment
from onSaveInstanceState()
to onCreateView()
on configuration change. Calling setRetainInstance(true)
will set the Bundle
to null on configuration change.
(我不知道,因为使用 setRetainInstance(真)
让的onSaveInstanceState()那种多余的,但我没有看到记录在API文档,所以我写了这个答案的行为)。
(I'm not sure a developer would actually attempt this since using setRetainInstance(true)
makes onSaveInstanceState()
kind of redundant, but I didn't see the behaviour documented in the API docs so I wrote up this answer).
如果两个 addToBackStack()
和 setRetainInstance(真)
被称为, setRetainInstance( )
部分改变了片段
的配置更改,相比之下,只有调用 addToBackStack()。
If both addToBackStack()
and setRetainInstance(true)
are called, setRetainInstance()
partly alters the Fragment
lifecycle method calls and parameter values on configuration changes, compared to calling only addToBackStack()
.
具体而言,在下面的测试中,只查看调用之间的差异 addToBackStack()
并调用 setRetainInstance(真)
为好,看到的配置变化会发生什么:
Specifically, in the test below, looking a differences between calling only addToBackStack()
and calling setRetainInstance(true)
as well, and seeing what happens on configuration change:
调用 addToBackStack()
而不是 setRetainInstance(真)
;
的onCreate()
和的onDestroy()
被调用。
从的onSaveInstanceState()
被接收为一个参数 onCreateView()
。通过捆绑
onCreate()
and onDestroy()
are called.
a bundle passed from onSaveInstanceState()
is received as a parameter in onCreateView()
.
调用这两个 addToBackStack()
和 setRetainInstance(真)
:
的onDestroy()
不叫。这是在文件档案的API文档。
从的onSaveInstanceState通过捆绑()
未在 onCreateView接受()
。传入的捆绑
为空。
onCreate()
and onDestroy()
are not called. This is metioned in the API docs.
a bundle passed from onSaveInstanceState()
is not received in onCreateView()
. The passed-in Bundle
is null.
与测试空记录的方法调用和参数测试:
A test with logged method calls and parameters tested for null:
在活动
:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
MyFragment fragment;
if (savedInstanceState != null) {
fragment = (MyFragment) getFragmentManager().findFragmentByTag("my_fragment_tag");
} else {
fragment = new MyFragment();
FragmentTransaction t = getFragmentManager().beginTransaction();
t.addToBackStack(null);//toggle this
t.add(android.R.id.content, fragment, "my_fragment_tag").commit();
}
}
在片段
:
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setRetainInstance(true);//toggle this
}
和
@Override
public void onSaveInstanceState(Bundle outState) {
outState.putString("test", "value");
super.onSaveInstanceState(outState);
}
测试1:片段生命周期,当 addToBackStack()
被调用,而 setRetainInstance(真)
是没有名为
[从纵向到横向旋转设备]
[Device rotated from portrait to landscape]
的onPause() 的onSaveInstanceState() 的onStop() onDestroyView() 的onDestroy() onDetach() onAttach() 的onCreate() onCreateView()与束参数!= NULL ONSTART() 在onResume() onPause() onSaveInstanceState() onStop() onDestroyView() onDestroy() onDetach() onAttach() onCreate() onCreateView() with bundle param != null onStart() onResume()试验2及3: setRetainInstance片段生命周期调用(真)
叫 addToBackStack()
叫/不叫(相同的结果):
Test 2 & 3: Fragment lifecycle calls with setRetainInstance(true)
called, addToBackStack()
called / not called (same result):
[从纵向到横向旋转设备]
[Device rotated from portrait to landscape]
的onPause() 的onSaveInstanceState() 的onStop() onDestroyView() onDetach() onAttach() onCreateView()与束参数== NULL ONSTART() 在onResume() onPause() onSaveInstanceState() onStop() onDestroyView() onDetach() onAttach() onCreateView() with bundle param == null onStart() onResume()相关推荐
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