目前,我希望在配置更改期间保留昂贵的数据结构.我选择不使用Bundle来处理它,因为昂贵的数据结构是不可分割的.
因此,我使用非UI片段(称为RetainInstanceFragment),其setRetainInstance(true)来保存数据结构.
public class RetainInstanceFragment extends Fragment {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Creating expensive data structure
expensiveDataStructure = CreateExpensiveDataStructure();
// Tell the framework to try to keep this fragment around
// during a configuration change.
setRetainInstance(true);
}
public ExpensiveDataStructure expensiveDataStructure = null;
}
UI片段(称为UIFragment)将从RetainInstanceFragment获取昂贵的数据结构.每当UIFragment上有配置更改时,UIFragment将始终尝试从FragmentManager获取“缓存”RetainInstanceFragment,然后才决定创建新的RetainInstanceFragment.
示例代码如下.
public class UIFragment extends SherlockListFragment
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
FragmentManager fm = getFragmentManager();
// Check to see if we have retained the worker fragment.
retainInstanceFragment = (RetainInstanceFragment)fm.findFragmentByTag("data");
// If not retained (or first time running),we need to create it.
if (retainInstanceFragment == null) {
retainInstanceFragment = new RetainInstanceFragment();
fm.beginTransaction().add(watchlistArrayFragment,"data").commit();
} else {
// We can re-use retainInstanceFragment.expensiveDataStructure even
// after configuration change.
}
}
}
但是,有一个问题.每当我摧毁旧的UIFragment并用新的UIFragment替换它时,我都希望旧的RetainInstanceFragment也会被销毁.以下是我如何销毁和创建新的UIFragment
public class MyFragmentActivity extends SlidingFragmentActivity
// Being triggered when there is different menu item in sliding menu being
// selected.
public void selectActiveContent(Country country) {
Fragment fragment = new UIFragment(country);
getSupportFragmentManager().beginTransaction().replace(R.id.content,fragment).commitAllowingStateLoss();
}
但旧的RetainInstanceFragment永远不会被破坏.
我的猜测是,也许我忘了在UIFragment中进行清理.因此,我添加以下代码
UIFragment
@Override
public void onDetach() {
super.onDetach();
// To differentiate whether this is a configuration changes,or we are
// removing away this fragment?
if (this.isRemoving()) {
FragmentManager fm = getFragmentManager();
fm.beginTransaction().remove(retainInstanceFragment).commit();
}
}
但是,它并不是一直有效.我执行了几次滑动菜单点击.
1. selectActiveContent() -> Create new UIFragment and new RetainInstanceFragment 2. selectActiveContent() -> Create new UIFragment,but re-use prevIoUs RetainInstanceFragment. (Wrong behavior) 3. selectActiveContent() -> Create new UIFragment,and new RetainInstanceFragment. 4. selectActiveContent() -> Create new UIFragment,but re-use prevIoUs RetainInstanceFragment. (Wrong behavior)
知道如何正确删除保留的实例片段吗？
