当方向发生变化时,片段viewState
仅在onStart
中恢复。
在onAttach
,onCreateView
,onViewCreated
和onActivityCreated
之后,甚至在onCreate
之后。
为什么?这太晚了。
我需要根据一些TextView值将db查询结果填充到ListView。目前我尝试在onViewCreated
中执行此操作。但是此步骤不会恢复视图状态。
我能早点强制恢复吗? 或者如何克服这个问题? 请问任何想法。
PS:我使用actionbarsherlock和依赖android支持-v4 r7库
PS2:如果我将在onStart
中加载数据,那么在onStop
之后恢复片段时它会执行其他查询(我可以通过添加一些布尔isLoaded
来解决这个问题 - 但这不是不是最佳解决方案。
答案 0 :(得分:12)
在Android API> = 17(Android 4.2 Jelly Beans)中有一种方法:
public void onViewStateRestored (Bundle savedInstanceState)
在onStart()
之前和onActivityCreated()
之后调用。
在Android API< 17没有这样的方法。但有两种解决方案:
Fragment
时不要依赖视图状态,并将所有必需的初始化状态保存为Fragment
状态(即覆盖Fragment#onSaveInstanceState()
)。稍后您可以在onCreate()
,onCreateView()
或onViewCreated()
。onStart()
执行初始化。答案 1 :(得分:4)
[编辑1 - - - - - - - ]
//检查片段后备堆栈是否已填充
//如果没有,请创建并填充布局。
//所以你的片段不会重新创建
YourFragment yourFragment = (YourFragment )fm.findFragmentById(R.id.fragment_container);
if (yourFragment == null) {
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.fragment_container, new YourFragment ());
ft.commit();
}
[编辑1 - - - - - - - ]
/**
* Listing 4-4: Fragment skeleton code
* Listing 4-5: Fragment lifecycle event handlers
*/
package com.paad.fragments;
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class MySkeletonFragment extends Fragment {
// Called when the Fragment is attached to its parent Activity.
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// Get a reference to the parent Activity.
}
// Called to do the initial creation of the Fragment.
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Initialize the Fragment.
}
// Called once the Fragment has been created in order for it to
// create its user interface.
@Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
// Create, or inflate the Fragment's UI, and return it.
// If this Fragment has no UI then return null.
return inflater.inflate(R.layout.my_fragment, container, false);
}
// Called once the parent Activity and the Fragment's UI have
// been created.
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
// Complete the Fragment initialization Ğ particularly anything
// that requires the parent Activity to be initialized or the
// Fragment's view to be fully inflated.
}
// Called at the start of the visible lifetime.
@Override
public void onStart(){
super.onStart();
// Apply any required UI change now that the Fragment is visible.
}
// Called at the start of the active lifetime.
@Override
public void onResume(){
super.onResume();
// Resume any paused UI updates, threads, or processes required
// by the Fragment but suspended when it became inactive.
}
// Called at the end of the active lifetime.
@Override
public void onPause(){
// Suspend UI updates, threads, or CPU intensive processes
// that don't need to be updated when the Activity isn't
// the active foreground activity.
// Persist all edits or state changes
// as after this call the process is likely to be killed.
super.onPause();
}
// Called to save UI state changes at the
// end of the active lifecycle.
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
// Save UI state changes to the savedInstanceState.
// This bundle will be passed to onCreate, onCreateView, and
// onCreateView if the parent Activity is killed and restarted.
super.onSaveInstanceState(savedInstanceState);
}
// Called at the end of the visible lifetime.
@Override
public void onStop(){
// Suspend remaining UI updates, threads, or processing
// that aren't required when the Fragment isn't visible.
super.onStop();
}
// Called when the Fragment's View has been detached.
@Override
public void onDestroyView() {
// Clean up resources related to the View.
super.onDestroyView();
}
// Called at the end of the full lifetime.
@Override
public void onDestroy(){
// Clean up any resources including ending threads,
// closing database connections etc.
super.onDestroy();
}
// Called when the Fragment has been detached from its parent Activity.
@Override
public void onDetach() {
super.onDetach();
}
}
来源:专业Android开发4 - Reto Meier
答案 2 :(得分:0)
您始终可以使用onConfigurationChanged()
自行处理方向更改。在这里查看一个很好的示例http://alexfu.tumblr.com/post/13926762386/android-dev-handling-fragment-recreation-manually