我有一个Activity使用 a在创建它们时将s设置为的类ViewPager中创建三个Fragments 。ViewPagerFragmentsetRetainInstace(true);
在我Fragment的一个里面，我正在显示一些可编辑的信息。这Fragment将启动DialogFragment编辑信息。
当用户不改变方向时，我可以更新信息并将结果发送回视图中的片段，但是，一旦我改变方向，并对Interface附加在DialogFragmentsonAttach()方法中的信息进行更新我我得到一个NullPointerException.
我不明白为什么，因为每次启动新DialogFragment的onAttach()方法总是被调用。
我应该如何解决这个问题？我可以保存接口的状态吗？如果是这样怎么办？
这是我的 DialogFragment 代码： GenericDialogFragment 类仅用于更改外观
public class Fragment1 extends GenericDialogFragment implements WebServiceResult{
// -------------------------------------------------------------------------
// Member Variables
//--------------------------------------------------------------------------
//Webservice Callback
private WSRequest mActiveRequest = null;
// The Current Context of the Application
private Context mClassContext = null;
// Interface reference for communication
private static CommunicateResults communicateResults = null;
// -------------------------------------------------------------------------
// New Instance Method
//--------------------------------------------------------------------------
public static Fragment1 newInstance(int userId, GenericObject [] objects, GenericGroup [] groups, Object currentObject){
// Initialize a new Fragment1
Fragment1 fragment = new Fragment1();
// Create a new Bundle
Bundle args = new Bundle();
fragment.setArguments(args);
// Return the Fragment1
return fragment;
}
// -------------------------------------------------------------------------
// Class Functions / Methods
//--------------------------------------------------------------------------
// States that the Interface is attached to the parent activity
@Override public void onAttach(Activity activity)
{
// Perform the Default Behavior
super.onAttach(activity);
Log.d("ONAttach()","On attach() is called" );
// Try
try{
// Attach the interface to the activity
communicateResults = (CommunicateResults) ((MainActivity) getActivity()).findFragment(EditableFragment1.class);
}catch(Exception ex){
// Print the stack trace
ex.printStackTrace();
}
}
// States that the Dialog's View has been Created
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
// Return the Inflated XML Layout
return inflater.inflate(R.layout.fragment1, container, false);
}
// States that the fragment has been created, last chance to update the UI
@Override
public void onActivityCreated(Bundle savedInstanceState){
// Perform the Default behavior
super.onActivityCreated(savedInstanceState);
mClassContext = getActivity();
// Get the Arguments passed into the Fragment instance
savedStateData = getArguments();
// Reference all the UI Elements in the View
// Add listeners to the Button Widgets
// If the savedInstanceState is not null, get the current object
if(savedStateData != null){
// Get the object out of the state data
mCurrentObject = savedStateData.getParcelable(STATE_DATA_CURRENT_OBJECT);
}
}
//-----------------------------------------------------------------------------
// Webservice Callback methods
//-----------------------------------------------------------------------------
// States that the web service has succeeded
@Override public void webserviceSucceeded(WebServiceBase finishedService, Object responseData)
{
Log.d("EDIT Object", responseData.toString());
if(responseData != null){
if(mDeletingObject){
// Send Back to the object to remove
communicateResults.sendBackData(mCurrentObject, ACTION_DELETE);
}else{
JSONObject tempObject = (JSONObject) responseData;
try{
// Parse Data ...
}catch(Exception ex){
ex.printStackTrace();
// TODO: The Object was deleted from the Lest
}
// If we are creating a object, bundle the information to pass to the parent activity
if(mCreatingObject){
// Create a new Workout Object
mCurrentObject = new Object();
// Callback to Parent Activity to notify that data has changed
communicateResults.sendBackData(mCurrentObject, ACTION_CREATE);
// Else the Object was updated
}else{
// Create a new Object
mCurrentObject = new Object();
// Callback to Parent Activity to notify that data has changed
communicateResults.sendBackData(mCurrentObject, ACTION_UPDATE);
}
}
}
// Dismiss the fragment
}
// States that the web service has failed
@Override
public void webserviceFailed(WebServiceBase finishedService,
Object errorData) {
// Display the Error
displayErrorData(errorData);
}
}