[英]Why does the fragment's onCreateView, onCreate, onActivityCreated are called
我有一个应用程序,处理片段和ViewPager。 我在ViewPager中有三个片段。 当您在它们之间切换时,它总是会导致其他两个片段调用它们的onCreateView方法。 只有当FragmentActivity被创建时,如何只做一次? 我已经阅读了一些问题并尝试了解决方案,但片段仍然具有相同的行为。
ListFragment onCreate调用了两次
onCreate()和onCreateView()调用的不仅仅是必需的(片段)
这是一些代码,如果它可以帮助你,那些人:
主要活动:
public class StartingActivity extends FragmentActivity implements View.OnClickListener {
ViewPager viewPager;
CirclePageIndicator pageIndicator;
Button discount;
Button qrCode;
Button pay;
TabHost tabHost;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.starting_layout);
viewPager = (ViewPager) findViewById(R.id.pager);
if (savedInstanceState == null) {
Fragment firstPage = Fragment.instantiate(this, FindTovarFragment.class.getName());
Fragment secondPage = Fragment.instantiate(this, MainWindowActivity.class.getName());
Fragment thirdPage = Fragment.instantiate(this, MapActivity.class.getName());
if ((firstPage != null && !firstPage.isDetached())|| (secondPage != null && !secondPage.isDetached()) || (thirdPage != null && !thirdPage.isDetached())) {
List<Fragment> viewPagerFragments = new ArrayList<Fragment>();
viewPagerFragments.add(firstPage);
viewPagerFragments.add(secondPage);
viewPagerFragments.add(thirdPage);
PageAdapter pageAdapter = new PageAdapter(getSupportFragmentManager(), viewPagerFragments);
viewPager.setAdapter(pageAdapter);
pageIndicator = (CirclePageIndicator) findViewById(R.id.circle);
pageIndicator.setViewPager(viewPager);
pageIndicator.setCurrentItem(pageAdapter.getCount() - 2);
}
}
}
MapActivity:
public class MapActivity extends Fragment implements OnMyLocationListener {
//Тэг для логов
private static final String TAG = "MapActivity";
List<Address> addressList;
private static final String STRING_LOCATION = "";
ArrayList<TorgCentr> randomTorgCentr;
ArrayList<String> torgCentrNames;
Context context;
AutoCompleteTextView searchTorgCentr;
OverlayManager overlayManager;
MapController mapController;
TextView textView;
double longitude;
double latitude;
double itemLongitude;
double itemLatitude;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
Log.d(TAG, "MapActivity onCreateView");
View view = (LinearLayout) inflater.inflate(R.layout.map_layout, container, false);
final MapView mapView = (MapView) view.findViewById(R.id.map);
textView = (TextView) view.findViewById(R.id.searchlocation);
searchTorgCentr = (AutoCompleteTextView) view.findViewById(R.id.autoCompleteTextView);
mapView.showBuiltInScreenButtons(true);
mapController = mapView.getMapController();
context = getActivity();
return view;
}
@Override
public void onResume() {
super.onResume();
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG, "MapActivity onCreate");
}
public void onActivityCreated(Bundle savedInstanceState) {
Log.d(TAG, "MapActivity onActivityCreated");
context = getActivity();
SetRightMapDisplayAddress rightMapDisplayAddress = new SetRightMapDisplayAddress();
rightMapDisplayAddress.execute(STRING_LOCATION);
DownloadSuperMarketsArray superMarketsArray = new DownloadSuperMarketsArray();
superMarketsArray.execute();
overlayManager = mapController.getOverlayManager();
overlayManager.getMyLocation().setEnabled(false);
super.onActivityCreated(savedInstanceState);
}
第二片段:
public class MainWindowActivity extends Fragment {
private static final String TAG = "MainWindowActivity";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
Log.d(TAG, "MainWindowActivity onCreateView");
View view = (RelativeLayout) inflater.inflate(R.layout.main_window_layout, container, false);
if (container == null) {
return null;
}
return view;
}
}
第三个:
public class FindTovarFragment extends Fragment {
private static final String TAG= "FindTovarFragment";
Context context;
ArrayList<Category> categories;
Spinner categoryContainer;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
Log.d(TAG, "FindTovarFragment onCreateView");
View view = (LinearLayout) inflater.inflate(R.layout.find_tovar_main_layout, container, false);
categoryContainer = (Spinner) view.findViewById(R.id.category);
return view;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.d(TAG, "FindTovarFragment onActivityCreated");
DownloadCategory downloadCategory = new DownloadCategory();
downloadCategory.execute();
}
MapActivity的日志:
06-20 11:06:37.709: DEBUG/MapActivity(1290): MapActivity onCreate
06-20 11:06:37.709: DEBUG/MapActivity(1290): MapActivity onCreateView
06-20 11:06:38.509: DEBUG/MapActivity(1290): MapActivity onActivityCreated
然后一次又一次:
06-20 11:07:53.239: DEBUG/MapActivity(1290): MapActivity onCreate
06-20 11:07:53.239: DEBUG/MapActivity(1290): MapActivity onCreateView
06-20 11:07:53.429: DEBUG/MapActivity(1290): MapActivity onActivityCreated
06-20 11:08:23.029: DEBUG/MapActivity(1290): MapActivity onCreate
06-20 11:08:23.039: DEBUG/MapActivity(1290): MapActivity onCreateView
06-20 11:08:23.269: DEBUG/MapActivity(1290): MapActivity onActivityCreated
非常感谢你提前。
默认情况下,ViewPager在内存中保留1页到当前页面的任一侧。 因此,当在当前页面的左/右滑动1页时,它不会重新创建这些页面。 但是当向左/向右滑动超过1页时,它会再次重新创建这些页面,因此称为OnCreateView(),OnCreate()。
如果应用程序使用少量页面3,您可以通过调用增加要保留的页数,
mViewPager.setOffscreenPageLimit(2);
这里描述
我会在android开发者文档中更改这个的架构:
http://developer.android.com/reference/android/support/v4/app/FragmentPagerAdapter.html
但我会改变一些事情......
1 - 我会改变这种方法:
/**
* The Fragment's UI is just a simple text view showing its
* instance number.
*/
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_pager_list, container, false);
View tv = v.findViewById(R.id.text);
((TextView)tv).setText("Fragment #" + mNum);
return v;
}
对于这样的事情,我们决定根据viewPager的位置填充哪个片段:
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
SupportFragmentManager ft = getChildFragmentManager().beginTransaction();
String tag = "";
Fragment fragment = null;
switch (mNum) {
case 0:
fragment = new MyFragmentZero();
tag = FragmentTags.TAG_0;
break;
case 1:
fragment = new MyFragmentOne();
tag = FragmentTags.TAG_3;
break;
case 2:
fragment = new MyFragmentTwo();
tag = FragmentTags.TAG_2;
break;
default:
break;
}
/*OPTIONAL We can pass arguments to the fragments
Bundle args = new Bundle();
args.putInt(Arguments.ARG_POSITION, mNum);
fragment.setArguments(args);*/
//Place the fragment in the container
ft.replace(R.id.fragment_container fragment, tag);
ft.commit();
//You need a base layout for all fragment and use nested fragments later or you can define the layout for each position(mNum) inside the switch.
return inflater.inflate(R.layout.fragment_layout_default_for_all_views, container,
false);
}
像这样你将有一个很好的架构,一旦它工作这样应该没问题。
无论如何,你必须知道viewPager如何在不同的位置填充片段。
当您从位置0开始时,将创建位置0上的片段和位置1中的一个片段。
然后当您滑动到位置1时,创建了2位置上的片段,因此您现在可以在不同位置创建三个片段(0,1,2 ..假设您在viewPager上只有3个页面)。
我们滑动到位置2,最后一个,并且第一个位置(0)上的片段被破坏,所以我们现在在位置2和3上有碎片。
我希望它有所帮助,如果您有任何问题,请告诉我。 干杯
最后我才弄清楚了。 只需要覆盖destroyItem方法,这样它就不会破坏对象。 希望这对某人有用。
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
Log.d(TAG, "destroy!");
}
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