我正在使用Xamarin开发android。我有一个显示WebView的片段和一个显示带有2个选项卡的PageViewer的页面。一切正常，直到我在我的Android设备上激活开发者选项“不要保持活动”。当我启动我的应用程序并且我继续回家时，每一件事都没关系，所以我继续使用WebViewPage，我将应用程序发送到后台，我恢复它，WebViewPage正确显示，但是当我去Home（我使用的是导航抽屉），正确地重新创建选项卡，但片段是空白的。我真的不明白为什么..似乎没有调用OnCreateView，并且在重新创建的Activity之后不调用我的适配器的GetItem（）。调试我看到了这个：系统首先调用这两个片段，但由于某种原因，当我重新创建我的标签时，片段是空白的。
这是我的代码：
MainActivity
namespace N****_AndroidOS {
[ Activity ( Label = "Niteko", /*LaunchMode = Android.Content.PM.LaunchMode.SingleInstance,*/ ScreenOrientation = ScreenOrientation.Portrait, Icon = "@drawable/icon" ) ]
public class MainActivity : AppCompatActivity {
private NavigationView m_nvNavigationView;
private DrawerLayout m_dlDrawerLayout;
private Toolbar m_tToolBar;
/* Fragments */
private CatalogShowerTabsFragment m_fCatalogWithTabShower;
private WebViewPageFragment m_fHowWeAre;
private WebViewPageFragment m_fTermsAndConds;
private WebViewPageFragment m_fInfoPrivacy;
private SettingsFragment m_fSettings;
private ContactUsFragment m_fContactUs;
private NotificationFragment m_fNotifications;
protected override void OnCreate( Bundle bundle ) {
base.OnCreate( bundle );
SetContentView( Resource.Layout.activity_nav_drawer );
SetupToolBar();
m_dlDrawerLayout = (DrawerLayout)FindViewById( Resource.Id.nav_drawer );
m_nvNavigationView = FindViewById<NavigationView>( Resource.Id.nav_view );
SupportActionBar.SetHomeAsUpIndicator( Resource.Drawable.ic_menu );
SupportActionBar.SetDisplayHomeAsUpEnabled( true );
SupportActionBar.SetDisplayUseLogoEnabled( true );
SupportActionBar.SetLogo( Resource.Drawable.ic_icon_header );
SupportActionBar.SetWindowTitle( Resources.GetString( Resource.String.title_home ) );
m_nvNavigationView.NavigationItemSelected += (sender, e ) => {
e.MenuItem.SetChecked( true );
//react to click here and swap fragments or navigate
ChangeFragment( e.MenuItem.ItemId );
m_dlDrawerLayout.CloseDrawers();
};
m_nvNavigationView.Menu.GetItem( 0 ).SetChecked( true );
m_fCatalogWithTabShower = null;
m_fHowWeAre = null;
m_fTermsAndConds = null;
m_fInfoPrivacy = null;
m_fSettings = null;
m_fContactUs = null;
m_fNotifications = null;
if ( bundle == null ) {
ChangeFragment( Resource.Id.nav_home );
}
else {
}
}
private void ChangeFragment( int iMenuID, object iArg = null ) {
RunOnUiThread( () => {
// Create a new fragment and a transaction.
Android.Support.V4.App.FragmentTransaction fragmentTx = (Android.Support.V4.App.FragmentTransaction) this.SupportFragmentManager.BeginTransaction();
Android.Support.V4.App.Fragment fragmentToShow = null;
bool isLogged = false;
ISharedPreferences prefs = PreferenceManager.GetDefaultSharedPreferences( this );
string eMail = prefs.GetString( ParamsInfo.PK_EMAIL, "" );
if ( string.IsNullOrEmpty( eMail ) ) {
isLogged = false;
}
else {
isLogged = true;
}
switch ( iMenuID ) {
case Resource.Id.nav_home:
SupportActionBar.SetDisplayUseLogoEnabled( true );
SupportActionBar.SetLogo( Resource.Drawable.Icon );
SupportActionBar.SetWindowTitle( Resources.GetString( Resource.String.title_home ) );
if ( m_fCatalogWithTabShower == null ) {
m_fCatalogWithTabShower = new CatalogShowerTabsFragment();
}
fragmentToShow = m_fCatalogWithTabShower;
break;
case Resource.Id.nav_howweare:
SupportActionBar.SetDisplayUseLogoEnabled( false );
SupportActionBar.SetWindowTitle( Resources.GetString( Resource.String.title_who ) );
if ( m_fHowWeAre == null ) {
m_fHowWeAre = new WebViewPageFragment();
m_fHowWeAre.WebPageID = ParamsInfo.PK_STATIC_HOWWEARE;
}
//fragmentTx.AddToBackStack( null );
fragmentToShow = m_fHowWeAre;
break;
}
if ( fragmentToShow != null ) {
// Replace the fragment that is in the View fragment_container (if applicable).
fragmentTx.Replace( Resource.Id.nav_contentframe, fragmentToShow );
// Add the transaction to the back stack.
//fragmentTx.AddToBackStack( null );
// Commit the transaction.
fragmentTx.Commit();
}
} );
}
}
调用CatalogShowerFragment以创建包含两个片段的页面浏览器
public class CatalogShowerTabsFragment : Android.Support.V4.App.Fragment {
private View m_vView;
private Adapter m_aViewPagerAdapter;
private bool m_bAlreadyFilled = false;
public override View OnCreateView( LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState ) {
// Use this to return your custom view for this Fragment
// return inflater.Inflate(Resource.Layout.YourFragment, container, false);
if ( !m_bAlreadyFilled ) {
m_vView = inflater.Inflate( Resource.Layout.CatalogWithTabShowerLayout, container, false );
var viewPager = m_vView.FindViewById<Android.Support.V4.View.ViewPager>( Resource.Id.htab_viewpager );
if ( viewPager != null ) {
setupViewPager( viewPager );
}
TabLayout tabLayout = m_vView.FindViewById<TabLayout>( Resource.Id.htab_tabs );
tabLayout.SetupWithViewPager( viewPager );
m_bAlreadyFilled = true;
}
return m_vView;
}
public override void OnDestroy() {
base.OnDestroy();
AndroidHUD.AndHUD.Shared.Dismiss( Activity );
}
class Adapter : Android.Support.V4.App.FragmentPagerAdapter {
List<V4Fragment> fragments = new List<V4Fragment>();
List<string> fragmentTitles = new List<string>();
public Adapter( V4FragmentManager fm ) : base ( fm ) {
}
public void AddFragment( V4Fragment fragment, string title ) {
fragments.Add( fragment );
fragmentTitles.Add( title );
}
public override V4Fragment GetItem( int position ) {
return fragments[ position ];
}
public override int Count {
get { return fragments.Count; }
}
public override Java.Lang.ICharSequence GetPageTitleFormatted( int position ) {
return new Java.Lang.String( fragmentTitles[ position ] );
}
}
/* Costruiamo la Tabbar per la selezione dei tipi di prodotti */
private void setupViewPager( Android.Support.V4.View.ViewPager viewPager ) {
if ( m_aViewPagerAdapter == null ) {
m_aViewPagerAdapter = new Adapter( Activity.SupportFragmentManager );
ItemsListCategoryFragment fragmentProduct = new ItemsListCategoryFragment();
fragmentProduct.ListType = ItemsListCategoryFragment.LIST_CATEGORY.LC_PRODUCTS;
ItemsListCategoryFragment fragmentApplications = new ItemsListCategoryFragment();
fragmentApplications.ListType = ItemsListCategoryFragment.LIST_CATEGORY.LC_APPLICATIONS;
m_aViewPagerAdapter.AddFragment( fragmentProduct, Resources.GetString( Resource.String.tab_productions_title ) );
m_aViewPagerAdapter.AddFragment( fragmentApplications, Resources.GetString( Resource.String.tab_applications_title ) );
viewPager.Adapter = m_aViewPagerAdapter;
viewPager.Adapter.NotifyDataSetChanged();
}
}
}
最后是碎片。
public enum LIST_CATEGORY {
LC_PRODUCTS
, LC_APPLICATIONS
}
private LIST_CATEGORY m_enListType;
private CategoryListResponseResult m_clrResponseResult;
private ItemsListCategoryShowerAdapter m_ilcCatergoryAdapter;
private List<CategoryModel> m_lCategoryModelList;
private Task m_tTask;
private View m_vView;
//Pull to refresh
private PullToRefresharp.Android.Widget.ListView m_lListView;
/* params */
private int m_iCurrentPage = 0;
private int m_iPageLimit = 10;
private bool m_bFirstTime = true;
private bool m_bNoMoreElem = false;
public static bool pezza = false;
public LIST_CATEGORY ListType {
set { m_enListType = value; }
get { return m_enListType; }
}
public ItemsListCategoryFragment( /*LIST_CATEGORY iListType*/ ) {
m_enListType = LIST_CATEGORY.LC_APPLICATIONS; //iListType;
m_tTask = Task.Factory.StartNew( () => {} );
}
public override void OnActivityCreated( Bundle savedInstanceState ) {
base.OnActivityCreated( savedInstanceState );
}
public override void OnCreate( Bundle savedInstanceState ) {
base.OnCreate( savedInstanceState );
}
public override View OnCreateView( LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState ) {
pezza = true;
if ( savedInstanceState != null ) {
m_enListType = (LIST_CATEGORY)( savedInstanceState.GetInt( ParamsInfo.PK_CATTYPE ) );
}
if ( m_vView == null ) {
m_vView = inflater.Inflate( Resource.Layout.CatalogGeneralListLayout, container, false );
m_lListView = m_vView.FindViewById<PullToRefresharp.Android.Widget.ListView>( Resource.Id.lwMyEventsPullToRefresh );
m_lListView.RefreshActivated += RefreshMyContent;
m_lListView.ItemClick += OnListItemClick;
m_lListView.ScrollStateChanged += (sender, e) => {
OnScrollStateChange( e.ScrollState );
};
GetAndFillListFromNetwork();
}
return m_vView;
}
public override void OnResume() {
base.OnResume();
}
private void RefreshMyContent( object sender, EventArgs e ) {
Activity.RunOnUiThread( () => {
m_iCurrentPage = 0;
m_bNoMoreElem = false;
m_bFirstTime = true;
GetAndFillListFromNetwork();
m_lListView.OnRefreshCompleted();
} );
}
public override void OnDestroy() {
base.OnDestroy();
AndroidHUD.AndHUD.Shared.Dismiss( Activity );
}
private void GetAndFillListFromNetwork() {
//AndHUD.Shared.Show( Activity, Resources.GetString( Resource.String.loading ) );
AndHUD.Shared.ShowToast( Activity, Resources.GetString( Resource.String.loading ), (MaskType)3, default(TimeSpan?), false );
m_tTask = m_tTask.ContinueWith( t => {
InformationData infoData = new InformationData();
if ( m_enListType == LIST_CATEGORY.LC_PRODUCTS ) {
infoData.AddParam( ParamsInfo.PK_CATTYPE, "0" ); //0: prodotti 1: applicazioni
}
else {
infoData.AddParam( ParamsInfo.PK_CATTYPE, "1" );
}
infoData.AddParam( ParamsInfo.PK_PAGENUM, m_iCurrentPage.ToString() );
infoData.AddParam( ParamsInfo.PK_PAGELIMIT, "10" );
m_clrResponseResult = (CategoryListResponseResult)FrontController.Instance.Execute( CommandType.COMMANDREQUEST.CR_ASYNC_GETCATEGORY, infoData );
Activity.RunOnUiThread( () => {
AndHUD.Shared.Dismiss( Activity );
switch ( m_clrResponseResult.Status ) {
case ResponseResult.RESPONDSTATUS.RS_SUCCESS:
if ( m_bFirstTime ) {
m_bFirstTime = false;
m_lCategoryModelList = new List<CategoryModel>();
m_lCategoryModelList.AddRange( m_clrResponseResult.data.categories );
m_ilcCatergoryAdapter = new ItemsListCategoryShowerAdapter( Activity, m_lCategoryModelList );
m_lListView.Adapter = m_ilcCatergoryAdapter;
}
else {
m_lCategoryModelList.AddRange( m_clrResponseResult.data.categories );
}
if ( m_clrResponseResult.data.categories.Count < m_iPageLimit ) {
m_bNoMoreElem = true;
}
m_ilcCatergoryAdapter.NotifyDataSetChanged();
break;
case ResponseResult.RESPONDSTATUS.RS_CONNECTION_ERROR:
PerformConnectionLost();
break;
}
} );
} );
}
public override void OnSaveInstanceState( Bundle outState ) {
outState.PutInt( ParamsInfo.PK_CATTYPE, (int)m_enListType );
base.OnSaveInstanceState( outState );
}
private void PerformConnectionLost() {
AndHUD.Shared.ShowError( Activity, Resources.GetString( Resource.String.err_connection_lost ), MaskType.None, new TimeSpan( 90, 90, 90, 90 ), OnOkMessageClick );
}
private void OnOkMessageClick() {
GetAndFillListFromNetwork();
}
private void OnListItemClick( object iSender, AdapterView.ItemClickEventArgs iEvent ) {
CategoryModel cm = m_lCategoryModelList[ iEvent.Position ];
Intent itemsDetailsActivity = new Intent( Activity, typeof( ItemsListDetailsActivity ) );
itemsDetailsActivity.PutExtra( ParamsInfo.PK_CAT_ID, cm.id );
itemsDetailsActivity.PutExtra( ParamsInfo.PK_CAT_TITLE, cm.label );
itemsDetailsActivity.PutExtra( ParamsInfo.PK_IMG_URL, cm.img );
if ( m_enListType == LIST_CATEGORY.LC_APPLICATIONS ) {
itemsDetailsActivity.PutExtra( ParamsInfo.PK_HEADER_TITLE, Resources.GetString( Resource.String.title_applications ) );
}
else {
itemsDetailsActivity.PutExtra( ParamsInfo.PK_HEADER_TITLE, Resources.GetString( Resource.String.title_products ) );
}
StartActivity( itemsDetailsActivity );
}
protected void OnScrollStateChange( ScrollState iScrollState ) {
if ( iScrollState == ScrollState.Idle ) {
if ( m_lListView.LastVisiblePosition == m_lListView.Adapter.Count - 1 ) {
/* richiamo i prossimi elementi */
if ( !m_bNoMoreElem ) {
++m_iCurrentPage;
GetAndFillListFromNetwork();
}
}
}
}
}
我真的无法理解为什么当我重新创建我的活动时这不起作用..似乎片段已经由系统默认创建了，但是我强迫我自己用一个新的页面浏览器重新构建，所以为什么碎片不显示？重建应用程序后，其他部分中的每个其他片段都会显示没有问题。
谢谢你。
答案 0 :(得分：0)
使用 FragmentStatePagerAdapter 代替 FragmentPagerAdapter ，一切正常！该死的机器人!!