[英]Bottom Navigation & Fragment Recreation
我在主活動上運行一個底部導航
private void BottomNavigation_NavigationItemSelected(object sender, BottomNavigationView.NavigationItemSelectedEventArgs e)
{
LoadFragment(e.Item.ItemId);
}
void LoadFragment(int id)
{
Android.Support.V4.App.Fragment fragment = null;
switch (id)
{
case Resource.Id.navigation_1:
fragment = Fragment1.NewInstance();
break;
case Resource.Id.navigation_2:
fragment = Fragment2.NewInstance();
break;
case Resource.Id.navigation_3:
fragment = Fragment3.NewInstance();
break;
}
if (fragment == null)
return;
SupportFragmentManager.BeginTransaction()
.Replace(Resource.Id.content_frame, fragment)
.Commit();
}
在我的Fragment1(即Resource.Id.navigation_1
)中,我正在刷新數據
public async override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
RefreshItems(false);
}
問題是,每次我單擊fragment1
navigation_1
,數據都會刷新。
我不想再次加載片段/數據。
Xamarin是否有可能?
您可以檢查是否也執行了當前片段這是一個函數
public Fragment find(String identifier) {
Fragment fragment = (Fragment) getSupportFragmentManager().findFragmentByTag(identifier);
return fragment;
}
在BottomNavigationView中,您必須像這樣檢查
if (find(fragment.getIdentifier()) != null) {
return;
}
我前一段時間會遇到這個問題,但是我正在開發本機kotlin代碼,下面是我用來處理此問題的代碼:
class Navigation(val supportFragmentManager: FragmentManager,
val filterIcon: ImageView ): BottomNavigationView.OnNavigationItemSelectedListener {
override fun onNavigationItemSelected(item: MenuItem): Boolean {
when(item.itemId){
R.id.menu_bottom_home ->{
changeFragment(HomeFragment(), Constants.FRAG_HOME_FRAGMENT)
filterIcon.visibility = View.VISIBLE
}
R.id.menu_bottom_favorites ->{
changeFragment(FavoritesFragment(), Constants.FRAG_FAVORITES_FRAGMENT)
filterIcon.visibility = View.INVISIBLE
}
R.id.menu_bottom_reservations ->{
changeFragment(ReservationFragment(), Constants.FRAG_RESERVATION_FRAGMENT)
filterIcon.visibility = View.INVISIBLE
}
R.id.menu_bottom_profile ->{
changeFragment(ProfileFragment(), Constants.FRAG_PROFILE_FRAGMENT)
filterIcon.visibility = View.INVISIBLE
}
}
return true
}
fun changeFragment(fragment: Fragment, tag : String){
var contains: Fragment? = null
var current: Fragment? = null
if(supportFragmentManager.fragments != null && supportFragmentManager.fragments.isNotEmpty()) {
contains = supportFragmentManager.fragments.firstOrNull { x -> x.tag == tag }
current = supportFragmentManager.fragments.first { x -> x.isVisible }
}
if(current != null){
supportFragmentManager.beginTransaction()
.hide(current).commit()
}
if(contains != null){
supportFragmentManager.beginTransaction()
.show(contains).commit()
}
else{
supportFragmentManager.beginTransaction()
.add(R.id.fl_fragment_container, fragment, tag)
.addToBackStack(tag)
.commit()
}
}
}
然后,只需要使用您的Navigation類設置setOnNavigationItemSelectedListener
,如下所示:
bnv_navigation.setOnNavigationItemSelectedListener(Navigation(supportFragmentManager, iv_filter_bar))
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