I am working on Xamarin.Forms and I have a situation where have to render 4 different (ContentPage) pages on Tabs.So I'm using TabbedPage and adding different paged to parent page. Now the issue is when I come to tabbedpage all 4 pages are getting renderd on different tabs. Is there any way so that I can see 4 tabs but when a particular tab is clicked at the time of click event it should load page dynamically.
Page_1 = new Page_1() { Title = "Page_1" , Icon="icon_1.png"};
Page_2 = new Page_2() { Title = "Page_2", Icon="icon_2png"};
Page_3 = new Page_3() { Title = "Page_3", Icon="icon_3.png"};
Page_4 = new Page_4() { Title = "page_4, Icon="icon_4.png"};
Children.Add(Page_1);
Children.Add(Page_2);
Children.Add(Page_3);
Children.Add(Page_4);
I want to load all pages dynamically.Any help ?
In your content page do
private bool _appeared = false;
public override void OnAppearing()
{
base.OnAppearing();
// To avoid repeating loading it. Remove if you want to refresh every time.
if (!_appeared)
{
// Load from here
_appeared = true;
}
}
This way they only load when the page is viewed
Related
I have a 'main' map page from which the user can either add data to the map or click on existing data to see the details. This is done with PushModalAsync() where I navigate to a new page. My problem is in both of those new pages I have a new map with a new MapView that is 'underneath' the MapView from the 'main' page. Both the MapView and Map itself are new objects on the secondary pages.
After navigating to my new pages, the previous MapView shows in the area of the screen where it existed (on 'main' page) where my new MapView also exists. In other words, on my new map pages my map is laid out differently and partially sits higher in the layout than the 'main' map does. The part that sits higher is the only part of the new map that is visible and I can interact with. The part that sits on the same area is the 'main' map view and I cannot interact with it and it blocks my new map.
I tried this with PushAsync as well (not modal) and nothing changed. How is one supposed to have multiple maps in an app across multiple pages? Is this even possible with ArcGIS? This app used to be with Google Maps/Apple and the exact same layout worked just fine.
Edit: Code here (with irrelevant parts removed) This page is navigated to from another page with a map on it wherein this map is covered if it is laid out in the same area of the first map. From this page I navigate to a 3rd page where both maps show up. Removal works successfully, however when I try to add I get an error saying I cannot add a null child to a view group:
public partial class EventDetails : ContentPage
{
public Xamarin.Forms.Grid MapGrid = new Xamarin.Forms.Grid()
{
RowDefinitions =
{
new RowDefinition { Height = 220 },
new RowDefinition { Height = GridLength.Auto }
},
ColumnDefinitions =
{
new ColumnDefinition { Width = 500 }
},
HorizontalOptions = LayoutOptions.Center
};
public Map DetailMap;
public MapView MyDetailMapView = new MapView();
public EventDetails(MapLog eventDetails, string strMapType)
{
DetailMap = new Map(BasemapType.ImageryWithLabels, eventDetails.Latitude, eventDetails.Longitude, iMapDetail);
MyDetailMapView.Map = DetailMap;
MyDetailMapView.ViewpointChanged += MyMapView_ViewpointChanged;
var scrollView = new ScrollView
{
Content = mainStack
};
MapGrid.Children.Add(MyDetailMapView, 0, 0);
MapGrid.Children.Add(scrollView, 0, 1);
Content = MapGrid;
}
#if __ANDROID__
protected override void OnAppearing()
{
if (!MapGrid.Children.Contains(MyDetailMapView))
{
try
{
MapGrid.Children.Add(MyDetailMapView);
}
catch (Exception ex)
{
DisplayAlert("Err", ex.Message, "Ok");
}
}
base.OnAppearing();
}
protected override void OnDisappearing()
{
if (MapGrid.Children.Contains(MyDetailMapView))
MapGrid.Children.Remove(MyDetailMapView);
base.OnDisappearing();
}
#endif
}
EDIT*: I updated my Xamarin Forms version and ARCGIS Runtime and now the solution to remove/add the map does work without issue.
I had other similar problems with having two maps for android in Xamarin Forms ArcGIS and the solution was removing the MapView from the visual tree when you navigate to the new page.
You need to remove the MapView before you Navigate to the second page by:
[your parent layout].Children.Remove(MyMapView);
await Navigation.PushAsync(new SecondPage());
And in your first page you need to make sure to add the MapView back to the Visual Tree when you come back to the page:
protected override void OnAppearing()
{
if (!GridMap.Children.Contains(MyMapView))
GridMap.Children.Add(MyMapView);
base.OnAppearing();
}
That solved all my problems with two maps. Thanks to this post in ESRI forum
Navigation between 2 MapViews in Xamarin Android
When I navigate to a new page, adding it to the stack, if it is not full height of the page, it shows part of that page and part of the previous page (like a modal). I have a Xamarin.Forms app which uses a master detail page. I have upgraded to Xamarin.Forms Nuget 2.3.3.168 and am on the latest Xamarin version for Visual Studio.
I also checked the Navigation stack when going to a new page and everything looks correct. I have 1 master page which is the menu and the detail page has a navigation page with more pages in the stack, they just display partially on top of each other.
The only other thing I have changed is when I needed to initialize my App() constructor by setting the MainPage to a new MasterDetail page because it was failing if I did not do that in the constructor for Android. Any ideas?
Here is my App.cs:
public App()
{
InitializeComponent();
var masterDetailPage = new MasterDetailPage
{
Master = new Page() { Title = "Title" },
Detail = new Page(),
IsPresented = false
};
App.Current.MainPage = masterDetailPage;
}
Then, when I figure out if the user is logged in or not, I reset the master detail page with this function:
public static void SetMainPage(Page newPage)
{
var rootPage = new NavigationPage(newPage) { BarBackgroundColor = Color.White};
_nav.Initialize(rootPage);
_dialogService.Initialize(rootPage);
App.Current.MainPage = new MasterDetailPage
{
Master = new Menu(),
Detail = rootPage,
BindingContext = new MowMagicMobileViewModelBase(),
IsPresented = false
};
}
Then from there I call Navigation PushAsync() to pop a page onto the stack.
Wow it was actually that I just did not set a background color at all. I guess if you do not explicitly set it for the page it is transparent, unless that gets inherited from somewhere?
I dont know if its the solution but i have masterdetail page too..
But my page is like this
Master = new MenuPage();// it is a content page
Detail = new NavigationPage(new HomePage());
try it to see
If you want to change background i did sth like that
public class NavigationPageBase:NavigationPage
{
public NavigationPageBase (ContentPage c):base(c)
{
/*if (c.GetType().Equals(typeof(LoginPage)))
SetHasNavigationBar(c, false);
else
SetHasNavigationBar(c, true);*/
SetHasNavigationBar(c, true);
BarBackgroundColor = Styles.toolbarColor;
BackgroundColor = Styles.bgPageColor;
}
}
and for detailpage you can use it for example like
Detail = new NavigationPageBase (new HomePage ());
And from your App() constructor you can do simply
MainPage = new MyMasterDetailPage();
Hope it helps
I need to add a custom tab item into my TabbedPage. That shouldn't be a page but an overlay view. It is "More" item for the bottom menu opening a more items menu over the currently shown page.
So far I found the following solution:
protected override void OnCurrentPageChanged()
{
base.OnCurrentPageChanged();
if (this.isInitialized)
{
if (CurrentPage.Title == "More")
{
CurrentPage = this.lastSelectedPage;
}
}
this.lastSelectedPage = CurrentPage;
}
It's enough to prevent opening the corresponding fake page. After this I need to show an overlay view and have no item how to do it from the tabbed page.
Another solution I'm working out now is to write a custom renderer for my tabbed page and manage all the custom work there. The question in this case is how to show my custom view over the existing content. I tried AddView (iOS) in the renderer but getting runtime exception.
public override void ItemSelected(UITabBar tabbar, UITabBarItem item)
{
base.ItemSelected(tabbar, item);
var view = new UILabel()
{
Text = "Test"
};
View.Add(view);
}
I have 2 pages in my Xamarin Forms app. My first page has 4 icons in the toolbar. My second page is a login page and has a tick and a cross in the toolbar.
I can't get the login page to show any icons unless I make it a navigation page. I also have to clear ToolBarItems on the first page before calling PushAsync() otherwise it complains there are too many toolbar items.
If I call PopAsync() on the login page it does not return to the first page. I'm guessing this is due to their being 2 navigation pages. I also tried PopToRootAsync().The back button works however.
My question is - how do I show different toolbar icons on 2 different pages in a way that allows navigation to work?
I'm testing this on Windows Phone 8.0
Here is the code calling the login page:
private async void ShowLoginPage()
{
ToolbarItems.Clear();
var page = new NavigationPage(new LoginPage());
await Navigation.PushAsync(page);
}
and here is the code to return to the first page:
private void Cancel()
{
Navigation.PopToRootAsync();
}
I'm running Xamarin.Forms v1.2.2.6243
One thing you could try is to keep your Login Page inside of a NavigationPage, and then instead of running PopAsync() within the Login Page after they have logged in successfully, simply replace the MainPage with your old Navigation page:
In your App class:
public NavigationPage AppNavPage = new NavigationPage(new FirstPage());
public App() {
MainPage = AppNavPage;
}
In your FirstPage:
private async void ShowLoginPage() {
ToolbarItems.Clear();
var page = new NavigationPage(new LoginPage());
await Navigation.PushAsync(page);
}
In Login Page:
private async void OnCreateClicked(object sender, EventArgs e) {
bool loginInfoIsGood = CheckLoginInfo(); //Check their login info
if(loginInfoIsGood) {
Application.Current.MainPage = App.AppNavPage;
}
}
Otherwise, I have also done a custom renderer for the NavigationRenderer on iOS to insert toolbar items onto the right side of the Navigation Bar and have overridden some Menu related stuff on Android to change the icon text/colors.
One option that you have, and one that I implemented in my own app, is a custom renderer that removes the navigation header from the app and then you could build your own custom header. With this approach, you do lose some of the native feel of the app, and you have to implement much of the transitional functionality your self. However, it gives you alot more control over the look.
CustomRenderer that removes the navigationBar:
//add using statements
// add all view here that need this custom header, might be able to build a
//base page that others inherit from, so that this will work on all pages.
[assembly: ExportRenderer(typeof(yourView), typeof(HeaderRenderer))]
class HeaderRenderer : PageRenderer
{
public override void ViewWillAppear(bool animated)
{
base.ViewWillAppear(animated);
this.NavigationController.SetNavigationBarHidden(true, true);
}
}
After this you can build a header view that can be placed on the top of every page (I am using xaml) so I don't know if it is relevant in you application.
Edit: You might need to change this renderer for differnt page types.
In a windows phone app,a page is navigated to another page and on pressing back button, goes back to previous page.Now in previous page the previous data has to be displayed. But its not displaying immediately and takes some time to load. How to solve this issue?
Overall the question is how to maintain the content of page(containing dynamic data) displayed in back navigation?
Use PhoneApplicationService class to keep the data while you navigate between the pages. Here is some samples. Actually, it's very easy:
protected override void OnNavigatedFrom(NavigationEventArgs args)
{
if (ContentPanel.Background is SolidColorBrush)
{
Color clr = (ContentPanel.Background as SolidColorBrush).Color;
if (args.Content is MainPage) (args.Content as MainPage).ReturnedColor = clr;
// save color
PhoneApplicationService.Current.State["Color"] = clr;
}
base.OnNavigatedFrom(args);
}
protected override void OnNavigatedTo(NavigationEventArgs args)
{
// restore color
if (PhoneApplicationService.Current.State.ContainsKey("Color"))
{
Color clr = (Color)PhoneApplicationService.Current.State["Color"];
ContentPanel.Background = new SolidColorBrush(clr);
}
base.OnNavigatedTo(args);
}
How to preserve and restore page state for Windows Phone
You can use single ton object of View Model to store data in a page provided all the controls are bind to a property in View Model.
Then if you do not clear the values of the controls when navigating away from the page, the data will be displayed in the page when you navigate back to that screen provided all the controls