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How to display a popup window on Xamarin

I am very new to Xamarin, so please excuse me for my simple questions.
Like the alert window on the screen, I want to open a second window that can be resized and positioned. Despite all my calls, I couldn't get it.
An absolute style div for those who know html.
Thanks in advance to friends who can give me an idea of how I can do it.

I think what you're looking for is a "Popup". It can be done by hand, but I recommend using a library like this one. It lets you customize your Popups however you want by creating custom pages for them, like this:
<?xml version="1.0" encoding="utf-8" ?>
<pages:PopupPage
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:pages="clr-namespace:Rg.Plugins.Popup.Pages;assembly=Rg.Plugins.Popup"
xmlns:animations="clr-namespace:Rg.Plugins.Popup.Animations;assembly=Rg.Plugins.Popup"
x:Class="MyProject.MyPopupPage">
<!--You can set an animation in the xaml file or in the csharp code behind-->
<pages:PopupPage.Animation>
<animations:ScaleAnimation
PositionIn="Center"
PositionOut="Center"
ScaleIn="1.2"
ScaleOut="0.8"
DurationIn="400"
DurationOut="300"
EasingIn="SinOut"
EasingOut="SinIn"
HasBackgroundAnimation="True"/>
</pages:PopupPage.Animation>
<!--You can use any elements here which are extended from Xamarin.Forms.View-->
<StackLayout
VerticalOptions="Center"
HorizontalOptions="Center"
Padding="20, 20, 20, 20">
<Label
Text="Test"/>
</StackLayout>
</pages:PopupPage>
If you want Popups that cover the whole screen, you can use modal pages, which are built into Xamarin. Check it here.

Is there any way to add background Image on navigationbar page by page on xamarin forms

Is there any way to add background Image on navigationbar page by page on xamarin forms?

The would need to write a custom render to change the background of the navigation bar. This is simply because the navigation bar does not have an option to change the background image.
https://books.google.co.uk/books/about/Xamarin_Forms_Solutions.html?id=wvt9DwAAQBAJ&printsec=frontcover&source=kp_read_button&redir_esc=y#v=onepage&q&f=false
There's a good very brief section about how to write custom renders is this ^ book (you can even find it in the preview without purchasing it).
An alternative solution would be to create a custom banner at the top of the page
https://forums.xamarin.com/discussion/126227/customizing-navigation-bar-or-action-bar-in-xamarin-forms[As mentioned in this answer2
<ContentPage NavigationPage.HasNavigationBar="false">
<StackLayout VerticalOptions="Start"
HorizontalOptions="FillAndExpand"
Orientation="Horizontal"
Padding="10,5,10,5>
<Image HorizontalOptions="StartAndExpand" source="yourimage.png"/>
<Label HorizontalOptions="CenterAndExpand" Text="ALL"/>
<Image HorizontalOptions="EndAndExpand" source="yourimage.png"/>
</StackLayout>
<StackLayout>
<!-- Place your code for page body-->
</StackLayout>
</ContentPage>
I've copied the code into here for simplicity and reference. This solution removes the navigation bar and allows you to create a custom banner on each page in XAML. In here you can change the layout as you please.

Display text while Page is loading in Xamarin Forms

I have a page that is quite heavy and its loading for about 1-2 sec after click. During this time I see loading page header and old page content, it looks so irresponsive. All I want to achive is to display temporary Label with content like "Loading..." or activityindicator as long as new page is loading but I have no idea how to do this. What is the better way to achive this? Thanks in advance

Based on your comments, you just want to display Busy indicator while you are loading the Data from your Api. You didn't posted your UI but I hope you understand how to use the below:
<Grid>
<YOUR-UI>
.....
.........
</YOUR-UI>
<ActivityIndicator VerticalOptions="Center" IsVisible="{Binding IsBusy}" IsRunning="{Binding IsBusy}"/>
</Grid>
In your ViewModel, Add IsBusy Property as below:
private bool _isBusy;
public bool IsBusy
{
get{return _isBusy;}
set { _isBusy=value; RaisePropertyChanged(); }
}
Then when you are Calling the API to load your Data do something like:
public async void LoadDataFromApi()
{
IsBusy=true; //Show the Indicator
var response= await YourService.Method(); //this is where you calling your api
//do other stuffs if you need to do;
IsBusy=false; //Hide the Indicator
}
Let me know if you need anymore help.

Based on your comments on other answer - instead of ActivityIndicator - you could use a simple frame that covers all the layout and make it visible only when data are loading i.e. Binding IsVisible to IsBusy property. Then set IsBusy to true before doing the heavy load job and set back to false afterwards as shown in previous answer.
For instance, assuming your UI is based on a Grid layout (in this example 3 rows/2 columns):
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="auto" />
<RowDefinition Height="*" />
<RowDefinition Height="auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<!-- Some XAML for the grid content -->
<!-- Here, Frame covers all the possible space defined using RowSpan/ColumnSpan -->
<Frame Grid.RowSpan="3" Grid.ColumnSpan="2" IsVisible="{Binding IsBusy}" BackgroundColor="LightGray">
<Label VerticalOptions="Center" HorizontalOptions="Center" Text="Loading Samples..." />
</Frame>
</Grid>
-------------------------------------------------
EDIT based on OP comments:
Bases on the code you provided (better paste it in SO next time ;)), you could try this:
Add a grid layout and a frame to the xaml page:
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="MyApp.Namespace"
xmlns:tabView="clr-namespace:Syncfusion.XForms.TabView;assembly=Syncfusion.SfTabView.XForms"
xmlns:sfPopup="clr-namespace:Syncfusion.XForms.PopupLayout;assembly=Syncfusion.SfPopupLayout.XForms"
BackgroundColor="#d4d4d4">
<ContentPage.ToolbarItems>
<ToolbarItem Icon="search_white_90.png"/>
</ContentPage.ToolbarItems>
<ContentPage.Content>
<Grid>
<tabView:SfTabView x:Name="ProductsTabView" VisibleHeaderCount="3" TabHeaderBackgroundColor="#A74B40" Items="{Binding}">
<tabView:SfTabView.SelectionIndicatorSettings>
<tabView:SelectionIndicatorSettings
Color="#fff" StrokeThickness="3"/>
</tabView:SfTabView.SelectionIndicatorSettings>
</tabView:SfTabView>
<Frame x:Name="theFrame" BackgroundColor="White">
<Label VerticalOptions="Center" HorizontalOptions="Center" Text="Loading Samples..." />
</Frame>
</Grid>
</ContentPage.Content>
</ContentPage>
ProductsTabView and theFrame will cover the same space on screen and frame will be available in code behind. Then you can show/hide theFrame before/afrer the hard work using IsVisible property:
public partial class ProviderPage : ContentPage
{
public ProviderPage()
{
InitializeComponent();
theFrame.IsVisible = true; // Show the Frame on top of tabView
ProductsTabView.Items = GetTabItemCollection();
theFrame.IsVisible = false; // Hide the Frame
}
...
As a side note, you don't use ViewModel at all. I strongly recommand you to check about what a ViewModel is and how to use them with MVVM pattern. It will make your life easier in the long run using Binding!
HIH & Happy coding!

Try https://github.com/aritchie/userdialogs, It's make you easily to implement loading
for example:
using (this.Dialogs.Loading("Loading text"))
{
//Do something i.e: await Task.Delay(3000);
}
OR
this.Dialogs.ShowLoading("Loading text");
//Do something i.e: await Task.Delay(3000);
this.Dialogs.HideLoading();
OR
https://github.com/aritchie/userdialogs/blob/master/src/Samples/Samples/ViewModels/ProgressViewModel.cs

I have a project for advanced page transitions in Xamarin.Forms that may help you. Try this:
Install this nuget: http://www.nuget.org/packages/Xamarin.Forms.Segues (it is currently only prerelease, so you'll need to check the box to see it)
Add this sample to your project: https://github.com/chkn/Xamarin.Forms.Segues/blob/master/Sample/Shared/Custom%20Segues/SpinnerSegue.cs
In the DoWork method of SpinnerSegue add the code to load the data.
In your code that navigates to the other page, replace Navigiation.PushAsync(new MyNewPage()) with new SpinnerSegue().ExecuteAsync(this, new MyNewPage())

Pivot overlapping other elements in WP 8.1 Universal app (and automatically changing margin)

The following XAML shows the content of a Windows Phone 8.1 Universal app page. The idea is to have a bar on top of a pivot. But the pivot is overlapping the bar whereas the sample grid in blue is working as expected.
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="50" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<Grid Background="{StaticResource PhoneAccentBrush}" Height="50" />
<Pivot Grid.Row="1" Background="Green" Width="200" HorizontalAlignment="Left" />
<Grid Grid.Row="1" Background="Blue" Width="200" HorizontalAlignment="Right" />
</Grid>
The resulting Page looks like this:
Where is this "negative margin" coming from?
How can it be avoided?
BTW: Just setting a margin is not a solution as it introduces other problems, for example a jumping GUI when using a SemanticZoom control, I need to know the root cause of the problem to solve it...
Info: It seems that the Windows Phone Pivot automatically changes the margin depending on the current screen settings (status bar shown/hidden). So if your app changes the state of the status bar in some circumstances you will end up having a jumping/changing pivot control.

I've found a solution and created a simple attached property for the Pivot control.
The attached property can be used this way:
<Pivot controls:PivotExtensions.DisableAutoMargin="True">
<PivotItem Header="A">
...
</PivotItem>
<PivotItem Header="B">
...
</PivotItem>
</Pivot>
The class with the attached property can be found here:
http://mytoolkit.codeplex.com/SourceControl/latest#MyToolkit.Extended.WinRT/Controls/PivotExtensions.cs
Downside: You cannot override the template anymore as the attached property changes the template already...

Overriding the control template doesn't seem to work; there is some code in the control that's setting the margin after construction. Also setting the Margin on the offending grid on the Loaded event doesn't work either, the negative margin code runs after that.
The only way I found to make the odd behavior go away was to ask your UI to overlap the status bar:
ApplicationView.GetForCurrentView()
.SetDesiredBoundsMode(ApplicationViewBoundsMode.UseCoreWindow);
Then the Pivot control figures that it doesn't need to try and cover the status bar. Note that you'll now have to give room in your page layout to prevent overlap with the status bar.

WPF Design question

Lets say i am developing a chat, first you come to a login window and when your logged in i want to use the same window but chaning the control :P how would be the best way to desight this?
is there any good way to implement this what root element should i use?
Thanks a lot!!

Take a look at Josh Smith's article in MSDN magazine (http://msdn.microsoft.com/en-us/magazine/dd419663.aspx). He describes an interesting method where you have a content presenter on your main window use data templates to switch out what the window is showing.

If you want to do this all within the same window, you could use a Grid as the root element and host a login element (possibly another grid for layout) and the chat window. These elements would stack on top of one another, depending upon the order in which you declare them. To hide the chat element initially, set its Visibility to Collapsed
You could then have the login element's Visibility set to Collapsed when the user submits their login details, and have the chat element's Visibility set to Visible.
I did something similar once and it worked well for me.
Hope that helps.
EDIT I knocked this together in Kaxaml for you to play with (and because I like playing with XAML):
<Page
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Grid VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
<Border x:Name="_loginForm" BorderBrush="#888" BorderThickness="3" CornerRadius="5"
HorizontalAlignment="Center" VerticalAlignment="Center" Padding="10" Visibility="Visible">
<Grid>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="100"/>
<ColumnDefinition Width="100"/>
</Grid.ColumnDefinitions>
<TextBlock Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="2" HorizontalAlignment="Center" Height="30">Welcome to chat</TextBlock>
<TextBlock Grid.Row="1" Grid.Column="0">User Name</TextBlock>
<TextBox Grid.Row="1" Grid.Column="1" x:Name="_userName" />
<TextBlock Grid.Row="2" Grid.Column="0">Password</TextBlock>
<TextBox Grid.Row="2" Grid.Column="1" x:Name="_password"></TextBox>
<Button Grid.Row="3" Grid.Column="1">Log In</Button>
</Grid>
</Border>
<DockPanel x:Name="_chatForm" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" LastChildFill="True" Visibility="Collapsed">
<DockPanel DockPanel.Dock="Bottom" LastChildFill="True" Height="70">
<Button DockPanel.Dock="Right" Width="70">_Send</Button>
<TextBox x:Name="_input" HorizontalAlignment="Stretch">Hello world</TextBox>
</DockPanel>
<ListBox x:Name="_messageHistory" />
</DockPanel>
</Grid>
</Page>
Initially the element _loginForm is visible. You'd attach a handler for the Log In button's Click event that would hide it, and show the _chatForm instead.
This example shows usage of several layout controls -- the Grid, DockPanel and StackPanel.

Alternatively, you can use a StackPanel for your layout. As a simple example, you can have 2 elements in your panel; a custom login control as well as the chat 'display' control. After successfully logging in, remove the custom login control from your stack so only the chat is visible.

It's WPF! Animate them in and out of view...you can do that now. There's a collaborative project on Google Code called Witty (a desktop Twitter client written in WPF), and they do something really cool that you might want to borrow from. Come to think of it, there's another WPF Twitter client (blu) that does similar animations that you might want to look at.
In Witty, the Settings dialog is a normal window, but when you switch between the tabs, a storyboard slides the part of the window you requested into view. I haven't debugged the app at this level, but I'm assuming that they have a horizontal StackPanel populated with containers that are fixed to the height and width of the dialog, and they slide them in and out with a storyboard.
Take a look at both of these apps for ideas. You may want to do something similar, but being that this is a WPF app, the sky is really the limit.
Witty
blu

There are already some answers here on, how to swap two elements at the view level. This post offers a way to more fundamentally create a modular application design with interchangeable views.
You could take a look at the Composite Application Library. It is a small library (developed by Microsoft) that among other things aid in making your application more modular. With this you can define regions of your GUI, that can have interchangeable views.
In your containing xaml import the CAL namespace and use RegionManager to define a region:
<Window ...
xmlns:cal="http://www.codeplex.com/CompositeWPF"
...>
...
<ItemsControl cal:RegionManager.RegionName="MyRegion" />
...
Then you can swap views in this region, preferably in a module:
_regionManager.Regions["MyRegion"].Add(new LoginView());
...swap...
_regionManager.Regions["MyRegion"].Add(new ChatView());
This is of course just an outline of what you can do. In order to implement this solution, you will have to look further in to CAL. It has great documentation and lots of examples to learn from.

I think a more intuitive solution is to use a Frame control as the base control of your window - and to use the NavigateService to change the source of the Frame to different Page controls (which could be defined in separate assemblies, or in your same project as different XAML files).
Your Window:
<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Frame Source="LogonPage.xaml" NavigationUIVisibility="Hidden" />
</Window>
And your separate LogonPage:
<Page
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Logon">
<!-- Your content of the page goes here... -->
</Page>