December 16, 2017

Bug : Java.Lang.NullPointerException,Attempt to invoke virtual method 'boolean android.graphics.Bitmap.isMutable()' on a null object reference

I have observed this above mentioned bug keeps on hitting when using Xamarin form,UI control "Frame" for android while it executes without any issues for iOS. 

In my previous post discussed about Frame border highlight issues in android. Frame control still has one or other problem with android and still remains a question mark why Xamarin team has not given any fix for this android specific problem.

July 16, 2017

How to fetch android sqlite db file from device in Mac Xamarin/Visul Studio.

Here i'm going to share one of the simple method to fetch sqlite database file from android device for xamarin or visul studio installed in mac machine. 
Recently when i was checking data stored in the sqlite db from android device, i couldn't do it easily as i fail to run ADB commands from my terminal.

Same if you are fetching DB file from Emulator it is pretty straight forward. 
Launch Device Monitor(Tools-> Device Monitor) 
select Emulator from left pane
select File Explorer from right pane 
Navigate to app data base file-> /data/data/com.appName.MyApp/databases/
Select required database file->"Pull a file from device" option from top right as shown in screen
Copy DB file to machine storage and open using sqlite db browser(http://sqlitebrowser.org/)

To fetch DB from android device using Windows machine we can use the following ADB command

May 25, 2017

Force Landscape or Portrait for a single page in Xamarin Form.

Device screen orientation in xamarin is usually configured from Host(Android/iOS) project as suggested here . But what if i need to change the screen orientation of one particular screen(say to landscape) in xamarin form and other screens are different (may be portrait), to do so there is no direct options available from xamarin form.
We will do the configuration in host project for the common screen orientation required throughout the application, to do any changes for particular screen need to touch back to the host project settings again because as of now there is no wrapper Form level API’s available. 

For example consider the scenario that my Form project contains the Five screens out of that, for Third screen i need give support for both Portrait and Landscape and for all other remaining screen only in portrait. This can be done in android as follows,

Use the MessageCenter class to send the message from the Form screen for which orientation need to be changed and receive the same from Android MainActivity class.

ThirdPage.xamal.cs
  public partial class ThirdPage : ContentPage
    {
        protected override void OnAppearing()
        { 
            base.OnAppearing(); 
           MessagingCenter.Send(this, "allowLandScapePortrait”);
        }
         //during page close setting back to portrait
        protected override void OnDisappearing()
        {
            base.OnDisappearing(); 
            MessagingCenter.Send(this, "preventLandScape");
        }
    }

May 22, 2017

Platform specific UI changes in Xamarin.Form


Brief: Walkthrough on the options available in xamarin form for changing UI element behaviour for specific platform.

Description: Xamarin form wrapper UI controls when it renders in each platform shows the native look and feel but still there are some quirks that has to be worked around to get the UI perfection.

For example if i add one label in my xamal page and on run in android and iOS shows the below output:
<?xml version="1.0" encoding="utf-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:local="clr-namespace:CodeLog" x:Class="CodeLog.CodeLogPage">
<RelativeLayout HorizontalOptions="FillAndExpand"  >
    <Label Text="Code Log" 
          FontSize="25" 
          FontFamily="Roboto-Bold" 
          HorizontalTextAlignment="Center" 
   HorizontalOptions="FillAndExpand" />  
</RelativeLayout>
</ContentPage>
In iOS label has been overlapped with toolbar. So alone for iOS we need add To padding(Tool bar height 20px).

This kind of changes for particular platform can be achieved by using the below mentioned approaches without using the Custom renderer.

1.Using a generic class OnPlatform
2.PlatformConfiguration(https://blog.xamarin.com/bringing-platform-specific-functionality-to-xamarin-forms-apps/)
3.Bindable Native Views in Xamal page (https://blog.xamarin.com/adding-bindable-native-views-directly-to-xaml/)
4.customisation with effects(https://blog.xamarin.com/customizing-xamarin-forms-controls-with-effects/)
In this article i will be making use of the OnPlatform for different UI control properties. From Xamarin.Forms version 2.3.4, Device.OnPlatform API has been deprecated with OnPlatform and On APIs.
 <?xml version="1.0" encoding="utf-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:local="clr-namespace:CodeLog" x:Class="CodeLog.CodeLogPage">
<RelativeLayout HorizontalOptions="FillAndExpand"  >
  <RelativeLayout.Margin>
    <OnPlatform x:TypeArguments="Thickness">
      <On Platform="iOS" Value="0,20,0,0" />
      <On Platform="Android, WinPhone, Windows" Value="0,0,0,0" />
    </OnPlatform>
  </RelativeLayout.Margin>
    <Label Text="Code Log" FontSize="25" FontFamily="Roboto-Bold" HorizontalTextAlignment="Center" 
  HorizontalOptions="FillAndExpand" />  
</RelativeLayout>
</ContentPage> 
Platform specific Text color:
 <Label Text="Code Log" FontSize="18" FontAttributes="Bold"  FontFamily="Roboto-Bold" XAlign="Center"  HorizontalTextAlignment="Center" 
 HorizontalOptions="FillAndExpand"
 RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=1}"> 
  <Label.TextColor>
    <OnPlatform x:TypeArguments="Color" iOS="Red" Android="Blue"  />
     </Label.TextColor> 
   </Label>  

February 15, 2017

ResolveLibraryProjectImport task failed unexpectedly in release mode in xamarin

This above mentioned error i got during my xamarin form project deployment in release mode. 
In my solution i have more then one project and this error indicates that linking between these project has been broken. If you are facing the same issue, then here i have listed out few scenarios that could help you to solve this issue:


1. Select the project in which error is pointing and Check the reference of other project and package. Reference with yellow triangle icon shows the broken reference. just delete it and re-add.
For any other project reference included in the current project, delete the current project reference and add the new one from release folder of that respective project.
 Or
Open "Configuration manager"