Corrado's Blog 2.0

Online thoughts of a technology funatic

Genymotion and VirtualBox install issue

I use Genymotion as Android emulator for my Xamarin work, I know that there are better alternatives like Microsoft’s Android emulator but since can’t turn on Hyper-V on my machine this is the solution that works best for me.

Haven’t done any Android development recently so since I need to prepare some demos for my forthcoming session at Future Decoded I checked my system and discovered that Android emulator wasn’t working anymore as happened in the past. Checked the logs but nothing evident was listed apart some in influent login error, I then tried to run VirtualBox alone and noted that it was not starting at all, no error nor messages, just nothing was happening.

Ok, let’s reinstall Genymotion to latest version, maybe recent Windows 10 Anniversay update broke something, did that, no errors but, nothing changed, ok, let’s try installing VirtualBox alone from Oracle site and BOOM! got a weird error message about an adapter not being created because it was not possible to rename it (WHAAAT?)

Fired up a search engine looking for solutions and found thousands of thread starting from 2010, some of them even suggesting to repave the entire machine, luckily among this tons of documentation my attention got catched by a guy that claimed to have solved using this steps:

  1. 1-Go to 
  2. C:\Program Files\Oracle\VirtualBox\drivers\network
    2-Go into each directory contained into network and install the drivers by tight clicking every .inf file and selection Install from popup menu

    image

    3-Go to Network Connections, right click the Ethernet adapter associated with VirtualBox and select Properties

    image

    4-On the network properties panel, click Install and select Services

    image

    5-Now select the Oracle’s VirtualBox driver and select OK

    image

    6-Be sure that VirtualBox NDIS driver is selected.

    image

    7-Complete Genymotion install, if not already done, otherwise, just download a device and runt it, if it is your lucky day, it should work.

    You can read the original answer here, it also worked for me of course.

    …and after this annoying procedure you can go back coding in relax. Smile

    HTH

    I am a Xamarin MVP!

    Xamarin, like Microsoft has its own MVP (Most Valuable Professional) program that awards people “who have demonstrated an exemplary commitment to helping others get the most out of their experience with Xamarin by sharing their passion, real-world knowledge, and technical expertise with developers all over the world.”

    I am pleased to announce that I’ve been awarded Xamarin MVP, and this makes me extremely proud and happy, being the first Italian in this close group of internationally known Xamarin experts, give me a high level of responsibility and I’ll do my best continuing sharing my technology passion.

    If you haven’t tried Xamarin yet, I encourage you to do it, a lot changed since 2014 when I started approaching it (no Forms yet…) it is now a mature product and if you’re eager to learn more Xamarin University is here to help.

    Thanks Xamarin!

    A Smart RecyclerView Adapter for Xamarin.Android

    RecyclerView is the recommended way to represents a collection of items in Android applications, the good and old ListView is now deprecated since RecyclerView offers a lot of improvements like flexible layout, item recyclying and enforces the ViewHolder pattern.

    If you’re new to RecyclerView in Xamarin Android I recommend this article from Xamarin site, since it is also the origin project I’ve used on this post and this is not a RecyclerView tutorial.
    This post originates since every time I need to use a RecyclerView, even for simple demos like this blog post, I end up rewriting the same boilerplate code, so I decided to create a simple generic adapter that simplifies things for me.

    Source code and demo is available on GitHub here, so get it and have a look if you want to know more about the internals, I’ll just show you how to use it updaing the original Xamarin demo.

    Just create a class that inherits from abstract SmartRecyclerAdapter<T> class

    as you see, you just have to implement two methods OnLookupViewItems and OnUpdateView: OnLookupViewItems is used to extract the view items from inflated layout and save them into provided generic viewholder
    OnUpdateView is used to update the same view items with the fresh values coming from provided Item.

    Let’s see now in action, exploring the code in MainActivity:

    Very simple: I created an instance of the PhotoRecyclerAdapter passing to its constructor: the RecyclerView, an ObservableCollection<T> as item source and the optional id of the layout to inflate to create the items views (more on this later)

    Since we’re using an ObservableCollection<T> the list is smart enough to automatically invoke the several NotifyXYZ methods when you add/remove/move items from the collection as when the “Clear+Add” button of the demo is clicked.

    What if you need to use different layouts depending on items properties? just override base class GetViewIdForType method and return an int that will be passed to the othere method you’ll have to override named OnGetViewId inside this method, depending on passed viewTypeId you’ll return the item id to inflate for such element.

    The adapter automatically raises an ItemSelected event when an item is clicked, passing null as RecyclerView parameter on PhotoRecyclerAdapter constructor, disables this behavior and you can implement your own item selection strategy.

    It’s just a starting point, hope you’ll like it. Smile

    AutoHide FloatingActionButton in Xamarin.Android

    My main phone is an Android and as a news app I use a 3rd party aggregator that, al nearly all Android apps today is based on Material Design.
    Using it everyday I couldn’t ignore a nice UI feature it exposes: it’s share button (a Material Design’s FloatinActionButton) fades out when you scroll the list vertically and it reappears when you scroll the list down.
    Being curious, I wanted to know how to create that effect using Xamarin.Android.

    This is my final result:

    hidefab

    Since there’s a lot of setup involved I won’t go too much into code detail and setup, you can grab the project source code from here https://github.com/corradocavalli/Xamarin.Android.HideMyFAB

    I’m assuming you have some basic knowledge of Material Design and  related steps to enable it into a Xamarin.Android app so and I’ll go straight to the point: The view you see is made up of a CoordinatorLayout that hosts a NestedScrollView that contains a series of CardViews and in the bottom right corner there is our FloatingActionButton.

    The trick of making it disappear is to add a custom behavior so that CoordinatorLayout knows that it has to invoke a behavior that takes care to hide/show it when something happen, in our case when user scrolls up or down.

    This is the required behavior

    Inside OnNestedStartScroll we inform the CoordinatorLayout that we want to receive scroll events when user scrolls vertically while inside OnNestedScroll we receive a reference to the FloatingActionButton (since we have applied the behavior to it) and depending on scroll direction we show/hide it.

    The hard part of migrating this code to Xamarin was fixing the weird compilation issues I was having, I thank community guy fex for giving me the hint to add the [Register] attribute at the top to the class definition and inheriting from CoordinatorLayout instead of my initial FloatingAction. No idea if this is a bug, I’ve seen someone already filed it on Bugzilla but still without any reply.

    Is now time to associate out behavior to the FloatinActionButton, I’ll do that using the standard approach to define the fully qualified path to the class inside strings.xml for better refactoring.

    and now it’s just a matter of attach it to the button

    If you use material design in your appls you’ll immediately recognize the now stanrdard elements, the only real new is the layout_behavior attribute applied to the FloatingActionButton that points to our custom behavior.

    There are indeed simpler alternatives like James Montemagno component available here but looks like it is now deprecated and I think that, once you know how to fix the ACW compilation issues, knowing how to use material design behaviors wont hurt.

    Enjoy Smile

    Using Xamarin Forms Effects

    Version 2.1 of Xamarin Forms introduced Effects, a nice alternative to custom renderers when all you need is to tweak some properties of the platform native control, they should be seen as an alternative to a custom renderer not as a substitute.

    Let’s quickly see how they work, let’s suppose we want to limit the amount of text that a user can type inside an entry, something that’s not natively possible with Xamarin Forms (at the time of this writing…)

    Create a new Xamarin Forms project and upgrade Xamarin.Forms assemblies to latest stable version greater than 2.1 , in my case is 2.1.0.6529

    image

    Effects are a mix of platform specific code and code that resides in application PCL library, let’s start with the PCL and create a class that uses RoutingEffect  as base class:

    public class MyEntryEffect : RoutingEffect { public MyEntryEffect() : base("MyCompanyName.EntryEffect") { } public int MaxLength { get; set; } }

    As you can see the constructor of this class invokes base constructor passing the fully qualified name of the platform specific effect to be created (“MyCompanyName.EntryEffect” more details on this soon)

    It’s time to apply our Effect (or as I prefer ‘extension’) to a Xamain Forms Entry, in my project I’ve added a MainView.xaml page and this is related XAML.

    <?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:demoEffects2="clr-namespace:DemoEffects2;assembly=DemoEffects2" x:Class="DemoEffects2.MainView"> <StackLayout VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand"> <Entry Placeholder="Try to type more than 5 chars.." > <Entry.Effects> <demoEffects2:MyEntryEffect MaxLength="5" /> </Entry.Effects> </Entry> </StackLayout> </ContentPage>

    Quite easy to understand: We added our custom MyEntryEffect effect to Entry’s Effects collection and set it’s MaxLength property to 5.

    Is now time to switch to platform specific projects and implement the code that reads the value of MaxLength property and applies this limit to platform specific control.

    Let’s start with Android:

    [assembly: ResolutionGroupName("MyCompanyName")] //Note: only one in a project please... [assembly: ExportEffect(typeof(EntryEffect), "EntryEffect")] namespace DemoEffects2.Droid { public class EntryEffect : PlatformEffect { protected override void OnAttached() { try { //We get the effect matching required type, we might have more than one defined on the same entry var pclEffect = (DemoEffects2.MyEntryEffect)this.Element.Effects.FirstOrDefault(e => e is DemoEffects2.MyEntryEffect); TextView editEntry = this.Control as TextView; editEntry?.SetFilters(new Android.Text.IInputFilter[] { new Android.Text.InputFilterLengthFilter(pclEffect.MaxLength) }); } catch (Exception ex) { //Catch any exception } } protected override void OnDetached() { } protected override void OnElementPropertyChanged(PropertyChangedEventArgs args) { base.OnElementPropertyChanged(args); try { if (args.PropertyName == "Your property name") { //Update control here... } } catch (Exception ex) { Console.WriteLine("Cannot set property on attached control. Error: ", ex.Message); } } } }

    Inside the Android project I have created an EntryEffect class that inherits from PlatformEffect and implemented two familiar overrides: OnAttached and OnDetached.

    As you might expect the first is invoked when Effect is applied to the control and can be used to initialize the property of Android’s native control while OnDetached is called when the effect is removed and can be used to perform any cleanup. 

    From inside this methods we have access to three fundamental properties:

    Container: The platform specific control used to implement the layout.

        • Control: The platform specific counterpart of Xamarin Forms control.

    Element: The Xamarin Forms control being rendered.

    Since Effect can be added to Effects collection of any control the code must take this into consideration and degrade gracefully in case actions cannot be completed due to a control type mismatch.

    Inside OnAttached we retrieve the PCL effect so that we can read it’s MaxLenght property and we cast the Control property to a TextView, if casting fails we simply do nothing otherwise we add a filter that limits the number of typed chars inside the TextView.

    Even if not used in this sample, the code includes OnElementPropertyChanged override that can be used when you want to be notified when a property of the control changes (e.g. IsFocused) and do something when this happens.

    Last, but absolutely not least come the two attributes ResolutionGroupName and ExportEffect

    ResolutionGroupName : Allows you to define a custom namespace for you effects to prevent naming collision, it must be used once in the platform specific project.

    ExportEffect: Is the name that’s used by initial effects discovery process and it accepts the type of the effect it is applied to and the name you want to export for discovery.

    The concatenation of ResolutionGroupName and ExportEffect id is used by RoutingEffect class (see it’s base constructor in preceding code) for proper identification.

    As for custom renderers is not necessary to implement the effect for each class, if undefined it simply gets ignored.

    Here’s the iOS effect version:

    [assembly: ResolutionGroupName("MyCompanyName")] //Note: only one in a project please... [assembly: ExportEffect(typeof(EntryEffect), "EntryEffect")] namespace DemoEffects2.iOS { public class EntryEffect : PlatformEffect { protected override void OnAttached() { try { //We get the effect matching required type, we might have more than one defined on the same entry var pclEffect = (DemoEffects2.MyEntryEffect)this.Element.Effects.FirstOrDefault(e => e is DemoEffects2.MyEntryEffect); UITextField editEntry = this.Control as UITextField; if (editEntry != null) { editEntry.ShouldChangeCharacters = (UITextField textField, NSRange range, string replacementString) => { // Calculate new length var length = textField.Text.Length - range.Length + replacementString.Length; return length <= pclEffect.MaxLength; }; } } catch (Exception ex) { //Catch any exception } } protected override void OnDetached() { } } }

    Simpler, but more flexible, Xamain Forms effects represent a valid alternative to Renderers, I’m pretty sure that we’ll see many open source effects coming from th Xamarin community.

    If you want to know more about Effects, this is the link to follow.

    Happy Effecting.

    Add a SnackBar to you Xamarin.Android app

    Material design introduced a new lightweight way to provide feedback to a user, something that sits between the AlertDialog and Toast alternatiives with a funny name: SnackBar.
    A Snackbar appears at the bottom of the view and can optionally display an additional custom button.

    Here are the basic steps to show a SnackBar:

    -Open Visual Studio and create a new blank Android app

    -Using Nuget add the Xamarin.Android.Support.Design library, this will let you target Android releases older than v21

    image

    • -Using the code generated by the template, lets make the SnackBar appear when the default button is pressed.

    -Add this code inside MainActivity’s OnCreate method

    protected override void OnCreate(Bundle bundle) { base.OnCreate(bundle); // Set our view from the "main" layout resource SetContentView(Resource.Layout.Main); // Get our button from the layout resource, // and attach an event to it Button button = FindViewById<Button>(Resource.Id.MyButton); button.Click += (s, e) => { //Creates the Snackbar Snackbar snackBar = Snackbar.Make(button, "Text", Snackbar.LengthIndefinite); //Show the snackbar snackBar.Show(); }; } }

    • -Compile the project and wait until build succeeds, be patient if operation takes more than than usual since this delay is due to the fact that the missing packages are downloading and their size is quite huge. If you stop compilation download will fail and you’ll start having a lot of “…invalid zip” error. in this case delete the zip folder mentioned on error message and try again.
    • -You’ll now see this error message:
    • image
    • -Let’s fix it adding the required theme (you can create your own deriving from Theme.AppCompat of course)
      [Activity(Label = "TestSnackBar2", MainLauncher = true, Icon = "@drawable/icon", Theme = "@style/Theme.AppCompat")]

    • -Run the project again and you’ll see this bar appear at the bottom of the view
    • image
    • -Quite sad indeed, luckily the SnackBar can be customized, so let’s add more code:
    button.Click += (s, e) => { //Creates the Snackbar and subscribes the button press event Snackbar snackBar = Snackbar.Make(button, "Text", Snackbar.LengthIndefinite).SetAction("Ok", (v) => { Console.WriteLine("Done"); }); //set action button text color snackBar.SetActionTextColor(Android.Graphics.Color.Green); //Set action button text size TextView txtAction = snackBar.View.FindViewById<TextView>(Resource.Id.snackbar_action); txtAction.SetTextSize(Android.Util.ComplexUnitType.Dip, 18); //Set message text size and color TextView txtMessage = snackBar.View.FindViewById<TextView>(Resource.Id.snackbar_text); txtMessage.SetTextColor(Android.Graphics.Color.Red); txtMessage.SetTextSize(Android.Util.ComplexUnitType.Dip, 12); //Show the snackbar snackBar.Show(); };

    • -And there you go, a custom SnackBar Smile
    • image

    If you’re wondering why you need to pass a reference to a view (Button in our case) as SnackBar first parameter is because internally it walks up the visual tree so that can properly position itself at bottom position.

     

    Xamarin.Android Status bar color not set

    Not a very descriptive title, but good for search engines Smile

    The problem: You’re using Xamarin.Android.Support.v7.AppCompat in order to have Material Design’s Toolbar available also devices running o pre-Lollipop (v.21) releases.

    You added a reference to the library:

    image

    Added the style:

    <style name="ParentMaterialTheme" parent="Theme.AppCompat.Light.NoActionBar"> <item name="colorPrimary">@color/colorPrimary</item> <item name="colorPrimaryDark">@color/colorPrimaryDark</item> <item name="colorAccent">@color/colorAccent</item> <item name="colorControlHighlight">#1ef1ab</item> <item name="colorButtonNormal">#f955f3</item> <item name="colorControlActivated">#0cf427</item> </style>

    Added the entry into AndroidManifest.xml:

    <application android:label="_02_StandaloneToolbar" android:theme="@style/MaterialTheme" />

    Created the toolbar:

    <android.support.v7.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="@color/colorPrimary" android:minHeight="?attr/actionBarSize" android:theme="@style/ToolbarTheme" app:popupTheme="@style/PopupTheme" android:id="@+id/toolbar"> </android.support.v7.widget.Toolbar>

    Included into Main.axaml:

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <include android:layout_width="match_parent" android:layout_height="wrap_content" layout="@layout/toolbar"/> </RelativeLayout>

    But when you run it, the status bar doesn’t follow colorPrimaryDark but it remains black Confused smile

    image

     

    Solution: add this line into Activity’s OnCreate method (yes, you have to use code)

    this.Window.AddFlags(WindowManagerFlags.DrawsSystemBarBackgrounds);

    And you’re done!

    image

    Xamarin Forms preview with Gorilla Player

    One of the major complaints about Xamarin Forms is the lack of designer with relative preview so, at the time of this writing, the development process is made up of a continuous sequence of: write XAML, deploy, see result, stop, edit XAML and try again, not a very convenient and productive way to work Sad smile

    GorillaPlayer is a tool from a company named UXDivers that provides real time XAML preview on any Emulator/Simulator speeding up development process.

    Note: GorillaPlayer is actually in beta and available via invite only, go request your invite here: www.gorillaplayer.com the player is available for both Visual Studio and Xamarin Studio (both Windows and iOS)

    Once you get the invite, download the installer for your platform, enter the invitation code and let the installer complete installation, I encourage you to select the “Install Player + SDK + Samples” option since it contains a fundamental component (a.k.a. The Player)

    image
    If everything goes well, you should now have a new element in your tray area (on Windows Platform)

    image

    Right clicking the icon you’ll see all Gorilla Player’s options, I suggest you to have a look at Getting Started Walkthrough

    image:

    In order to see your XAML output you must install the Gorilla Player App in target emulator/simulator (in alternative using included Gorilla Player’s SDK, the player can be integrated directly in your app, see SDK page for more details) the player will try to connect with the host running on your machine

    image

    and once connection is completed (you have both automatic and manual setup options)  you’ll see the monkey smiling and ready to render your XAML

    image

    Let’s see some XAML then!

    While the player app is running, create a brand new Xamarin Forms app (or open an existing one…) and open/add a XAML page, you should see the preview live on the emulator/simulator, if not check Gorilla Player’s option under: Tools->Gorilla Player (in Visual Studio) if not connected select the Connect option and check Follow me option

    image

    Note: using Stick to this XAML will let you freeze the rendered XAML while working on another file.

    If Gorilla can’t render your XAML you’ll see an error message like this:

    image

    Otherwise you’ll get the final output, here’s a demo XAML fragment:

    <ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="GorillaTest.Views.MyView"> <ContentPage.Resources> <ResourceDictionary> <Style x:Key="MyLabelStyle" TargetType="Label"> <Setter Property="HorizontalOptions" Value="Center" /> <Setter Property="VerticalOptions" Value="CenterAndExpand" /> <Setter Property="FontSize" Value="20" /> </Style> </ResourceDictionary> </ContentPage.Resources> <StackLayout BackgroundColor="Teal"> <Image Source="icon.png" WidthRequest="100" HeightRequest="100" /> <Label Text="Gorilla Player Rocks!" Style="{StaticResource MyLabelStyle}" TextColor="White" /> </StackLayout> </ContentPage>

    image

    As you see the Player supports every XAML element including Images, Styles, Resources, etc it also support ContentViews (see here)

    But what about design time data? : If you have a ListView I presume you want to see how it renders at runtime right? luckily Gorilla Player has a great support for design time data too, with several options (see here) probably the quickest one is to use add a json file with sample data to your project.

    Let’s take this XAML as example (taken from Gorilla’s demo MyCoolCompanyApp)

    <ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="MyCoolCompanyApp.MyPeople" xmlns:common="clr-namespace:UXDivers.Artina.Player;assembly=UXDivers.Artina.Player.Common" BackgroundColor="#455a64" xmlns:local="clr-namespace:MyCoolCompanyApp;assembly=MyCoolCompanyApp"> <ContentPage.Content> <Grid> <Image Opacity="0.5" x:Name="img" Source="bridge_bg.png" Scale="1.5" Aspect="AspectFill"/> <StackLayout Padding="10,30,20,0"> <ListView ItemsSource="{Binding .}" SeparatorVisibility="None" BackgroundColor="Transparent" SeparatorColor="#DFDFDF" HasUnevenRows="false" RowHeight="120"> <ListView.ItemTemplate> <DataTemplate> <ViewCell> <local:MyPeopleTemplate /> </ViewCell> </DataTemplate> </ListView.ItemTemplate> </ListView> </StackLayout> </Grid> </ContentPage.Content> </ContentPage>

    The output rendered by Gorilla Player is:

    image

    Awesome! but since we are at design time, were do the ListView data come from? If you look at PCL project you’ll see that it includes a SampleData.json file

    image

    with this content:

    { "MyPeopleTemplate.xaml": { "Name": "John Silverstain", "City": "MELBOURNE", "Department": "Marketing", "Color": "Red", "Age": 29, "Followers": 243, "Photo": "friend_thumbnail_27.jpg" }, "MyPeople.xaml": [ { "Name": "John Silverstain", "City": "MELBOURNE", "Department":"Marketing", "Color":"Red", "Age":29, "Followers":243, "Photo":"friend_thumbnail_27.jpg" }, { "Name": "Pam Tailor", "City": "SIDNEY", "Department":"Design", "Age":32, "Followers":24, "Photo":"friend_thumbnail_75.jpg" }, { "Name": "Casy Niman", "City": "HOBART", "Department":"Accounts", "Age":58, "Followers":267, "Photo":"friend_thumbnail_93.jpg" }, { "Name": "Gorge Tach", "City": "NEWCASTLE", "Department":"Design", "Age":29, "Followers":127, "Photo":"friend_thumbnail_55.jpg" }, { "Name": "Cristina Maciel", "City": "HOBART", "Department":"Mobile Dev.", "Age":32, "Followers":80, "Photo":"friend_thumbnail_31.jpg" }, { "Name": "Simon Deuva", "City": "MELBOURNE", "Department":"Media", "Age":58, "Followers":420, "Photo":"friend_thumbnail_34.jpg" } ] }

    As you see, the file contains a set of sample data, in json format, that will be associated to each page (MyPeopleTemplate.xaml and MyPeople.xaml in this case) ideally simulating the same data that the associated ViewModel will provide at runtime. in the docs you’ll find alternative design time solutions like using a Json data class or a Plain object.

    While in beta, the product is already very stable and a total life saver if you do Xamarin Forms development so I encourage you to give it a try and help the team fixing all issues so that we can get an official v 1.0 soon.

    Issues can be filed here.

    Happy Gorilla rendering! Smile

    Use IDEA IDE for Android UI design with Visual Studio and Xamarin

    While Xamarin did a monster job integrating Android and iOS designers in both Visual Studio and Xamarin Studio as soon as your project becomes larger you’ll soon hit their limitations, that why many pro developers end up using native designers for UI design. This post is about how to use IntelliJ IDEA based IDEs for Android UI design together with Visual Studio, following the same approach we use with Blend for Windows development.

    Step 1: install your favorite IDE: Android Studio or IntelliJ IDEA (they’re practically the same since Android Studio is based on IntelliJ IDEA)

    Step 2: Install XamarIdea extension for Visual Studio, this extension, recently updated for Visual Studio 2015, will make integration between the two IDEs a lot faster, thanks to Egor Bogatov (@EgorBo) for sharing.
    No idea if something similar exists for Xamarin Studio (sorry, I’m not an pro Xamarin Studio user)

    Step 3: Create a new blank Android app using Visual Studio

    image

    and wait until initial project skeleton creation process ends.

    Step 4: Right-click the Main.axml file inside Resources\layout folder and you should see a new option: Open in IDEA/Android Studio

    image

    click it and you’ll get an initial configuration dialog that should point to IDEA/Android Studio path, if not select it manually, together with other plugin options

    image

    click Ok, and you’ll see a warning dialog saying that your project needs some modifications:

    image

    These modifications are necessary since Android layout files use a different extension (.xml) and project structure is slightly different than Xamarin Android apps, just say yes; unfortunately these changes will prevent you to use the integrated Xamarin Android designer further unless you rename the layout file back to .axml. Click Yes, and you’ll get a final dialog reminding you to recompile your project inside Android IDE and that plugin options are available under Visual Studio’s Tools menu:

    image

    Step 5: Switch to IDEA IDE and, for sure, rebuild the project

    image

    On the left you’ll see the project structure, under app node expand the Resources folder and you’ll see the familiar Android folder structure together with your renamed main.xml file.

    image

    Double click it to open the designer.

    image

    I won’t go into design detail since there are lots of demo tutorials on JetBrains’s site, just want you to see some of the plus of IDEA and why it is more productive than Visual Studio’s integrated editor/designer.

    Step 5: Design

    -Select and delete the autogenerated button from design surface.
    -Let’s change root LinearLayout to a RelativeLayout using the Component tree window in the upper right corner.

    image

    -Drag a Plain Text to design surface until top tooltip shows CenterVertical/CenterHorizontal

    image

    -Set layout_width to match_parent using Properties window (hint: if you need to search for a property just start typing to select matching properties Smile)

    -Let use xml editor to add left and right margins: Switch to text, select the EditText and start typing: ma, YES! full intellisense to the rescue!

    image

    -Do you want to create a style that you can reuse with others EditTexts? just right click the edit text and use Refactor –> Extract Style menu

    image

    Select the properties you want to export (this dialog will look familiar to Reshaper users) and click OK

    image

    the layout xml has been changed to:

    <EditText android:id="@+id/editText" style="@style/MyEditTextStyle"/>

    and a styles.xml file has been created for you under values folder:

    image

    Of course you can edit the styles.xml file with full intellisense / editors support

    image

    Step 6-Back to Visual Studio

    Save the project and switch back to Visual Studio, your main.xml file is automatically updated, but unfortunately the new files that have been added to the project, like styles.xml in our demo, must be added manually to the project.

    Add styles.xml under values folder, compile and continue developing your app using Visual Studio.

    Closing:

    I’ve just scratched the surface of IDEA design productivity features, I encourage you to give it a try, I’m sure you’ll love it.

    Have fun exploring!

    PS: Did I tell you that IDEA renders AppCompat’s widgets instead of a boring dark gray box? Winking smile

    Fixing SDWebImage issue on Xamarin.iOS

    Loading an image into an ImageView control using Xamarin.iOS is a straightforward process:

    • Add a ImageView to a ViewController and give it a name (e.g: MyImage)
    • Add an image to Resources folder (e.g Users.png) and be sure that related Build Action is set to BundleResource.
    • And add this code:
          public override async void ViewDidLoad() { base.ViewDidLoad(); MyImage.Image=UIImage.FromBundle("Users.png"); }

        And you’re done, as alternative you can also use UIImage.FromFile, in this case the call is asynchronous and doesn’t use caching, while former is synchronous and does caching.

        Ok, but what if I want to show an image from a web url? things gets more complicated since you have to do the entire downloading process manually, something like:

        public async Task<UIImage> FromUrl(string imageUrl) { var httpClient = new HttpClient(); var contents = await httpClient.GetByteArrayAsync(imageUrl); return UIImage.LoadFromData(NSData.FromArray(contents)); }

        And use it this way:

        MyImage.Image = await this.FromUrl("http://thechromenews.com/wp-content/uploads/2015/11/Apple-Logo-4.png");

        Cool, but what if I want to use caching, show a placeholder or fire some code when downloading completes? well, that’s more code to write and since this is a quite common task you’ll be happy to know that there’s a component that does that for you.

        Look for SDWebImage on Xamarin Component Store and add it to your project:

        image

        Doing that adds to ImageView control a SetImage extension method that accepts a Uri and does all the work for you, usage is very easy, just write something like:

        NSUrl url=new NSUrl("http://thechromenews.com/wp-content/uploads/2015/11/Apple-Logo-4.png"); MyImage.SetImage(url,null,null);

        If you try this code you’ll discover that it doesn’t work, why? is the component buggy? well no, if you try it on older iOS versions it works fine.

        Also this quite common alternative raises an exception on iOS 9.x

        private UIImage FromUri(string uri) { using (var url = new NSUrl(uri)) using (var data = NSData.FromUrl(url)) return UIImage.LoadFromData(data); }

        Ok, so what is the problem? well Apple decided that starting from iOS 9.0 all communications must use ATS (app transport security) and if you want to change this behavior you have to add an entry into info.plist file.

        This blog post describes ATS in detail and I encourage you to read it: http://ste.vn/2015/06/10/configuring-app-transport-security-ios-9-osx-10-11/

        To cut a long story short: Add this entry to your info.plist

        <key>NSAppTransportSecurity</key> <dict> <key>NSAllowsArbitraryLoads</key> <true/> </dict>

        And everything will work as expected. Smile

        HTH

        Older Posts »