Develop Reference

Failed to open directory Xamarin Forms

I have recently created a HelloWorld project with Xamarin Forms to develop a mobile app. But, I don't know what happen but I cannot launch the app with Android Device Manager or even my own phone, not even the first time. This is the error:
I am using android version 10.0 to compile and for the device manager the version 10.0 also. At the manifest I also have version 10.0 for Android minimum version required and Android target version. I guess the version is not the problem, but I don't know what could be because, I haven't programmed anything yet. So I don't understand why the error is "The system cannot fint the specified file". I check the access route with File Explorer of Windows and there is the directory.

Unbelievable. My windows 10 user has an accent mark on the name: Adrián. But the problem was with the path of the project, because I change the name to: Adrian, but the path was still having the accent mark: C:\Users\Adrián. So that is very probably the problem. I know I could change the username from the path, but I think it is a bit difficult than to create a new user, besides, I don't want more problems with another programs installed. I created a new windows user, obviously, without any weird character and then I could work with Xamarin Forms. I think you learn a new thing every day.

Had the same issue when my project was called Städteam1. I created a new solution and project named Stadteam1 and it works right away. So I guess avoid using any letters that aren't part of standard English in any of the folder or filenames.

Android device manager: Cannot change ObservableCollection during a CollectionChanged event

I'll start off by saying I'm doing this on a school computer (high school), I have full permission to do this and my teacher enters her admin credentials when needed but I can't figure out why it's throwing this error. I followed Microsoft's guide on installing the android emulator for Xamarin in Visual Studio and should have all the prerequisites installed correctly but when I attempt to create a device in android device manager it gets stuck on creating, and when I close it and visit the log I get this at the error:
[20-03-10 19:17:23.90] [SaveInner] CreateAvdAsync failure: System.InvalidOperationException: Cannot change ObservableCollection during a CollectionChanged event.
at System.Collections.ObjectModel.ObservableCollection`1.CheckReentrancy()
at System.Collections.ObjectModel.ObservableCollection`1.InsertItem(Int32 index, T item)
at Xamarin.DeviceManager.Common.ViewModels.MainWindowViewModel.<>c__DisplayClass9_0.<AvdManager_AvdAdded>b__0()
at System.Windows.Threading.DispatcherOperation.InvokeDelegateCore()
at System.Windows.Threading.DispatcherOperation.InvokeImpl()
Any ideas as to how to fix this? I'm unsure what I should do but am very eager to get this completely installed.
Edit: Came back to the same class 2 days later and it fixed itself. Not sure what was wrong.

I had the same issue. I was able to work around this problem by first starting the ADM from Visual Studio, then selecting "+ New" in the ADM, rather than from the Visual Studio menu item "Create Android Emulator...".
In my case, it may be related to the need to download a new image for running a device type for Android TV and maybe for any case where a new image must be downloaded.
Microsoft: this is a bug that should be resolved.

Cannot create new Android Application Project

So, I'm trying to start a new Android project, but I can't get through the first step.
Everything looks good to me, but the 'Next' button just won't light up for me.
Of note, the 'Theme' menu starts off on 'Holo Light with Dark Action Bar' and a red X next to it. This will stay red after changing it (even to 'none') unless it's the first thing I do when I get to this form. Seems weird. Anyone have any idea what's going on here?
There is nothing listed in 'Compile With', but I do have SDK Platforms installed and up to date.

I ended up trashing my adt directory and re-downloading the bundle from Google in order to get it to properly "update" to 21.1.

The problem is that the any sdk platform is not installed on your computer thats why the compile with field is empty and next button is not shown so first installed any one of the SDK platform.
Launch Android SDK manager and installed any SDK platform.

absolute beginner opening my first app in eclipse, what file to open

Hi I know this is a real silly question but I am following the instructions to create an app for android. Im currently here... http://developer.android.com/training/basics/firstapp/running-app.html
Ive already set up my first app as per instuctions, Ive enabled debugging on my phone, but now Im unsure what file to open in eclipse before clicking "Run as"-> "Android Application".
Any help would be great thanks

You don't need to open or close any file(s) for running the app, just make sure the project you want to run is selected in the project explorer on the left side. But I assume that you only have one project at this time so everything should work as expected
EDIT
If you want to test your app on a real device from Eclipse, make sure the required device drivers are installed. You can go to Run -> Run Configurations -> target and check if your device is listed. In case that is not, some drivers are missing.

Select your MainActivity and click run. It will prompt a box where you can choose weather you want to run in device or in emulator.
To run in real device See my post. It will help you.

xml error in Eclipse after updating Android SDK Tools

This is the error I'm getting in my layout XML files:
error!
NotFoundException: null
Exception details are logged in Window > Show View > Error Log
The following classes could not be found:
- TextView (Change to android.widget.TextView, Fix Build Path, Edit XML)
This happened after updating my SDK tools in Eclipse. However, I can still compile my code, I just can't see the graphical part of my layout.
Recently, I also added the RootTools library, could that also be the cause?
Thank you!

I had the same problem. And it turned out to be a very strange thing.
In my strings.xml file I had a line
<string name="email_seperator_char">\#</string>
And this was causing the problem. Even if I use the escape character for # sign preview was not working after SDK update.
SOLUTION:
I just added a space in front of it and voila, it worked.
<string name="email_seperator_char"> \#</string>
I know it is strange and it may not be acceptable for some apps to have an space infront of it. But that was ok for my app. Hope this helps.
And in design mode, in graphical layout, you have a new icon, (android icon), click and select 8 minimum.

I'm not sure it helps in your case, but I found out what was the problem with mine. To support older Android devices, I lowered my project build target to API level 7 (Android 2.1) from the previous value of API Level 8 (Android 2.2).
There might be an issue with the 2.1 layout renderer, it kept crashing on my TextView's property android:textAppearance="?android:attr/textAppearanceMedium". Even when I removed it, rendering was working but had a strange appearance (grey background, tiny black text). Switching the API level back fixed the layout editor straight away.
To change it, go to your project properties, select Android on the right, then tick the box next to your desired API level under Project Build Target.

I ve got the same issue just a minutes ago, try to lower the API level, press the andorid green icon in the layout editor screen and on the dropdown menu select API 7. I think it would be work out.

I've been having similar issues. After reading a number of these posts, I've found that there is probably a bug in the layout renderer for Android 4.0.3. An error message is listed (ROOT
Exception details are logged in Window > Show View > Error Log) even when all parts of the project are set to Android 4.0.3 and SDK 15.
If I set the layout renderer to Android 2.2 and leave everything else set to Android 4.0.3, SDK 15, then it all appears to work just fine.
I hope this is useful.

there is something wrong in your TextView
one time I wrote this which cause the problem
android:textAppearance="#android:attr/textAppearanceLarge"
the Eclipse can`t tell that is wrong but the design view crashes,when I realized that,I change # to ?
android:textAppearance="?android:attr/textAppearanceLarge"
then all comes to normal