Develop Reference

Open a new Activity Xamarin restarts my application

Using Xamarin.Forms I have my main application running Forms. But I have Mapbox Navigation which is Xamarin.Android that I am using, I ma trying to open the navigation from Forms so I am doing the following:
FORMS CODE
public interface INavigation
{
void StartNativeIntentOrActivity();
}
The void above is then called through DependencyService in Forms
XAMARIN.ANDROID Code
using Android.Content;
using MapleLMCApp.Classes;
using MapleLMCApp.Droid;
using MapleLMCApp.Droid.NavigationUI;
using System;
using Xamarin.Forms;
[assembly: Xamarin.Forms.Dependency(typeof(NavInitializer))]
namespace MapleLMCApp.Droid
{
class NavInitializer : INavigation
{
public void StartNativeIntentOrActivity()
{
//Begin Navigation Form
try
{
var intent = new Intent(Android.App.Application.Context, typeof(EmbeddedNavigationActivity));
intent.SetFlags(ActivityFlags.NewTask);
Android.App.Application.Context.StartActivity(intent);
}
catch (Exception ex)
{
LogFileCreation lg = new LogFileCreation();
lg.CreateLog(ex.ToString(), "NAV Initilizer Error");
}
}
}
}
The above works perfectly in the emulator for API <28 and API >28
The second I try the code above on my Huawei P30 Pro the second the new activity appears the App restarts itself or auto closes...
Any ideas on what might be causing this? some security setting or Manifest property that needs to be set or something along those lines?

There is a fetchRoute() event that starts as the new activity opens. This has an error on the P30 Pro due to culture variants on double parse...It was attempting to parse 27,33 as a double and needed to be 27.33
The form now opens without any issues

'Activity1.OnNewIntent(Content.Intent)': no suitable method found to override

I implemented App Center push notifications in my MonoGame Android project and everything seems to work, because I receive the notifications on my Android device that I have sent from my App Center account. But in this tutorial, they mention that you should add this code to your Acitivity class if your LaunchMode is SingleInstance, but the code isn't working. I get two error messages.
Tutorial: see Intercept push notifications, Additional setup
Is this code really necessary when you have an Android project without a splashscreen? Would it make a difference if I add a splashscreen to my project?
What is this code doing and how could I use it in a MonoGame Android project if it would be necessary?
protected override void OnNewIntent(Android.Content.Intent intent)
{
base.OnNewIntent(intent);
Push.CheckLaunchedFromNotification(this, intent);
}
The type or namespace name 'Content' does not exist in the namespace
(are you missing an assembly reference?)
'Activity1.OnNewIntent(Content.Intent)': no suitable method found to
override (CS0115)
using Android.App;
using Android.Content.PM;
using Android.OS;
using Android.Views;
using Microsoft.AppCenter;
using Microsoft.AppCenter.Analytics;
using Microsoft.AppCenter.Crashes;
using Microsoft.AppCenter.Push;
namespace Newapp.Android
{
[Activity(Label = "Newapp.Android"
, MainLauncher = true
, Icon = "#drawable/icon"
, Theme = "#style/Theme.Splash"
, AlwaysRetainTaskState = true
, LaunchMode = LaunchMode.SingleInstance
, ScreenOrientation = ScreenOrientation.FullUser
, ConfigurationChanges = ConfigChanges.Orientation | ConfigChanges.Keyboard | ConfigChanges.KeyboardHidden | ConfigChanges.ScreenSize)]
public class Activity1 : Microsoft.Xna.Framework.AndroidGameActivity
{
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
if (!AppCenter.Configured)
{
Push.PushNotificationReceived += (sender, e) =>
{
// Add the notification message and title to the message
var summary = $"Push notification received:" +
$"\n\tNotification title: {e.Title}" +
$"\n\tMessage: {e.Message}";
// If there is custom data associated with the notification,
// print the entries
if (e.CustomData != null)
{
summary += "\n\tCustom data:\n";
foreach (var key in e.CustomData.Keys)
{
summary += $"\t\t{key} : {e.CustomData[key]}\n";
}
}
// Send the notification summary to debug output
System.Diagnostics.Debug.WriteLine(summary);
};
}
AppCenter.Start("{Your App Secret}", typeof(Analytics), typeof(Crashes), typeof(Push));
var g = new Game1();
SetContentView((View)g.Services.GetService(typeof(View)));
g.Run();
}
protected override void OnNewIntent(Android.Content.Intent intent)
{
base.OnNewIntent(intent);
Push.CheckLaunchedFromNotification(this, intent);
}
}
}

You're seeing the compiler error because the namespace in your project ends with Android so it's trying to find NewApp.Android.Content.Intent not Android.Content.Intent. You can fix the error by changing your namespace to not end with Android, or you can use global:: when referencing the global Android namespace:
protected override void OnNewIntent(global::Android.Content.Intent intent)
{
base.OnNewIntent(intent);
Push.CheckLaunchedFromNotification(this, intent);
}

External Storage for Xamarin on visual studio

I'm currently working on Xamarin using Visual Studio to try and build and create an app that reads a bar code and saves the integer it gets from it in a .txt file. I have managed to make the code both read the bar code and save it however i was wondering if there is a way i could save it in a more accessible file, as right now its saving in internal storage and the only way i can reach it is through adb console.
Is there a way for me to perhaps save the integers on a .txt file on my laptop? I'm currently testing it on my physical phone and its connected to my laptop via a USB cable.
Here is my code:
using Android.App;
using Android.Widget;
using Android.OS;
using System;
using Android.Content;
using ZXing.Mobile;
using System.IO;
namespace Scanner
{
[Activity(Label = "Scanner", MainLauncher = true, Icon = "#drawable/icon")]
public class MainActivity : Activity
{
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
// Set our view from the "main" layout resource
SetContentView (Resource.Layout.Main);
Button buttonScan = FindViewById<Button>(Resource.Id.buttonScan);
TextView scanText = FindViewById<TextView>(Resource.Id.scanText);
var documents = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
var BarcodesFile = Path.Combine(documents, "Barcodes.txt");
buttonScan.Click += async (sender, e) =>
{
MobileBarcodeScanner.Initialize(Application);
var scanner = new ZXing.Mobile.MobileBarcodeScanner();
var result = await scanner.Scan();
if (result != null)
File.AppendAllText(BarcodesFile, "Scanned Barcode: " + result.Text);
scanText.Text = File.ReadAllText(BarcodesFile);
};
}
}
}

So if api is an idea. I have not used any api yet for those requirements but when I think about txt I immediately thought about pastebin.
https://pastebin.com/api enter code here
That might be usefull to check out. Goodluck!;)

Simple database app won't retrieve value

I'm in the process of learning SQLite and wanted to make my own very simple proof of concept app where I simply store and retrieve a value from a database. I use the NuGet package SQLite-net by Krueger.
My problem is everything seems to work except it doesn't retrieve the value, it crashes at "string a = db.GetAsync(0).Result.storedvalue.ToString();", only saying multiple errors ocurred. Is there something wrong with this line, or perhaps is there something wrong with how I store values in the first place?
Here is the complete C# code for the app:
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using SQLite;
using System.IO;
using System.Reflection;
namespace SimpleDatabaseTest
{
[Activity(Label = "SimpleDatabaseTest", MainLauncher = true, Icon = "#drawable/icon")]
public class MainActivity : Activity
{
SQLiteConnection db;
int i;
int k;
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
// set our view from the "main" layout resource
SetContentView(Resource.Layout.Main);
// create database
db = new SQLiteConnection(Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal),"test.sqlite"));
db.CreateTable<somevalues>();
// set up enter_value and show_value
EditText enter_value = FindViewById<EditText>(Resource.Id.enter_value);
TextView show_value = FindViewById<TextView>(Resource.Id.show_value);
// store value button
Button store_value = FindViewById<Button>(Resource.Id.store_value);
store_value.Click += delegate
{
somevalues newTable = new somevalues();
i = int.Parse(enter_value.Text);
newTable.storedvalue = i;
k = newTable.id;
db.Insert(newTable);
Toast toast = Toast.MakeText(ApplicationContext, k.ToString(), ToastLength.Long); //enter_value.Text
toast.Show();
};
// retrieve value button
Button retrieve_value = FindViewById<Button>(Resource.Id.retrieve_value);
retrieve_value.Click += delegate
{
somevalues some = db.Get<somevalues>("id");
//string a = some.storedvalue.ToString();
//Toast toast = Toast.MakeText(ApplicationContext, a, ToastLength.Long);
//toast.Show();
//show_value.Text = a;
};
}
}
}

Xamarin/Android - Issue reading locally stored photo from camera - no read access

I'm trying to create a simple test app to take photos in Android, using Xamarin. When I get this app working (or so I hope), i'll use the code in a real app that I'm working on. I'm using the following recipe from Xamarin as my basis:
http://docs.xamarin.com/recipes/android/other_ux/camera_intent/take_a_picture_and_save_using_camera_app/
The major difference is that I need to store images locally, and not on the SD card. I'm able to successfully take a picture (with the Android simulator). I can see the file in the file structure using ADB and can successfully copy and open the file on my PC. However, I'm unsuccessfull in accessing the file in the app, probably due to user rights.
Please note that I was successfull in creating my own .txt files, and reading them back using either System.IO and Java.IO.
Please review the following code. My app crashes when using "System.IO.File.ReadAllText" and gives me "Access to the path "/data/data/CameraAppDemo.CameraAppDemo/files/photo.jpg" is denied.". And whatever I try (absolute, relative paths, uri's), objBitmap is always null.
ADB says that "photo.jpg" has -rwxrwx--- rights, and though I'm not entirely sure, I think that should be more than sufficient
On the other hand, maybe the intent still has a lock on "photo.jpg"? Or something else is going on...
And one final note, I'm using System.IO.File.ReadAllText just for testing purposes. I experimented with stream readers as well, but with the same result. Also, though I believe this step is unnecessary, I enabled "WriteExternalStore" in the Manifest
namespace CameraAppDemo
{
using System;
using System.Collections.Generic;
using Android.App;
using Android.Content;
using Android.Content.PM;
using Android.Graphics;
using Android.OS;
using Android.Provider;
using Android.Widget;
using Java.IO;
using Environment = Android.OS.Environment;
using Uri = Android.Net.Uri;
[Activity(Label = "Camera App Demo", MainLauncher = true)]
public class MainActivity : Activity
{
private File _file;
private string _basePath;
private ImageView _imageView;
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
base.OnActivityResult(requestCode, resultCode, data);
var objBitmap = BitmapFactory.DecodeFile(_file.AbsolutePath) ;
Console.WriteLine ("objBitmap = null : " + (objBitmap == null).ToString ());
var strOutput = System.IO.File.ReadAllText (FileManager.BasePath + "/photo.jpg");
Console.WriteLine (strOutput);
}
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
SetContentView(Resource.Layout.Main);
FileManager.SetupFolderStructure();
if (IsThereAnAppToTakePictures())
{
Button button = FindViewById<Button>(Resource.Id.myButton);
_imageView = FindViewById<ImageView>(Resource.Id.imageView1);
button.Click += TakeAPicture;
}
}
private bool IsThereAnAppToTakePictures()
{
Intent intent = new Intent(MediaStore.ActionImageCapture);
IList<ResolveInfo> availableActivities = PackageManager.QueryIntentActivities(intent, PackageInfoFlags.MatchDefaultOnly);
return availableActivities != null && availableActivities.Count > 0;
}
private void TakeAPicture(object sender, EventArgs eventArgs)
{
System.IO.Directory.Delete (FileManager.BasePath, true);
_basePath = FileManager.BasePath;
_file = new Java.IO.File (_basePath, "photo.jpg");
Intent intent = new Intent(MediaStore.ActionImageCapture);
intent.PutExtra(MediaStore.ExtraOutput, Uri.FromFile(_file));
StartActivityForResult(intent, 0);
}
}
}
//Part of the FileManager class:
using System;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using Android.Graphics;
namespace CameraAppDemo
{
public class FileManager
{
public static string BasePath {
get {
var libraryPath = Environment.GetFolderPath (Environment.SpecialFolder.Personal);
if (Directory.Exists (libraryPath) == false) {
Directory.CreateDirectory (libraryPath);
}
return libraryPath;
}
}
}
}
==== Edit ====
It seems that I'm simply not able to read the file. As an ex-webdeveloper, I'm fairly new to programming for mobile, let alone the combo of C# and Java and I'm still learning a lot.
Anyway, I added the following lines:
Console.WriteLine("Setting file :" + _file.SetReadable (true));
Console.WriteLine("Can read :" + _file.CanRead());
Both cases return False. I can't read the file, and I am unable to give read access.
So, any ideas? Is this by design? Can I tell the Intent for taking images to give me read access, or is there another workaround?
If everything fails, I'm hoping to workaround the problem by saving to the SD card first and then copying the file to the local filesystem. But that's something I rather would not do; I can't guarantee that the end users have an SD card, and the pictures should not be deleted by accident.