I'm getting a string by an intent in MainActivity.cs of the Android-project. I'm using a Sharedproject. The string is a barcode which is updated by the intent if a barcode is scanned. I want to show the barcode-string in a Entry or Label of the .xaml-file via data binding.
The problem is that the barcode only updates in the Entry and in the Label aswell, if I manually clicked the entry. How can I make sure the Label or the Entry is updated when the string from the intent is changing?
Code:
MainActivity.cs:
public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
{
public static MainActivity Instance;
myBroadcastReceiver receiver;
BarcodeModel barcodeModel;
protected override void OnCreate(Bundle savedInstanceState)
{
TabLayoutResource = Resource.Layout.Tabbar;
ToolbarResource = Resource.Layout.Toolbar;
base.OnCreate(savedInstanceState);
// Barcode
MainActivity.Instance = this;
receiver = new myBroadcastReceiver();
barcodeModel = new BarcodeModel();
Xamarin.Essentials.Platform.Init(this, savedInstanceState);
global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
LoadApplication(new App());
}
public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
{
Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);
base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
}
protected override void OnResume()
{
base.OnResume();
// Register the broadcast receiver dynamically
RegisterReceiver(receiver, new IntentFilter(Resources.GetString(Resource.String.activity_intent_filter_action)));
}
protected override void OnPause()
{
base.OnPause();
UnregisterReceiver(receiver);
}
public void DisplayResult(Intent intent)
{
// Output the scanned barcode to ViewModel
barcodeModel.decodedData = intent.GetStringExtra(Resources.GetString(Resource.String.datawedge_intent_key_data));
}
}
// Broadcast receiver to receive scanned data
[BroadcastReceiver(Enabled = true)]
public class myBroadcastReceiver : BroadcastReceiver
{
public override void OnReceive(Context context, Intent intent)
{
String action = intent.Action;
if (action.Equals(MainActivity.Instance.Resources.GetString(Resource.String.activity_intent_filter_action)))
{
// A barcode has been scanned
MainActivity.Instance.RunOnUiThread(() => MainActivity.Instance.DisplayResult(intent));
}
}
}
}
ViewModel:
public class BarcodeModel : INotifyPropertyChanged
{
private string data;
public event PropertyChangedEventHandler PropertyChanged;
public BarcodeModel()
{
}
protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public string decodedData
{
get { return data; }
set { data = value; OnPropertyChanged(); }
}
ContentPage:
<Label Text="{Binding decodedData}"
HorizontalOptions="StartAndExpand"
VerticalOptions="Center"
TextColor="Accent"/>
<Entry Keyboard="Text"
Placeholder="No Object selected"
VerticalOptions="Center"
HorizontalOptions="StartAndExpand"
x:Name="eintrag"
Text="{Binding decodedData}"/>
BindingContext in .xaml.cs: BindingContext = new BarcodeModel();
The model you changing in the Android project is not the same one as your bindingContext, so it doesn't work.
Solution:
Use messagingCenter to send the model from your Android project to your shared project and update the model there:
In the Android project, send the message everytime you scanned a barode:
public void DisplayResult(Intent intent)
{
// Output the scanned barcode to ViewModel
barcodeModel.decodedData = intent.GetStringExtra(Resources.GetString(Resource.String.datawedge_intent_key_data));
barcodeModel.decodedData = "test";
MessagingCenter.Send<object, BarcodeModel>(new object(), "barCodeScanned", barcodeModel);
}
In the shared project, subscribe to that message and update the model:
public partial class MainPage : ContentPage
{
BarcodeModel barCodeModel;
public MainPage()
{
InitializeComponent();
barCodeModel = new BarcodeModel();
barCodeModel.decodedData = "defaultValue";
this.BindingContext = barCodeModel;
MessagingCenter.Subscribe<object, BarcodeModel>(new object(), "barCodeScanned", (sender, arg) =>
{
BarcodeModel tempbarCodeModel = arg as BarcodeModel;
barCodeModel.decodedData = tempbarCodeModel.decodedData;
});
}
}
I uploaded my test project here and feel free to ask me any question.