Question

I am able to invoke the barcode scanner via intents, but when I try to capture the values returned by the scan based on this, I get the following errors when trying to build the solution.

• Android.Content.Intent’ does not contain a definition for ‘getStringExtras’ and no extension method ‘getStringExtras’ accepting a first argument of type ‘Android.Content.Intent’ could be found (are you missing a using directive or an assembly reference?)
• The name ‘RESULT_CANCELED’ does not exist in the current context
• The name ‘RESULT_OK’ does not exist in the current context

Here is my code for both invoking the scanner and trying to return results.
Click event is in onCreate. onActivityResult is a method in the same.cs, same class, same namespace as the scan.Click event.

    Button scan = (Button)FindViewById(Resource.Id.scan);
        scan.Click += (o, e) =>
        {
            Intent intent = new Intent("com.google.zxing.client.android.SCAN");
            intent.SetPackage("com.google.zxing.client.android");
            intent.PutExtra("com.google.zxing.client.android.SCAN.SCAN_MODE", "QR_CODE_MODE");
            StartActivityForResult(intent, 0);
        };

    public void onActivityResult(int requestCode, int resultCode, Intent intent)
    {
        if (requestCode == 0)
        {
            if (resultCode == RESULT_OK)
            {
                String contents = intent.getStringExtra("SCAN_RESULT");
                String format = intent.getStringExtra("SCAN_RESULT_FORMAT");
            }
            else if (resultCode == RESULT_CANCELED)
            {

            }
        }
    }

Answer 1

The problem here is that your onActivityResult method has not been properly translated from Java to Mono for Android.

It should look more like:

protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
    if (requestCode == 0)
    {
        if (resultCode == Result.Ok)
        {
            String contents = data.GetStringExtra("SCAN_RESULT");
            String format = data.GetStringExtra("SCAN_RESULT_FORMAT");
        }
        else if (resultCode == Result.Canceled)
        {

        }
    }
}

The highlights of the translation are:

1. Correct signature (and override) for OnActivityResult
2. Use the Result enumeration
3. The getStringExtra method in Java is GetStringExtra in C#