I have implemented a Xamarin.Forms App focused on Android which should scan barcodes on different pages. (Followed this description ‚https://blog.xamarin.com/barcode-scanning-made-easy-with-zxing-net-for-xamarin-forms/‘ (Thanks! James Montemagno))
I initialize the scanner control (defined in xaml) in the constructor of the codebehind class:
<ContentPage.Content> <AbsoluteLayout> <AbsoluteLayout.Children> <z:ZXingScannerView x:Name="zScanner" AbsoluteLayout.LayoutBounds="0.5,0.5,1,1" AbsoluteLayout.LayoutFlags="All" HorizontalOptions="FillAndExpand" IsScanning="True" OnScanResult="ZScanner_OnOnScanResult" VerticalOptions="FillAndExpand" /> <z:ZXingDefaultOverlay x:Name="zOverlay" ShowFlashButton="False" AbsoluteLayout.LayoutBounds="0.5,0.5,1,1" AbsoluteLayout.LayoutFlags="All" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" /> ….
For embedding into the own page layout I use the ZXingScannerView-Control.
public TicketScan()
{
InitializeComponent();
// https://components.xamarin.com/gettingstarted/zxing.net.mobile.forms
// https://blog.xamarin.com/barcode-scanning-made-easy-with-zxing-net-for-xamarin-forms/
var zXingOptions = new MobileBarcodeScanningOptions()
{
DelayBetweenContinuousScans = 1000, // msec
UseFrontCameraIfAvailable = false,
PossibleFormats = new List<BarcodeFormat>(new[]
{
BarcodeFormat.EAN_8,
BarcodeFormat.EAN_13,
BarcodeFormat.CODE_128,
BarcodeFormat.QR_CODE
}),
TryHarder = true //Gets or sets a flag which cause a deeper look into the bitmap.
};
zScanner.Options = zXingOptions;
// https://github.com/Redth/ZXing.Net.Mobile/issues/427
zOverlay.BindingContext = zOverlay;
fab.Clicked = OnClick_AddFabButton;
}
The first scan page works as expected.
When I leave the page I pause the scanner here:
protected override void OnDisappearing()
{
base.OnDisappearing();
zScanner.IsScanning = false;
}
(Otherwise the scanner will scan on each further page even if no scanner control is on the page (?!) And the camera works all the time.)
On a second page I try to initialize the scanner on the same way and set IsScanning = true.
protected override void OnAppearing()
{
zScanner.IsScanning = true;
base.OnAppearing();
}
But on this second page I see only a frozen camera picture (maybe the last shot from the first usage)
How can I use the ZXing scanner component for Xamarin.Forms on different pages without turned on camera for the whole camera usage?
thx
Show working example please. Just be sure to meet MVVM. No handlers, only commands and bindings.