I am trying to implement ZXing Barcode scanner on my Andriod app built using Visual Studio. I am getting this error when I try to click the button to scan it:
System.NullReferenceException: Object reference not set to an instance of an object.
This is ScanActivity.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using ZXing.Mobile;
namespace Shopinator
{
[Activity(Label = "ScanActivity")]
public class ScanActivity : Activity
{
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
SetContentView(Resource.Layout.ScanLayout);
Button scanCodeSrc = FindViewById<Button>(Resource.Id.scanCode);
Button goBackSrc = FindViewById<Button>(Resource.Id.goBackBtn);
scanCodeSrc.Click += scanCodeSrc_Click;
goBackSrc.Click += goBackSrc_Click;
}
public async void scanCodeSrc_Click(object sender, EventArgs e)
{
MobileBarcodeScanner.Initialize(Application);
MobileBarcodeScanner scanner = new MobileBarcodeScanner();
var result = await scanner.Scan();
if (result != null)
Console.WriteLine("Scanned Barcode: " + result.Text);
}
private void goBackSrc_Click(object sender, EventArgs e)
{
StartActivity(typeof(MainMenuActivity));
}
}
}
This is ScanLayout.axml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#2579BF"
android:orientation="vertical">
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:layout_margin="10dp"
android:orientation="vertical">
<TextView
android:text="Welcome to the Product Scan page, please press the scan button and proceed with scanning the barcode/qrcode."
android:textAppearance="?android:attr/textAppearanceLarge"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/scanPageHelp" />
<Button
android:id="@+id/scanCode"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@id/password"
android:layout_marginTop="10dp"
android:background="#000000"
android:text="PRESS HERE TO SCAN"
android:textColor="@android:color/white" />
<Button
android:id="@+id/goBackBtn"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@id/password"
android:layout_marginTop="10dp"
android:background="#000000"
android:text="Go back to the Main Menu"
android:textColor="@android:color/white" />
</LinearLayout>
This is my first android app on xamarin.
Android Project in MainActivity.cs in OnCreate:
ZXing.Mobile.MobileBarcodeScanner.Initialize(Application);
If you just wire up from scratch your "MainPage" will not be in a navigation context and will die like this. Put your MainPage in a navigation context. Complete "simple" version of Zxing here - https://github.com/jhealy/xammutts/tree/master/ZXingPlaySLN/ZXingPlay .
public App()
{
InitializeComponent();
// jhealy: this MUST be a nav page, watch out
// MainPage = new ZXingPlay.MainPage();
MainPage = new NavigationPage(new ZXingPlay.MainPage());
}
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