Manage camera buffer lifetime and limit preview listeners

.gitignore

@@ -5,6 +5,7 @@ obj
 [Oo]bj
 [Dd]ebug*/
 [Rr]elease*/
+_ReSharper.Caches/
 
 *.unsuccessfulbuild
 *.pidb

Sample.NetAndroid/AndroidManifest.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.thetasoft.android_net_sample" android:versionCode="1" android:versionName="1.0" android:installLocation="auto">
+	<application android:allowBackup="true" android:icon="@mipmap/launcher" android:label="ZXing.Net.Mobile" android:supportsRtl="true"></application>
+	<uses-permission android:name="android.permission.INTERNET" />
+	<uses-permission android:name="android.permission.CAMERA" />
+	<uses-permission android:name="android.permission.FLASHLIGHT" />
+	<uses-permission android:name="android.permission.VIBRATE" />
+	<uses-sdk android:minSdkVersion="34" android:targetSdkVersion="34" />
+</manifest>

Sample.NetAndroid/FragmentActivity.cs

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+using System;
+using System.Collections.Generic;
+using ZXing.Mobile;
+using Android.OS;
+using Android.App;
+using Android.Widget;
+using Android.Content.PM;
+
+namespace Sample.NetAndroid;
+
+[Activity(Label = "ZXing.Net.Mobile", Theme = "@style/Theme.AppCompat.Light", ConfigurationChanges = ConfigChanges.Orientation | ConfigChanges.KeyboardHidden)]
+public class FragmentActivity : AndroidX.Fragment.App.FragmentActivity
+{
+	ZXingScannerFragment scanFragment;
+
+	protected override void OnCreate(Bundle savedInstanceState)
+	{
+		base.OnCreate(savedInstanceState);
+
+		SetContentView(Resource.Layout.FragmentActivity);
+	}
+
+	protected override void OnResume()
+	{
+		base.OnResume();
+
+
+		if (scanFragment == null)
+		{
+			scanFragment = new ZXingScannerFragment();
+
+			SupportFragmentManager.BeginTransaction()
+			   .Replace(Resource.Id.fragment_container, scanFragment)
+			   .Commit();
+		}
+
+		Scan();
+	}
+
+	public override void OnRequestPermissionsResult(int requestCode, string[] permissions, Permission[] grantResults) =>
+		Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);
+
+	protected override void OnPause()
+	{
+		scanFragment?.StopScanning();
+
+		base.OnPause();
+	}
+
+	void Scan()
+	{
+		var opts = new MobileBarcodeScanningOptions
+		           {
+			           PossibleFormats = new List<ZXing.BarcodeFormat> { ZXing.BarcodeFormat.All_1D },
+			           ScanningArea = ScanningArea.From(0f, 0.49f, 1f, 0.51f),
+			           CameraResolutionSelector = availableResolutions =>
+			                                      {
+				                                      foreach (var ar in availableResolutions)
+				                                      {
+					                                      Console.WriteLine("Resolution: " + ar.Width + "x" + ar.Height);
+				                                      }
+
+				                                      return null;
+			                                      },
+			           AutoRotate = true
+		           };
+
+		scanFragment.StartScanning(
+			result =>
+			{
+				// Null result means scanning was cancelled
+				if (result == null || string.IsNullOrEmpty(result.Text))
+				{
+					Toast.MakeText(this, "Scanning Cancelled", ToastLength.Long).Show();
+					return;
+				}
+
+				// Otherwise, proceed with result
+				RunOnUiThread(() => Toast.MakeText(this, "Scanned: " + result.Text, ToastLength.Short).Show());
+			},
+			opts);
+	}
+}

Sample.NetAndroid/ImageActivity.cs

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+namespace Sample.NetAndroid;
+
+[Activity(Label = "ImageActivity")]
+public class ImageActivity : Activity
+{
+	ImageView imageBarcode;
+
+	protected override void OnCreate(Bundle bundle)
+	{
+		base.OnCreate(bundle);
+
+		SetContentView(Resource.Layout.ImageActivity);
+
+		imageBarcode = FindViewById<ImageView>(Resource.Id.imageBarcode);
+
+		var barcodeWriter =
+			new ZXing.Mobile.BarcodeWriter { Format = ZXing.BarcodeFormat.QR_CODE, Options = new ZXing.Common.EncodingOptions { Width = 300, Height = 300 } };
+		var barcode = barcodeWriter.Write("ZXing.Net.Mobile");
+
+		imageBarcode.SetImageBitmap(barcode);
+	}
+}

Sample.NetAndroid/MainActivity.cs

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+using Android.Content.PM;
+using Android.Views;
+using AndroidX.Fragment.App;
+using Xamarin.Essentials;
+using ZXing.Mobile;
+
+namespace Sample.NetAndroid
+{
+	[Activity(
+		Label = "@string/app_name",
+		MainLauncher = true,
+		Theme = "@style/Theme.AppCompat.Light",
+		ConfigurationChanges = ConfigChanges.Orientation | ConfigChanges.KeyboardHidden)]
+	public class MainActivity : Activity
+	{
+		MobileBarcodeScanner scanner;
+		Button buttonScanCustomView;
+		Button buttonScanDefaultView;
+		Button buttonContinuousScan;
+		Button buttonFragmentScanner;
+		Button buttonGenerate;
+
+		protected override void OnCreate(Bundle? savedInstanceState)
+		{
+			base.OnCreate(savedInstanceState);
+
+			Platform.Init(Application);
+
+			// Set our view from the "main" layout resource
+			SetContentView(Resource.Layout.activity_main);
+
+			//Create a new instance of our Scanner
+			scanner = new MobileBarcodeScanner();
+
+			buttonScanDefaultView = FindViewById<Button>(Resource.Id.buttonScanDefaultView);
+			buttonScanDefaultView.Click +=
+				async delegate
+				{
+					//Tell our scanner to use the default overlay
+					scanner.UseCustomOverlay = false;
+
+					//We can customize the top and bottom text of the default overlay
+					scanner.TopText = "Hold the camera up to the barcode\nAbout 6 inches away";
+					scanner.BottomText = "Wait for the barcode to automatically scan!";
+
+					//Start scanning
+					var result = await scanner.Scan();
+
+					HandleScanResult(result);
+				};
+
+			buttonContinuousScan = FindViewById<Button>(Resource.Id.buttonScanContinuous);
+			buttonContinuousScan.Click +=
+				delegate
+				{
+					scanner.UseCustomOverlay = false;
+
+					//We can customize the top and bottom text of the default overlay
+					scanner.TopText = "Hold the camera up to the barcode\nAbout 6 inches away";
+					scanner.BottomText = "Wait for the barcode to automatically scan!";
+
+					var opt = new MobileBarcodeScanningOptions();
+					opt.DelayBetweenContinuousScans = 3000;
+
+					//Start scanning
+					scanner.ScanContinuously(opt, HandleScanResult);
+				};
+
+			Button flashButton;
+			View zxingOverlay;
+
+			buttonScanCustomView = this.FindViewById<Button>(Resource.Id.buttonScanCustomView);
+			buttonScanCustomView.Click +=
+				async delegate
+				{
+					//Tell our scanner we want to use a custom overlay instead of the default
+					scanner.UseCustomOverlay = true;
+
+					//Inflate our custom overlay from a resource layout
+					zxingOverlay = LayoutInflater.FromContext(this).Inflate(Resource.Layout.ZxingOverlay, null);
+
+					//Find the button from our resource layout and wire up the click event
+					flashButton = zxingOverlay.FindViewById<Button>(Resource.Id.buttonZxingFlash);
+					flashButton.Click += (sender, e) => scanner.ToggleTorch();
+
+					//Set our custom overlay
+					scanner.CustomOverlay = zxingOverlay;
+
+					//Start scanning!
+					var result = await scanner.Scan(new MobileBarcodeScanningOptions { AutoRotate = true });
+
+					HandleScanResult(result);
+				};
+
+			buttonFragmentScanner = FindViewById<Button>(Resource.Id.buttonFragment);
+			buttonFragmentScanner.Click += delegate { StartActivity(typeof(FragmentActivity)); };
+
+			buttonGenerate = FindViewById<Button>(Resource.Id.buttonGenerate);
+			buttonGenerate.Click += delegate { StartActivity(typeof(ImageActivity)); };
+		}
+
+		void HandleScanResult(ZXing.Result result)
+		{
+			var msg = "";
+
+			if (result != null && !string.IsNullOrEmpty(result.Text))
+				msg = "Found Barcode: " + result.Text;
+			else
+				msg = "Scanning Canceled!";
+
+			RunOnUiThread(() => Toast.MakeText(this, msg, ToastLength.Short).Show());
+		}
+	}
+}

Sample.NetAndroid/Resources/AboutResources.txt

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+Images, layout descriptions, binary blobs and string dictionaries can be included 
+in your application as resource files.  Various Android APIs are designed to 
+operate on the resource IDs instead of dealing with images, strings or binary blobs 
+directly.
+
+For example, a sample Android app that contains a user interface layout (main.xml),
+an internationalization string table (strings.xml) and some icons (drawable-XXX/icon.png) 
+would keep its resources in the "Resources" directory of the application:
+
+Resources/
+    drawable/
+        icon.png
+
+    layout/
+        main.xml
+
+    values/
+        strings.xml
+
+In order to get the build system to recognize Android resources, set the build action to
+"AndroidResource".  The native Android APIs do not operate directly with filenames, but 
+instead operate on resource IDs.  When you compile an Android application that uses resources, 
+the build system will package the resources for distribution and generate a class called "Resource" 
+(this is an Android convention) that contains the tokens for each one of the resources 
+included. For example, for the above Resources layout, this is what the Resource class would expose:
+
+public class Resource {
+    public class Drawable {
+        public const int icon = 0x123;
+    }
+
+    public class Layout {
+        public const int main = 0x456;
+    }
+
+    public class Strings {
+        public const int first_string = 0xabc;
+        public const int second_string = 0xbcd;
+    }
+}
+
+You would then use Resource.Drawable.icon to reference the drawable/icon.png file, or 
+Resource.Layout.main to reference the layout/main.xml file, or Resource.Strings.first_string 
+to reference the first string in the dictionary file values/strings.xml.

Sample.NetAndroid/Resources/layout/FragmentActivity.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+              android:orientation="vertical"
+              android:layout_width="fill_parent"
+              android:layout_height="fill_parent">
+  <TextView
+    android:text="Top View"
+    android:textAppearance="?android:attr/textAppearanceLarge"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:id="@+id/textView1"
+    android:gravity="center" />
+  <FrameLayout
+    android:id="@+id/fragment_container"
+    android:layout_width="wrap_content"
+    android:layout_height="wrap_content"
+    android:layout_weight="1" />
+  <TextView
+    android:text="Bottom View"
+    android:textAppearance="?android:attr/textAppearanceLarge"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:id="@+id/textView2"
+    android:gravity="center" />
+</LinearLayout>

Sample.NetAndroid/Resources/layout/ImageActivity.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+              android:orientation="vertical"
+              android:layout_width="fill_parent"
+              android:layout_height="fill_parent"
+              android:minWidth="25px"
+              android:minHeight="25px">
+  <ImageView
+    android:src="@android:drawable/ic_menu_gallery"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:id="@+id/imageBarcode" />
+</LinearLayout>

Sample.NetAndroid/Resources/layout/ZxingOverlay.xml

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+<?xml version="1.0" encoding="utf-8"?>
+
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+              android:orientation="vertical"
+              android:layout_width="fill_parent"
+              android:layout_height="fill_parent"
+              android:minWidth="25px"
+              android:minHeight="25px"
+              android:background="@android:color/transparent"
+              android:weightSum="1.0">
+  <LinearLayout
+    android:orientation="horizontal"
+    android:minWidth="25px"
+    android:minHeight="25px"
+    android:layout_width="fill_parent"
+    android:layout_height="wrap_content"
+    android:id="@+id/linearLayout1"
+    android:layout_weight="0.3">
+    <TextView
+      android:text="Place a barcode in the camera viewfinder to scan it.  Barcode will scan Automatically."
+      android:layout_width="wrap_content"
+      android:layout_height="fill_parent"
+      android:id="@+id/textView1"
+      android:gravity="center"
+      android:layout_weight="0"
+      android:layout_marginRight="20dp"
+      android:textSize="12sp"
+      android:layout_marginLeft="5dp"
+      android:background="@android:color/transparent"
+      android:textColor="#ffffffff" />
+  </LinearLayout>
+  <TextView
+    android:layout_width="fill_parent"
+    android:layout_height="wrap_content"
+    android:id="@+id/textView2"
+    android:layout_weight="0.5" />
+  <LinearLayout
+    android:orientation="vertical"
+    android:minWidth="25px"
+    android:minHeight="25px"
+    android:layout_width="fill_parent"
+    android:layout_height="wrap_content"
+    android:id="@+id/linearLayout2"
+    android:layout_weight="0.2"
+    android:layout_gravity="center">
+    <TextView
+      android:text="Try to avoid shadows and glare.  Hold the device back about 6 inches from the barcode."
+      android:layout_width="fill_parent"
+      android:layout_height="wrap_content"
+      android:id="@+id/textView3"
+      android:layout_marginLeft="30dp"
+      android:layout_marginRight="30dp"
+      android:layout_gravity="center"
+      android:textColor="#ffffffff"
+      android:textSize="12sp"
+      android:layout_weight="1"
+      android:gravity="center" />
+    <Button
+      android:text="Flash On"
+      android:layout_width="fill_parent"
+      android:layout_height="wrap_content"
+      android:id="@+id/buttonZxingFlash"
+      android:layout_marginLeft="20dp"
+      android:layout_marginRight="20dp"
+      android:layout_gravity="bottom"
+      android:layout_marginBottom="20dp" />
+  </LinearLayout>
+</LinearLayout>