From 9db2085ed13cc7bd8955321703afe8eb5caf9212 Mon Sep 17 00:00:00 2001
From: Giorgos Papadopoulos <giorgos@giorgos.nl>
Date: Tue, 19 Oct 2021 12:29:36 +0200
Subject: [PATCH 1/2] allow the user to focus on touch

---
 .../rijksoverheid/ctr/qrscanner/PreviewExt.kt | 48 +++++++++++++++++++
 .../ctr/qrscanner/QrCodeScannerFragment.kt    |  3 ++
 2 files changed, 51 insertions(+)
 create mode 100644 qrscanner/src/main/java/nl/rijksoverheid/ctr/qrscanner/PreviewExt.kt

diff --git a/qrscanner/src/main/java/nl/rijksoverheid/ctr/qrscanner/PreviewExt.kt b/qrscanner/src/main/java/nl/rijksoverheid/ctr/qrscanner/PreviewExt.kt
new file mode 100644
index 000000000..44557ed38
--- /dev/null
+++ b/qrscanner/src/main/java/nl/rijksoverheid/ctr/qrscanner/PreviewExt.kt
@@ -0,0 +1,48 @@
+package nl.rijksoverheid.ctr.qrscanner
+
+import android.annotation.SuppressLint
+import android.view.MotionEvent
+import android.view.ViewTreeObserver
+import androidx.camera.core.*
+import androidx.camera.view.PreviewView
+import timber.log.Timber
+
+fun PreviewView.focusOnTouch(cameraControl: CameraControl) {
+    viewTreeObserver.addOnGlobalLayoutListener(object : ViewTreeObserver.OnGlobalLayoutListener {
+        @SuppressLint("ClickableViewAccessibility")
+        override fun onGlobalLayout() {
+            if (measuredWidth > 0 && measuredHeight > 0) {
+                viewTreeObserver.removeOnGlobalLayoutListener(this)
+
+                setOnTouchListener { _, event ->
+                    return@setOnTouchListener when (event.action) {
+                        MotionEvent.ACTION_DOWN -> {
+                            true
+                        }
+                        MotionEvent.ACTION_UP -> {
+                            val factory: MeteringPointFactory = SurfaceOrientedMeteringPointFactory(
+                                width.toFloat(), height.toFloat()
+                            )
+                            val autoFocusPoint = factory.createPoint(event.x, event.y)
+                            try {
+                                cameraControl.startFocusAndMetering(
+                                    FocusMeteringAction.Builder(
+                                        autoFocusPoint,
+                                        FocusMeteringAction.FLAG_AF
+                                    ).apply {
+                                        // focus only when the user taps the preview
+                                        disableAutoCancel()
+                                    }.build()
+                                )
+                            } catch (e: CameraInfoUnavailableException) {
+                                Timber.d("ERROR", "cannot access camera", e)
+                            }
+                            true
+                        }
+                        else -> false // Unhandled event.
+                    }
+                }
+            }
+        }
+    })
+}
diff --git a/qrscanner/src/main/java/nl/rijksoverheid/ctr/qrscanner/QrCodeScannerFragment.kt b/qrscanner/src/main/java/nl/rijksoverheid/ctr/qrscanner/QrCodeScannerFragment.kt
index 8376f7211..cc7888c5d 100644
--- a/qrscanner/src/main/java/nl/rijksoverheid/ctr/qrscanner/QrCodeScannerFragment.kt
+++ b/qrscanner/src/main/java/nl/rijksoverheid/ctr/qrscanner/QrCodeScannerFragment.kt
@@ -15,7 +15,9 @@ import android.content.pm.PackageManager
 import android.graphics.Paint
 import android.os.Bundle
 import android.util.DisplayMetrics
+import android.view.MotionEvent
 import android.view.View
+import android.view.ViewTreeObserver
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.camera.core.*
 import androidx.camera.lifecycle.ProcessCameraProvider
@@ -224,6 +226,7 @@ abstract class QrCodeScannerFragment : Fragment(R.layout.fragment_scanner) {
                 cameraSelector,
                 cameraPreview
             ).also { camera ->
+                previewView.focusOnTouch(camera.cameraControl)
                 // If device supports flash, enable flash functionality
                 if (camera.cameraInfo.hasFlashUnit()) {
                     binding.toolbar.menu.findItem(R.id.flash)?.let { flashItem ->

From d7d27bfee3b06f6fb964f357ce455e6765bcfc7f Mon Sep 17 00:00:00 2001
From: Giorgos Papadopoulos <giorgos@giorgos.nl>
Date: Wed, 3 Nov 2021 14:38:28 +0100
Subject: [PATCH 2/2] experiment with tap on screen camera focus

---
 .../nl/rijksoverheid/ctr/qrscanner/QrCodeScannerFragment.kt | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/qrscanner/src/main/java/nl/rijksoverheid/ctr/qrscanner/QrCodeScannerFragment.kt b/qrscanner/src/main/java/nl/rijksoverheid/ctr/qrscanner/QrCodeScannerFragment.kt
index cc7888c5d..b68ceded4 100644
--- a/qrscanner/src/main/java/nl/rijksoverheid/ctr/qrscanner/QrCodeScannerFragment.kt
+++ b/qrscanner/src/main/java/nl/rijksoverheid/ctr/qrscanner/QrCodeScannerFragment.kt
@@ -226,7 +226,11 @@ abstract class QrCodeScannerFragment : Fragment(R.layout.fragment_scanner) {
                 cameraSelector,
                 cameraPreview
             ).also { camera ->
-                previewView.focusOnTouch(camera.cameraControl)
+                try {
+                    previewView.focusOnTouch(camera.cameraControl)
+                } catch (exception: Exception) {
+                    Timber.e(exception)
+                }
                 // If device supports flash, enable flash functionality
                 if (camera.cameraInfo.hasFlashUnit()) {
                     binding.toolbar.menu.findItem(R.id.flash)?.let { flashItem ->