From 052ee9c7e5d60ab2e5418d6cd0a1953356030f4c Mon Sep 17 00:00:00 2001
From: dankito <git@dankito.net>
Date: Fri, 4 Oct 2024 07:29:51 +0200
Subject: [PATCH] Implemented pinch to zoom for reading EPC QR Codes

---
 .../ui/service/QrCodeService.android.kt       | 34 +++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/composeApp/src/androidMain/kotlin/net/codinux/banking/ui/service/QrCodeService.android.kt b/composeApp/src/androidMain/kotlin/net/codinux/banking/ui/service/QrCodeService.android.kt
index 9982a4c..be0d0fe 100644
--- a/composeApp/src/androidMain/kotlin/net/codinux/banking/ui/service/QrCodeService.android.kt
+++ b/composeApp/src/androidMain/kotlin/net/codinux/banking/ui/service/QrCodeService.android.kt
@@ -1,6 +1,7 @@
 package net.codinux.banking.ui.service
 
 import android.Manifest
+import android.view.ScaleGestureDetector
 import androidx.camera.core.*
 import androidx.camera.lifecycle.ProcessCameraProvider
 import androidx.camera.view.PreviewView
@@ -50,7 +51,6 @@ actual object QrCodeService {
         AndroidView(factory = { previewView }, modifier = Modifier.fillMaxSize())
     }
 
-    @Composable
     private fun setupCameraView(previewView: PreviewView, mainActivity: MainActivity, resultCallback: (QrCodeReadResult) -> Unit) {
         val cameraProviderFuture = ProcessCameraProvider.getInstance(mainActivity)
 
@@ -79,8 +79,9 @@ actual object QrCodeService {
                 cameraProvider.unbindAll()
 
                 // Bind use cases to camera
-                cameraProvider.bindToLifecycle(mainActivity, cameraSelector, preview, imageAnalyzer)
+                val camera = cameraProvider.bindToLifecycle(mainActivity, cameraSelector, preview, imageAnalyzer)
 
+                configureCameraControl(camera, previewView, mainActivity)
             } catch (e: Exception) {
                 log.error(e) { "Use case binding failed" }
             }
@@ -88,6 +89,35 @@ actual object QrCodeService {
         }, ContextCompat.getMainExecutor(mainActivity))
     }
 
+    private fun configureCameraControl(
+        camera: Camera,
+        previewView: PreviewView,
+        mainActivity: MainActivity
+    ) {
+        // Listen to pinch gestures
+        val listener = object : ScaleGestureDetector.SimpleOnScaleGestureListener() {
+            override fun onScale(detector: ScaleGestureDetector): Boolean {
+                // Get the camera's current zoom ratio
+                val currentZoomRatio = camera.cameraInfo.zoomState.value?.zoomRatio ?: 0F
+
+                // Get the pinch gesture's scaling factor
+                val delta = detector.scaleFactor
+
+                // Update the camera's zoom ratio. This is an asynchronous operation that returns
+                // a ListenableFuture, allowing you to listen to when the operation completes.
+                camera.cameraControl.setZoomRatio(currentZoomRatio * delta)
+
+                return true // Return true, as the event was handled
+            }
+        }
+        val scaleGestureDetector = ScaleGestureDetector(mainActivity, listener)
+
+        previewView.setOnTouchListener { _, event ->
+            scaleGestureDetector.onTouchEvent(event)
+            true
+        }
+    }
+
 }