Show camera preview

app/src/main/java/com/nekdenis/camera/MainActivity.kt

@@ -1,19 +1,31 @@
 package com.nekdenis.camera
 
 import android.Manifest
+import android.content.Context
 import android.content.pm.PackageManager
 import android.os.Bundle
-import android.widget.Toast
+import android.view.ViewGroup
 import androidx.activity.ComponentActivity
-import androidx.activity.compose.setContent
+import androidx.camera.core.CameraSelector
+import androidx.camera.lifecycle.ProcessCameraProvider
+import androidx.camera.view.PreviewView
 import androidx.compose.material.MaterialTheme
 import androidx.compose.material.Surface
 import androidx.compose.material.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.platform.LocalLifecycleOwner
 import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.viewinterop.AndroidView
 import androidx.core.app.ActivityCompat
 import androidx.core.content.ContextCompat
 import com.nekdenis.camera.ui.theme.CameraComposeWorkshopTheme
+import android.widget.Toast
+import androidx.activity.compose.setContent
+import androidx.lifecycle.LifecycleOwner
+import com.google.common.util.concurrent.ListenableFuture
 
 class MainActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
@@ -59,10 +71,41 @@ class MainActivity : ComponentActivity() {
                 // A surface container using the 'background' color from the theme
                 Surface(color = MaterialTheme.colors.background) {
                     Greeting("Android")
+                    CameraPreview()
                 }
             }
         }
     }
+
+    @Composable
+    fun CameraPreview(
+        modifier: Modifier = Modifier,
+        cameraSelector: CameraSelector = CameraSelector.DEFAULT_BACK_CAMERA,
+        scaleType: PreviewView.ScaleType = PreviewView.ScaleType.FILL_CENTER,
+    ) {
+        val lifecycleOwner = LocalLifecycleOwner.current
+        val context = LocalContext.current
+        val previewView = remember { PreviewView(context) }
+        val cameraProviderFuture = remember {
+            ProcessCameraProvider.getInstance(context)
+                .configureCamera(previewView, lifecycleOwner, cameraSelector, context)
+        }
+        AndroidView(
+            modifier = modifier,
+            factory = {
+                previewView.apply {
+                    this.scaleType = scaleType
+                    layoutParams = ViewGroup.LayoutParams(
+                        ViewGroup.LayoutParams.MATCH_PARENT,
+                        ViewGroup.LayoutParams.MATCH_PARENT
+                    )
+                    // Preview is incorrectly scaled in Compose on some devices without this
+                    implementationMode = PreviewView.ImplementationMode.COMPATIBLE
+                }
+
+                previewView
+            })
+    }
 }
 
 
@@ -77,4 +120,31 @@ fun DefaultPreview() {
     CameraComposeWorkshopTheme {
         Greeting("Android")
     }
+}
+
+private fun ListenableFuture<ProcessCameraProvider>.configureCamera(
+    previewView: PreviewView,
+    lifecycleOwner: LifecycleOwner,
+    cameraSelector: CameraSelector,
+    context: Context
+): ListenableFuture<ProcessCameraProvider> {
+    addListener({
+        val preview = androidx.camera.core.Preview.Builder()
+            .build()
+            .apply {
+                setSurfaceProvider(previewView.surfaceProvider)
+            }
+
+        try {
+            get().apply {
+                unbindAll()
+                bindToLifecycle(
+                    lifecycleOwner, cameraSelector, preview
+                )
+            }
+        } catch (exc: Exception) {
+            TODO("process errors")
+        }
+    }, ContextCompat.getMainExecutor(context))
+    return this
 }