[camera] Add Android & iOS implementations for pausing the camera preview

packages/camera/camera/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.9.2
+
+* Added functions to pause and resume the camera preview.
+
 ## 0.9.1+1
 
 * Replace `device_info` reference with `device_info_plus` in the [README.md](README.md)

packages/camera/camera/android/src/main/java/io/flutter/plugins/camera/Camera.java

@@ -126,6 +126,8 @@ class Camera
   private MediaRecorder mediaRecorder;
   /** True when recording video. */
   private boolean recordingVideo;
+  /** True when the preview is paused. */
+  private boolean pausedPreview;
 
   private File captureFile;
 
@@ -428,8 +430,10 @@ private void refreshPreviewCaptureSession(
     }
 
     try {
-      captureSession.setRepeatingRequest(
-          previewRequestBuilder.build(), cameraCaptureCallback, backgroundHandler);
+      if (!pausedPreview) {
+        captureSession.setRepeatingRequest(
+            previewRequestBuilder.build(), cameraCaptureCallback, backgroundHandler);
+      }
 
       if (onSuccessCallback != null) {
         onSuccessCallback.run();
@@ -834,33 +838,36 @@ public void setFocusMode(final Result result, @NonNull FocusMode newMode) {
      * For focus mode an extra step of actually locking/unlocking the
      * focus has to be done, in order to ensure it goes into the correct state.
      */
-    switch (newMode) {
-      case locked:
-        // Perform a single focus trigger.
-        lockAutoFocus();
-        if (captureSession == null) {
-          Log.i(TAG, "[unlockAutoFocus] captureSession null, returning");
-          return;
-        }
-
-        // Set AF state to idle again.
-        previewRequestBuilder.set(
-            CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_IDLE);
-
-        try {
-          captureSession.setRepeatingRequest(
-              previewRequestBuilder.build(), null, backgroundHandler);
-        } catch (CameraAccessException e) {
-          if (result != null) {
-            result.error("setFocusModeFailed", "Error setting focus mode: " + e.getMessage(), null);
+    if (!pausedPreview) {
+      switch (newMode) {
+        case locked:
+          // Perform a single focus trigger.
+          if (captureSession == null) {
+            Log.i(TAG, "[unlockAutoFocus] captureSession null, returning");
+            return;
+          }
+          lockAutoFocus();
+
+          // Set AF state to idle again.
+          previewRequestBuilder.set(
+              CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_IDLE);
+
+          try {
+            captureSession.setRepeatingRequest(
+                previewRequestBuilder.build(), null, backgroundHandler);
+          } catch (CameraAccessException e) {
+            if (result != null) {
+              result.error(
+                  "setFocusModeFailed", "Error setting focus mode: " + e.getMessage(), null);
+            }
+            return;
           }
-          return;
-        }
-        break;
-      case auto:
-        // Cancel current AF trigger and set AF to idle again.
-        unlockAutoFocus();
-        break;
+          break;
+        case auto:
+          // Cancel current AF trigger and set AF to idle again.
+          unlockAutoFocus();
+          break;
+      }
     }
 
     if (result != null) {
@@ -966,6 +973,19 @@ public void unlockCaptureOrientation() {
     cameraFeatures.getSensorOrientation().unlockCaptureOrientation();
   }
 
+  /** Pause the preview from dart. */
+  public void pausePreview() throws CameraAccessException {
+    this.pausedPreview = true;
+    this.captureSession.stopRepeating();
+  }
+
+  /** Resume the preview from dart. */
+  public void resumePreview() {
+    this.pausedPreview = false;
+    this.refreshPreviewCaptureSession(
+        null, (code, message) -> dartMessenger.sendCameraErrorEvent(message));
+  }
+
   public void startPreview() throws CameraAccessException {
     if (pictureImageReader == null || pictureImageReader.getSurface() == null) return;
     Log.i(TAG, "startPreview");
@@ -1022,8 +1042,8 @@ public void onError(String errorCode, String errorMessage) {
   private void setImageStreamImageAvailableListener(final EventChannel.EventSink imageStreamSink) {
     imageStreamReader.setOnImageAvailableListener(
         reader -> {
-          // Use acquireNextImage since image reader is only for one image.
           Image img = reader.acquireNextImage();
+          // Use acquireNextImage since image reader is only for one image.
           if (img == null) return;
 
           List<Map<String, Object>> planes = new ArrayList<>();

packages/camera/camera/android/src/main/java/io/flutter/plugins/camera/MethodCallHandlerImpl.java

@@ -339,6 +339,22 @@ public void onMethodCall(@NonNull MethodCall call, @NonNull final Result result)
           }
           break;
         }
+      case "pausePreview":
+        {
+          try {
+            camera.pausePreview();
+            result.success(null);
+          } catch (Exception e) {
+            handleException(e, result);
+          }
+          break;
+        }
+      case "resumePreview":
+        {
+          camera.resumePreview();
+          result.success(null);
+          break;
+        }
       case "dispose":
         {
           if (camera != null) {

packages/camera/camera/android/src/test/java/io/flutter/plugins/camera/CameraTest.java

@@ -744,6 +744,33 @@ public void unlockCaptureOrientation_shouldUnlockCaptureOrientation() {
     verify(mockSensorOrientationFeature, times(1)).unlockCaptureOrientation();
   }
 
+  @Test
+  public void pausePreview_shouldPausePreview() throws CameraAccessException {
+    camera.pausePreview();
+
+    assertEquals(TestUtils.getPrivateField(camera, "pausedPreview"), true);
+    verify(mockCaptureSession, times(1)).stopRepeating();
+  }
+
+  @Test
+  public void resumePreview_shouldResumePreview() throws CameraAccessException {
+    camera.resumePreview();
+
+    assertEquals(TestUtils.getPrivateField(camera, "pausedPreview"), false);
+    verify(mockCaptureSession, times(1)).setRepeatingRequest(any(), any(), any());
+  }
+
+  @Test
+  public void resumePreview_shouldSendErrorEventOnCameraAccessException()
+      throws CameraAccessException {
+    when(mockCaptureSession.setRepeatingRequest(any(), any(), any()))
+        .thenThrow(new CameraAccessException(0));
+
+    camera.resumePreview();
+
+    verify(mockDartMessenger, times(1)).sendCameraErrorEvent(any());
+  }
+
   private static class TestCameraFeatureFactory implements CameraFeatureFactory {
     private final AutoFocusFeature mockAutoFocusFeature;
     private final ExposureLockFeature mockExposureLockFeature;

packages/camera/camera/android/src/test/java/io/flutter/plugins/camera/MethodCallHandlerImplTest.java

@@ -0,0 +1,69 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package io.flutter.plugins.camera;
+
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import android.app.Activity;
+import android.hardware.camera2.CameraAccessException;
+import io.flutter.plugin.common.BinaryMessenger;
+import io.flutter.plugin.common.MethodCall;
+import io.flutter.plugin.common.MethodChannel;
+import io.flutter.plugins.camera.utils.TestUtils;
+import io.flutter.view.TextureRegistry;
+import org.junit.Before;
+import org.junit.Test;
+
+public class MethodCallHandlerImplTest {
+
+  MethodChannel.MethodCallHandler handler;
+  MethodChannel.Result mockResult;
+  Camera mockCamera;
+
+  @Before
+  public void setUp() {
+    handler =
+        new MethodCallHandlerImpl(
+            mock(Activity.class),
+            mock(BinaryMessenger.class),
+            mock(CameraPermissions.class),
+            mock(CameraPermissions.PermissionsRegistry.class),
+            mock(TextureRegistry.class),
+            null);
+    mockResult = mock(MethodChannel.Result.class);
+    mockCamera = mock(Camera.class);
+    TestUtils.setPrivateField(handler, "camera", mockCamera);
+  }
+
+  @Test
+  public void onMethodCall_pausePreview_shouldPausePreviewAndSendSuccessResult()
+      throws CameraAccessException {
+    handler.onMethodCall(new MethodCall("pausePreview", null), mockResult);
+
+    verify(mockCamera, times(1)).pausePreview();
+    verify(mockResult, times(1)).success(null);
+  }
+
+  @Test
+  public void onMethodCall_pausePreview_shouldSendErrorResultOnCameraAccessException()
+      throws CameraAccessException {
+    doThrow(new CameraAccessException(0)).when(mockCamera).pausePreview();
+
+    handler.onMethodCall(new MethodCall("pausePreview", null), mockResult);
+
+    verify(mockResult, times(1)).error("CameraAccess", null, null);
+  }
+
+  @Test
+  public void onMethodCall_resumePreview_shouldResumePreviewAndSendSuccessResult() {
+    handler.onMethodCall(new MethodCall("resumePreview", null), mockResult);
+
+    verify(mockCamera, times(1)).resumePreview();
+    verify(mockResult, times(1)).success(null);
+  }
+}

packages/camera/camera/android/src/test/java/io/flutter/plugins/camera/utils/TestUtils.java

@@ -33,4 +33,15 @@ public static <T> void setPrivateField(T instance, String fieldName, Object newV
       Assert.fail("Unable to mock private field: " + fieldName);
     }
   }
+
+  public static <T> Object getPrivateField(T instance, String fieldName) {
+    try {
+      Field field = instance.getClass().getDeclaredField(fieldName);
+      field.setAccessible(true);
+      return field.get(instance);
+    } catch (Exception e) {
+      Assert.fail("Unable to mock private field: " + fieldName);
+      return null;
+    }
+  }
 }

packages/camera/camera/example/ios/Runner.xcodeproj/project.pbxproj

@@ -18,6 +18,7 @@
 		97C147011CF9000F007C117D /* LaunchScreen.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 97C146FF1CF9000F007C117D /* LaunchScreen.storyboard */; };
 		A513685080F868CF2695CE75 /* libPods-RunnerTests.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 5555DD51E06E67921CFA83DD /* libPods-RunnerTests.a */; };
 		D065CD815D405ECB22FB1BBA /* libPods-Runner.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 2A4F2DE74AE0C572296A00BF /* libPods-Runner.a */; };
+		E487C86026D686A10034AC92 /* CameraPreviewPauseTests.m in Sources */ = {isa = PBXBuildFile; fileRef = E487C85F26D686A10034AC92 /* CameraPreviewPauseTests.m */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -68,6 +69,7 @@
 		97C147021CF9000F007C117D /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		A4725B4F24805CD3CA67828F /* Pods-Runner.release.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Runner.release.xcconfig"; path = "Target Support Files/Pods-Runner/Pods-Runner.release.xcconfig"; sourceTree = "<group>"; };
 		D1FF8C34CA9E9BE702C5EC06 /* Pods-RunnerTests.release.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-RunnerTests.release.xcconfig"; path = "Target Support Files/Pods-RunnerTests/Pods-RunnerTests.release.xcconfig"; sourceTree = "<group>"; };
+		E487C85F26D686A10034AC92 /* CameraPreviewPauseTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = CameraPreviewPauseTests.m; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -96,6 +98,7 @@
 				03BB766A2665316900CE5A93 /* CameraFocusTests.m */,
 				03BB767226653ABE00CE5A93 /* CameraOrientationTests.m */,
 				03BB766C2665316900CE5A93 /* Info.plist */,
+				E487C85F26D686A10034AC92 /* CameraPreviewPauseTests.m */,
 			);
 			path = RunnerTests;
 			sourceTree = "<group>";
@@ -359,6 +362,7 @@
 			buildActionMask = 2147483647;
 			files = (
 				03BB766B2665316900CE5A93 /* CameraFocusTests.m in Sources */,
+				E487C86026D686A10034AC92 /* CameraPreviewPauseTests.m in Sources */,
 				334733EA2668111C00DCC49E /* CameraOrientationTests.m in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;

packages/camera/camera/example/ios/RunnerTests/CameraPreviewPauseTests.m

@@ -0,0 +1,50 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+@import camera;
+@import XCTest;
+@import AVFoundation;
+#import <OCMock/OCMock.h>
+
+@interface FLTCam : NSObject <FlutterTexture,
+                              AVCaptureVideoDataOutputSampleBufferDelegate,
+                              AVCaptureAudioDataOutputSampleBufferDelegate>
+@property(assign, nonatomic) BOOL isPreviewPaused;
+- (void)pausePreviewWithResult:(FlutterResult)result;
+- (void)resumePreviewWithResult:(FlutterResult)result;
+@end
+
+@interface CameraPreviewPauseTests : XCTestCase
+@property(readonly, nonatomic) FLTCam* camera;
+@end
+
+@implementation CameraPreviewPauseTests
+
+- (void)setUp {
+  _camera = [[FLTCam alloc] init];
+}
+
+- (void)testPausePreviewWithResult_shouldPausePreview {
+  XCTestExpectation* resultExpectation =
+      [self expectationWithDescription:@"Succeeding result with nil value"];
+  [_camera pausePreviewWithResult:^void(id _Nullable result) {
+    XCTAssertNil(result);
+    [resultExpectation fulfill];
+  }];
+  [self waitForExpectationsWithTimeout:2.0 handler:nil];
+  XCTAssertTrue(_camera.isPreviewPaused);
+}
+
+- (void)testResumePreviewWithResult_shouldResumePreview {
+  XCTestExpectation* resultExpectation =
+      [self expectationWithDescription:@"Succeeding result with nil value"];
+  [_camera resumePreviewWithResult:^void(id _Nullable result) {
+    XCTAssertNil(result);
+    [resultExpectation fulfill];
+  }];
+  [self waitForExpectationsWithTimeout:2.0 handler:nil];
+  XCTAssertFalse(_camera.isPreviewPaused);
+}
+
+@end

packages/camera/camera/example/lib/main.dart

@@ -530,7 +530,16 @@ class _CameraExampleHomeState extends State<CameraExampleHome>
                   cameraController.value.isRecordingVideo
               ? onStopButtonPressed
               : null,
-        )
+        ),
+        IconButton(
+          icon: const Icon(Icons.pause_presentation),
+          color:
+              cameraController != null && cameraController.value.isPreviewPaused
+                  ? Colors.red
+                  : Colors.blue,
+          onPressed:
+              cameraController == null ? null : onPausePreviewButtonPressed,
+        ),
       ],
     );
   }
@@ -747,6 +756,23 @@ class _CameraExampleHomeState extends State<CameraExampleHome>
     });
   }
 
+  Future<void> onPausePreviewButtonPressed() async {
+    final CameraController? cameraController = controller;
+
+    if (cameraController == null || !cameraController.value.isInitialized) {
+      showInSnackBar('Error: select a camera first.');
+      return;
+    }
+
+    if (cameraController.value.isPreviewPaused) {
+      await cameraController.resumePreview();
+    } else {
+      await cameraController.pausePreview();
+    }
+
+    if (mounted) setState(() {});
+  }
+
   void onPauseButtonPressed() {
     pauseVideoRecording().then((_) {
       if (mounted) setState(() {});