add CameraPreview quarterTurns paramater

Author: mjl0602

lib/src/widget/camera_picker.dart

@@ -34,6 +34,7 @@ class CameraPicker extends StatefulWidget {
     this.maximumRecordingDuration = const Duration(seconds: 15),
     this.theme,
     this.resolutionPreset = ResolutionPreset.max,
+    this.quarterTurns = 0,
     CameraPickerTextDelegate textDelegate,
   })  : assert(
           isAllowRecording == true || isOnlyAllowRecording != true,
@@ -50,6 +51,10 @@ class CameraPicker extends StatefulWidget {
             : DefaultCameraPickerTextDelegate());
   }
 
+  /// Quarter rotate turns.
+  /// 摄像机视图旋转次数
+  final int quarterTurns;
+
   /// Whether the picker can record video.
   /// 选择器是否可以录像
   final bool isAllowRecording;
@@ -81,6 +86,7 @@ class CameraPicker extends StatefulWidget {
     bool isOnlyAllowRecording = false,
     Duration maximumRecordingDuration = const Duration(seconds: 15),
     ThemeData theme,
+    int cameraQuarterTurns = 0,
     CameraPickerTextDelegate textDelegate,
     ResolutionPreset resolutionPreset = ResolutionPreset.max,
   }) async {
@@ -99,6 +105,7 @@ class CameraPicker extends StatefulWidget {
           isAllowRecording: isAllowRecording,
           isOnlyAllowRecording: isOnlyAllowRecording,
           theme: theme,
+          quarterTurns: cameraQuarterTurns,
           textDelegate: textDelegate,
           resolutionPreset: resolutionPreset,
         ),
@@ -533,8 +540,7 @@ class CameraPickerState extends State<CameraPicker> {
         children: <Widget>[
           const Spacer(),
           // TODO(Alex): There's an issue tracking NPE of the camera plugin, so switching is temporary disabled .
-          if ((cameras?.length ?? 0) > 1)
-            switchCamerasButton,
+          if ((cameras?.length ?? 0) > 1) switchCamerasButton,
         ],
       ),
     );
@@ -683,9 +689,12 @@ class CameraPickerState extends State<CameraPicker> {
           children: <Widget>[
             if (isInitialized)
               Center(
-                child: AspectRatio(
-                  aspectRatio: cameraController.value.aspectRatio,
-                  child: CameraPreview(cameraController),
+                child: RotatedBox(
+                  quarterTurns: widget.quarterTurns ?? 0,
+                  child: AspectRatio(
+                    aspectRatio: cameraController.value.aspectRatio,
+                    child: CameraPreview(cameraController),
+                  ),
                 ),
               )
             else