为什么不让我使用相机控制器拍照？

问题描述

我正在尝试使用全屏相机创建应用程序。实时摄像机供稿以及按钮反馈都可以正常工作。似乎在_controller.takePicture(path)行有问题，因为“ IS INITIALIZED”打印语句返回true。我将路径，路径提供者和相机依赖项放在pubspec.yaml中。

CameraController的初始化

cameras = await availableCameras();
    var frontCamera = cameras.first;

    _controller = CameraController(frontCamera,ResolutionPreset.high);
    try {
      await _controller.initialize();
    } catch (e) {
    }
    print('Controller Is Init:' + _controller.value.isInitialized.toString());
    displayPreview();

child: GestureDetector(
                  behavior: HitTestBehavior.translucent,child:Container(
                  child: Icon(Icons.camera,color: Colors.white,size: 60,)),onTap: () async {
                    print('IS INITIALIZED'+_controller.value.isInitialized.toString());
                    try {
                      await _controller.takePicture(path);
                    }
                    catch(e){
                      print('E:'+e);
                    }

错误：

E/MethodChannel#plugins.Flutter.io/camera(28109): Failed to handle method call
E/MethodChannel#plugins.Flutter.io/camera(28109): java.lang.NullPointerException
E/MethodChannel#plugins.Flutter.io/camera(28109):   at java.io.File.<init>(File.java:283)
E/MethodChannel#plugins.Flutter.io/camera(28109):   at io.Flutter.plugins.camera.Camera.takePicture(Camera.java:227)
E/MethodChannel#plugins.Flutter.io/camera(28109):   at io.Flutter.plugins.camera.MethodCallHandlerImpl.onMethodCall(MethodCallHandlerImpl.java:77)
E/MethodChannel#plugins.Flutter.io/camera(28109):   at io.Flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:230)
E/MethodChannel#plugins.Flutter.io/camera(28109):   at io.Flutter.embedding.engine.dart.DartMessenger.handleMessageFromDart(DartMessenger.java:85)
E/MethodChannel#plugins.Flutter.io/camera(28109):   at io.Flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:664)
E/MethodChannel#plugins.Flutter.io/camera(28109):   at android.os.MessageQueue.nativePollOnce(Native Method)
E/MethodChannel#plugins.Flutter.io/camera(28109):   at android.os.MessageQueue.next(MessageQueue.java:336)
E/MethodChannel#plugins.Flutter.io/camera(28109):   at android.os.Looper.loop(Looper.java:197)
E/MethodChannel#plugins.Flutter.io/camera(28109):   at android.app.ActivityThread.main(ActivityThread.java:8125)
E/MethodChannel#plugins.Flutter.io/camera(28109):   at java.lang.reflect.Method.invoke(Native Method)
E/MethodChannel#plugins.Flutter.io/camera(28109):   at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
E/MethodChannel#plugins.Flutter.io/camera(28109):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)
E/Flutter (28109): [ERROR:Flutter/lib/ui/ui_dart_state.cc(166)] Unhandled Exception: type 'CameraException' is not a subtype of type 'String'
E/Flutter (28109): #0      _VisualPageState.build.<anonymous closure> (package:ourearth2020/screens/VisualPage.dart:209:36)
E/Flutter (28109): <asynchronous suspension>
E/Flutter (28109): #1      _VisualPageState.build.<anonymous closure> (package:ourearth2020/screens/VisualPage.dart)
E/Flutter (28109): #2      GestureRecognizer.invokeCallback (package:Flutter/src/gestures/recognizer.dart:184:24)
E/Flutter (28109): #3      TapGestureRecognizer.handleTapUp (package:Flutter/src/gestures/tap.dart:524:11)
E/Flutter (28109): #4      BaseTapGestureRecognizer._checkUp (package:Flutter/src/gestures/tap.dart:284:5)
E/Flutter (28109): #5      BaseTapGestureRecognizer.handlePrimaryPointer (package:Flutter/src/gestures/tap.dart:219:7)
E/Flutter (28109): #6      PrimaryPointerGestureRecognizer.handleEvent (package:Flutter/src/gestures/recognizer.dart:477:9)
E/Flutter (28109): #7      PointerRouter._dispatch (package:Flutter/src/gestures/pointer_router.dart:78:12)
E/Flutter (28109): #8      PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:Flutter/src/gestures/pointer_router.dart:124:9)
E/Flutter (28109): #9      _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:377:8)
E/Flutter (28109): #10     PointerRouter._dispatchEventToRoutes (package:Flutter/src/gestures/pointer_router.dart:122:18)
E/Flutter (28109): #11     PointerRouter.route (package:Flutter/src/gestures/pointer_router.dart:108:7)
E/Flutter (28109): #12     GestureBinding.handleEvent (package:Flutter/src/gestures/binding.dart:220:19)
E/Flutter (28109): #13     GestureBinding.dispatchEvent (package:Flutter/src/gestures/binding.dart:200:22)
E/Flutter (28109): #14     GestureBinding._handlePointerEvent (package:Flutter/src/gestures/binding.dart:158:7)
E/Flutter (28109): #15     GestureBinding._flushPointerEventQueue (package:Flutter/src/gestures/binding.dart:104:7)
E/Flutter (28109): #16     GestureBinding._handlePointerDataPacket (package:Flutter/src/gestures/binding.dart:88:7)
E/Flutter (28109): #17     _rootRunUnary (dart:async/zone.dart:1206:13)
E/Flutter (28109): #18     _CustomZone.runUnary (dart:async/zone.dart:1100:19)
E/Flutter (28109): #19     _CustomZone.runUnaryguarded (dart:async/zone.dart:1005:7)
E/Flutter (28109): #20     _invoke1 (dart:ui/hooks.dart:283:10)
E/Flutter (28109): #21     _dispatchPointerDataPacket (dart:ui/hooks.dart:192:5)

解决方法

这看起来像您作为参数提供的path不是String而是CameraException。

要创建路径，可以执行此操作（需要path_provider）：

final path = (await getTemporaryDirectory()).path + '${DateTime.now()}.png';

android-camera dart