Flutter 为什么不让我用相机控制器拍照？

我试图创建一个应用程序使用全屏相机。实时摄像机反馈与按钮反馈一样有效。似乎

\u controller.takePicture（path）

行有问题，因为“is INITIALIZED”print语句返回true。我将路径、路径提供程序和摄影机依赖项放在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();

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)

E/MethodChannel#plugins.flatter.io/camera（28109）：无法处理方法调用
E/MethodChannel#plugins.flatter.io/camera（28109）：java.lang.NullPointerException
E/MethodChannel#plugins.flatter.io/camera（28109）：位于java.io.File.（File.java:283）
E/MethodChannel#plugins.flatter.io/camera（28109）：at io.flatter.plugins.camera.camera.takePicture（camera.java:227）
E/MethodChannel#plugins.flatter.io/camera（28109）：at io.flatter.plugins.camera.MethodCallHandlerImpl.onMethodCall（MethodCallHandlerImpl.java:77）
E/MethodChannel#plugins.flatter.io/camera（28109）：在io.flatter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage（MethodChannel.java:230）
E/MethodChannel#plugins.flatter.io/camera（28109）：at-io.flatter.embedding.engine.dart.DartMessenger.handleMessageFromDart（DartMessenger.java:85）
E/MethodChannel#plugins.flatter.io/camera（28109）：at io.flatter.embedding.engine.flatterjni.handlePlatformMessage（flatterjni.java:664）
E/MethodChannel#plugins.flatter.io/camera（28109）：位于android.os.MessageQueue.nativePollOnce（本机方法）
E/MethodChannel#plugins.flatter.io/camera（28109）：位于android.os.MessageQueue.next（MessageQueue.java:336）
E/MethodChannel#plugins.flatter.io/camera（28109）：位于android.os.Looper.loop（Looper.java:197）
E/MethodChannel#plugins.flatter.io/camera（28109）：位于android.app.ActivityThread.main（ActivityThread.java:8125）
E/MethodChannel#plugins.flatter.io/camera（28109）：位于java.lang.reflect.Method.invoke（本机方法）
E/MethodChannel#plugins.flatter.io/camera（28109）：位于com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run（RuntimeInit.java:496）
E/MethodChannel#plugins.flatter.io/camera（28109）：位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:1100）
E/flatter（28109）：[错误：flatter/lib/ui/ui\u dart\u state.cc（166）]未处理的异常：类型“CameraException”不是类型“String”的子类型
E/颤振（28109）：#0u VisualPageState.build。（包装：ourearth2020/screens/VisualPage.dart:209:36）
E/颤振（28109）：
E/颤振（28109）：#1 VisualPageState.build。（包装：ourearth2020/screens/VisualPage.dart）
E/flatter（28109）：#2 GestureRecognitizer.invokeCallback（包：flatter/src/signatures/Recognitizer.dart:184:24）
E/flatter（28109）：#3 TapGestureRecognitor.handleTapUp（软件包：flatter/src/signatures/tap.dart:524:11）
E/颤振（28109）：#4 BaseTapgestureRecognitor.#检查（软件包：颤振/src/手势/tap.省道：284:5）
E/flatter（28109）：#5 BaseTapgestureRecognitor.handlePrimaryPointer（包：flatter/src/signatures/tap.dart:219:7）
E/颤振（28109）：#6 PrimaryPointerTestureRecognizer.handleEvent（包：颤振/src/手势/识别器。dart:477:9）
E/flatter（28109）：#7点路由器。#调度（包：flatter/src/signatures/pointer#router。dart:78:12）
E/颤振（28109）：#8点外部。#调度事件路线。（包装：颤振/src/signatures/pointer_router.省道：124:9）
E/flatter（28109）：#9#LinkedHashMapMixin.forEach（dart:collection patch/compact#u hash.dart:377:8）
E/flatter（28109）：#10点外部。#调度事件路由（包：flatter/src/signatures/pointer#路由器。dart:122:18）
E/flatter（28109）：#11 PointerRouter.route（包：flatter/src/signatures/pointer_router.dart:108:7）
E/flatter（28109）：#12 GestureBinding.handleEvent（包装：flatter/src/signatures/binding.dart:220:19）
E/flatter（28109）：#13 GestureBinding.dispatchEvent（包：flatter/src/signatures/binding.dart:200:22）
电子/颤振（28109）：#14手势绑定。#手持点事件（包装：颤振/src/手势/绑定。省道：158:7）
E/flatter（28109）：#15个手势绑定。(u flushpointerreeventqueue（包装：flatter/src/signatures/binding.dart:104:7）
E/flatter（28109）：#16个手势绑定。"handlepointerdata包（包：flatter/src/signatures/binding.dart:88:7）
E/颤振（28109）：#17 35;根运行单位（dart:async/zone.dart:1206:13）
E/flatter（28109）：#18 _CustomZone.runUnary（dart:async/zone.dart:1100:19）
E/flatter（28109）：#19 _CustomZone.rununaryarcheed（dart:async/zone.dart:1005:7）
E/颤振（28109）：#20 _调用1（省道：ui/挂钩。省道：283:10）
E/flatter（28109）：#21 dispatchPointerDataPacket（dart:ui/hooks.dart:192:5）

这看起来像是您作为参数提供的

路径

不是

字符串

，而是

CameraException

要创建路径，您可以这样做（需要）：

---

另外，我可以不保存路径，而是将其存储在一个文件中，然后显示它吗？

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)

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