我使用image_picker库（https://pub.dartlang.org/packages/image_picker#-readme-tab-）允许用户从他们的照片库/图库中选择一个配置文件图像。在iOS上，用户只能访问照片中的照片，但在Android上，用户可以转到文件管理器并选择其他文件类型，如音频。只需检查null，就不能保证用户选择了图像。
在Dart / Flutter中是否有一种方法可以确保_imageFile是一个能够成功使用FileImage构造函数的图像？
Future getImage() async {
if(currentUser.isLoggedIn) {
_imageFile = await ImagePicker.pickImage(source: ImageSource.gallery);
setState(() {
if (_imageFile != null) {
currentUser.profileImage = FileImage(_imageFile);
uploadImage();
} else {
print('no image selected');
}
});
}
从文件管理器中选择音频文件时，以下是错误报告：
E/flutter (14947): [ERROR:flutter/lib/ui/painting/codec.cc(97)] Failed decoding image. Data is either invalid, or it is encoded using an unsupported format.
I/flutter (14947): ══╡ EXCEPTION CAUGHT BY IMAGE RESOURCE SERVICE ╞════════════════════════════════════════════════════
I/flutter (14947): The following _Exception was thrown resolving an image codec:
I/flutter (14947): Exception: operation failed
I/flutter (14947):
I/flutter (14947): When the exception was thrown, this was the stack:
I/flutter (14947): #0 FileImage._loadAsync (package:flutter/src/painting/image_provider.dart:579:12)
I/flutter (14947): <asynchronous suspension>
I/flutter (14947): #1 FileImage.load (package:flutter/src/painting/image_provider.dart:564:14)
I/flutter (14947): #2 ImageProvider.resolve.<anonymous closure>.<anonymous closure> (package:flutter/src/painting/image_provider.dart:299:46)
I/flutter (14947): #3 ImageCache.putIfAbsent (package:flutter/src/painting/image_cache.dart:157:22)
I/flutter (14947): #4 ImageProvider.resolve.<anonymous closure> (package:flutter/src/painting/image_provider.dart:299:23)
I/flutter (14947): #5 SynchronousFuture.then (package:flutter/src/foundation/synchronous_future.dart:38:29)
I/flutter (14947): #6 ImageProvider.resolve (package:flutter/src/painting/image_provider.dart:296:9)
I/flutter (14947): #7 DecorationImagePainter.paint (package:flutter/src/painting/decoration_image.dart:239:55)
I/flutter (14947): #8 _BoxDecorationPainter._paintBackgroundImage (package:flutter/src/painting/box_decoration.dart:414:19)
I/flutter (14947): #9 _BoxDecorationPainter.paint (package:flutter/src/painting/box_decoration.dart:432:5)
I/flutter (14947): #10 RenderDecoratedBox.paint (package:flutter/src/rendering/proxy_box.dart:1968:16)
I/flutter (14947): #11 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2104:7)
I/flutter (14947): #12 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:173:13)
I/flutter (14947): #13 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:123:15)
I/flutter (14947): #14 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2104:7)
I/flutter (14947): #15 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:173:13)
I/flutter (14947): #16 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:123:15)
I/flutter (14947): #17 RenderPointerListener.paint (package:flutter/src/rendering/proxy_box.dart:2645:11)
I/flutter (14947): #18 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2104:7)
I/flutter (14947): #19 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:173:13)
I/flutter (14947): #20 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:123:15)
I/flutter (14947): #21 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2104:7)
I/flutter (14947): #22 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:173:13)
I/flutter (14947): #23 RenderShiftedBox.paint (package:flutter/src/rendering/shifted_box.dart:70:15)
I/flutter (14947): #24 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2104:7)
I/flutter (14947): #25 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:173:13)
I/flutter (14947): #26 _RenderStack&RenderBox&ContainerRenderObjectMixin&RenderBoxContainerDefaultsMixin.defaultPaint (package:flutter/src/rendering/box.dart:2273:15)
I/flutter (14947): #27 RenderStack.paintStack (package:flutter/src/rendering/stack.dart:594:5)
I/flutter (14947): #28 RenderStack.paint (package:flutter/src/rendering/stack.dart:602:7)
I/flutter (14947): #29 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2104:7)
I/flutter (14947): #30 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:173:13)
I/flutter (14947): #31 RenderShiftedBox.paint (package:flutter/src/rendering/shifted_box.dart:70:15)
I/flutter (14947): #32 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2104:7)
I/flutter (14947): #33 PaintingContext.paintChild (package:flutter/src/rendering/object.dart:173:13)
I/flutter (14947): #34 _RenderProxyBox&RenderBox&RenderObjectWithChildMixin&RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:123:15)
I/flutter (14947): #35 RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2104:7)
I/flutter (14947): #36 PaintingContext._repaintCompositedChild (package:flutter/src/rendering/object.dart:128:11)
I/flutter (14947): #37 PaintingContext.repaintCompositedChild (package:flutter/src/rendering/object.dart:96:5)
I/flutter (14947): #38 PipelineOwner.flushPaint (package:flutter/src/rendering/object.dart:859:29)
I/flutter (14947): #39 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:338:19)
I/flutter (14947): #40 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:701:13)
I/flutter (14947): #41 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:275:5)
I/flutter (14947): #42 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1008:15)
I/flutter (14947): #43 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:948:9)
I/flutter (14947): #44 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:860:5)
I/flutter (14947): #48 _invoke (dart:ui/hooks.dart:219:10)
I/flutter (14947): #49 _drawFrame (dart:ui/hooks.dart:178:3)
I/flutter (14947): (elided 3 frames from package dart:async)
I/flutter (14947):
I/flutter (14947): Path: /data/user/0/com.undauntedathlete.UndauntedGolf/cache/image_picker2760241735413495899jpg
I/flutter (14947): ════════════════════════════════════════════════════════════════════════════════════════════════════
imho这是你正在使用的文件管理器中的一个错误，因为image_picker插件确实请求pickImageIntent.setType("image/*");（例如，Google Drive提供商只允许选择图像）。
所以基本上你必须自己检查一下。我认为有三种方法，取决于您需要解决方案的复杂程度。
File.path是否以已知的图像文件扩展名结束的低质量检查..（你可以使用例如已经包含mime的good list of extensions dart包。File之后，使用ImageFile.resolve尝试解析图像，然后将其设置在Image本身上（捕获错误并警告用户）这显然取决于你的要求，如果你让用户选择一个图像并立即上传它，nr 2.将是最有意义的。如果您首先让用户预览图像使用nr 3. - 或者如果您只是上传它，那么让用户上传图像并进行服务器端检查甚至是有意义的。因此，例如，用户可以选择服务器可能能够处理的SVG，但是颤动不能（无论如何都是开箱即用的）。