android - 断言宽度 > 0.0' : is not true when placing single Image in Container in FittedBox 失败

Question

当我将 Image.network 放置在作为 FittedBox 子项的 Row 或 Container 中时，查看它会导致错误/崩溃。

FittedBox 实际上使用一个函数作为其子项，该函数根据图像数量返回一个小部件。当有两个图像时，它返回一个 Row ，其中每个图像都是它的子图像，它可以正常工作，但是当只有一个图像时，无论我返回一个以图像作为其子图像的 Container 还是一个带有 Single 子图像的 Row ，都会发生错误成为形象。

            Container(
              child: FittedBox(child: status.statusFiles()),
            ),

状态文件:

    return Container(
        child: 
          Image.network(
            this.files[0].thumbnailUrl,
            fit: BoxFit.contain,
          ),
        );

我希望 FittedBox 包含适合的最大尺寸的图像，但在呈现小部件时出现以下错误

I/flutter (26617): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter (26617): The following assertion was thrown during performLayout():
I/flutter (26617): 'package:flutter/src/rendering/box.dart': Failed assertion: line 307 pos 12: 'width > 0.0': is not
I/flutter (26617): true.
...
I/flutter (26617): When the exception was thrown, this was the stack:
I/flutter (26617): #2      BoxConstraints.constrainSizeAndAttemptToPreserveAspectRatio (package:flutter/src/rendering/box.dart:307:12)
I/flutter (26617): #3      RenderFittedBox.performLayout (package:flutter/src/rendering/proxy_box.dart:2275:26)
I/flutter (26617): #4      RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (26617): #5      RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:738:15)
I/flutter (26617): #6      RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (26617): #7      RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:798:17)
I/flutter (26617): #8      RenderObject.layout (package:flutter/src/rendering/object.dart:1634:7)
I/flutter (26617): #9      RenderPadding.performLayout (package:flutter/src/rendering/shifted_box.dart:199:11)
...
I/flutter (26617): The following RenderObject was being processed when the exception was fired:
I/flutter (26617):   RenderFittedBox#d752c relayoutBoundary=up8 NEEDS-LAYOUT NEEDS-PAINT
I/flutter (26617):   creator: FittedBox ← Container ← Column ← Expanded ← Row ← Padding ← Container ←
I/flutter (26617):   RepaintBoundary-[<16>] ← IndexedSemantics ← NotificationListener<KeepAliveNotification> ←
I/flutter (26617):   KeepAlive ← AutomaticKeepAlive ← ⋯
I/flutter (26617):   parentData: offset=Offset(0.0, 0.0); flex=null; fit=null (can use size)
I/flutter (26617):   constraints: BoxConstraints(0.0<=w<=339.4, 0.0<=h<=Infinity)
I/flutter (26617):   size: MISSING
I/flutter (26617):   fit: contain
I/flutter (26617):   alignment: center
I/flutter (26617):   textDirection: ltr
I/flutter (26617): This RenderObject had the following descendants (showing up to depth 5):
I/flutter (26617):   RenderSemanticsAnnotations#df6f3 relayoutBoundary=up9 NEEDS-PAINT
I/flutter (26617):     RenderImage#63da1 relayoutBoundary=up10 NEEDS-PAINT
I/flutter (26617): ════════════════════════════════════════════════════════════════════════════════════════════════════

Answer 1

之前的解决方案都不适合我，因为我使用了 fit: Boxfit.fitWidth 并且我确实需要祖先的高度取决于图像宽度。

我的解决方案是将图像包裹在 ConstrainedBox 中并手动应用 min. 1 的高度和宽度:

ConstrainedBox(
      constraints: BoxConstraints(maxHeight: maxHeight),
      child: Hero(
        tag: 'SettingsPic',
        child: Container(
          width: double.infinity,
          decoration: BoxDecoration(
              borderRadius: BorderRadius.vertical(bottom: Radius.circular(25)),
              boxShadow: [BoxShadow(
                  color: Colors.black.withOpacity(0.2),
                  blurRadius: 10
              )]
          ),
          child: ClipRRect(
            borderRadius: BorderRadius.vertical(bottom: Radius.circular(25)),
            child: FittedBox(
              fit: BoxFit.fitWidth,
              alignment: Alignment.bottomCenter,
              child: ConstrainedBox(
                constraints: BoxConstraints(minWidth: 1, minHeight: 1), // here
                child: Image.asset(
                  'resources/images/background.png',
                ),
              ),
            ),
          ),
        ),
      ),
    )