我正在使用MonoTouch / Mono for Android，目前正在创建我自己的UIColor子类。不知怎的，我不能按照我想要的方式使我的工厂方法工作（但我确实有一个解决办法）。
以下代码导致我崩溃：
using System;
#if ANDROID
// TODO: T.B.I.
#else
using MonoTouch.UIKit;
#endif
namespace OurCompany.Core
{
public class Color : UIColor
{
public Color (float r, float g, float b, float a) : base(r, g, b, a)
{
}
// our webservice sends color strings in the following ugly format:
// 0,255,100,1.0
public static Color FromColorString (string colorString)
{
var comps = colorString != null ? colorString.Split (new char[] {','}) : null;
if (comps == null || comps.Length != 4) {
return null;
}
float r = 0.0f, g = 0.0f, b = 0.0f, a = 1.0f;
float.TryParse (comps [0], out r);
float.TryParse (comps [1], out g);
float.TryParse (comps [2], out b);
float.TryParse (comps [3], out a);
return new Color (r, g, b, a);
}
}
}
将return语句更改为以下内容时，我没有遇到任何崩溃：
return (Color)UIColor.FromRGBA (
r > 0 ? r / 255 : 0.0f,
g > 0 ? g / 255 : 0.0f,
b > 0 ? b / 255 : 0.0f,
a
);
这个return语句的主要区别在于创建了一个UIColor对象并将其类型化为Color对象，而在崩溃版本中，我使用我的参数实例化了一个Color对象。在以这种方式实例化基类时，可能会出现问题？我很困惑。
最后是崩溃的堆栈跟踪：
堆栈跟踪：
at (wrapper managed-to-native) MonoTouch.ObjCRuntime.Messaging.IntPtr_objc_msgSendSuper (intptr,intptr) <IL 0x00026, 0xffffffff>
at MonoTouch.UIKit.UIColor.get_CGColor () [0x00021] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIColor.g.cs:476
at MonoTouch.UIKit.UIColor.GetRGBA (single&,single&,single&,single&) [0x00000] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIColor.cs:51
at MonoTouch.UIKit.UIColor.ToString () [0x00000] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIColor.cs:141
at string.FormatHelper (System.Text.StringBuilder,System.IFormatProvider,string,object[]) [0x00168] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/String.cs:1890
at string.Format (System.IFormatProvider,string,object[]) [0x00000] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/String.cs:1820
at string.Format (string,object[]) [0x00000] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/String.cs:1815
at OurCompany.Core.AppDefaults.ToString () [0x00000] in /Volumes/Development/Mono/OurCompany/OurCompany.Core.Cloned/DL/AppDefaults.cs:78
at string.FormatHelper (System.Text.StringBuilder,System.IFormatProvider,string,object[]) [0x00168] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/String.cs:1890
at string.Format (System.IFormatProvider,string,object[]) [0x00000] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/String.cs:1820
at string.Format (string,object) [0x00000] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/String.cs:1800
at System.IO.TextWriter.Write (string,object) [0x00000] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.IO/TextWriter.cs:191
at System.IO.TextWriter.WriteLine (string,object) [0x00000] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.IO/TextWriter.cs:305
at System.IO.SynchronizedWriter.WriteLine (string,object) [0x0000c] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.IO/TextWriter.cs:598
at System.Console.WriteLine (string,object) [0x00000] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/Console.cs:459
at OurCompany.Core.AppDefaults..ctor (System.IO.MemoryStream) [0x0012b] in /Volumes/Development/Mono/OurCompany/OurCompany.Core.Cloned/DL/AppDefaults.cs:73
at OurCompany.Core.HomeScreenService/<LoadAppDefaultsAsync>c__AnonStorey2.<>m__2 (byte[],System.Exception) [0x0000f] in /Volumes/Development/Mono/OurCompany/OurCompany.Core.Cloned/SAL/HomeScreenService.cs:47
at OurCompany.Core.ServiceRequest/<LoadRequestAsync>c__AnonStorey4.<>m__4 (object,System.Net.DownloadDataCompletedEventArgs) [0x00022] in /Volumes/Development/Mono/OurCompany/OurCompany.Core.Cloned/SAL/ServiceRequest.cs:31
at System.Net.WebClient.OnDownloadDataCompleted (System.Net.DownloadDataCompletedEventArgs) [0x00011] in /Developer/MonoTouch/Source/mono/mcs/class/System/System.Net/WebClient.cs:1388
at System.Net.WebClient.<DownloadDataAsync>m__D (object) [0x00019] in /Developer/MonoTouch/Source/mono/mcs/class/System/System.Net/WebClient.cs:1037
at System.Threading.Thread.StartInternal () [0x00032] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.Threading/Thread.cs:699
at (wrapper runtime-invoke) object.runtime_invoke_void__this__ (object,intptr,intptr,intptr) <IL 0x0004e, 0xffffffff>
原生堆栈跟踪：
0 OurCompanyiOS 0x0009148c mono_handle_native_sigsegv + 284
1 OurCompanyiOS 0x00005568 mono_sigsegv_signal_handler + 248
2 libsystem_c.dylib 0x99d7686b _sigtramp + 43
3 ??? 0xffffffff 0x0 + 4294967295
4 CoreFoundation 0x012c3ae0 __CFStringAppendFormatCore + 16208
5 CoreFoundation 0x012bfaab CFStringCreateWithFormatAndArguments + 107
6 CoreFoundation 0x01348da1 +[NSException raise:format:] + 65
7 UIKit 0x028f7f34 -[UIColor CGColor] + 82
8 ??? 0x100a2743 0x0 + 269100867
9 ??? 0x140ee158 0x0 + 336519512
10 ??? 0x140edcbc 0x0 + 336518332
11 ??? 0x140eda18 0x0 + 336517656
12 ??? 0x0fbf703a 0x0 + 264204346
13 ??? 0x13e03a8c 0x0 + 333462156
14 ??? 0x140e9394 0x0 + 336499604
15 ??? 0x140e90c8 0x0 + 336498888
16 ??? 0x0fbf703a 0x0 + 264204346
17 ??? 0x13e03a8c 0x0 + 333462156
18 ??? 0x13ecd1b0 0x0 + 334287280
19 ??? 0x13ecd110 0x0 + 334287120
20 ??? 0x13ecd0a7 0x0 + 334287015
21 ??? 0x13eccffe 0x0 + 334286846
22 ??? 0x13eccf68 0x0 + 334286696
23 ??? 0x13ebb838 0x0 + 334215224
24 ??? 0x13ebb0c8 0x0 + 334213320
25 ??? 0x13ea481a 0x0 + 334120986
26 ??? 0x13ea42e9 0x0 + 334119657
27 ??? 0x13e167f2 0x0 + 333539314
28 ??? 0x13e150d7 0x0 + 333533399
29 ??? 0x0fbf4070 0x0 + 264192112
30 OurCompanyiOS 0x00009922 mono_jit_runtime_invoke + 722
31 OurCompanyiOS 0x0016c4ae mono_runtime_invoke + 126
32 OurCompanyiOS 0x0016c61c mono_runtime_delegate_invoke + 140
33 OurCompanyiOS 0x001a7522 start_wrapper + 466
34 OurCompanyiOS 0x001d94ba thread_start_routine + 154
35 OurCompanyiOS 0x002008ad GC_start_routine + 93
36 libsystem_c.dylib 0x99d8a557 _pthread_start + 344
37 libsystem_c.dylib 0x99d74cee thread_start + 34
=================================================================
Got a SIGSEGV while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries
used by your application.
=================================================================
答案 0 :(得分：0)
好吧，我意识到我做错了什么，我应该更清楚地检查错误信息。
我的AppDefaults类有以下ToString（）方法（由MonoDevelop自动完成，可能仍然依赖于我以前的UIColor实现）：
public override string ToString ()
{
return string.Format ("[AppDefaults: name={0}, appId={1}, userId={2}, themeId={3}, parallaxEnabled={4}, themeModifyDate={5}, tabBarColor={6}, tabColor={7}, backButtonColor={8}]", name, appId, userId, themeId, parallaxEnabled, themeModifyDate, tabBarColor, tabColor, backButtonColor);
}
错误消息还显示了在尝试为颜色类编写字符串值时发生错误的提示：
at MonoTouch.UIKit.UIColor.GetRGBA (single&,single&,single&,single&) [0x00000] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIColor.cs:51
at MonoTouch.UIKit.UIColor.ToString () [0x00000] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIColor.cs:141
at string.FormatHelper (System.Text.StringBuilder,System.IFormatProvider,string,object[]) [0x00168] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System/String.cs:1890
所以最终修复很容易：从类中禁用我的ToString()方法。我讨厌我浪费了6个小时这个明显的错误，但是这样的事情总是在使用新框架时发生......
编辑：也许我也可以在我的自定义Color子类中覆盖我的ToString()方法，尽管这本身似乎并不能防止崩溃。我确实意识到如果一些随机的人可以使用这段代码，我需要防止将来发生这种崩溃。
编辑2：查看崩溃日志似乎初始化可能无法正常工作。我看到很多null个值（0x000 ....）。调用GetRGBA（）时出错。也许我需要覆盖UIColor基类的一些成员才能使这个方法有效？我可以想象在我的自定义GetRGBA()类而不是Color基类上调用UIColor，导致失败。
编辑3：这家伙可能为我的问题选择了更好的方法。也许这将是我需要的修复：
http://codebetter.com/petervanooijen/2010/09/28/monotouch-drawing-an-image-pixel-by-pixel/
编辑4：我决定根据最后一个链接重构我的代码。我的自定义颜色类将存储颜色的属性，并有一个或多个方法来创建原生颜色对象（例如iOS上的UIColor，Android的相应颜色对象）。