我的MonoTouch版本信息： 版本号：20401003 Git修订版：2f1746af36f421d262dcd2b0542ce86b12158f02 建设日期：2010-12-23 23:13:38 + 0000
使用以下代码显示MFMailComposeViewController并将其作为对话框正常工作：
if (MFMailComposeViewController.CanSendMail) {
MFMailComposeViewController mail;
mail = new MFMailComposeViewController ();
mail.SetSubject ("Subject Test");
mail.SetMessageBody ("Body Test", false);
mail.Finished += HandleMailFinished;
this.navigationController.PresentModalViewController (mail, true);
} else {
new UIAlertView ("Mail Failed", "Mail Failed", null, "OK", null).Show ();
}
但是，一旦用户选择取消|删除草稿或取消|保存草稿或发送，应用程序抛出运行时错误，如下所示：
Stacktrace:
at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication.UIApplicationMain (int,string[],intptr,intptr) <0x00004>
at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication.UIApplicationMain (int,string[],intptr,intptr) <0x00004>
at MonoTouch.UIKit.UIApplication.Main (string[],string,string) [0x00038] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:26
at MonoTouch.UIKit.UIApplication.Main (string[]) [0x00000] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:31
at MailDialog.Application.Main (string[]) [0x00000] in /Users/rrkhan/Projects/Sandbox/MailDialog/Main.cs:15
at (wrapper runtime-invoke) <Module>.runtime_invoke_void_object (object,intptr,intptr,intptr) <IL 0x0001d, 0x00043>
Native stacktrace:
0 MailDialog 0x000be66f mono_handle_native_sigsegv + 343
1 MailDialog 0x0000e43e mono_sigsegv_signal_handler + 313
2 libSystem.B.dylib 0x903e946b _sigtramp + 43
3 ??? 0xffffffff 0x0 + 4294967295
4 MessageUI 0x01a9f6b7 -[MFMailComposeController _close] + 284
5 UIKit 0x01f682f1 -[UIActionSheet(Private) _buttonClicked:] + 258
6 UIKit 0x01be1a6e -[UIApplication sendAction:to:from:forEvent:] + 119
7 UIKit 0x01c701b5 -[UIControl sendAction:to:forEvent:] + 67
8 UIKit 0x01c72647 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527
9 UIKit 0x01c711f4 -[UIControl touchesEnded:withEvent:] + 458
10 UIKit 0x01c060d1 -[UIWindow _sendTouchesForEvent:] + 567
11 UIKit 0x01be737a -[UIApplication sendEvent:] + 447
12 UIKit 0x01bec732 _UIApplicationHandleEvent + 7576
13 GraphicsServices 0x03eb7a36 PurpleEventCallback + 1550
14 CoreFoundation 0x00df9064 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
15 CoreFoundation 0x00d596f7 __CFRunLoopDoSource1 + 215
16 CoreFoundation 0x00d56983 __CFRunLoopRun + 979
17 CoreFoundation 0x00d56240 CFRunLoopRunSpecific + 208
18 CoreFoundation 0x00d56161 CFRunLoopRunInMode + 97
19 GraphicsServices 0x03eb6268 GSEventRunModal + 217
20 GraphicsServices 0x03eb632d GSEventRun + 115
21 UIKit 0x01bf042e UIApplicationMain + 1160
22 ??? 0x0a1e4bd9 0x0 + 169757657
23 ??? 0x0a1e4b12 0x0 + 169757458
24 ??? 0x0a1e4515 0x0 + 169755925
25 ??? 0x0a1e4451 0x0 + 169755729
26 ??? 0x0a1e44ac 0x0 + 169755820
27 MailDialog 0x0000e202 mono_jit_runtime_invoke + 1360
28 MailDialog 0x001c92af mono_runtime_invoke + 137
29 MailDialog 0x001caf6b mono_runtime_exec_main + 714
30 MailDialog 0x001ca891 mono_runtime_run_main + 812
31 MailDialog 0x00094fe8 mono_jit_exec + 200
32 MailDialog 0x0027cf05 main + 3494
33 MailDialog 0x00002ca1 _start + 208
34 MailDialog 0x00002bd0 start + 40
Debug info from gdb:
warning: Could not find object file "/var/folders/Ny/NyElTwhDGD8kZMqIEeLGXE+++TI/-Tmp-//cc6F1tBs.o" - no debug information available for "template.m".
warning: .o file "/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(zlib-helper.x86.42.o)" more recent than executable timestamp in "/Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog"
warning: Could not open OSO file /Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(zlib-helper.x86.42.o) to scan for pubtypes for objfile /Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog
warning: .o file "/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(monotouch-glue.x86.42.o)" more recent than executable timestamp in "/Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog"
warning: Could not open OSO file /Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(monotouch-glue.x86.42.o) to scan for pubtypes for objfile /Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog
warning: .o file "/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(gc.x86.42.o)" more recent than executable timestamp in "/Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog"
warning: Could not open OSO file /Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(gc.x86.42.o) to scan for pubtypes for objfile /Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog
Error connecting stdout and stderr (127.0.0.1:10001)
warning: .o file "/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(monotouch-glue.x86.42.o)" more recent than executable timestamp in "/Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog"
warning: Couldn't open object file '/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(monotouch-glue.x86.42.o)'
Attaching to process 9992.
Reading symbols for shared libraries . done
Reading symbols for shared libraries ....................................................................................................................... done
0x9038e459 in read$UNIX2003 ()
8 0x903a8a12 in __workq_kernreturn ()
7 "WebThread" 0x903830fa in mach_msg_trap ()
6 0x903b10a6 in __semwait_signal ()
5 0x90383136 in semaphore_wait_trap ()
4 0x903830fa in mach_msg_trap ()
3 0x903a8a12 in __workq_kernreturn ()
2 "com.apple.libdispatch-manager" 0x903a9982 in kevent ()
* 1 "com.apple.main-thread" 0x9038e459 in read$UNIX2003 ()
Thread 8 (process 9992):
#0 0x903a8a12 in __workq_kernreturn ()
#1 0x903a8fa8 in _pthread_wqthread ()
#2 0x903a8bc6 in start_wqthread ()
Thread 7 (process 9992):
#0 0x903830fa in mach_msg_trap ()
#1 0x90383867 in mach_msg ()
#2 0x00df94a6 in __CFRunLoopServiceMachPort ()
#3 0x00d56874 in __CFRunLoopRun ()
#4 0x00d56240 in CFRunLoopRunSpecific ()
#5 0x00d56161 in CFRunLoopRunInMode ()
#6 0x04f7c423 in RunWebThread ()
#7 0x903b085d in _pthread_start ()
#8 0x903b06e2 in thread_start ()
Thread 6 (process 9992):
#0 0x903b10a6 in __semwait_signal ()
#1 0x903dcee5 in nanosleep$UNIX2003 ()
#2 0x903dce23 in usleep$UNIX2003 ()
#3 0x0027714c in monotouch_pump_gc ()
#4 0x903b085d in _pthread_start ()
#5 0x903b06e2 in thread_start ()
Thread 5 (process 9992):
#0 0x90383136 in semaphore_wait_trap ()
#1 0x0015ae1d in finalizer_thread (unused=0x0) at ../../../../mono/metadata/gc.c:1026
#2 0x002034a3 in start_wrapper (data=0x7b16ba0) at ../../../../mono/metadata/threads.c:661
#3 0x002448e2 in thread_start_routine (args=0x8037e34) at ../../../../mono/io-layer/wthreads.c:286
#4 0x00274357 in GC_start_routine (arg=0x6ff7f60) at ../../../libgc/pthread_support.c:1390
#5 0x903b085d in _pthread_start ()
#6 0x903b06e2 in thread_start ()
Thread 4 (process 9992):
#0 0x903830fa in mach_msg_trap ()
#1 0x90383867 in mach_msg ()
#2 0x0011cc46 in mach_exception_thread (arg=0x0) at ../../../../mono/mini/mini-darwin.c:138
#3 0x903b085d in _pthread_start ()
#4 0x903b06e2 in thread_start ()
Thread 3 (process 9992):
#0 0x903a8a12 in __workq_kernreturn ()
#1 0x903a8fa8 in _pthread_wqthread ()
#2 0x903a8bc6 in start_wqthread ()
Thread 2 (process 9992):
#0 0x903a9982 in kevent ()
#1 0x903aa09c in _dispatch_mgr_invoke ()
#2 0x903a9559 in _dispatch_queue_invoke ()
#3 0x903a92fe in _dispatch_worker_thread2 ()
#4 0x903a8d81 in _pthread_wqthread ()
#5 0x903a8bc6 in start_wqthread ()
Thread 1 (process 9992):
#0 0x9038e459 in read$UNIX2003 ()
#1 0x000be81f in mono_handle_native_sigsegv (signal=11, ctx=0xbfffd238) at ../../../../mono/mini/mini-exceptions.c:1826
#2 0x0000e43e in mono_sigsegv_signal_handler (_dummy=10, info=0xbfffd1f8, context=0xbfffd238) at ../../../../mono/mini/mini.c:4846
#3 <signal handler called>
#4 0x028d6a63 in objc_msgSend ()
#5 0x01ad469f in __func__.24012 ()
#6 0x01a9f6b7 in -[MFMailComposeController _close] ()
#7 0x01f682f1 in -[UIActionSheet(Private) _buttonClicked:] ()
#8 0x01be1a6e in -[UIApplication sendAction:to:from:forEvent:] ()
#9 0x01c701b5 in -[UIControl sendAction:to:forEvent:] ()
#10 0x01c72647 in -[UIControl(Internal) _sendActionsForEvents:withEvent:] ()
#11 0x01c711f4 in -[UIControl touchesEnded:withEvent:] ()
#12 0x01c060d1 in -[UIWindow _sendTouchesForEvent:] ()
#13 0x01be737a in -[UIApplication sendEvent:] ()
#14 0x01bec732 in _UIApplicationHandleEvent ()
#15 0x03eb7a36 in PurpleEventCallback ()
#16 0x00df9064 in __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ ()
#17 0x00d596f7 in __CFRunLoopDoSource1 ()
#18 0x00d56983 in __CFRunLoopRun ()
#19 0x00d56240 in CFRunLoopRunSpecific ()
#20 0x00d56161 in CFRunLoopRunInMode ()
#21 0x03eb6268 in GSEventRunModal ()
#22 0x03eb632d in GSEventRun ()
#23 0x01bf042e in UIApplicationMain ()
#24 0x0a1e4bd9 in ?? ()
#25 0x0a1e4b12 in ?? ()
#26 0x0a1e4515 in ?? ()
#27 0x0a1e4451 in ?? ()
#28 0x0a1e44ac in ?? ()
#29 0x0000e202 in mono_jit_runtime_invoke (method=0xa806e6c, obj=0x0, params=0xbfffedbc, exc=0x0) at ../../../../mono/mini/mini.c:4733
#30 0x001c92af in mono_runtime_invoke (method=0xa806e6c, obj=0x0, params=0xbfffedbc, exc=0x0) at ../../../../mono/metadata/object.c:2615
#31 0x001caf6b in mono_runtime_exec_main (method=0xa806e6c, args=0xa6a34e0, exc=0x0) at ../../../../mono/metadata/object.c:3581
#32 0x001ca891 in mono_runtime_run_main (method=0xa806e6c, argc=0, argv=0xbfffeef4, exc=0x0) at ../../../../mono/metadata/object.c:3355
#33 0x00094fe8 in mono_jit_exec (domain=0x6f8fe58, assembly=0xa200730, argc=1, argv=0xbfffeef0) at ../../../../mono/mini/driver.c:1094
#34 0x0027cf05 in main ()
=================================================================
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.
=================================================================
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object
at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
at MonoTouch.UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00038] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:26
at MonoTouch.UIKit.UIApplication.Main (System.String[] args) [0x00000] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:31
at MailDialog.Application.Main (System.String[] args) [0x00000] in /Users/rrkhan/Projects/Sandbox/MailDialog/Main.cs:15
我有一个非常简单的示例项目来说明问题。如果需要，我可以发给你。
答案 0 :(得分：2)
你允许在C＃状态完成之前收集你的MFMailComposeViewController，重构你的类基本上是这样的：
public class Container {
MFMailComposeViewController mail;
public void Foo () {
if (MFMailComposeViewController.CanSendMail) {
mail = new MFMailComposeViewController ();
mail.SetSubject ("Subject Test");
mail.SetMessageBody ("Body Test", false);
mail.Finished += HandleMailFinished;
this.navigationController.PresentModalViewController (mail, true);
}
}
public void HandleMailFinished (...) {
// existing logic
mail.Dispose ();
mail = null;
}
}