经营你的iOS应用日志（二）：异常日志

来源：互联网发布：万能电子狗升级软件编辑：程序博客网时间：2024/04/29 15:50

言归正传。开发iOS应用，解决Crash问题始终是一个难题。Crash分为两种，一种是由EXC_BAD_ACCESS引起的，原因是访问了不属于本进程的内存地址，有可能是访问已被释放的内存；另一种是未被捕获的Objective-C异常（NSException），导致程序向自身发送了SIGABRT信号而崩溃。其实对于未捕获的Objective-C异常，我们是有办法将它记录下来的，如果日志记录得当，能够解决绝大部分崩溃的问题。这里对于UI线程与后台线程分别说明。

先看UI线程。iOS SDK提供了NSSetUncaughtExceptionHandler函数，用法如：

NSSetUncaughtExceptionHandler( handleRootException );

这样在UI线程发生未捕获异常后，进程崩溃之前，handleRootException会被执行。这个函数实现如下

static void handleRootException( NSException* exception )
{
    NSString* name = [ exception name ];
    NSString* reason = [ exception reason ];
    NSArray* symbols = [ exception callStackSymbols ]; // 异常发生时的调用栈
    NSMutableString* strSymbols = [ [ NSMutableString alloc ] init ]; // 将调用栈拼成输出日志的字符串
    for ( NSString* item in symbols )
    {
        [ strSymbols appendString: item ];
        [ strSymbols appendString: @"\r\n" ];
    }

    // 写日志，级别为ERROR
    writeCinLog( __FUNCTION__, CinLogLevelError, @"[ Uncaught Exception ]\r\nName: %@, Reason: %@\r\n[ Fe Symbols Start ]\r\n%@[ Fe Symbols End ]", name, reason, strSymbols );
    [ strSymbols release ];
    
    // 这儿必须Hold住当前线程，等待日志线程将日志成功输出，当前线程再继续运行
    blockingFlushLogs( __FUNCTION__ );

    // 写一个文件，记录此时此刻发生了异常。这个挺有用的哦
    NSDictionary* dict = [ NSDictionary dictionaryWithObjectsAndKeys:
            currentCinLogFileName(), @"LogFile",                // 当前日志文件名称
            currentCinLogFileFullPath(), @"LogFileFullPath",    // 当前日志文件全路径
            [ NSDate date ], @"TimeStamp",                        // 异常发生的时刻
            nil ];
    NSString* path = [ NSString stringWithFormat: @"%@/Documents/", NSHomeDirectory() ];
    NSString* lastExceptionLog = [ NSString stringWithFormat: @"%@LastExceptionLog.txt", path ];
    [ dict writeToFile: lastExceptionLog atomically: YES ];
    
}

而我们的日志组件必须实现blockingFlushLogs函数，确保进程在日志完全写入文件后再退出。这个实现应该很简单吧。

当应用下次启动时，我们可以检查，如果有LastExceptionLog.txt，则弹窗引导测试人员将日志发过来。如果iPhone上面配置了EMail帐户，可以很简单的调用MFMailComposeViewController将日志文件作为附件发送，当然也可以想其它办法。

记得正式发布的版本要将它条件编译去掉哦。

其中文件中的最后一条ERROR即为导致崩溃的异常，而从ERROR之前的日志可以看出当前程序的运行情况。ERROR如下：

<- 03-20 17:21:43 ERROR -> [UI] -[CinUIRunLoopActionManager(Protected) handleRootException:]
[ Uncaught Exception ]
Name: NSDestinationInvalidException, Reason: *** -[CinThreadRunLoopActionManager performSelector:onThread:withObject:waitUntilDone:modes:]: target thread exited while waiting for the perform
[ Fe Symbols Start ]
0   CoreFoundation                      0x340c88d7 __exceptionPreprocess + 186
1   libobjc.A.dylib                     0x343181e5 objc_exception_throw + 32
2   CoreFoundation                      0x340c87b9 +[NSException raise:format:] + 0
3   CoreFoundation                      0x340c87db +[NSException raise:format:] + 34
4   Foundation                          0x35a12493 -[NSObject(NSThreadPerformAdditions) performSelector:onThread:withObject:waitUntilDone:modes:] + 998
5   Foundation                          0x35a3afb5 -[NSObject(NSThreadPerformAdditions) performSelector:onThread:withObject:waitUntilDone:] + 108
6   MyiOSapplication                    0x0022b7e9 -[CinThreadRunLoopActionManager(Protected) performAction:] + 144
13  UIKit                               0x374b36b5 -[UIViewController _setViewAppearState:isAnimating:] + 144
14  UIKit                               0x374b38c1 -[UINavigationController viewWillAppear:] + 288
15  UIKit                               0x374b36b5 -[UIViewController _setViewAppearState:isAnimating:] + 144
16  UIKit                               0x3750e61b -[UIViewController beginAppearanceTransition:animated:] + 190
17  UIKit                               0x3750b415 -[UITabBarController transitionFromViewController:toViewController:transition:shouldSetSelected:] + 184
18  UIKit                               0x3750b357 -[UITabBarController transitionFromViewController:toViewController:] + 30
19  UIKit                               0x3750ac91 -[UITabBarController _setSelectedViewController:] + 300
20  UIKit                               0x3750a9c5 -[UITabBarController setSelectedIndex:] + 240
21  MyiOSapplication                    0x0007ef1d +[Utility ResetCurrentTabIndex] + 172
22  MyiOSapplication                    0x001a87bd -[UIViewController(statusBar) dismissModalViewControllerAnimatedEx:] + 416
23  MyiOSapplication                    0x001793fb -[ImageProcessingViewController save:] + 690
24  CoreFoundation                      0x34022435 -[NSObject performSelector:withObject:withObject:] + 52
25  UIKit                               0x3748c9eb -[UIApplication sendAction:to:from:forEvent:] + 62
26  UIKit                               0x3748c9a7 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 30
27  UIKit                               0x3748c985 -[UIControl sendAction:to:forEvent:] + 44
28  UIKit                               0x3748c6f5 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 492
29  UIKit                               0x3748d02d -[UIControl touchesEnded:withEvent:] + 476
30  UIKit                               0x3748b50f -[UIWindow _sendTouchesForEvent:] + 318
31  UIKit                               0x3748af01 -[UIWindow sendEvent:] + 380
32  UIKit                               0x374714ed -[UIApplication sendEvent:] + 356
33  UIKit                               0x37470d2d _UIApplicationHandleEvent + 5808
34  GraphicsServices                    0x308a3df3 PurpleEventCallback + 882
35  CoreFoundation                      0x3409c553 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 38
36  CoreFoundation                      0x3409c4f5 __CFRunLoopDoSource1 + 140
37  CoreFoundation                      0x3409b343 __CFRunLoopRun + 1370
38  CoreFoundation                      0x3401e4dd CFRunLoopRunSpecific + 300
39  CoreFoundation                      0x3401e3a5 CFRunLoopRunInMode + 104
40  GraphicsServices                    0x308a2fcd GSEventRunModal + 156
41  UIKit                               0x3749f743 UIApplicationMain + 1090
42  MyiOSapplication                    0x000d4ccb main + 174
43  MyiOSapplication                    0x000039c8 start + 40
[ Fe Symbols End ]

可以看到，即使我们没有编译时生成的符号文件，也能够打印出调用栈上的每个函数的名称，只是没有文件名和行号。

那么，除了UI线程之外，自己创建的后台线程呢？运行NSRunLoop的后台线程的线程函数应该如下：

- ( void ) threadProc: ( NSString* )threadName
{
    NSThread* current = [ NSThread currentThread ];
    [ current setName: threadName ];
    NSAutoreleasePool *pool = [ [ NSAutoreleasePool alloc ] init ];
    
    // 一个没有实际作用的NSTimer，确保NSRunLoop不退出。不知道有没有更好的办法啊
    _dummyTimer = [ [ NSTimer timerWithTimeInterval: 10.0
                                             target: self
                                           selector: @selector( dummyTimerProc: )
                                           userInfo: nil
                                            repeats: YES ] retain ];
    
    NSRunLoop *r = [ NSRunLoop currentRunLoop ];
    [ r addTimer: _dummyTimer forMode: NSDefaultRunLoopMode ];
    @try {
        // 启动后台线程的NSRunLoop
        [ r run ];
    }
    @catch ( NSException *exception ) {
        [ self handleRootException: exception ];
        // 一旦在线程根上捕捉到未知异常，记录异常后本线程退出
    }
    @finally {
        [ _dummyTimer invalidate ];
        [ _dummyTimer release ];
        [ pool release ];
    }
}

后台线程的handleRootException与UI线程基本一致。不过为了测试人员更加方便，其实只要不是UI线程发生未捕获异常，都可以先引导用户发送日志，再把进程崩溃掉。

转自：http://www.cnblogs.com/alario/archive/2012/03/28/2421574.html

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