JAVA高级面试进阶训练营视频教程

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demo地址：https://github.com/easonoutlook/UncaughtExceptionHandler

IOS SDK中提供了一个现成的函数 NSSetUncaughtExceptionHandler 用来做异常处理，但功能非常有限，而引起崩溃的大多数原因如：内存访问错误，重复释放等错误就无能为力了，因为这种错误它抛出的是Signal，所以必须要专门做Signal处理。首先定义一个UncaughtExceptionHandler类，.h头文件的代码如下：

#import <UIKit/UIKit.h>

@interface UncaughtExceptionHandler : NSObject

{

BOOL dismissed;

}

@end

void InstallUncaughtExceptionHandler();

 

然后在.mm文件实现InstallUncaughtExceptionHandler()，如下：

void InstallUncaughtExceptionHandler()

{

signal(SIGABRT, MySignalHandler);

signal(SIGILL, MySignalHandler);

signal(SIGSEGV, MySignalHandler);

signal(SIGFPE, MySignalHandler);

signal(SIGBUS, MySignalHandler);

signal(SIGPIPE, MySignalHandler);

}

 

这样，当应用发生错误而产生上述Signal后，就将会进入我们自定义的回调函数MySignalHandler。为了得到崩溃时的现场信息，还可以加入一些获取CallTrace及设备信息的代码，.mm文件的完整代码如下：

#import "UncaughtExceptionHandler.h"

#include <libkern/OSAtomic.h>

#include <execinfo.h>

NSString * const UncaughtExceptionHandlerSignalExceptionName = @"UncaughtExceptionHandlerSignalExceptionName";

NSString * const UncaughtExceptionHandlerSignalKey = @"UncaughtExceptionHandlerSignalKey";

NSString * const UncaughtExceptionHandlerAddressesKey = @"UncaughtExceptionHandlerAddressesKey";

volatile int32_t UncaughtExceptionCount = 0;

const int32_t UncaughtExceptionMaximum = 10;

const NSInteger UncaughtExceptionHandlerSkipAddressCount = 4;

const NSInteger UncaughtExceptionHandlerReportAddressCount = 5;

@implementation UncaughtExceptionHandler

+ (NSArray *)backtrace

{

        void* callstack[128];

 int frames = backtrace(callstack, 128);

 char **strs = backtrace_symbols(callstack, frames); 

 int i;

 NSMutableArray *backtrace = [NSMutableArray arrayWithCapacity:frames];

 for (

 i = UncaughtExceptionHandlerSkipAddressCount;

 i < UncaughtExceptionHandlerSkipAddressCount +

UncaughtExceptionHandlerReportAddressCount;

i++)

 {

 [backtrace addObject:[NSString stringWithUTF8String:strs]];

 }

 free(strs); 

 return backtrace;

}

- (void)alertView:(UIAlertView *)anAlertView clickedButtonAtIndex:(NSInteger)anIndex

{

if (anIndex == 0)

{

dismissed = YES;

}

}

- (void)handleException:(NSException *)exception

{

UIAlertView *alert =

[[[UIAlertView alloc]

initWithTitle:NSLocalizedString(@"Unhandled exception", nil)

message:[NSString stringWithFormat:NSLocalizedString(

@"You can try to continue but the application may be unstable.\n"

@"%@\n%@", nil),

[exception reason],

[[exception userInfo] objectForKey:UncaughtExceptionHandlerAddressesKey]]

delegate:self

cancelButtonTitle:NSLocalizedString(@"Quit", nil)

otherButtonTitles:NSLocalizedString(@"Continue", nil), nil]

autorelease];

[alert show];

CFRunLoopRef runLoop = CFRunLoopGetCurrent();

CFArrayRef allModes = CFRunLoopCopyAllModes(runLoop);

while (!dismissed)

{

for (NSString *mode in (NSArray *)allModes)

{

CFRunLoopRunInMode((CFStringRef)mode, 0.001, false);

}

}

CFRelease(allModes);

NSSetUncaughtExceptionHandler(NULL);

signal(SIGABRT, SIG_DFL);

signal(SIGILL, SIG_DFL);

signal(SIGSEGV, SIG_DFL);

signal(SIGFPE, SIG_DFL);

signal(SIGBUS, SIG_DFL);

signal(SIGPIPE, SIG_DFL);

if ([[exception name] isEqual:UncaughtExceptionHandlerSignalExceptionName])

{

kill(getpid(), [[[exception userInfo] objectForKey:UncaughtExceptionHandlerSignalKey] intValue]);

}

else

{

[exception raise];

}

}

@end

NSString* getAppInfo()

{

    NSString *appInfo = [NSString stringWithFormat:@"App : %@ %@(%@)\nDevice : %@\nOS Version : %@ %@\nUDID : %@\n",

                          [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleDisplayName"],

                          [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleShortVersionString"],

                          [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleVersion"],

                          [UIDevice currentDevice].model,

                          [UIDevice currentDevice].systemName,

                          [UIDevice currentDevice].systemVersion,

                          [UIDevice currentDevice].uniqueIdentifier];

    NSLog(@"Crash!!!! %@", appInfo);

    return appInfo;

}

void MySignalHandler(int signal)

{

int32_t exceptionCount = OSAtomicIncrement32(&UncaughtExceptionCount);

if (exceptionCount > UncaughtExceptionMaximum)

{

return;

}

 

NSMutableDictionary *userInfo =

[NSMutableDictionary

dictionaryWithObject:[NSNumber numberWithInt:signal]

forKey:UncaughtExceptionHandlerSignalKey];

NSArray *callStack = [UncaughtExceptionHandler backtrace];

[userInfo

setObject:callStack

forKey:UncaughtExceptionHandlerAddressesKey];

[[[[UncaughtExceptionHandler alloc] init] autorelease]

performSelectorOnMainThread:@selector(handleException:)

withObject:

[NSException

exceptionWithName:UncaughtExceptionHandlerSignalExceptionName

reason:

[NSString stringWithFormat:

NSLocalizedString(@"Signal %d was raised.\n"

                                          @"%@", nil),

signal, getAppInfo()]

userInfo:

[NSDictionary

dictionaryWithObject:[NSNumber numberWithInt:signal]

forKey:UncaughtExceptionHandlerSignalKey]]

waitUntilDone:YES];

}

void InstallUncaughtExceptionHandler()

{

signal(SIGABRT, MySignalHandler);

signal(SIGILL, MySignalHandler);

signal(SIGSEGV, MySignalHandler);

signal(SIGFPE, MySignalHandler);

signal(SIGBUS, MySignalHandler);

signal(SIGPIPE, MySignalHandler);

}

 

在应用自身的 didFinishLaunchingWithOptions 前，加入一个函数：

- (void)installUncaughtExceptionHandler

{

InstallUncaughtExceptionHandler();

}

 

最后，在 didFinishLaunchingWithOptions 中加入这一句代码就行了：

[self InstallUncaughtExceptionHandler];

现在，基本上所有崩溃都能Hold住了。崩溃时将会显示出如下的对话框：

 

这样在崩溃时还能从容地弹出对话框，比起闪退来，用户也不会觉得那么不爽。然后在下次启动时还可以通过邮件来发送Crash文件到邮箱，这就看各个应用的需求了。