如何让IOS应用从容地崩溃

转自：http://blog.csdn.net/weiqubo/article/details/8067896

虽然大家都不愿意看到程序崩溃，但可能崩溃是每个应用必须面对的现实，既然崩溃已经发生，无法阻挡了，那我们就让它崩也崩得淡定点吧。

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[i]]];
 }
 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];

• 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。