iOS中App崩溃问题是在所难免的，那如何在崩溃之前给用户一些提示，或是可以将这些崩溃信息发送给自己，以便于自己修正呢？前段时间做项目时，一直没添加这方面的功能，这两天没事从网上看了些资料，顺便自己做了个Demo测试了一下，今天把我了解的东西整理一下。

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。

Demo运行环境:Xcode7.3, iOS9.3

步骤一：定义一个UncaughtExceptionHandler类

UncaughtExceptionHandler.h内容：

#import <UIKit/UIKit.h>

@interface UncaughtExceptionHandler : NSObject
{
  BOOL dismissed;
}

@end

void InstallUncaughtExceptionHandler();

UncaughtExceptionHandler.m内容：

#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(@"程序出现问题啦", nil) message:[NSString stringWithFormat:NSLocalizedString(@"崩溃信息\n"@"%@\n%@", nil), [exception reason], [[exception userInfo] objectForKey:UncaughtExceptionHandlerAddressesKey]] delegate:self cancelButtonTitle:NSLocalizedString(@"离开", nil) otherButtonTitles:nil];
    [alert show];
    CFRunLoopRef runLoop = CFRunLoopGetCurrent();
    CFArrayRef allModes = CFRunLoopCopyAllModes(runLoop);
    while (!dismissed)
    {
        for (NSString *mode in (__bridge 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 : %@ %@\n",
                         [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleDisplayName"],
                         [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleShortVersionString"],
                         [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleVersion"],
                         [UIDevice currentDevice].model,
                         [UIDevice currentDevice].systemName,
                         [UIDevice currentDevice].systemVersion];
    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];
    // 创建一个OC异常对象
    NSException *ex = [NSException exceptionWithName:UncaughtExceptionHandlerSignalExceptionName reason:[NSString stringWithFormat:NSLocalizedString(@"Signal %d was raised.\n"@"%@", nil), signal, getAppInfo()] userInfo:userInfo];
    // 处理异常消息
    [[[UncaughtExceptionHandler alloc] init] performSelectorOnMainThread:@selector(handleException:) withObject:ex waitUntilDone:YES];
}

void InstallUncaughtExceptionHandler()
{
    signal(SIGABRT, MySignalHandler);
    signal(SIGILL, MySignalHandler);
    signal(SIGSEGV, MySignalHandler);
    signal(SIGFPE, MySignalHandler);
    signal(SIGBUS, MySignalHandler);
    signal(SIGPIPE, MySignalHandler);
}

步骤二：在AppDelegate中导入本类

#import "UncaughtExceptionHandler.h"

- (void)installUncaughtExceptionHandler
{
    InstallUncaughtExceptionHandler();
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    [self installUncaughtExceptionHandler];
    return YES;
}

效果图如下：

崩溃截图.png

当然，也可以把这些崩溃信息通过邮箱发送给自己，这个根据项目需求来自定义。

[参考]http://www.111cn.net/sj/ios8/89772.htm