前言
- 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
- 本文主要介绍APP运行时第二种Crash自动防护功能，暂时涵盖容器，字符串，没找到对应的函数，后台返回NSNull导致的崩溃，计时器，kvo，不在主线程中更新UI等崩溃
- 有空再来慢慢补充其他类型
Demo地址：KJExceptionDemo
设计原理
利用 Objective-C 语言的动态特性，采用AOP面向切面编程的设计思想，交换方法然后拦截处理崩溃信息
image
| 方法 | 功能 |
|---|---|
| class_getInstanceMethod | 获取实例方法 |
| class_getClassMethod | 获取类方法 |
| method_getImplementation | 获取一个方法的实现 |
| method_setImplementation | 设置一个方法的实现 |
| method_getTypeEncoding | 获取方法实现的编码类型 |
| class_addMethod | 添加方法实现 |
| class_replaceMethod | 用一个方法的实现，替换另一个方法的实现，即aIMP 指向 bIMP，但是bIMP不一定指向aIMP |
| method_exchangeImplementations | 交换两个方法的实现，即 aIMP -> bIMP, bIMP -> aIMP |
交换实例方法
void kExceptionMethodSwizzling(Class clazz, SEL original, SEL swizzled){
Method originalMethod = class_getInstanceMethod(clazz, original);
Method swizzledMethod = class_getInstanceMethod(clazz, swizzled);
if (class_addMethod(clazz, original, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))) {
class_replaceMethod(clazz, swizzled, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
}else{
method_exchangeImplementations(originalMethod, swizzledMethod);
}
}
交换类方法
void kExceptionClassMethodSwizzling(Class clazz, SEL original, SEL swizzled){
Method originalMethod = class_getClassMethod(clazz, original);
Method swizzledMethod = class_getClassMethod(clazz, swizzled);
Class metaclass = objc_getMetaClass(NSStringFromClass(clazz).UTF8String);
if (class_addMethod(metaclass, original, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))) {
class_replaceMethod(metaclass, swizzled, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
}else{
method_exchangeImplementations(originalMethod, swizzledMethod);
}
}
常见Crash和解决方案
一、没找到对应的函数 - Unrecognized Selector Sent to Instance
| 类型 | 原因 |
|---|---|
| SEL | unrecognized selector sent to instance .h定义但.m没实现 |
| SEL | performSelector: 调用不存在的方法 |
| SEL | delegate 回调前没有判空而是直接调用 |
| SEL | id 类型没有判断类型，强行调用真实类型不存在的方法 |
| SEL | copy 修饰的可变的字符串 \ 字典 \ 数组 \ 集合 \ Data，调用可变的方法 |
消息转发流程图：
image.png
解决方案：
- 交换方法
methodSignatureForSelector:和forwardInvocation: - 对象调用方法经过三个阶段
- 消息发送：查询cache和方法列表，找到了直接调用，找不到方法会进入下个阶段
- 动态解析: 调用实例方法
resolveInstanceMethod或类方法resolveClassMethod里面可以有一次动态添加方法的机会 - 消息转发：首先会判断是否有其他对象可以处理方法
forwardingTargetForSelector返回一个新的对象，如果没有新的对象进行处理，会调用methodSignatureForSelector方法返回方法签名，然后调用forwardInvocation
- 选择在消息转发的最后一步来做处理，
methodSignatureForSelector:消息获得函数的参数和返回值，然后[self respondsToSelector:aSelector]判断是否有该方法，如果没有返回函数签名，创建一个NSInvocation对象并发送给forwardInvocation
二、容器越界 - 数组和字典
| 类型 | 原因 |
|---|---|
| NSArray | 数组索引越界、插入空对象 |
| NSDictionary | key、value 为空 |
备注：可变的都继承自不可变的，所有可变的分类中，重复的方法就不用再次替换
解决方案：
- 交换方法，然后防护处理，简单举个例子，NSArray 是一个类簇，它真正的类型是
__NSArrayI，交换方法如下
Class __NSArrayI = objc_getClass("__NSArrayI");
/// 越界崩溃方式一：[array objectAtIndex:0];
kExceptionMethodSwizzling(__NSArrayI, @selector(objectAtIndex:), @selector(kj_objectAtIndex:));
/// 越界崩溃方式二：array[0];
kExceptionMethodSwizzling(__NSArrayI, @selector(objectAtIndexedSubscript:), @selector(kj_objectAtIndexedSubscript:));
交换后的处理
- (instancetype)kj_objectAtIndex:(NSUInteger)index{
NSArray *temp = nil;
@try {
temp = [self kj_objectAtIndex:index];
}@catch (NSException *exception) {
NSString *string = @"🍉🍉 crash：";
if (self.count == 0) {
string = [string stringByAppendingString:@"数组个数为零"];
}else if (self.count <= index) {
string = [string stringByAppendingString:@"数组索引越界"];
}
[KJCrashManager kj_crashDealWithException:exception CrashTitle:string];
}@finally {
return temp;
}
}
三、KVO
| 类型 | 原因 |
|---|---|
| KVO | 添加了监听，没有移除 |
解决方案：
- 交换
removeObserver:forKeyPath:方法，
- (void)kj_removeObserver:(NSObject*)observer forKeyPath:(NSString *)keyPath{
@try {
[self kj_removeObserver:observer forKeyPath:keyPath];
}@catch (NSException *exception) {
NSString *string = @"🍉🍉 crash：添加观察者后没有移除观察者导致";
[KJCrashManager kj_crashDealWithException:exception CrashTitle:string];
}@finally {
}
}
四、NSTimer
| 类型 | 原因 |
|---|---|
| NSTimer | 没有 invalidate，直接销毁 |
| NSTimer | NStimer 与 target 强引用，内存泄漏 |
解决方案：
- 交换
scheduledTimerWithTimeInterval:target:selector:userInfo:repeats:方法 - 定义一个抽象类
KJProxyProtector，NSTimer实例强引用抽象类，而在抽象类中弱引用target，这样target和NSTimer之间的关系也就是弱引用，意味着target可以自由的释放，从而解决循环引用的问题
五、后台返回NSNull导致的崩溃
| 类型 | 原因 |
|---|---|
| NSNull | 后台返回NSNull导致的崩溃 |
解决方案：
- 交换方法
methodSignatureForSelector:和forwardInvocation:
六、UIKit Called on Non-Main Thread
解决方案：
- 交换
setNeedsLayout、layoutIfNeeded、layoutSubviews、setNeedsUpdateConstraints方法 -
[NSThread isMainThread]判断当前线程是否为主线程，如果不是则在主线程执行
异常收集
一、防护类型
目前提供以下七种
typedef NS_OPTIONS(NSInteger, KJCrashProtectorType) {
KJCrashProtectorTypeContainer = 1 << 0,// 数组和字典
KJCrashProtectorTypeString = 1 << 1,// 字符串
KJCrashProtectorTypeUnrecognizedSelector = 1 << 2,// 没找到对应的函数
KJCrashProtectorTypeNSNull = 1 << 3,// 后台返回NSNull导致的崩溃
KJCrashProtectorTypeTimer = 1 << 4,// 计时器
KJCrashProtectorTypeKVO = 1 << 5,// kvo
KJCrashProtectorTypeUINonMain = 1 << 6,// 不在主线程中刷新UI
};
二、开启防护
采用多枚举方式，来快速设置需要开发的防护
/// 开启全部防护
+ (void)kj_openAllCrashProtectorManager:(kExceptionBlock)block{
if (block) [KJCrashManager kj_crashBlock:block];
[self kj_openCrashProtectorType:
KJCrashProtectorTypeContainer |
KJCrashProtectorTypeString |
KJCrashProtectorTypeUnrecognizedSelector |
KJCrashProtectorTypeNSNull |
KJCrashProtectorTypeTimer |
KJCrashProtectorTypeKVO];
}
/// 开启指定类型防护
+ (void)kj_openCrashProtectorType:(KJCrashProtectorType)type{
if (type & KJCrashProtectorTypeContainer) {
[NSArray kj_openCrashExchangeMethod];
[NSMutableArray kj_openCrashExchangeMethod];
[NSDictionary kj_openCrashExchangeMethod];
[NSMutableDictionary kj_openCrashExchangeMethod];
}
if (type & KJCrashProtectorTypeString) {
[NSString kj_openCrashExchangeMethod];
[NSMutableString kj_openCrashExchangeMethod];
[NSAttributedString kj_openCrashExchangeMethod];
[NSMutableAttributedString kj_openCrashExchangeMethod];
}
if (type & KJCrashProtectorTypeUnrecognizedSelector) {
[NSObject kj_openUnrecognizedSelectorExchangeMethod];
}
if (type & KJCrashProtectorTypeNSNull) {
[NSNull kj_openNullExchangeMethod];
}
if (type & KJCrashProtectorTypeTimer) {
[NSTimer kj_openCrashExchangeMethod];
}
if (type & KJCrashProtectorTypeKVO) {
[NSObject kj_openKVOExchangeMethod];
}
if (type & KJCrashProtectorTypeUINonMain) {
[UIView kj_openCrashExchangeMethod];
}
}
三、解析异常消息
采用正则表达式来匹配出来方法名
/// 解析异常消息
+ (NSString*)kj_analysisCallStackSymbols:(NSArray<NSString*>*)callStackSymbols{
__block NSString *msg = nil;
NSString *pattern = @"[-\\+]\\[.+\\]";// 匹配出来的格式为 +[类名 方法名] 或者 -[类名 方法名]
NSRegularExpression *regularExp = [[NSRegularExpression alloc] initWithPattern:pattern options:NSRegularExpressionCaseInsensitive error:nil];
for (NSInteger i = 2; i < callStackSymbols.count; i++) {
NSString *matchesString = callStackSymbols[i];
[regularExp enumerateMatchesInString:matchesString options:NSMatchingReportProgress range:NSMakeRange(0, matchesString.length) usingBlock:^(NSTextCheckingResult * _Nullable result, NSMatchingFlags flags, BOOL * _Nonnull stop) {
if (result) {
NSString *tempMsg = [matchesString substringWithRange:result.range];
NSString *className = [tempMsg componentsSeparatedByString:@" "].firstObject;
className = [className componentsSeparatedByString:@"["].lastObject;
if (![className hasSuffix:@")"] && [NSBundle bundleForClass:NSClassFromString(className)] == [NSBundle mainBundle]) {
msg = tempMsg;
}
*stop = YES;
}
}];
if (msg.length) break;
}
return msg;
}
熟悉又讨厌的崩溃
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[0]'
*** First throw call stack:(
0 CoreFoundation 0x0000000103dca126 __exceptionPreprocess + 242
1 libobjc.A.dylib 0x0000000103c54f78 objc_exception_throw + 48
2 CoreFoundation 0x0000000103e46cdb _CFThrowFormattedException + 194
3 CoreFoundation 0x0000000103e5221e -[__NSPlaceholderDictionary initWithCapacity:].cold.1 + 0
4 CoreFoundation 0x0000000103e351f7 -[__NSPlaceholderDictionary initWithObjects:forKeys:count:] + 227
5 CoreFoundation 0x0000000103dc8da3 +[NSDictionary dictionaryWithObjects:forKeys:count:] + 49
6 KJExtensionHandler 0x00000001033b715f -[ViewController viewDidLoad] + 815
7 UIKitCore 0x000000010d7ac73b -[UIViewController _sendViewDidLoadWithAppearanceProxyObjectTaggingEnabled] + 88
8 UIKitCore 0x000000010d7b1022 -[UIViewController loadViewIfRequired] + 1084
9 UIKitCore 0x000000010d6e800e -[UINavigationController _updateScrollViewFromViewController:toViewController:] + 162
10 UIKitCore 0x000000010d6e82f8 -[UINavigationController _startTransition:fromViewController:toViewController:] + 154
11 UIKitCore 0x000000010d6e9371 -[UINavigationController _startDeferredTransitionIfNeeded:] + 851
12 UIKitCore 0x000000010d6ea6dc -[UINavigationController __viewWillLayoutSubviews] + 150
13 UIKitCore 0x000000010d6caf1e -[UILayoutContainerView layoutSubviews] + 217
14 UIKitCore 0x000000010e43d9ce -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 2874
15 QuartzCore 0x0000000105546d87 -[CALayer layoutSublayers] + 258
16 QuartzCore 0x000000010554d239 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 575
17 QuartzCore 0x0000000105558f91 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 65
18 QuartzCore 0x0000000105499078 _ZN2CA7Context18commit_transactionEPNS_11TransactionEdPd + 496
19 QuartzCore 0x00000001054cfe13 _ZN2CA11Transaction6commitEv + 783
20 UIKitCore 0x000000010defe27a __34-[UIApplication _firstCommitBlock]_block_invoke_2 + 81
21 CoreFoundation 0x0000000103d385db __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
22 CoreFoundation 0x0000000103d379ef __CFRunLoopDoBlocks + 434
23 CoreFoundation 0x0000000103d3240c __CFRunLoopRun + 899
24 CoreFoundation 0x0000000103d31b9e CFRunLoopRunSpecific + 567
25 GraphicsServices 0x000000010c7ebdb3 GSEventRunModal + 139
26 UIKitCore 0x000000010dee0af3 -[UIApplication _run] + 912
27 UIKitCore 0x000000010dee5a04 UIApplicationMain + 101
28 KJExtensionHandler 0x00000001033ea92a main + 122
29 libdyld.dylib 0x00000001065eb415 start + 1
30 ??? 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
防崩处理之后的效果
2020-12-29 15:49:27.649011+0800 KJExceptionDemo[7987:427289]
************ crash 日志 ************
标题：🍉🍉 crash：ViewController 类出现未找到类方法
异常原因：test_UnrecognizedSelector 🚗🚗类方法未找到🚗🚗
异常地址：-[ViewController testUnrecognizedSelector]
2020-12-29 15:49:27.651701+0800 KJExceptionDemo[7987:427289]
************ crash 日志 ************
标题：🍉🍉 crash：ViewController 类出现未找到实例方法
异常原因：testCrash:xx: 🚗🚗实例方法未找到🚗🚗
异常地址：-[ViewController testUnrecognizedSelector]
2020-12-29 15:49:27.654808+0800 KJExceptionDemo[7987:427289]
************ crash 日志 ************
标题：🍉🍉 crash：数组插入数据为空
异常原因：*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil
异常地址：-[ViewController testContainer]
2020-12-29 15:49:27.657423+0800 KJExceptionDemo[7987:427289]
************ crash 日志 ************
标题：🍉🍉 crash：数组更改索引越界
异常原因：*** -[__NSArrayM setObject:atIndexedSubscript:]: index 4 beyond bounds [0 .. 2]
异常地址：-[ViewController testContainer]
2020-12-29 15:49:27.661423+0800 KJExceptionDemo[7987:427289]
************ crash 日志 ************
标题：🍉🍉 crash：字符串长度不够
异常原因：*** -[__NSCFConstantString kj_substringFromIndex:]: Index 10 out of bounds; string length 3
异常地址：-[ViewController testString]
<a id="Cocoapods安装"></a>Cocoapods安装
pod 'KJExceptionDemo'
