iOS开发基础133-崩溃预防
现代移动应用的用户体验依赖于其稳定性和可靠性。然而，在开发过程中，我们时常会遇到各种崩溃问题。崩溃不仅会影响用户的使用体验，还可能损害应用的声誉。因此，本文将详细介绍一个名为CrashPrevention的工具类，它能够为iOS开发者提供多方面的崩溃预防措施，借助该工具类，开发者能够有效减少崩溃的发生，并提升应用的稳定性。
CrashPrevention工具类概述
CrashPrevention是一个易于集成的工具类，专为iOS应用中的多种常见崩溃情况提供预防措施。通过调用相关方法，开发者可以开启针对数组操作、字典操作、未识别的选择器、通知中心、键值观察（KVO）、字符串操作、多线程操作以及UI线程操作的保护机制。特别值得一提的是，CrashPrevention让开发者可以通过一个全局的 isDebug 标志，灵活控制是否启用这些崩溃预防措施。
CrashPrevention.h 头文件
首先，我们来看一下CrashPrevention的头文件，其中定义了所有的预防方法：
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@interface CrashPrevention : NSObject
// 设置是否在 Debug 模式中启用崩溃预防
+ (void)setDebugMode:(BOOL)isDebug;
// 启用所有崩溃保护
+ (void)enableAllCrashPrevention;
// 启用各类崩溃保护
+ (void)enableArrayProtection;
+ (void)enableDictionaryProtection;
+ (void)enableSelectorProtection;
+ (void)enableNotificationProtection;
+ (void)enableKVOCrashProtection;
+ (void)enableStringProtection;
+ (void)enableThreadSafetyProtection;
+ (void)enableUIThreadProtection;
@end
CrashPrevention.m 实现文件
接下来，我们深入了解实现文件的设计思路和具体代码。
全局Debug标志
@implementation CrashPrevention
// 用于记录是否在 Debug 模式下启用崩溃预防
static BOOL debugModeEnabled = NO;
// 设置是否在 Debug 模式中启用崩溃预防
+ (void)setDebugMode:(BOOL)isDebug {
debugModeEnabled = isDebug;
}
通过 static BOOL debugModeEnabled，我们可以记录是否启用调试模式，基于此标志决定是否启用崩溃预防功能。
启用所有崩溃保护
+ (void)enableAllCrashPrevention {
if (!debugModeEnabled) {
return;
}
[self enableArrayProtection];
[self enableDictionaryProtection];
[self enableSelectorProtection];
[self enableNotificationProtection];
[self enableKVOCrashProtection];
[self enableStringProtection];
[self enableThreadSafetyProtection];
[self enableUIThreadProtection];
}
该方法通过检查 debugModeEnabled 标志，决定是否依次启用各类崩溃保护。
数组越界保护
+ (void)enableArrayProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleInstanceMethod:NSClassFromString(@"__NSArrayI")
original:@selector(objectAtIndex:)
swizzled:@selector(safe_objectAtIndex:)];
[self swizzleInstanceMethod:NSClassFromString(@"__NSArrayM")
original:@selector(objectAtIndex:)
swizzled:@selector(safe_objectAtIndex:)];
});
}
- (id)safe_objectAtIndex:(NSUInteger)index {
if (index < self.count) {
return [self safe_objectAtIndex:index];
} else {
@try {
NSLog(@"Array index out of bound: %lu", (unsigned long)index);
} @catch (NSException *exception) {
// 处理异常
}
return nil;
}
}
通过 Method Swizzling，我们可以将数组的 objectAtIndex: 方法替换为安全版本。在越界的情况下，返回 nil 并记录日志，而不会崩溃。
字典键值检查保护
+ (void)enableDictionaryProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleInstanceMethod:NSClassFromString(@"__NSDictionaryI")
original:@selector(objectForKey:)
swizzled:@selector(safe_objectForKey:)];
});
}
- (id)safe_objectForKey:(id)key {
if (key) {
return [self safe_objectForKey:key];
} else {
@try {
NSLog(@"Attempted to access dictionary with nil key");
} @catch (NSException *exception) {
// 处理异常
}
return nil;
}
}
类似地，通过 Method Swizzling，我们可以将 objectForKey: 方法替换为安全版本，防止使用 nil 作为键值时的崩溃。
消息转发保护
+ (void)enableSelectorProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Method forwardMethod = class_getInstanceMethod([self class], @selector(forwardingMethod:));
class_addMethod([self class], NSSelectorFromString(@"unrecognizedSelectorHandler"), method_getImplementation(forwardMethod), method_getTypeEncoding(forwardMethod));
});
}
- (void)forwardingMethod:(SEL)aSelector {}
+ (BOOL)resolveInstanceMethod:(SEL)sel {
if (!debugModeEnabled) {
return [super resolveInstanceMethod:sel];
}
class_addMethod([self class], sel, class_getMethodImplementation([self class], @selector(forwardingMethod:)), "v@:");
return YES;
}
通过添加一个默认的 forwardingMethod: ，我们防止调用未实现的方法时崩溃。
通知中心保护
+ (void)enableNotificationProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleInstanceMethod:[NSNotificationCenter class]
original:@selector(addObserver:selector:name:object:)
swizzled:@selector(safe_addObserver:selector:name:object:)];
[self swizzleInstanceMethod:[NSNotificationCenter class]
original:@selector(removeObserver:name:object:)
swizzled:@selector(safe_removeObserver:name:object:)];
});
}
- (void)safe_addObserver:(NSObject *)observer selector:(SEL)aSelector name:(NSString *)aName object:(id)anObject {
if (observer) {
[[NSNotificationCenter defaultCenter] safe_addObserver:observer selector:aSelector name:aName object:anObject];
} else {
@try {
NSLog(@"Attempted to add a nil observer for name: %@", aName);
} @catch (NSException *exception) {
// 处理异常
}
}
}
- (void)safe_removeObserver:(NSObject *)observer name:(NSString *)aName object:(id)anObject {
if (observer) {
[[NSNotificationCenter defaultCenter] safe_removeObserver:observer name:aName object:anObject];
} else {
@try {
NSLog(@"Attempted to remove a nil observer for name: %@", aName);
} @catch (NSException *exception) {
// 处理异常
}
}
}
在添加和移除观察者时进行空检查，防止空观察者导致的崩溃。
KVO 保护
+ (void)enableKVOCrashProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleInstanceMethod:[NSObject class]
original:@selector(addObserver:forKeyPath:options:context:)
swizzled:@selector(safe_addObserver:forKeyPath:options:context:)];
[self swizzleInstanceMethod:[NSObject class]
original:@selector(removeObserver:forKeyPath:)
swizzled:@selector(safe_removeObserver:forKeyPath:)];
});
}
- (void)safe_addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath options:(NSKeyValueObservingOptions)options context:(void *)context {
if (observer && keyPath) {
[self safe_addObserver:observer forKeyPath:keyPath options:options context:context];
} else {
@try {
NSLog(@"Attempted to add observer with nil observer or key path: %@", keyPath);
} @catch (NSException *exception) {
// 处理异常
}
}
}
- (void)safe_removeObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath {
if (observer && keyPath) {
[self safe_removeObserver:observer forKeyPath:keyPath];
} else {
@try {
NSLog(@"Attempted to remove observer with nil observer or key path: %@", keyPath);
} @catch (NSException *exception) {
// 处理异常
}
}
}
在添加和移除KVO时进行必要检查，确保参数合法，防止崩溃。
字符串越界检查
+ (void)enableStringProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleInstanceMethod:NSClassFromString(@"__NSCFConstantString")
original:@selector(substringFromIndex:)
swizzled:@selector(safe_substringFromIndex:)];
});
}
- (NSString *)safe_substringFromIndex:(NSUInteger)from {
if (from <= self.length) {
return [self safe_substringFromIndex:from];
} else {
@try {
NSLog(@"String index out of bound: %lu", (unsigned long)from);
} @catch (NSException *exception) {
// 处理异常
}
return nil;
}
}
通过交换NSString的相关方法，确保在越界访问时返回 nil 并记录日志，从而避免崩溃。
线程安全保护
+ (void)enableThreadSafetyProtection {
if (!debugModeEnabled) {
return;
}
// 实现是与具体使用场景相关的，需要结合项目实际情况实现
}
这部分的实现高度依赖于具体的使用场景，比如可以使用 dispatch_barrier_async、NSLock 等技术实现。
UI线程保护
+ (void)enableUIThreadProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleInstanceMethod:[UIView class]
original:@selector(setNeedsLayout)
swizzled:@selector(safe_setNeedsLayout)];
});
}
- (void)safe_setNeedsLayout {
if ([NSThread isMainThread]) {
[self safe_setNeedsLayout];
} else {
dispatch_async(dispatch_get_main_queue(), ^{
[self safe_setNeedsLayout];
});
@try {
NSLog(@"setNeedsLayout was called off the main thread. Fixed by dispatching to main queue.");
} @catch (NSException *exception) {
// 处理异常
}
}
}
确保UI操作总在主线程进行，如果不是，则调度到主线程执行，并记录警告日志。
方法交换
#pragma mark - Method Swizzling
+ (void)swizzleInstanceMethod:(Class)cls original:(SEL)originalSelector swizzled:(SEL)swizzledSelector {
Method originalMethod = class_getInstanceMethod(cls, originalSelector);
Method swizzledMethod = class_getInstanceMethod(cls, swizzledSelector);
BOOL didAddMethod = class_addMethod(cls, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));
if (didAddMethod) {
class_replaceMethod(cls, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
}
@end
核心方法交换逻辑，通过 Method Swizzling 替换原有的方法实现。
使用CrashPrevention工具类
在应用启动时初始化CrashPrevention，并设置是否启用调试模式：
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// 设置 Debug 模式
#ifdef DEBUG
[CrashPrevention setDebugMode:YES];
#else
[CrashPrevention setDebugMode:NO];
#endif
[CrashPrevention enableAllCrashPrevention];
return YES;
}
总结
CrashPrevention工具类为iOS开发者提供了多个方面的崩溃预防措施，通过简单调用，即可为数组、字典、未识别选择器、通知中心、KVO、字符串、多线程和UI线程的操作提供全面的保护。特别是通过 isDebug 标志，让开发者可以灵活控制这些预防措施在调试阶段和正式发布中的启用状态。借助这一工具类，开发者能够有效减少崩溃问题的发生，提升应用的稳定性和用户体验。
最后附上完整代码：
CrashPrevention.h文件
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@interface CrashPrevention : NSObject
// 设置是否在 Debug 模式中启用崩溃预防
+ (void)setDebugMode:(BOOL)isDebug;
// 启用所有崩溃保护
+ (void)enableAllCrashPrevention;
// 启用各类崩溃保护
+ (void)enableArrayProtection;
+ (void)enableDictionaryProtection;
+ (void)enableSelectorProtection;
+ (void)enableNotificationProtection;
+ (void)enableKVOCrashProtection;
+ (void)enableStringProtection;
+ (void)enableThreadSafetyProtection;
+ (void)enableUIThreadProtection;
@end
CrashPrevention.m文件
#import "CrashPrevention.h"
#import <objc/runtime.h>
@implementation CrashPrevention
// 用于记录是否在 Debug 模式下启用崩溃预防
static BOOL debugModeEnabled = NO;
// 设置是否在 Debug 模式中启用崩溃预防
+ (void)setDebugMode:(BOOL)isDebug {
debugModeEnabled = isDebug;
}
// 启用所有崩溃保护
+ (void)enableAllCrashPrevention {
if (!debugModeEnabled) {
return;
}
[self enableArrayProtection];
[self enableDictionaryProtection];
[self enableSelectorProtection];
[self enableNotificationProtection];
[self enableKVOCrashProtection];
[self enableStringProtection];
[self enableThreadSafetyProtection];
[self enableUIThreadProtection];
}
#pragma mark - Array Protection
+ (void)enableArrayProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleInstanceMethod:NSClassFromString(@"__NSArrayI")
original:@selector(objectAtIndex:)
swizzled:@selector(safe_objectAtIndex:)];
[self swizzleInstanceMethod:NSClassFromString(@"__NSArrayM")
original:@selector(objectAtIndex:)
swizzled:@selector(safe_objectAtIndex:)];
});
}
- (id)safe_objectAtIndex:(NSUInteger)index {
if (index < self.count) {
return [self safe_objectAtIndex:index];
} else {
@try {
NSLog(@"Array index out of bound: %lu", (unsigned long)index);
} @catch (NSException *exception) {
// 处理异常
} @finally {
return nil;
}
}
}
#pragma mark - Dictionary Protection
+ (void)enableDictionaryProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleInstanceMethod:NSClassFromString(@"__NSDictionaryI")
original:@selector(objectForKey:)
swizzled:@selector(safe_objectForKey:)];
[self swizzleInstanceMethod:NSClassFromString(@"__NSDictionaryM")
original:@selector(objectForKey:)
swizzled:@selector(safe_objectForKey:)];
});
}
- (id)safe_objectForKey:(id)key {
if (key) {
return [self safe_objectForKey:key];
} else {
@try {
NSLog(@"Attempted to access dictionary with nil key");
} @catch (NSException *exception) {
// 处理异常
} @finally {
return nil;
}
}
}
#pragma mark - Selector Protection
+ (void)enableSelectorProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Method forwardMethod = class_getInstanceMethod([self class], @selector(forwardingMethod:));
class_addMethod([self class], NSSelectorFromString(@"unrecognizedSelectorHandler"), method_getImplementation(forwardMethod), method_getTypeEncoding(forwardMethod));
});
}
- (void)forwardingMethod:(SEL)aSelector {}
+ (BOOL)resolveInstanceMethod:(SEL)sel {
if (!debugModeEnabled) {
return [super resolveInstanceMethod:sel];
}
class_addMethod([self class], sel, class_getMethodImplementation([self class], @selector(forwardingMethod:)), "v@:");
return YES;
}
#pragma mark - Notification Protection
+ (void)enableNotificationProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleInstanceMethod:[NSNotificationCenter class]
original:@selector(addObserver:selector:name:object:)
swizzled:@selector(safe_addObserver:selector:name:object:)];
[self swizzleInstanceMethod:[NSNotificationCenter class]
original:@selector(removeObserver:name:object:)
swizzled:@selector(safe_removeObserver:name:object:)];
[self swizzleInstanceMethod:[NSNotificationCenter class]
original:@selector(removeObserver:)
swizzled:@selector(safe_removeObserver:)];
});
}
- (void)safe_addObserver:(NSObject *)observer selector:(SEL)aSelector name:(NSString *)aName object:(id)anObject {
if (observer) {
[[NSNotificationCenter defaultCenter] safe_addObserver:observer selector:aSelector name:aName object:anObject];
} else {
@try {
NSLog(@"Attempted to add a nil observer for name: %@", aName);
} @catch (NSException *exception) {
// 处理异常
} @finally {
// 什么也不做
}
}
}
- (void)safe_removeObserver:(NSObject *)observer {
if (observer) {
[[NSNotificationCenter defaultCenter] safe_removeObserver:observer];
} else {
@try {
NSLog(@"Attempted to remove a nil observer");
} @catch (NSException *exception) {
// 处理异常
} @finally {
// 什么也不做
}
}
}
- (void)safe_removeObserver:(NSObject *)observer name:(NSString *)aName object:(id)anObject {
if (observer) {
[[NSNotificationCenter defaultCenter] safe_removeObserver:observer name:aName object:anObject];
} else {
@try {
NSLog(@"Attempted to remove a nil observer for name: %@", aName);
} @catch (NSException *exception) {
// 处理异常
} @finally {
// 什么也不做
}
}
}
#pragma mark - KVO Protection
+ (void)enableKVOCrashProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleInstanceMethod:[NSObject class]
original:@selector(addObserver:forKeyPath:options:context:)
swizzled:@selector(safe_addObserver:forKeyPath:options:context:)];
[self swizzleInstanceMethod:[NSObject class]
original:@selector(removeObserver:forKeyPath:)
swizzled:@selector(safe_removeObserver:forKeyPath:)];
});
}
- (void)safe_addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath options:(NSKeyValueObservingOptions)options context:(void *)context {
if (observer && keyPath) {
[self safe_addObserver:observer forKeyPath:keyPath options:options context:context];
} else {
@try {
NSLog(@"Attempted to add observer with nil observer or key path: %@", keyPath);
} @catch (NSException *exception) {
// 处理异常
} @finally {
// 什么也不做
}
}
}
- (void)safe_removeObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath {
if (observer && keyPath) {
[self safe_removeObserver:observer forKeyPath:keyPath];
} else {
@try {
NSLog(@"Attempted to remove observer with nil observer or key path: %@", keyPath);
} @catch (NSException *exception) {
// 处理异常
} @finally {
// 什么也不做
}
}
}
#pragma mark - String Protection
+ (void)enableStringProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleInstanceMethod:NSClassFromString(@"__NSCFConstantString")
original:@selector(substringFromIndex:)
swizzled:@selector(safe_substringFromIndex:)];
[self swizzleInstanceMethod:NSClassFromString(@"__NSCFConstantString")
original:@selector(substringToIndex:)
swizzled:@selector(safe_substringToIndex:)];
[self swizzleInstanceMethod:NSClassFromString(@"__NSCFConstantString")
original:@selector(substringWithRange:)
swizzled:@selector(safe_substringWithRange:)];
});
}
- (NSString *)safe_substringFromIndex:(NSUInteger)from {
if (from <= self.length) {
return [self safe_substringFromIndex:from];
} else {
@try {
NSLog(@"String index out of bound: %lu", (unsigned long)from);
} @catch (NSException *exception) {
// 处理异常
} @finally {
return nil;
}
}
}
- (NSString *)safe_substringToIndex:(NSUInteger)to {
if (to <= self.length) {
return [self safe_substringToIndex:to];
} else {
@try {
NSLog(@"String index out of bound: %lu", (unsigned long)to);
} @catch (NSException *exception) {
// 处理异常
} @finally {
return nil;
}
}
}
- (NSString *)safe_substringWithRange:(NSRange)range {
if (range.location + range.length <= self.length) {
return [self safe_substringWithRange:range];
} else {
@try {
NSLog(@"String range out of bound: %@", NSStringFromRange(range));
} @catch (NSException *exception) {
// 处理异常
} @finally {
return nil;
}
}
}
#pragma mark - Thread Safety Protection
+ (void)enableThreadSafetyProtection {
if (!debugModeEnabled) {
return;
}
// 实现是与具体使用场景相关的，需要结合项目实际情况实现
}
#pragma mark - UI Thread Protection
+ (void)enableUIThreadProtection {
if (!debugModeEnabled) {
return;
}
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleInstanceMethod:[UIView class]
original:@selector(setNeedsLayout)
swizzled:@selector(safe_setNeedsLayout)];
[self swizzleInstanceMethod:[UIView class]
original:@selector(setNeedsDisplay)
swizzled:@selector(safe_setNeedsDisplay)];
[self swizzleInstanceMethod:[UIView class]
original:@selector(setNeedsDisplayInRect:)
swizzled:@selector(safe_setNeedsDisplayInRect:)];
});
}
- (void)safe_setNeedsLayout {
if ([NSThread isMainThread]) {
[self safe_setNeedsLayout];
} else {
dispatch_async(dispatch_get_main_queue(), ^{
[self safe_setNeedsLayout];
});
@try {
NSLog(@"setNeedsLayout was called off the main thread. Fixed by dispatching to main queue.");
} @catch (NSException *exception) {
// 处理异常
} @finally {
// 什么也不做
}
}
}
- (void)safe_setNeedsDisplay {
if ([NSThread isMainThread]) {
[self safe_setNeedsDisplay];
} else {
dispatch_async(dispatch_get_main_queue(), ^{
[self safe_setNeedsDisplay];
});
@try {
NSLog(@"setNeedsDisplay was called off the main thread. Fixed by dispatching to main queue.");
} @catch (NSException *exception) {
// 处理异常
} @finally {
// 什么也不做
}
}
}
- (void)safe_setNeedsDisplayInRect:(CGRect)rect {
if ([NSThread isMainThread]) {
[self safe_setNeedsDisplayInRect:rect];
} else {
dispatch_async(dispatch_get_main_queue(), ^{
[self safe_setNeedsDisplayInRect:rect];
});
@try {
NSLog(@"setNeedsDisplayInRect: was called off the main thread. Fixed by dispatching to main queue.");
} @catch (NSException *exception) {
// 处理异常
} @finally {
// 什么也不做
}
}
}
#pragma mark - Method Swizzling
+ (void)swizzleInstanceMethod:(Class)cls original:(SEL)originalSelector swizzled:(SEL)swizzledSelector {
Method originalMethod = class_getInstanceMethod(cls, originalSelector);
Method swizzledMethod = class_getInstanceMethod(cls, swizzledSelector);
BOOL didAddMethod = class_addMethod(cls, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));
if (didAddMethod) {
class_replaceMethod(cls, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
}
@end
iOS开发基础133-崩溃预防的更多相关文章
- iOS开发基础-九宫格坐标(2)之模型
在iOS开发基础-九宫格(1)中,属性变量 apps 是从plist文件中加载数据的,在 viewDidLoad 方法中的第20行.26行中,直接通过字典的键名来获取相应的信息,使得 ViewCont ...
- IOS开发基础知识碎片-导航
1:IOS开发基础知识--碎片1 a:NSString与NSInteger的互换 b:Objective-c中集合里面不能存放基础类型,比如int string float等,只能把它们转化成对象才可 ...
- iOS开发——总结篇&IOS开发基础知识
IOS开发基础知识 1:Objective-C语法之动态类型(isKindOfClass, isMemberOfClass,id) 对象在运行时获取其类型的能力称为内省.内省可以有多种方法实现. 判断 ...
- IOS开发基础环境搭建
一.目的 本文的目的是windows下IOS开发基础环境搭建做了对应的介绍,大家可根据文档步骤进行mac环境部署: 二.安装虚拟机 下载虚拟机安装文件绿色版,点击如下文件安装 获取安装包: ...
- iOS开发基础-九宫格坐标(6)
继续对iOS开发基础-九宫格坐标(5)中的代码进行优化. 优化思路:把字典转模型部分的数据处理操作也拿到模型类中去实现,即将 ViewController 类实现中 apps 方法搬到 WJQAppI ...
- iOS开发基础-九宫格坐标(5)
继续在iOS开发基础-九宫格坐标(4)的基础上进行优化. 一.改进思路 1)iOS开发基础-九宫格坐标(4)中 viewDidLoad 方法中的第21.22行对控件属性的设置能否拿到视图类 WJQAp ...
- iOS开发基础-九宫格坐标(4)
对iOS开发基础-九宫格坐标(3)的代码进行进一步优化. 新建一个 UIView 的子类,并命名为 WJQAppView ,将 appxib.xib 中的 UIView 对象与新建的视图类进行关联. ...
- iOS开发基础-九宫格坐标(3)之Xib
延续iOS开发基础-九宫格坐标(2)的内容,对其进行部分修改. 本部分采用 Xib 文件来创建用于显示图片的 UIView 对象. 一.简单介绍 Xib 和 storyboard 的比较: 1) X ...
- iOS开发基础-图片切换(4)之懒加载
延续:iOS开发基础-图片切换(3),对(3)里面的代码用懒加载进行改善. 一.懒加载基本内容 懒加载(延迟加载):即在需要的时候才加载,修改属性的 getter 方法. 注意:懒加载时一定要先判断该 ...
- iOS开发基础-图片切换(3)之属性列表
延续:iOS开发基础-图片切换(2),对(2)里面的代码用属性列表plist进行改善. 新建 Property List 命名为 Data 获得一个后缀为 .plist 的文件. 按如图修改刚创建的文 ...
随机推荐
- FFmpeg下载编译、代码结构以及编译系统
从这里开始,就要踏上学习FFmpeg的旅程了,使用的FFmpeg版本5.0.1 1.ubuntu下,如何下载并编译FFmpeg源码 打开FFmpeg官网 Download FFmpeg,我们可以通过g ...
- 微软的文本转语音服务Microsoft.CognitiveServices.Speech
微软的Edge 浏览器里的大声朗读里-"晓晓" 很接近自然人,比起其它平台的强很多. 在AZURE 可免费体验,每月限额50万字,每个语音转换不超过10分钟长度. C# 调用: u ...
- 理解Vue 3响应式系统原理
title: 理解Vue 3响应式系统原理 date: 2024/5/28 15:44:47 updated: 2024/5/28 15:44:47 categories: 前端开发 tags: Vu ...
- C#笔记 picturebox功能实现（滚动放大，拖动）
代码链接 1. picturebox上的坐标与原图中坐标的转换 (1) 由于图片的长宽比例和picturebox的长宽比例不同,所以图片不想拉伸的话,左右或者上下会有留白.将picturebox的si ...
- http1.1 的默认长连接 Connection: keep-alive 与 TCP KeepAlive 之间区别
HTTP 长连接,也称为 HTTP 持久连接(HTTP Persistent Connection)或 HTTP 连接重用,是一种在 HTTP 协议中实现的机制. 在传统的 HTTP 通信中,每个 H ...
- INFINI Labs 产品更新 | Easysearch 新增分词插件、Gateway 支持邮件发送等功能
INFINI Labs 产品又更新啦~,本次更新概要如下:Easysearch 新增了分词插件.优化了生命周期管理功能等:Gateway 新增 smtp 过滤器来支持邮件的发送,支持自动跳过因为异常关 ...
- 找不到 .NETFramework,Version=v5.0 的引用程序集。要解决此问题，请为此框架版本安装开发人员工具包(SDK/目标包)或者重新定向应用程序。
找不到 .NETFramework,Version=v5.0 的引用程序集.要解决此问题,请为此框架版本安装开发人员工具包(SDK/目标包)或者重新定向应用程序. visual studio 2019 ...
- core dump 路径定义以及监控
Core Dump 是什么? Core Dump 是指进程异常退出时,操作系统将进程的内存状态保存到文件中,这个文件就是 Core Dump 文件,中文一般翻译为"核心转储",哈, ...
- 百度面试：如何用Redis实现限流？
高并发系统有三大特征:限流.缓存和熔断,所以限流已经成为当下系统开发中必备的功能了.那么,什么是限流?如何实现限流?使用 Redis 能不能实现限流?接下来我们一起来看. 1.什么是限流? 限流是指在 ...
- 🌟 简单理解 React 的 createContext 和 Provider 🚀
在 React 应用中,我们经常需要在组件之间共享状态和数据.而 React 的 createContext 和 Provider 就是为了解决这个问题而诞生的. createContext:创建自定 ...