iOS 经验总结
1.主线程在动画未结束时进行操作可能导致应用崩溃
如下，当dismissViewControllerAnimated:为YES时，由于后续有页面显示，就在应用中导致了崩溃
- (void)imagePickerController:(UIImagePickerController *)picker
didFinishPickingMediaWithInfo:(NSDictionary *)info {
UIImage *image = [info objectForKey:UIImagePickerControllerEditedImage];
self.decoding = YES;
[picker dismissViewControllerAnimated:NO completion:nil];
__block ZXingWidgetController *tempSelf = self;
tempSelf.imageDecoder = [tempSelf decodeImage:image cropRect:CGRectZero];
}
2.当发现界面未按代码运行进行刷新时，如tableview reloaddata，界面未刷新，可能是因为reloaddata不是在主线程导致
3.简单时间间隔
static long long timeSince1970 = 0;
long long timeNowSice1970 = [[NSDate date] timeIntervalSince1970];
//间隔5秒刷新
if (timeNowSice1970 - timeSince1970 > 5.f) {
}else {
}
timeSince1970 = timeNowSice1970;
4.简单多线程支持
互斥锁使用格式
@synchronized(锁对象) { // 需要锁定的代码 }
5.URL中查找字段，CS 需要查找的字段名
+(NSString *)jiexi:(NSString *)CS webaddress:(NSString *)webaddress
{
NSError *error;
NSString *regTags=[[NSString alloc] initWithFormat:@"(^|&|\\?)+%@=+([^&]*)(&|$)",CS];
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:regTags
options:NSRegularExpressionCaseInsensitive
error:&error];
// 执行匹配的过程
// NSString *webaddress=@"http://wgpc.wzsafety.gov.cn/dd/adb.htm?adc=e12&xx=lkw&dalsjd=12";
NSArray *matches = [regex matchesInString:webaddress
options:0
range:NSMakeRange(0, [webaddress length])];
for (NSTextCheckingResult *match in matches) {
//NSRange matchRange = [match range];
//NSString *tagString = [webaddress substringWithRange:matchRange]; // 整个匹配串
// NSRange r1 = [match rangeAtIndex:1];
// if (!NSEqualRanges(r1, NSMakeRange(NSNotFound, 0))) { // 由时分组1可能没有找到相应的匹配，用这种办法来判断
// //NSString *tagName = [webaddress substringWithRange:r1]; // 分组1所对应的串
// return @"";
// }
NSString *tagValue = [webaddress substringWithRange:[match rangeAtIndex:2]]; // 分组2所对应的串
// NSLog(@"分组2所对应的串:%@\n",tagValue);
return tagValue;
}
return @"";
}
- (NSDictionary*)parseURLParams:(NSString *)query {
NSArray *pairs = [query componentsSeparatedByString:@"&"];
NSMutableDictionary *params = [[NSMutableDictionary alloc] init];
for (NSString *pair in pairs) {
NSArray *kv = [pair componentsSeparatedByString:@"="];
NSString *val =
[kv[1] stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
params[kv[0]] = val;
}
return params;
}
6. 日期创建
- (NSDate *)checkDate
{
//2014.23.0.0
NSDateComponents *components = [[NSDateComponents alloc] init];
components.timeZone = [NSTimeZone systemTimeZone];
components.year = 2014;
components.month = 12;
components.day = 23;
components.minute = 0;
components.second = 0;
components.hour = 0;
NSDate *date = [[[NSCalendar currentCalendar] dateFromComponents:components] dateByAddingTimeInterval:[[NSTimeZone systemTimeZone] secondsFromGMT]];
return date;
}
7、透明的navgationbar
NSDictionary *(^MenuDicBlock)(enum TReservationStatus state) =/*此处不需要加返回值，由return决定类型*/ ^(enum TReservationStatus state) {
return @{};
}
9.arc，非arc公用
#if __has_feature(objc_arc) && __clang_major__ >= 3
#define OBJC_ARC_ENABLED 1
#endif // __has_feature(objc_arc)
#if OBJC_ARC_ENABLED
#define OBJC_RETAIN(object) (object)
#define OBJC_COPY(object) (object)
#define OBJC_RELEASE(object) object = nil
#define OBJC_AUTORELEASE(object) (object)
#else
#define OBJC_RETAIN(object) [object retain]
#define OBJC_COPY(object) [object copy]
#define OBJC_RELEASE(object) [object release], object = nil
#define OBJC_AUTORELEASE(object) [object autorelease]
#endif
10 GCD定时器注意事项
如果对定时器用了suspend暂停，那么在销毁定时器前，一定要调用对应次数的resume，否则会导致崩溃。
每一次suspend，resume都将会将内部的一个cout值加减1。
http://stackoverflow.com/questions/9572055/dispatch-source-cancel-on-a-suspended-timer-causes-exc-bad-instruction
11.tableview卡顿与ios性能问题
http://blog.sina.com.cn/s/blog_8c08ed5f0102vt0q.html
http://www.keakon.net/2011/07/26/利用预渲染加速iOS设备的图像显示
12.进入当前app权限设置页面
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:UIApplicationOpenSettingsURLString]];
