iphone学习（原创＋搜集）
网络上搜索，不断更新中…
1.断点处查看变量内容：
po objc:输出［objc descripton];
print (int)[objc retainCount]:输出[objc retainCount)。 注：print [objc retainCount]不行。
print (CGRect)[view frame]:输出view.frame。 注：print [view frame] 或 print (CGRect)view.frame 不行。
2.修改UIAlertView背景：
theAlert.layer.contents = (id)[UIImageObjc CGImage];
3.减少图片在程序的缓存，尤其大图片画在更小的范围内时。
代码
- (UIImage *)rescaleImageToSize:(CGSize)size {
CGRect rect = CGRectMake(0.0, 0.0, size.width, size.height);
UIGraphicsBeginImageContext(rect.size);
[self drawInRect:rect]; // scales image to rect
UIImage *resImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return resImage;
}
CGRect rect = CGRectMake(0.0, 0.0, size.width, size.height);
UIGraphicsBeginImageContext(rect.size);
[self drawInRect:rect]; // scales image to rect
UIImage *resImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return resImage;
}
4.使用不长时间cache的UIImage：
代码
+ (UIImage *)myImageNamed:(NSString *)name{
name = [name substringToIndex:name.length - 4];
NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:@"png"];
return [UIImage imageWithContentsOfFile:path];
}
name = [name substringToIndex:name.length - 4];
NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:@"png"];
return [UIImage imageWithContentsOfFile:path];
}
5.计算String的Label范围 ：
代码
CGSize calcLabelSize(NSString *string, UIFont *font, NSInteger lines, float lineWidth) {
float lineHeight = [ @"Fake line" sizeWithFont: font ].height; // Calculate the height of one line.
if ( string == nil ) {
return CGSizeMake(lineWidth, lineHeight);
}
NSMutableString *tmpString = [[NSMutableString alloc] init];
[tmpString setString:[string stringByReplacingOccurrencesOfString:@"<br />" withString:@"\n"]];
int numLines = [tmpString sizeWithFont: font constrainedToSize: CGSizeMake(lineWidth, lineHeight*1000.0f) lineBreakMode: UILineBreakModeTailTruncation ].height / lineHeight; // Get the total height, divide by the height of one line to get the # of lines.
[tmpString release];
if ( numLines > lines )
numLines = lines; // Set the number of lines to the maximum allowed if it goes over.
numLines += 1; //rena add
return CGSizeMake(lineWidth, (lineHeight*(float)numLines)); // multiply the # of lines by the height of one line and return.
}
float lineHeight = [ @"Fake line" sizeWithFont: font ].height; // Calculate the height of one line.
if ( string == nil ) {
return CGSizeMake(lineWidth, lineHeight);
}
NSMutableString *tmpString = [[NSMutableString alloc] init];
[tmpString setString:[string stringByReplacingOccurrencesOfString:@"<br />" withString:@"\n"]];
int numLines = [tmpString sizeWithFont: font constrainedToSize: CGSizeMake(lineWidth, lineHeight*1000.0f) lineBreakMode: UILineBreakModeTailTruncation ].height / lineHeight; // Get the total height, divide by the height of one line to get the # of lines.
[tmpString release];
if ( numLines > lines )
numLines = lines; // Set the number of lines to the maximum allowed if it goes over.
numLines += 1; //rena add
return CGSizeMake(lineWidth, (lineHeight*(float)numLines)); // multiply the # of lines by the height of one line and return.
}
6.NSData格式化：
该格式可以指定以下内容:
NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];[outputFormatter setDateFormat:@"HH:mm 'on' EEEE MMMM d"];
NSString *newDateString = [outputFormatter stringFromDate:formatterDate];
01 |
G: 公元时代，例如AD公元 |
02 |
yy: 年的后2位 |
03 |
yyyy: 完整年 |
04 |
MM: 月，显示为1-12 |
05 |
MMM: 月，显示为英文月份简写,如 Jan |
06 |
MMMM: 月，显示为英文月份全称，如 Janualy |
07 |
dd: 日，2位数表示，如02 |
08 |
d: 日，1-2位显示，如 2 |
09 |
EEE: 简写星期几，如Sun |
10 |
EEEE: 全写星期几，如Sunday |
11 |
aa: 上下午，AM/PM |
12 |
H: 时，24小时制，0-23 |
13 |
K：时，12小时制，0-11 |
14 |
m: 分，1-2位 |
15 |
mm: 分，2位 |
16 |
s: 秒，1-2位 |
17 |
ss: 秒，2位 |
18 |
S: 毫秒 |
7.宏定义
// 是否高清屏
#define isRetina ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(640, 960), [[UIScreen mainScreen] currentMode].size) : NO)
// 是否iPad
#define isPad (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad)
// 是否模拟器
#define isSimulator (NSNotFound != [[[UIDevice currentDevice] model] rangeOfString:@"Simulator"].location)
