ios代碼小技巧

1.得到屏幕圖像
- (UIImage *)imageFromView: (UIView *) theView
{
    
    UIGraphicsBeginImageContext(theView.frame.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    [theView.layer renderInContext:context];
    UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return theImage;
}

2.label的動態size

- (CGSize)labelAutoCalculateRectWith:(NSString*)text FontSize:(CGFloat)fontSize MaxSize:(CGSize)maxSize

{
    
    NSMutableParagraphStyle* paragraphStyle = [[NSMutableParagraphStyle alloc]init];
    
    paragraphStyle.lineBreakMode=NSLineBreakByWordWrapping;
    
    NSDictionary* attributes =@{NSFontAttributeName:[UIFont fontWithName:@"MicrosoftYaHei" size:fontSize],NSParagraphStyleAttributeName:paragraphStyle.copy};
    
    CGSize labelSize = [text boundingRectWithSize:maxSize options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading|NSStringDrawingTruncatesLastVisibleLine attributes:attributes context:nil].size;
    
    labelSize.height=ceil(labelSize.height);
    return labelSize;
    
}

3.時間戳轉化爲時間

-(NSString*)TimeTrasformWithDate:(NSString *)dateString
{
    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
    [formatter setDateFormat:@"YY-MM-dd HH:mm"];
    [formatter setTimeZone:[NSTimeZone timeZoneWithName:@"Asia/Beijing"]];
    
    NSString *date = [formatter stringFromDate:[NSDate dateWithTimeIntervalSince1970:dateString.integerValue]];
    //NSLog(@"date1:%@",date);
    return date;
    
}

4.RGB轉化成顏色

+ (UIColor *)colorFromHexRGB:(NSString *)inColorString
{
    UIColor *result = nil;
    unsigned int colorCode = 0;
    unsigned char redByte, greenByte, blueByte;
    
    if (nil != inColorString)
    {
        NSScanner *scanner = [NSScanner scannerWithString:inColorString];
        (void) [scanner scanHexInt:&colorCode]; // ignore error
    }
    redByte = (unsigned char) (colorCode >> 16);
    greenByte = (unsigned char) (colorCode >> 8);
    blueByte = (unsigned char) (colorCode); // masks off high bits
    result = [UIColor
              colorWithRed: (float)redByte / 0xff
              green: (float)greenByte/ 0xff
              blue: (float)blueByte / 0xff
              alpha:1.0];
    return result;
}

5.加邊框

UIRectCorner corners=UIRectCornerTopLeft | UIRectCornerTopRight;
    UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:view.bounds
                                                   byRoundingCorners:corners
                                                         cornerRadii:CGSizeMake(4, 0)];
    CAShapeLayer *maskLayer = [CAShapeLayer layer];
    maskLayer.frame         = view.bounds;
    maskLayer.path          = maskPath.CGPath;
    view.layer.mask         = maskLayer;
6.//壓縮圖片
+ (UIImage*)imageWithImageSimple:(UIImage*)image scaledToSize:(CGSize)newSize
{
    //建立一個圖形上下文形象
    UIGraphicsBeginImageContext(newSize);
    // 告訴舊圖片畫在這個新的環境,所需的
    // new size
    [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
    //獲取上下文的新形象
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    // 結束上下文
    UIGraphicsEndImageContext();
    return newImage;
}

7.textfield的placeholder
 
        [textF setValue:[UIColor whiteColor] forKeyPath:@"_placeholderLabel.textColor"];
        [textF setValue:[UIFont boldSystemFontOfSize:15] forKeyPath:@"_placeholderLabel.font"];
8.

butLeft. imageEdgeInsets = UIEdgeInsetsMake (7 , 5 , 7 , 25  );
    butLeft.contentHorizontalAlignment = UIControlContentHorizontalAlignmentCenter;
9.//調用此方法改變label最後2個字符的大小
- (void)label:(UILabel *)label BehindTextSize:(NSInteger)integer
{
    NSMutableAttributedString *mutaString = [[NSMutableAttributedString alloc] initWithString:label.text];
    
    [mutaString addAttribute:NSFontAttributeName value:[UIFont boldSystemFontOfSize:16] range:NSMakeRange(label.text.length-2, 2)];
    label.attributedText = mutaString;
}

10.- (void)ChangeLabelTextColor:(UILabel *)label
{
    NSMutableAttributedString *mutaString = [[NSMutableAttributedString alloc] initWithString:label.text];
    
    [mutaString addAttribute:NSForegroundColorAttributeName value:[UIColor colorWithRed:207/255.0 green:34/255.0 blue:42/255.0 alpha:1] range:NSMakeRange(0, 5)];
    label.attributedText = mutaString;
}

11.

if ([tableView respondsToSelector:@selector(setSeparatorInset:)]) {
        
        [tableView setSeparatorInset:UIEdgeInsetsZero];
        
    }
    if ([[UIDevice currentDevice].systemVersion floatValue] >= 8.0) {
        if ([tableView respondsToSelector:@selector(setLayoutMargins:)]) {
        
        [tableView setLayoutMargins:UIEdgeInsetsZero];
        
    }
    }
    
    // Do any additional setup after loading the view.
}
- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath

{
    
    if ([cell respondsToSelector:@selector(setSeparatorInset:)]) {
        
        [cell setSeparatorInset:UIEdgeInsetsZero];
        
    }
    if ([[UIDevice currentDevice].systemVersion floatValue] >= 8.0) {
        if ([cell respondsToSelector:@selector(setLayoutMargins:)]) {
        
        [cell setLayoutMargins:UIEdgeInsetsZero];
        
    }
    }
    
    
}
12。圖片變灰度

-(UIImage *) grayscaleImage: (UIImage *) image
{
    CGSize size = image.size;
    CGRect rect = CGRectMake(0.0f, 0.0f, image.size.width,
                             image.size.height);
    // Create a mono/gray color space
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
    CGContextRef context = CGBitmapContextCreate(nil, size.width,
                                                 size.height, 8, 0, colorSpace, kCGImageAlphaNone);
    CGColorSpaceRelease(colorSpace);
    // Draw the image into the grayscale context
    CGContextDrawImage(context, rect, [image CGImage]);
    CGImageRef grayscale = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    // Recover the image
    UIImage *img = [UIImage imageWithCGImage:grayscale];
    CFRelease(grayscale);
    return img;
}
13.16進制轉rgb

#define UIColorFromRGB(rgbValue) [UIColor colorWithRed:((float)((rgbValue & 0xFF0000) >> 16))/255.0 green:((float)((rgbValue & 0xFF00) >> 8))/255.0 blue:((float)(rgbValue & 0xFF))/255.0 alpha:1.0]