多年iOS开发经验总结(二)

1、设置UILabel行间距

NSMutableAttributedString* attrString = [[NSMutableAttributedString  alloc] initWithString:label.text];    
NSMutableParagraphStyle *style = [[NSMutableParagraphStyle alloc] init];
[style setLineSpacing:20];
[attrString addAttribute:NSParagraphStyleAttributeName value:style range:NSMakeRange(0, label.text.length)];      
label.attributedText = attrString;

2、当使用-performSelector:withObject:withObject:afterDelay:方法时，需要传入多参数问题

  // 方法一、// 把参数放进一个数组／字典，直接把数组／字典当成一个参数传过去，具体方法实现的地方再解析这个数组／字典
NSArray * array =  [NSArray arrayWithObjects: @"first", @"second", nil];
[self performSelector:@selector(fooFirstInput:) withObject: array afterDelay:15.0];

// 方法二、// 使用NSInvocationSEL aSelector = NSSelectorFromString(@"doSoming:argument2:");
  NSInteger argument1 = 10;
  NSString *argument2 = @"argument2";    if([self respondsToSelector:aSelector]) {
    NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[self methodSignatureForSelector:aSelector]];
    [inv setSelector:aSelector];
    [inv setTarget:self];
    [inv setArgument:&(argument1) atIndex:2];
    [inv setArgument:&(argument2) atIndex:3];
    [inv performSelector:@selector(invoke) withObject:nil afterDelay:15.0];
}

3、UILabel显示不同颜色字体

NSMutableAttributedString * string = [[NSMutableAttributedString alloc] initWithString:label.text];
[string addAttribute:NSForegroundColorAttributeName value:  [UIColor redColor] range:NSMakeRange(0,5)];
[string addAttribute:NSForegroundColorAttributeName value:[UIColor greenColor] range:NSMakeRange(5,6)];
[string addAttribute:NSForegroundColorAttributeName value:[UIColor blueColor] range:NSMakeRange(11,5)];
label.attributedText = string;

4、比较两个CGRect/CGSize/CGPoint是否相等

if (CGRectEqualToRect(rect1, rect2)) { // 两个区域相等       
     // do some
}     
 if (CGPointEqualToPoint(point1, point2)) { // 两个点相等     
     // do some
}    
if (CGSizeEqualToSize(size1, size2)) { // 两个size相等        
    // do some
}

5、比较两个NSDate相差多少小时

  NSDate* date1 = someDate; 
  NSDate* date2 = someOtherDate; 
  NSTimeInterval distanceBetweenDates = [date1 timeIntervalSinceDate:date2]; 
  double secondsInAnHour = 3600;// 除以3600是把秒化成小时，除以60得到结果为相差的分钟数
   NSInteger hoursBetweenDates = distanceBetweenDates / secondsInAnHour;

7、播放一张张连续的图片

// 加入现在有三张图片分别为animate_1、animate_2、animate_3// 
方法一
    imageView.animationImages = @[[UIImage imageNamed:@"animate_1"], [UIImage imageNamed:@"animate_2"], [UIImage imageNamed:@"animate_3"]];
imageView.animationDuration = 1.0;
// 方法二
    imageView.image = [UIImage animatedImageNamed:@"animate_" duration:1.0];
// 方法二解释下，这个方法会加载animate_为前缀的，后边0-1024，也就是animate_0、animate_1一直到animate_1024

8、加载gif图片

  推荐使用这个框架 [FLAnimatedImage](https://github.com/Flipboard/FLAnimatedImage)

9、防止离屏渲染为image添加圆角

// image分类
- (UIImage *)circleImage
{// NO代表透明
UIGraphicsBeginImageContextWithOptions(self.size, NO, 1);
// 获得上下文
CGContextRef ctx = UIGraphicsGetCurrentContext();
// 添加一个圆
CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
// 方形变圆形
CGContextAddEllipseInRect(ctx, rect);
// 裁剪
CGContextClip(ctx);
// 将图片画上去
[self drawInRect:rect];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();UIGraphicsEndImageContext();return image;
}

14、判断两个rect是否有交叉

 if (CGRectIntersectsRect(rect1, rect2))
  {
  }

16、将一个view保存为pdf格式

- (void)createPDFfromUIView:(UIView*)aView saveToDocumentsWithFileName:(NSString*)aFilename
{   
 NSMutableData *pdfData = [NSMutableData data];  
 UIGraphicsBeginPDFContextToData(pdfData, aView.bounds, nil);   
 UIGraphicsBeginPDFPage();    
CGContextRef pdfContext = UIGraphicsGetCurrentContext();
[aView.layer renderInContext:pdfContext];      
UIGraphicsEndPDFContext();    
NSArray* documentDirectories =   NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask,YES);    
NSString* documentDirectory = [documentDirectories objectAtIndex:0];    
NSString* documentDirectoryFilename = [documentDirectory stringByAppendingPathComponent:aFilename];
[pdfData writeToFile:documentDirectoryFilename atomically:YES];   
 NSLog(@"documentDirectoryFileName: %@",documentDirectoryFilename);
}

19、保存UIImage到本地

NSArray *paths =     NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,     NSUserDomainMask, YES);
NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"Image.png"];

[UIImagePNGRepresentation(image) writeToFile:filePath atomically:YES];

20、键盘上方增加工具栏

UIToolbar *keyboardDoneButtonView = [[UIToolbar alloc] init];
[keyboardDoneButtonView sizeToFit];
UIBarButtonItem *doneButton = [[UIBarButtonItem alloc] initWithTitle:@"Done"
                                                           style:UIBarButtonItemStyleBordered target:self
                                                          action:@selector(doneClicked:)];
[keyboardDoneButtonView setItems:[NSArray arrayWithObjects:doneButton, nil]];
  txtField.inputAccessoryView = keyboardDoneButtonView;

22、在image上绘制文字并生成新的image

UIFont *font = [UIFont boldSystemFontOfSize:12];
UIGraphicsBeginImageContext(image.size);
[image drawInRect:CGRectMake(0,0,image.size.width,image.size.height)];
CGRect rect = CGRectMake(point.x, point.y, image.size.width, image.size.height);
[[UIColor whiteColor] set];
[text drawInRect:CGRectIntegral(rect) withFont:font]; 
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

29、动画修改label上的文字

// 方法一

    CATransition *animation = [CATransition animation];
  animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
  animation.type = kCATransitionFade;
  animation.duration = 0.75;
  [self.label.layer addAnimation:animation forKey:@"kCATransitionFade"];    
  self.label.text = @"New";
  // 方法二
  [UIView transitionWithView:self.label
                  duration:0.25f
                   options:UIViewAnimationOptionTransitionCrossDissolve
                animations:^{                        
                self.label.text = @"Well done!";

                } completion:nil];
      // 方法三
        [UIView animateWithDuration:1.0
                 animations:^{                         
                self.label.alpha = 0.0f;                         
                self.label.text = @"newText";      
                                   self.label.alpha = 1.0f;
                 }];

35、获取手机RAM容量

// 需要导入#import <mach/mach.h>
mach_port_t host_port;   
 mach_msg_type_number_t host_size;    
vm_size_t pagesize;

host_port = mach_host_self();
host_size = sizeof(vm_statistics_data_t) / sizeof(integer_t);
host_page_size(host_port, &pagesize);  
vm_statistics_data_t vm_stat;   
 if (host_statistics(host_port, HOST_VM_INFO, (host_info_t)&vm_stat, &host_size) != KERN_SUCCESS) {
    NSLog(@"Failed to fetch vm statistics");
}    /* Stats in bytes */
natural_t mem_used = (vm_stat.active_count +
                      vm_stat.inactive_count +
                      vm_stat.wire_count) * pagesize;    natural_t mem_free = vm_stat.free_count * pagesize;    natural_t mem_total = mem_used + mem_free;
NSLog(@"已用: %u 可用: %u 总共: %u", mem_used, mem_free, mem_total);