IOS7 根据字符串求尺寸

一、先用xcode创建一个单视图工程

主界面为

为NSString写个求size的分类

#import "NSString+Size.h"

@implementation NSString (Size)

- (CGSize)textSizeWithFont:(UIFont *)font constrainedToSize:(CGSize)size lineBreakMode:(NSLineBreakMode)lineBreakMode

{

    CGSize textSize;

    if (CGSizeEqualToSize(size, CGSizeZero))

    {

        //            NSDictionary *attributes = @{NSFontAttributeName:font}

        NSDictionary *attributes = [NSDictionary dictionaryWithObject:font forKey:NSFontAttributeName];

        //            textSize = [self sizeWithAttributes:attributes];

        //            textSize = []

        

        textSize = [self sizeWithAttributes:attributes];

    }

    else

    {

        NSStringDrawingOptions option = NSStringDrawingTruncatesLastVisibleLine | NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading;

        //NSStringDrawingTruncatesLastVisibleLine如果文本内容超出指定的矩形限制，文本将被截去并在最后一个字符后加上省略号。 如果指定了NSStringDrawingUsesLineFragmentOrigin选项，则该选项被忽略 NSStringDrawingUsesFontLeading计算行高时使用行间距。（译者注：字体大小+行间距=行高）

        NSDictionary *attributes = [NSDictionary dictionaryWithObject:font forKey:NSFontAttributeName];

        CGRect rect = [self boundingRectWithSize:size

                                        options:option

                                     attributes:attributes

                                        context:nil];

        

        textSize = rect.size;

    }

    return textSize;

}

@end

主代码实现：

ViewController.h

#import <UIKit/UIKit.h>

#import "NSString+Size.h"

@interface ViewController : UIViewController

@property (weak, nonatomic) IBOutlet UITextField *mTextField;

@property (weak, nonatomic) IBOutlet UILabel *outTextField;

- (IBAction)switchKeboardInput:(id)sender;

+(CGSize)sizeOfContent:(NSString *)name;

@end

ViewController.m文件

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad

{

    [super viewDidLoad];

// Do any additional setup after loading the view, typically from a nib.

}

- (void)viewDidAppear:(BOOL)animated

{

    [super viewDidAppear:animated];

    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(changeKeyBoard:) name:UIKeyboardWillChangeFrameNotification object:nil]; //键盘改变事件

}

- (void)viewWillDisappear:(BOOL)animated

{

    

}

-(void)changeKeyBoard:(NSNotification *)aNotifacation

{

    //求字符串的长度

    CGSize textSize = [ViewController sizeOfContent: _mTextField.text];

    NSString *str = [NSString stringWithFormat:@"宽度为%.2f,高度为%.2f",textSize.width,textSize.height];

    _outTextField.text = str;

}

+ (CGSize)sizeOfContent:(NSString *)name

{

    if (name.length == 0) {

        return CGSizeMake(0, 0);

    }

    NSMutableString *string = [NSMutableString stringWithString:name];

    return [string textSizeWithFont:[UIFont systemFontOfSize:15] constrainedToSize:CGSizeMake(100, 1000) lineBreakMode:NSLineBreakByWordWrapping];  //一行宽度最大为 100 高度1000

}

- (IBAction)switchKeboardInput:(id)sender

{

    [_mTextField resignFirstResponder];

}

@end

运行结果：