iOS－在画布上写文字

有时候需要自定义一个UIView，然后在自定义的UIView上输出一段文字。如下面的例子和演示图。

需要注意的是以下几点：

1. ios7 采用方法 [_text drawInRect:rect withAttributes:attribute]; 而ios7之前是采用[_text drawInRect:self.bounds withFont:font]。

2.CGSize sizeText = [_text boundingRectWithSize:self.bounds.size
                                              options:NSStringDrawingUsesLineFragmentOrigin
                                           attributes:@{
                                                        NSFontAttributeName:font,//设置文字的字体
                                                        NSKernAttributeName:@10,//文字之间的字距
                                                        }
                                              context:nil].size 用来计算单行或多行文字的高度和宽度

ZJQView02.h

#import <UIKit/UIKit.h>

@interface ZJQView02 : UIView

@property (nonatomic,strong) NSString* text;

@end

ZJQView02.m

#import "ZJQView02.h"
#define IOS7 [[[UIDevice currentDevice]systemVersion] floatValue] >= 7.0 //判断SDK版本号是否是7.0或7。0以上

@implementation ZJQView02

-(instancetype)initWithFrame:(CGRect)frame{
    self=[super initWithFrame:frame];
    if (self) {}
    return self;
}

-(void)drawRect:(CGRect)rect{
    //An opaque type that represents a Quartz 2D drawing environment.
    //一个不透明类型的Quartz 2D绘画环境,相当于一个画布,你可以在上面任意绘画
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    /*写文字*/
    UIFont  *font = [UIFont boldSystemFontOfSize:12.0];//定义默认字体
    if (IOS7) {
        NSMutableParagraphStyle* paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
        paragraphStyle.lineBreakMode = NSLineBreakByCharWrapping;
        paragraphStyle.alignment=NSTextAlignmentCenter;//文字居中：发现只能水平居中，而无法垂直居中
        NSDictionary* attribute = @{
                                    NSForegroundColorAttributeName:[UIColor redColor],//设置文字颜色
                                    NSFontAttributeName:font,//设置文字的字体
                                    NSKernAttributeName:@10,//文字之间的字距
                                    NSParagraphStyleAttributeName:paragraphStyle,//设置文字的样式
                                    };
        
        //计算文字的宽度和高度：支持多行显示
        CGSize sizeText = [_text boundingRectWithSize:self.bounds.size
                                              options:NSStringDrawingUsesLineFragmentOrigin
                                           attributes:@{
                                                        NSFontAttributeName:font,//设置文字的字体
                                                        NSKernAttributeName:@10,//文字之间的字距
                                                        }
                                              context:nil].size;
        
        CGFloat width = self.bounds.size.width;
        CGFloat height = self.bounds.size.height;
        
        //为了能够垂直居中，需要计算显示起点坐标x,y
        CGRect rect = CGRectMake((width-sizeText.width)/2, (height-sizeText.height)/2, sizeText.width, sizeText.height);
        [_text drawInRect:rect withAttributes:attribute];
    }else{
        CGContextSetRGBFillColor (context,  1, 0, 0, 1.0);//设置填充颜色:红色
        [_text drawInRect:self.bounds withFont:font];
    }
}

@end

ViewController990.h

#import <UIKit/UIKit.h>
#import "ZJQView02.h"

@interface ViewController990 : UIViewController
{
@private
    
    ZJQView02* zjqView02;
}
@end

ViewController990.m

#import "ViewController990.h"
#import "MyLog.h"
#define IOS7 [[[UIDevice currentDevice]systemVersion] floatValue] >= 7.0 //判断SDK版本号是否是7.0或7。0以上


@interface ViewController990 ()

@end

@implementation ViewController990

- (void)viewDidLoad {
    [super viewDidLoad];
    [self doInit];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}

-(void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];
    zjqView02.center=CGPointMake(self.view.center.x, (self.view.bounds.size.height-zjqView02.frame.origin.y)/2);//移到屏幕中心点
    [MyLog logViews:self.view.window];
}

-(void) doInit {
    //IOS7版本特殊处理
    if (IOS7) {
        self.edgesForExtendedLayout=UIRectEdgeNone;
    }
    self.view.backgroundColor=[UIColor whiteColor];
    zjqView02 = [[ZJQView02 alloc]initWithFrame:CGRectMake(50, 50, 200, 60)];
    zjqView02.backgroundColor=[UIColor yellowColor];
    [email protected]"我是测试文字我是测试文字";
    
    [self.view addSubview:zjqView02];
}

@end

执行效果如下：

iOS－在画布上写文字

项目工程请参考附近中的demo010.zip

iOS－在画布上写文字

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