用iOS中的字母繪製實心圓圈7

Question

新的ios 7手機應用程序具有收藏夾部分。在該部分中，聯繫人的姓名將顯示在圓圈內的聯繫人的初始位置的旁邊。

這是如何繪製的？使用drawrect還是已經存在，併爲此創建對象？

Answer 1

下面是一個UIView子類，它將做你想做的。它將正確地確定和定位圈內的一個或多個字母。下面是它的外觀與在各種尺寸1-3字母（32，64，128，256）：

與用戶定義的運行時的可用性在界面生成器屬性，可以甚至配置從視圖在IB內。只需將text屬性設置爲運行時屬性，並將backgroundColor設置爲所需的圓形顏色即可。

下面的代碼：

@interface MELetterCircleView : UIView 

/** 
* The text to display in the view. This should be limited to 
* just a few characters. 
*/ 
@property (nonatomic, strong) NSString *text; 

@end 



@interface MELetterCircleView() 

@property (nonatomic, strong) UIColor *circleColor; 

@end 

@implementation MELetterCircleView 

- (instancetype)initWithFrame:(CGRect)frame text:(NSString *)text 
{ 
    NSParameterAssert(text); 
    self = [super initWithFrame:frame]; 
    if (self) 
    { 
     self.text = text; 
    } 

    return self; 
} 

// Override to set the circle's background color. 
// The view's background will always be clear. 
-(void)setBackgroundColor:(UIColor *)backgroundColor 
{ 
    self.circleColor = backgroundColor; 
    [super setBackgroundColor:[UIColor clearColor]]; 
} 


- (void)drawRect:(CGRect)rect 
{ 
    CGContextRef context = UIGraphicsGetCurrentContext(); 

    [self.circleColor setFill]; 
    CGContextAddArc(context, CGRectGetMidX(rect), CGRectGetMidY(rect), 
          CGRectGetWidth(rect)/2, 0, 2*M_PI, YES); 
    CGContextFillPath(context); 

    [self drawSubtractedText:self.text inRect:rect inContext:context]; 

} 

- (void)drawSubtractedText:(NSString *)text inRect:(CGRect)rect 
       inContext:(CGContextRef)context 
{ 
    CGContextSaveGState(context); 

    // Magic blend mode 
    CGContextSetBlendMode(context, kCGBlendModeDestinationOut); 


    CGFloat pointSize = 
      [self optimumFontSizeForFont:[UIFont boldSystemFontOfSize:100.f] 
           inRect:rect 
           withText:text]; 

    UIFont *font = [UIFont boldSystemFontOfSize:pointSize]; 

    // Move drawing start point for centering label. 
    CGContextTranslateCTM(context, 0, 
          (CGRectGetMidY(rect) - (font.lineHeight/2))); 

    CGRect frame = CGRectMake(0, 0, CGRectGetWidth(rect), font.lineHeight)]; 
    UILabel *label = [[UILabel alloc] initWithFrame:frame]; 
    label.font = font; 
    label.text = text; 
    label.textAlignment = NSTextAlignmentCenter; 
    label.backgroundColor = [UIColor clearColor]; 
    [label.layer drawInContext:context]; 

    // Restore the state of other drawing operations 
    CGContextRestoreGState(context); 
} 

-(CGFloat)optimumFontSizeForFont:(UIFont *)font inRect:(CGRect)rect 
         withText:(NSString *)text 
{ 
    // For current font point size, calculate points per pixel 
    CGFloat pointsPerPixel = font.lineHeight/font.pointSize; 

    // Scale up point size for the height of the label. 
    // This represents the optimum size of a single letter. 
    CGFloat desiredPointSize = rect.size.height * pointsPerPixel; 

    if ([text length] == 1) 
    { 
      // In the case of a single letter, we need to scale back a bit 
      // to take into account the circle curve. 
      // We could calculate the inner square of the circle, 
      // but this is a good approximation. 
     desiredPointSize = .80*desiredPointSize; 
    } 
    else 
    { 
     // More than a single letter. Let's make room for more. 
     desiredPointSize = desiredPointSize/[text length]; 
    } 

    return desiredPointSize; 
} 
@end