视图背景颜色渐变

• 使用layer方式实现

---

//初始化视图
    self.comfirmButton.frame = CGRectMake(139, 0, self.width - 139, self.height);
    //初始化CAGradientlayer对象，使它的大小为对象的大小
    CAGradientLayer *layer = [CAGradientLayer layer];
    layer.frame = self.comfirmButton.bounds;
    //将layer对象添加到视图
    [self.comfirmButton.layer addSublayer:layer];
    //渐变区域的起始点
    layer.startPoint = CGPointMake(0, 0);
    //渐变区域的终点
    layer.endPoint = CGPointMake(1, 0);
    //颜色数组
    layer.colors = @[(__bridge id)[UIColor colorWithHexString:@"FF7171"].CGColor,(__bridge id)[UIColor colorWithHexString:@"FF71A1"].CGColor];
    //设置颜色的分割点
    layer.locations = @[@(0.5f),@(1.0f)];

---

---

• 使用上下文的方式实现

  • .h中的方法
  • 类目

  
  typedef enum  {
      topToBottom = 0,//从上到小
      leftToRight = 1,//从左到右
      upleftTolowRight = 2,//左上到右下
      uprightTolowLeft = 3,//右上到左下
  }GradientType;
  

    ```
    + (UIButton *)changeButtonTitleAndImagePointWith:(UIButton *)button
    ```
  

---

外部方法

+ (UIButton *)changeButtonTitleAndImagePointWith:(UIButton *)button
{
    CGFloat imageW = button.imageView.frame.size.width;
    CGFloat imageH = button.imageView.frame.size.height;
    
    CGFloat titleW = button.titleLabel.frame.size.width;
    CGFloat titleH = button.titleLabel.frame.size.height;
    
    //图片上文字下
    [button setTitleEdgeInsets:UIEdgeInsetsMake(0, -imageW, imageH + 10, 0.f)];
    [button setImageEdgeInsets:UIEdgeInsetsMake(titleH, 0.f, 0.f,-titleW)];
    
    return button;
}

私有方法

+ (UIButton *)changeColorArray:(NSMutableArray*)colorArray ByGradientType:(GradientType)gradientType button:(UIButton *)button
{
    UIImage *backImage = [button buttonImageFromColors:colorArray ByGradientType:gradientType button:button];
    [button setBackgroundImage:backImage forState:UIControlStateNormal];
    return button;
}
- (UIImage*) buttonImageFromColors:(NSArray*)colors ByGradientType:(GradientType)gradientType button:(UIButton *)button{
    NSMutableArray *ar = [NSMutableArray array];
    for(UIColor *c in colors) {
        [ar addObject:(id)c.CGColor];
    }
    UIGraphicsBeginImageContextWithOptions(button.frame.size, YES, 1);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSaveGState(context);
    CGColorSpaceRef colorSpace = CGColorGetColorSpace([[colors lastObject] CGColor]);
    CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (CFArrayRef)ar, NULL);
    CGPoint start;
    CGPoint end;
    
    switch (gradientType) {
        case 0:////从上到小
            start = CGPointMake(0.0, 0.0);
            end = CGPointMake(0.0, button.frame.size.height);
            break;
        case 1:////从左到右
            start = CGPointMake(0.0, 0.0);
            end = CGPointMake(button.frame.size.width, 0.0);
            break;
        case 2:////左上到右下
            start = CGPointMake(0.0, 0.0);
            end = CGPointMake(button.frame.size.width, button.frame.size.height);
            break;
        case 3: ////右上到左下
            start = CGPointMake(button.frame.size.width, 0.0);
            end = CGPointMake(0.0, button.frame.size.height);
            break;
        default:
            break;
    }
    CGContextDrawLinearGradient(context, gradient, start, end, kCGGradientDrawsBeforeStartLocation | kCGGradientDrawsAfterEndLocation);
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    CGGradientRelease(gradient);
    CGContextRestoreGState(context);
    CGColorSpaceRelease(colorSpace);
    UIGraphicsEndImageContext();
    return image;
}

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