• 貝瑟爾路徑與C語言路徑結(jié)合.

- (void)drawRect:(CGRect)rect {
    //獲取上下文
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    //創(chuàng)建橢圓路徑
    UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(100, 50, 200, 100)];
    /**
     *  矩陣操作必須在添加路徑之前
     */
    //縮放
    CGContextScaleCTM(ctx, 0.5, 0.5);
    //移動
    CGContextTranslateCTM(ctx, 20, 200);
    //旋轉(zhuǎn)
    CGContextRotateCTM(ctx, M_PI_2);
    //將路徑添加至上下文
    CGContextAddPath(ctx, path.CGPath);
    //設(shè)置顏色
    [[UIColor redColor] set];
    //渲染上下文
    CGContextFillPath(ctx);
}

效果圖:

原圖

縮放

位移

旋轉(zhuǎn)

注意:這幾種效果可疊加.

• 繪制文字:

- (void)drawRect:(CGRect)rect {
    //創(chuàng)建富文本字典
    NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
    //設(shè)置富文本字體
    dict[NSFontAttributeName] = [UIFont systemFontOfSize:20];
    //設(shè)置富文本背景顏色
//    dict[NSBackgroundColorAttributeName] = [UIColor redColor];
    //設(shè)置繪制線寬
    dict[NSStrokeWidthAttributeName] = @10;
    //創(chuàng)建shadow對象
    NSShadow *shadow = [[NSShadow alloc] init];
    //設(shè)置shadow模糊度
    shadow.shadowBlurRadius = 2;
    //設(shè)置shadow的顏色
    shadow.shadowColor = [UIColor orangeColor];
    //設(shè)置shadow的偏移量
    shadow.shadowOffset = CGSizeMake(5, 5);
    //設(shè)置富文本陰影效果
    dict[NSShadowAttributeName] = shadow;
    //創(chuàng)建文字
    NSString *str = @"iOS基礎(chǔ)知識";
    //繪制文字
    [str drawAtPoint:CGPointMake(50, 50) withAttributes:dict];
}

效果圖:

繪制文字

• 繪制圖片:

- (void)drawRect:(CGRect)rect {
    //創(chuàng)建圖片,同時設(shè)置圖片內(nèi)容,此方法創(chuàng)建的image的尺寸與圖片尺寸相同
    UIImageView *imageV = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"Snip20160427_8"]];
    //通過此方法繪制圖片時,坐標(biāo)默認(rèn)在父控件的原點位置
    [imageV drawRect:CGRectMake(100, 50, imageV.frame.size.width, imageV.frame.size.height)];
}


- (void)drawRect:(CGRect)rect {
//    image.size = CGSizeMake(50, 50);
    //繪制圖片,可控制坐標(biāo)位置
UIImage *image = [UIImage imageNamed:@"Snip20160427_10"];
    [image drawAtPoint:CGPointMake(50, 50)];
}

效果圖:

drawRect

drawAtPoint

• 雪花效果:

//定義變量
static CGFloat snow = 0;
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    //創(chuàng)建image
    UIImage *image = [UIImage imageNamed:@"Snip20160427_10"];
    //繪制圖片
    [image drawAtPoint:CGPointMake(0, snow)];
    //設(shè)置image的位置下移
    snow += 10;
    //重復(fù)
    if (snow > self.frame.size.height) {
        snow = 0;
    }
}
- (void)awakeFromNib{
    //創(chuàng)建定時器
    CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(timeChange)];
    //添加主運(yùn)行循環(huán)
    [link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes]; 
}
//定時器調(diào)用的方法
- (void)timeChange{
    //重繪
    [self setNeedsDisplay];
}

效果圖:

雪花效果