[iOS - (void)drawRect:(CGRect)rect] 绘制一个居中的矩形

使用到: CGRectInset CGRectoffset UIEdgeInsetsInsetRect 这三个函数的使用情况

//CGRectInset 将原来的矩形放大或者缩小，正表示缩小，－表示放大。 CGRect rect= CGRectMake(20, 50, 100, 80); CGRect rect1=CGRectInset(rect, -10, 20); NSLog(@"%@",p(rect1)); //输出结果：2014-11-22 18:48:55.351 TestCGRectInset[8893:60b] {{10, 70}, {120, 40}} //CGRectOffset 这个函数就是将原来矩形的坐标点变化一下，就是左上角点 CGRect rect= CGRectMake(20, 50, 100, 80); CGRect rect1=CGRectOffset(rect, -10, 20); NSLog(@"%@",p(rect1)); //输出结果：2014-11-22 18:51:58.217 TestCGRectInset[8913:60b] {{10, 70}, {100, 80}} //UIEdgeInsetsInsetRect 表示在原来的rect基础上根据边缘距离内切一个rect出来 CGRect rect= CGRectMake(20, 50, 100, 80); UIEdgeInsets ed=UIEdgeInsetsMake(-3, -4, -5, -6); CGRect r= UIEdgeInsetsInsetRect(rect, ed); NSLog(@"%@",p(r));

绘制代码如下:

- (void)drawRect:(CGRect)rect { // rect.size.height = 140; // rect.size.width = 180; // rect请设置为屏幕宽高 const CGFloat RECT_PADDING = 8.0; rect = CGRectInset(rect, (rect.size.width-180)/2, (rect.size.height-140)/2); const CGFloat ROUND_RECT_CORNER_RADIUS = 5.0; CGPathRef roundRectPath = NewPathWithRoundRect(rect, ROUND_RECT_CORNER_RADIUS); CGContextRef context = UIGraphicsGetCurrentContext(); const CGFloat BACKGROUND_OPACITY = 0.85; CGContextSetRGBFillColor(context, 0, 0, 0, BACKGROUND_OPACITY); CGContextAddPath(context, roundRectPath); CGContextFillPath(context); const CGFloat STROKE_OPACITY = 0.25; CGContextSetRGBStrokeColor(context, 1, 1, 1, STROKE_OPACITY); CGContextAddPath(context, roundRectPath); CGContextStrokePath(context); CGPathRelease(roundRectPath); } CGPathRef NewPathWithRoundRect(CGRect rect, CGFloat cornerRadius) { // // Create the boundary path // CGMutablePathRef path = CGPathCreateMutable(); CGPathMoveToPoint(path, NULL, rect.origin.x, rect.origin.y + rect.size.height - cornerRadius); // Top left corner CGPathAddArcToPoint(path, NULL, rect.origin.x, rect.origin.y, rect.origin.x + rect.size.width, rect.origin.y, cornerRadius); // Top right corner CGPathAddArcToPoint(path, NULL, rect.origin.x + rect.size.width, rect.origin.y, rect.origin.x + rect.size.width, rect.origin.y + rect.size.height, cornerRadius); // Bottom right corner CGPathAddArcToPoint(path, NULL, rect.origin.x + rect.size.width, rect.origin.y + rect.size.height, rect.origin.x, rect.origin.y + rect.size.height, cornerRadius); // Bottom left corner CGPathAddArcToPoint(path, NULL, rect.origin.x, rect.origin.y + rect.size.height, rect.origin.x, rect.origin.y, cornerRadius); // Close the path at the rounded rect CGPathCloseSubpath(path); return path; }

如图: