UIButton,送给多数开发者的释疑文章,关于如何正确调整imageView及titleLabel的位置

一些开发者知道通过imageEdgeInsets及titleEdgeInsets可以调整imageView及titleLabel的位置,但不知道如何正确计算,基本上都是通过多次调整相应的值达到期望的目标(次数过多可能会失去信心),究其原因就是不能正确理解imageEdgeInsets及titleEdgeInsets.

下面步入主题.

如果button的bounds足够大(宽度至少是imageView宽度与titleLabel宽度之和,高度至少为imageView高度与titleLabel高度中的最大值),那么就可以同时显示imageView及titleLabel,如下图:

如果,想要得到imageView及titleLabel都居中显示,且要达到imageView在上,titleLabel在下的效果(通过设置imageView及titleLabel的frame是无法达到这样的效果的),如下图:

此时,button的bounds也要足够大(宽度至少是imageView宽度与titleLabel宽度之和,高度至少为imageView高度与titleLabel高度之和),并且,需要修改button的imageEdgeInsets及titleEdgeInsets.可参考下面的代码:

 1 // 这里的图片,必须有Xcode.png及[email protected],便于得到正确的以设备点为单位的宽度及高度
 2 UIImage *buttonImage = [UIImage imageNamed:@"Xcode"];  3 CGFloat buttonImageViewWidth = CGImageGetWidth(buttonImage.CGImage);  4 CGFloat buttonImageViewHeight = CGImageGetWidth(buttonImage.CGImage);  5 if ([UIScreen mainScreen].scale == 2.0f) {// iOS 4.0+
 6     buttonImageViewWidth *= 0.5f;  7     buttonImageViewHeight *= 0.5f;  8 }  9 NSString *buttonTitle = @"中华人民共和国"; 10 UIFont *buttonTitleFont = [UIFont systemFontOfSize:17.0f]; 11 CGSize buttonTitleLabelSize = [buttonTitle sizeWithFont:buttonTitleFont]; 12 // button宽度,至少为imageView宽度与titleLabel宽度之和
13 CGFloat buttonWidth = buttonImageViewWidth + buttonTitleLabelSize.width; 14 // button高度,至少为imageView高度与titleLabel高度之和
15 CGFloat buttonHeight = buttonImageViewHeight + buttonTitleLabelSize.height; 16 
17 UIButton *b = [[UIButton alloc] init]; 18 [b setCenter:CGPointMake(160, 160)]; 19 [b setBounds:CGRectMake(0, 0, buttonWidth, buttonHeight)]; 20 [b.titleLabel setFont:buttonTitleFont]; 21 [b setBackgroundColor:[UIColor redColor]]; 22 
23 [b setImage:buttonImage forState:UIControlStateNormal]; 24 [b.imageView setBackgroundColor:[UIColor greenColor]]; 25 
26 [b setTitle:buttonTitle forState:UIControlStateNormal]; 27 [b setTitleColor:[UIColor blackColor] forState:UIControlStateNormal]; 28 [b setTitleColor:[UIColor scrollViewTexturedBackgroundColor] forState:UIControlStateHighlighted]; 29 [b.titleLabel setBackgroundColor:[UIColor whiteColor]]; 30 
31 [self.view addSubview:b]; 32 
33 CGPoint buttonBoundsCenter = CGPointMake(CGRectGetMidX(b.bounds), CGRectGetMidY(b.bounds)); 34 // 找出imageView最终的center
35 CGPoint endImageViewCenter = CGPointMake(buttonBoundsCenter.x, CGRectGetMidY(b.imageView.bounds)); 36 // 找出titleLabel最终的center
37 CGPoint endTitleLabelCenter = CGPointMake(buttonBoundsCenter.x, CGRectGetHeight(b.bounds)-CGRectGetMidY(b.titleLabel.bounds)); 38 // 取得imageView最初的center
39 CGPoint startImageViewCenter = b.imageView.center; 40 // 取得titleLabel最初的center
41 CGPoint startTitleLabelCenter = b.titleLabel.center; 42 // 设置imageEdgeInsets
43 CGFloat imageEdgeInsetsTop = endImageViewCenter.y - startImageViewCenter.y; 44 CGFloat imageEdgeInsetsLeft = endImageViewCenter.x - startImageViewCenter.x; 45 CGFloat imageEdgeInsetsBottom = -imageEdgeInsetsTop; 46 CGFloat imageEdgeInsetsRight = -imageEdgeInsetsLeft; 47 b.imageEdgeInsets = UIEdgeInsetsMake(imageEdgeInsetsTop, imageEdgeInsetsLeft, imageEdgeInsetsBottom, imageEdgeInsetsRight); 48 // 设置titleEdgeInsets
49 CGFloat titleEdgeInsetsTop = endTitleLabelCenter.y-startTitleLabelCenter.y; 50 CGFloat titleEdgeInsetsLeft = endTitleLabelCenter.x - startTitleLabelCenter.x; 51 CGFloat titleEdgeInsetsBottom = -titleEdgeInsetsTop; 52 CGFloat titleEdgeInsetsRight = -titleEdgeInsetsLeft; 53 b.titleEdgeInsets = UIEdgeInsetsMake(titleEdgeInsetsTop, titleEdgeInsetsLeft, titleEdgeInsetsBottom, titleEdgeInsetsRight); 54 
55 [b release];