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:
//
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
UIImage *buttonImage =
[UIImage imageNamed:@"Xcode"];
CGFloat
buttonImageViewWidth =
CGImageGetWidth(buttonImage.CGImage);
CGFloat
buttonImageViewHeight =
CGImageGetWidth(buttonImage.CGImage);
if ([UIScreen
mainScreen].scale == 2.0f) {// iOS 4.0+
buttonImageViewWidth *=
0.5f;
buttonImageViewHeight *=
0.5f;
}
NSString *buttonTitle =
@"中华人民共和国";
UIFont *buttonTitleFont =
[UIFont systemFontOfSize:17.0f];
CGSize
buttonTitleLabelSize = [buttonTitle
sizeWithFont:buttonTitleFont];
//
button宽度,至少为imageView宽度与titleLabel宽度之和
CGFloat buttonWidth =
buttonImageViewWidth +
buttonTitleLabelSize.width;
//
button高度,至少为imageView高度与titleLabel高度之和
CGFloat buttonHeight =
buttonImageViewHeight +
buttonTitleLabelSize.height;
UIButton *b = [[UIButton
alloc] init];
[b
setCenter:CGPointMake(160, 160)];
[b
setBounds:CGRectMake(0, 0, buttonWidth,
buttonHeight)];
[b.titleLabel
setFont:buttonTitleFont];
[b
setBackgroundColor:[UIColor redColor]];
[b setImage:buttonImage
forState:UIControlStateNormal];
[b.imageView
setBackgroundColor:[UIColor greenColor]];
[b setTitle:buttonTitle
forState:UIControlStateNormal];
[b setTitleColor:[UIColor
blackColor] forState:UIControlStateNormal];
[b setTitleColor:[UIColor
scrollViewTexturedBackgroundColor]
forState:UIControlStateHighlighted];
[b.titleLabel
setBackgroundColor:[UIColor whiteColor]];
[self.view
addSubview:b];
CGPoint
buttonBoundsCenter = CGPointMake(CGRectGetMidX(b.bounds),
CGRectGetMidY(b.bounds));
//
找出imageView最终的center
CGPoint
endImageViewCenter = CGPointMake(buttonBoundsCenter.x,
CGRectGetMidY(b.imageView.bounds));
//
找出titleLabel最终的center
CGPoint
endTitleLabelCenter = CGPointMake(buttonBoundsCenter.x,
CGRectGetHeight(b.bounds)-CGRectGetMidY(b.titleLabel.bounds));
//
取得imageView最初的center
CGPoint
startImageViewCenter = b.imageView.center;
//
取得titleLabel最初的center
CGPoint
startTitleLabelCenter = b.titleLabel.center;
//
设置imageEdgeInsets
CGFloat
imageEdgeInsetsTop = endImageViewCenter.y -
startImageViewCenter.y;
CGFloat
imageEdgeInsetsLeft = endImageViewCenter.x -
startImageViewCenter.x;
CGFloat
imageEdgeInsetsBottom = -imageEdgeInsetsTop;
CGFloat
imageEdgeInsetsRight = -imageEdgeInsetsLeft;
b.imageEdgeInsets =
UIEdgeInsetsMake(imageEdgeInsetsTop, imageEdgeInsetsLeft,
imageEdgeInsetsBottom, imageEdgeInsetsRight);
//
设置titleEdgeInsets
CGFloat
titleEdgeInsetsTop =
endTitleLabelCenter.y-startTitleLabelCenter.y;
CGFloat
titleEdgeInsetsLeft = endTitleLabelCenter.x -
startTitleLabelCenter.x;
CGFloat
titleEdgeInsetsBottom = -titleEdgeInsetsTop;
CGFloat
titleEdgeInsetsRight = -titleEdgeInsetsLeft;
b.titleEdgeInsets =
UIEdgeInsetsMake(titleEdgeInsetsTop, titleEdgeInsetsLeft,
titleEdgeInsetsBottom, titleEdgeInsetsRight);
[b
release];