UIButton 垂直对齐不起作用 [英] UIButton vertical alignment doesn't work

问题描述

我不明白为什么在下面的代码中，标题对齐不是保持在顶部.

I can't figure why in the following code, the title alignment isn't remain Top.

UIButton *btn2 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
btn2.titleLabel.font = [UIFont systemFontOfSize:53];
btn2.frame = CGRectMake(20, 20, 270, 44);
[btn2 setTitle:@"test1 test2 test3 test4 test5 test6 test7" forState:UIControlStateNormal];
[btn2 setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
btn2.titleLabel.minimumFontSize = 1.0;
btn2.titleLabel.adjustsFontSizeToFitWidth = YES;
btn2.titleLabel.numberOfLines = 1;
btn2.contentVerticalAlignment = UIControlContentVerticalAlignmentTop;

推荐答案

这种行为是由于按钮的 titleLabel 的 baselineAdjustment 默认属性造成的.如果你将它设置为 UIBaselineAdjustmentNone，你应该会得到你想要的效果.

This behavior is due to the baselineAdjustment default property of the button's titleLabel. If you set this to UIBaselineAdjustmentNone, you should get the effect you're looking for.

btn2.titleLabel.baselineAdjustment = UIBaselineAdjustmentNone;

来自 UILabel 的 rel="nofollow">docs:

From the docs for UILabel:

控制文本基线的调整方式需要缩小以适应标签.

baselineAdjustment

Controls how text baselines are adjusted when text needs to shrink to fit in the label.

@property(nonatomic) UIBaselineAdjustment baselineAdjustment

讨论

如果 adjustsFontSizeToFitWidth 属性设置为 YES，则此属性控制需要调整字体大小时文本基线的行为.此属性的默认值为 UIBaselineAdjustmentAlignBaselines.此属性仅在 numberOfLines 属性设置为 1 时有效.

Discussion

If the adjustsFontSizeToFitWidth property is set to YES, this property controls the behavior of the text baselines in situations where adjustment of the font size is required. The default value of this property is UIBaselineAdjustmentAlignBaselines. This property is effective only when the numberOfLines property is set to 1.

和

相对于其基线位置调整文本.

UIBaselineAdjustmentAlignBaselines

Adjust text relative to the position of its baseline.

适用于 iOS 2.0 及更高版本.

Available in iOS 2.0 and later.

相对于其边界框的中心调整文本.

Adjust text based relative to the center of its bounding box.

适用于 iOS 2.0 及更高版本.

Available in iOS 2.0 and later.

相对于边界框的左上角调整文本.这是默认调整.

Adjust text relative to the top-left corner of the bounding box. This is the default adjustment.

适用于 iOS 2.0 及更高版本.

Available in iOS 2.0 and later.

请注意，UILabel 的默认调整与按钮的 titleLabel 的默认调整不同.

Note that the default adjustment for UILabel differs from that of a button's titleLabel.

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