为何用作UIBarButtonItem的UIButton高度无法改变？

Hey there! Let's figure out why your UIButton's height isn't cooperating and get that perfect circle working for your UIBarButtonItem.

Why Your Button Height Isn't Adjusting #

A few missteps are causing the issue:

• You’re modifying hasMessageBtn.layer.frame instead of the button’s own frame. The layer’s frame is tied to the button’s bounds, so tweaking it directly won’t change the button’s actual visible size.
• You initialized the button with just [UIButton alloc] but skipped calling an init method like initWithFrame:. That leaves the button with an undefined initial size, which makes it hard to control later.
• UIBarButtonItem applies its own Auto Layout constraints to custom views. Hardcoding frames can get overridden by these system constraints, leading to unexpected sizing.

Fixed Code for the Perfect Circle Button #

Here’s the corrected implementation with best practices:

// 1. Properly initialize the button with a defined frame
UIButton *hasMessageBtn = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 24, 24)];
hasMessageBtn.backgroundColor = [UIColor orangeColor];

// 2. Set up the rounded corners correctly
hasMessageBtn.layer.cornerRadius = hasMessageBtn.bounds.size.width / 2; // Dynamic radius for perfect circle
hasMessageBtn.layer.masksToBounds = YES; // Critical to clip the button to the rounded shape

// 3. Add your tap action
[hasMessageBtn addTarget:self action:@selector(openMessages:) forControlEvents:UIControlEventTouchUpInside];

// 4. Lock in the size with Auto Layout (prevents UIBarButtonItem from resizing it)
hasMessageBtn.translatesAutoresizingMaskIntoConstraints = NO;
[NSLayoutConstraint activateConstraints:@[
    [hasMessageBtn.widthAnchor constraintEqualToConstant:24],
    [hasMessageBtn.heightAnchor constraintEqualToConstant:24]
]];

// 5. Create the UIBarButtonItem with your custom button
UIBarButtonItem *messages = [[UIBarButtonItem alloc] initWithCustomView:hasMessageBtn];

Quick Tips to Remember #

• Always use a proper init method (like initWithFrame:) for UIButton to set its initial dimensions.
• Using bounds.size.width / 2 for corner radius means your button stays a perfect circle even if you adjust its size later, no hardcoding needed.
• Don’t forget masksToBounds = YES — without it, the button’s content will bleed outside the rounded corners, and you won’t see the circle effect.
• Adding explicit width/height constraints ensures UIBarButtonItem doesn’t override your desired size, which is a common gotcha with custom bar button items.

内容的提问来源于stack exchange，提问作者Austin Berenyi