UIButton contentVerticalAlignment 不居中按钮图像

Question

我以编程方式创建了一个 UIButton 并设置了它的图像，但图像不会垂直居中，它总是呈现在按钮的底部。

这是我的代码：

CGFloat logoutButtonSize = self.profileItem.detailView.frame.size.height;
CGFloat logoutButtonX = self.profileItem.detailView.frame.size.width - logoutButtonSize - 8;
CGRect logoutButtonFrame = CGRectMake(logoutButtonX, 0, logoutButtonSize, logoutButtonSize);
UIButton *logoutButton = [[UIButton alloc] initWithFrame:logoutButtonFrame];
[logoutButton setImage:[UIImage imageNamed:@"logout.png"] forState:UIControlStateNormal];
logoutButton.imageView.contentMode = UIViewContentModeCenter;
logoutButton.contentMode = UIViewContentModeCenter;
[logoutButton addTarget:self
                 action:@selector(confirmLogout)
       forControlEvents:UIControlEventTouchUpInside];
logoutButton.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleHeight;
logoutButton.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
logoutButton.contentHorizontalAlignment = UIControlContentHorizontalAlignmentCenter;

为按钮的 imageView 设置不同的背景颜色后，我可以看到它仍然与底部对齐：

（蓝色 = 按钮，红色 = 图像视图）

为什么它不起作用？

Answer 1

根据您发布的图片，看起来按钮本身在底部被剪裁，而不是图片没有垂直居中。

您的代码：

CGRect logoutButtonFrame = CGRectMake(logoutButtonX, 0, logoutButtonSize, logoutButtonSize);

说按钮（蓝色矩形）应该是方形的。然而在您发布的图片中，蓝色矩形是120 x 88。

按钮的底部未显示，因此看起来您的图像未居中。

顺便说一句，您应该不需要太多正在使用的代码：

    // define the frame size
    CGFloat logoutButtonSize = self.profileItem.detailView.frame.size.height;
    CGFloat logoutButtonX = self.profileItem.detailView.frame.size.width - logoutButtonSize - 8;
    CGRect logoutButtonFrame = CGRectMake(logoutButtonX, 0, logoutButtonSize, logoutButtonSize);

    // instantiate the UIButton
    UIButton *logoutButton = [[UIButton alloc] initWithFrame:logoutButtonFrame];

    // set the image
    [logoutButton setImage:[UIImage imageNamed:@"logout.png"] forState:UIControlStateNormal];

    // add the button action target
    [logoutButton addTarget:self
                     action:@selector(confirmLogout)
           forControlEvents:UIControlEventTouchUpInside];

    // set the resizing mask properties
    logoutButton.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleHeight;

    // shouldn't need any of the following
    //logoutButton.imageView.contentMode = UIViewContentModeCenter;
    //logoutButton.contentMode = UIViewContentModeCenter;
    //logoutButton.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
    //logoutButton.contentHorizontalAlignment = UIControlContentHorizontalAlignmentCenter;

Answer 2

第 1 点

AFAIK, UIControlContentVerticalAlignmentCenter & contentHorizontalAlignment 用于文本对齐而不是图像....

第 2 点

UIButton *logoutButton = [[UIButton alloc] initWithFrame:logoutButtonFrame]; 将创建与自定义按钮相对的基本按钮（如

UIButton * logoutButton = [UIButton buttonWithType:UIButtonTypeCustom];
[logoutButton setBackgroundImage:[UIImage imageNamed:@"logout.png"] forControlEvents:UIControlEventTouchUpInside];
[logoutButton addTarget:self action:@selector(confirmLogout) forControlEvents:UIControlEventTouchUpInside];
[logoutButton setTitle:@"" forState:UIControlStateNormal];
logoutButton.frame = CGRectMake(logoutButtonX, 0, logoutButtonSize, logoutButtonSize);
[self.view addSubview: logoutButton];

现在要调整图像，

continueButton.imageView.contentMode = UIViewContentModeScaleAspectFit;

你已经完成了......

最后

您的代码不起作用，因为您的 UIButton 不是自定义按钮。