UIButton contentVerticalAlignment不会使按钮图像居中

Question

我以编程方式创建了一个UIButton并设置了它的图像，但图像只是垂直居中，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）

为什么不起作用？

Answer 1

根据您发布的图片，看起来按钮本身被剪裁在底部，而不是图像没有垂直居中。

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，在您发布的图像中，蓝色矩形为120 x 88。

您的按钮底部未显示，因此看起来像，就像您的图片没有居中一样。

顺便说一下，您不需要使用太多代码：

    // 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＆amp; contentHorizontalAlignment用于文本对齐，而不用于图像....

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＆lt; iOS 6）。下面是编程按钮的方法。

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;

你完成了......

最后

您的代码无效，因为您的UIButton不是自定义按钮。