UIButton contentVerticalAlignment不會使按鈕圖像居中

Question

我以編程方式創建了一個UIButton並設置了它的圖像，但是該圖像不會垂直居中，而是始終在按鈕的底部進行渲染。

這是我的代碼：

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;

在為按鈕的imageView設置了鮮明的背景色之后，我可以看到它仍然與底部對齊：

（藍色=按鈕，紅色=圖片視圖）

為什么不起作用？

Answer 1

根據您發布的圖像，看起來按鈕本身在底部被裁剪，而不是圖像未垂直居中。

您的代碼：

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

表示按鈕（藍色矩形）應為正方形。 但是，在您發布的圖像中，藍色矩形是120 x 88 。

您的按鈕的底部未顯示，因此看起來圖像未居中。

順便說一句，您不需要太多正在使用的代碼：

    // 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

點1

AFAIK， UIControlContentVerticalAlignmentCenter和contentHorizontalAlignment用於文本對齊而不用於圖像...。

點2

UIButton *logoutButton = [[UIButton alloc] initWithFrame:logoutButtonFrame]; 將創建與“自定義”按鈕相對的基本按鈕（例如<iOS 6）。 以下是您應如何以編程方式設置按鈕的方式。

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];

現在要調整圖像

continueButton.imageView.contentMode = UIViewContentModeScaleAspectFit;

大功告成...

最后

您的代碼無法正常工作，因為您的UIButton不是“自定義”按鈕。