UIView 底部边框? [英] UIView bottom border?

问题描述

对于 UIScrollView *toScrollView(即屏幕的宽度)，我想添加一个灰色的底部边框(与 iPhone 原生的撰写视图的 to-field 边框完全一样)消息应用).

To a UIScrollView *toScrollView (which is the width of the screen), I want to add a gray bottom border (exactly like that of the to-field of the compose view of the iPhone's native Messages app).

为了实现这一点，我遵循了Cocoa Touch:如何更改 UIView 的边框颜色和厚度? 并使用自定义 UINavigationBar 覆盖顶部边框并制作 toScrollView 的 x 坐标-1 &宽度 322 使左 &右边框刚好在屏幕外.

To achieve this, I followed Cocoa Touch: How To Change UIView's Border Color And Thickness? and just covered the top border with the custom UINavigationBar and made the toScrollView's x-coordinate -1 & width 322 so that the left & right borders are just off screen.

这看起来不错，但这有点像黑客，我想知道是否有更好的方法来做到这一点.

This looks fine, but it's sort of a hack, and I was wondering if there's a better way to do this.

- (void)viewDidLoad {
    [super viewDidLoad];

    // Add UINavigationBar *navigationBar at top.
    self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]
                                             initWithBarButtonSystemItem:UIBarButtonSystemItemCancel
                                             target:self action:@selector(cancelAction)];
    UINavigationBar *navigationBar = [[UINavigationBar alloc]
                                      initWithFrame:CGRectMake(0.0f, 0.0f, 320.0f, 44.0f)];
    navigationBar.items = [NSArray arrayWithObject:self.navigationItem];

    // Add UIScrollView *toScrollView below navigationBar.
    UIScrollView *toScrollView = [[UIScrollView alloc]
                                  initWithFrame:CGRectMake(-1.0f, 43.0f, 322.0f, 45.0f)];
    toScrollView.backgroundColor = [UIColor whiteColor];
    toScrollView.layer.borderColor = [UIColor colorWithWhite:0.8f alpha:1.0f].CGColor;
    toScrollView.layer.borderWidth = 1.0f;
    [self.view addSubview:toScrollView];
    [self.view addSubview:navigationBar]; // covers top of toScrollView
}

推荐答案

正如@ImreKelényi 建议的那样，您可以使用 CALayer 而不是使用 UIView:>

Instead of using a UIView, as @ImreKelényi suggests, you can use a CALayer:

// Add a bottomBorder.
CALayer *bottomBorder = [CALayer layer];

bottomBorder.frame = CGRectMake(0.0f, 43.0f, toScrollView.frame.size.width, 1.0f);

bottomBorder.backgroundColor = [UIColor colorWithWhite:0.8f 
                                                 alpha:1.0f].CGColor;

[toScrollView.layer addSublayer:bottomBorder];

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