ios - 在 SELECTED 分段控件的底部添加边框

Question

我正在尝试为选定的分段控件添加边框。目前，我有代码将 3px 的边框设置到整个分段控件的底部:

CALayer *bottomBorder = [CALayer layer];
bottomBorder.borderColor = [UIColor redColor].CGColor;
bottomBorder.borderWidth = 3;
bottomBorder.frame = CGRectMake(0, self.segmentedControl.frame.size.height - bottomBorder.borderWidth, self.segmentedControl.frame.size.width, bottomBorder.borderWidth);
[self.segmentedControl.layer addSublayer:bottomBorder];

但是，我只想将此边框添加到选定的分段控件。我该怎么做？

Answer 1

您可以使用以下代码动态添加选择:

// Removing previous selection
[bottomBorder removeFromSuperlayer];

// Creating new layer for selection
bottomBorder             = [CALayer layer];
bottomBorder.borderColor = [UIColor redColor].CGColor;
bottomBorder.borderWidth = 3;

// Calculating frame
CGFloat width            = self.segmentedControl.frame.size.width/3;
CGFloat x                = self.segmentedControl.selectedSegmentIndex * width;
CGFloat y                = self.segmentedControl.frame.size.height - bottomBorder.borderWidth;
bottomBorder.frame       = CGRectMake(x, y,width, bottomBorder.borderWidth);

// Adding selection to segment
[self.segmentedControl.layer addSublayer:bottomBorder];

选择新选择时，您需要删除先前的选择，为此，将 bottomborder 层作为成员变量。