您不必选择隐式样式，它涉及使用QuartzCore框架编写一些代码：

//first, you
#import <QuartzCore/QuartzCore.h>

//.....

//Here I add a UITextView in code, it will work if it's added in IB too
UITextView *textView = [[UITextView alloc] initWithFrame:CGRectMake(50, 220, 200, 100)];

//To make the border look very close to a UITextField
[textView.layer setBorderColor:[[[UIColor grayColor] colorWithAlphaComponent:0.5] CGColor]];
[textView.layer setBorderWidth:2.0];

//The rounded corner part, where you specify your view's corner radius:
textView.layer.cornerRadius = 5;
textView.clipsToBounds = YES;

它仅适用于 OS 3.0 及更高版本，但我想现在它无论如何都是事实上的平台。