如果在 uitextview 中按下 Shift 键（修饰键），则检测/获取通知

I'm trying to figure out if there is any way in which we can detect if shift key is pressed or if any notification is sent when shift key is pressed in UIKeyboard

- (BOOL) textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)string

does not get called for shift key press since it is a modifier key.

不知道您是否需要结合其他文本来了解它，还是只检测单次Shift点击，但这是我检测前者的解决方案：

就我而言，这只是其中的一个字符：

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)inText

这会将大写文本转换为小写并设置 shiftPressed 值（如果文本是非字母文本则忽略）

//Shift Detection
BOOL shiftPressed = NO;

//Detect non letter characters
NSCharacterSet *letterCharacterSet = [NSCharacterSet letterCharacterSet];
NSString *trimmedText = [text stringByTrimmingCharactersInSet:letterCharacterSet];

if ([text length] == 1) {  
    if (![trimmedText length]) 
    {            
        NSString *upperCaseString = [text uppercaseString];
        if ([upperCaseString isEqualToString:text]) {
            NSString *lowerCaseString = [text lowercaseString];
            text = lowerCaseString;
            shiftPressed = YES;
        }
    }
}