1.只有这2种数字键盘才有效果。UIKeyboardTypeNumberPad，UIKeyboardTypePhonePad
2.keyboardAppearance ＝ UIKeyboardAppearanceAlert

- (void)textViewDidBeginEditing:(UITextView *)textView{
     NSArray *ws = [[UIApplication sharedApplication] windows];
     for(UIView *w in ws){
         NSArray *vs = [w subviews];
         for(UIView *v in vs){
             if([[NSString stringWithUTF8String:object_getClassName(v)]
isEqualToString:@"UIKeyboard"]){
                 v.backgroundColor = [UIColor redColor];
             }
         }
     }
 }