iOS UITextView First line indentation Undo input Implementation code for reverse undo input

#import ""
@interface ViewController ()<UITextViewDelegate>{
  UITextView *_textView;
  NSUndoManager *_undomanager;
  NSInteger _length;
  UIButton *undobutton;
  UIButton *redobutton;
}
@end
@implementation ViewController
- (void)viewDidLoad {
  [super viewDidLoad];
  UIBarButtonItem *undoItem = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemUndo target:self action:@selector(undoitem)];
  UIBarButtonItem *redoItem = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemRedo target:self action:@selector(redoitem)];
   = undoItem;
   = redoItem;
  [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyBoardShow:) name:UIKeyboardWillShowNotification object:nil];
  [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyBoardHidden:) name:UIKeyboardWillHideNotification object:nil];
  _length = 0;
//Initialize NSUndoManager  _undomanager = [[NSUndoManager alloc] init];
  _textView = [[UITextView alloc]initWithFrame:CGRectMake(0, 200, , 400)];
  _textView.backgroundColor = [UIColor yellowColor];
  _textView.delegate = self;
  _textView.font = [UIFont systemFontOfSize:15];
  _textView. = 5;
  _textView. = YES;
  _textView.textColor = [UIColor blackColor];
  _textView.text = @" ";//Set the initial text, otherwise the paragraph will not be reflected.  NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
   = 5;  //Line spacing   = 30;  /**First row indent width*/
   = NSTextAlignmentLeft;
  NSDictionary *attributes = @{
                 NSFontAttributeName:[UIFont systemFontOfSize:13],
                 NSParagraphStyleAttributeName:paragraphStyle
                 };
  _textView.attributedText = [[NSAttributedString alloc] initWithString:_textView.text attributes:attributes];
//Notification of listening to textview text changes [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(changeTextViewText) name:UITextViewTextDidChangeNotification object:nil];
  [ addSubview:_textView];
}
-(void)redoitem{
  //Anti-revocation  [_undomanager redo];
}
-(void)undoitem{
  //Revoke  [_undomanager undo];
}
-(void)keyBoardShow:(NSNotification *)noti{
  NSDictionary *dic = ;
  NSValue *aValue = [dic objectForKey:UIKeyboardFrameEndUserInfoKey];
  CGRect keyboardRect = [aValue CGRectValue];
  int height = ;
  [_textView setContentInset:UIEdgeInsetsMake(0, 0, height, 0)];
}
-(void)keyBoardHidden:(NSNotification *)noti{
  [_textView setContentInset:UIEdgeInsetsMake(0, 0, 0, 0)];
}
- (void)setMyObjectTitle:(NSString *)newTitle{
  //Judge the current state of NSUndoManager, which is in a state of revocation or counter-revocation-(void)textViewDidChange:(UITextView *)textView
  if (_undomanager.isUndoing) {
    NSInteger length = ;
    if (_textView.>0) {
      //Get      _textView.text = [_textView.text substringWithRange:NSMakeRange(0, _textView. - length)];
      [_undomanager registerUndoWithTarget:self
                    selector:@selector(setMyObjectTitle:)
                     object:newTitle];
    }
  }else if (_undomanager.isRedoing){
    _textView.text = [_textView.text stringByAppendingString:newTitle];
    [_undomanager registerUndoWithTarget:self
                  selector:@selector(setMyObjectTitle:)
                   object:newTitle];
  }else{
    NSString *currentText = _textView.text;
    if (newTitle != currentText) {
      _textView.text = currentText;
      [_undomanager registerUndoWithTarget:self
                    selector:@selector(setMyObjectTitle:)
                     object:newTitle];
    }else{
      _textView.text = newTitle;
    }
  }
}
-(void)changeTextViewText{
  if (_textView.>0) {
     = YES;
  }else{
     = NO;
     = NO;
  }
  NSString *text ;
  if (_length != 0) {
    NSInteger textLength = _textView.;
    if (textLength > _length) {
      NSInteger newLength = textLength - _length;
      text = [NSString stringWithFormat:@"%@",[_textView.text substringWithRange:NSMakeRange(_length, newLength)]];
    }else{
      text = _textView.text;
    }
  }else{
    text = _textView.text;
  }
  _length = _textView.;
  [self setMyObjectTitle:text];
}