iOS UITextView 首行缩进 撤销输入 反撤销输入的实现代码

 最近公司涉及到作家助手的功能,能撤销输入的文字,并能反撤销被撤销掉的文字。

该功能类似ios系统的摇一摇撤销输入。

当时也特迷茫，不知道从何下手，后来搜索了大量的资料，终于完成了这个功能，现在就将该功能的实现写出来，共勉。

这个功能涉及到ios原生类：nsundomanager。这个类挺强大。废话不多说,直接上代码。

#import "viewcontroller.h"
@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)];
  self.navigationitem.leftbarbuttonitem = undoitem;
  self.navigationitem.rightbarbuttonitem = 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;
//初始化nsundomanager
  _undomanager = [[nsundomanager alloc] init];
  _textview = [[uitextview alloc]initwithframe:cgrectmake(0, 200, self.view.frame.size.width, 400)];
  _textview.backgroundcolor = [uicolor yellowcolor];
  _textview.delegate = self;
  _textview.font = [uifont systemfontofsize:15];
  _textview.layer.cornerradius = 5;
  _textview.layer.maskstobounds = yes;
  _textview.textcolor = [uicolor blackcolor];
  _textview.text = @" ";//要设置初始文本,不然段落体现不出来。
  nsmutableparagraphstyle *paragraphstyle = [[nsmutableparagraphstyle alloc] init];
  paragraphstyle.linespacing = 5;  //行间距
  paragraphstyle.firstlineheadindent = 30;  /**首行缩进宽度*/
  paragraphstyle.alignment = nstextalignmentleft;
  nsdictionary *attributes = @{
                 nsfontattributename:[uifont systemfontofsize:13],
                 nsparagraphstyleattributename:paragraphstyle
                 };
  _textview.attributedtext = [[nsattributedstring alloc] initwithstring:_textview.text attributes:attributes];
//监听textview文本改动的通知
 [[nsnotificationcenter defaultcenter]addobserver:self selector:@selector(changetextviewtext) name:uitextviewtextdidchangenotification object:nil];
  [self.view addsubview:_textview];
}
-(void)redoitem{
  //反撤销
  [_undomanager redo];
}
-(void)undoitem{
  //撤销
  [_undomanager undo];
}
-(void)keyboardshow:(nsnotification *)noti{
  nsdictionary *dic = noti.userinfo;
  nsvalue *avalue = [dic objectforkey:uikeyboardframeenduserinfokey];
  cgrect keyboardrect = [avalue cgrectvalue];
  int height = keyboardrect.size.height;
  [_textview setcontentinset:uiedgeinsetsmake(0, 0, height, 0)];
}
-(void)keyboardhidden:(nsnotification *)noti{
  [_textview setcontentinset:uiedgeinsetsmake(0, 0, 0, 0)];
}
- (void)setmyobjecttitle:(nsstring *)newtitle{
  //判断当前nsundomanager的状态，是处于撤销或者反撤销的状态
-(void)textviewdidchange:(uitextview *)textview
  if (_undomanager.isundoing) {
    nsinteger length = newtitle.length;
    if (_textview.text.length>0) {
      //获取 
      _textview.text = [_textview.text substringwithrange:nsmakerange(0, _textview.text.length - 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.text.length>0) {
    undobutton.enabled = yes;
  }else{
    undobutton.enabled = no;
    redobutton.enabled = no;
  }
  nsstring *text ;
  if (_length != 0) {
    nsinteger textlength = _textview.text.length;
    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.text.length;
  [self setmyobjecttitle:text];
}

总结

以上所述是小编给大家介绍的ios uitextview 首行缩进 撤销输入 反撤销输入的实现代码，希望对大家有所帮助