Set Caret position in Input with AngularJS

问题:

I need to change the caret position of an input, where a given number of digits is added (Example).

app.controller('MainCtrl', function($scope, $element, $timeout, $filter) {
  //$scope.val = '12';
  $scope.$watch('val', function(newValue, oldValue) {
    if (!isNaN(newValue)) {
      if (newValue.length > 3) {
        //Set Caret Position  
      }
    }
  });
});

Is it possible to do something like this example?

I need for example :

Input: 1234.

so the caret position will be 2.

New digit: 9

final: 12934

Thanks in advance.

回答1:

I think that such kind of things look better in directives. For example:

app.directive('caret', function() {

    function setCaretPosition(elem, caretPos) {
        if (elem !== null) {
            if (elem.createTextRange) {
                var range = elem.createTextRange();
                range.move('character', caretPos);
                range.select();
            } else {
                if (elem.setSelectionRange) {
                    elem.focus();
                    elem.setSelectionRange(caretPos, caretPos);
                } else
                    elem.focus();
            }
        }
    }

    return {
        scope: {value: '=ngModel'},
        link: function(scope, element, attrs) {
            var caret = Number(attrs.caret);
            scope.$watch('value', function(newValue, oldValue) {
                if (newValue && newValue != oldValue && !isNaN(newValue) && newValue.length > (caret + 1)) {
                    setCaretPosition(element[0], caret);
                }
            });
        }
    };
});

Usage:

<input ng-model='val' caret="2" />

I used setCaretPosition function for cross browser cursor positioning from this answer.

Demo: http://plnkr.co/edit/5RSgzvyd8YOTaXPsYr8A?p=preview

回答2:

I think that the best approach for this is to make a reusable directive as we are dealing with DOM manipulation.

Link to the demo: http://plnkr.co/edit/qlGi64VO1AOrNpxoKA68?p=preview

var app = angular.module('angularjs-starter', []);

app.controller('MainCtrl', function($scope, $element, $timeout, $filter) {
  $scope.$watch('val', function(newValue, oldValue) {
    if (!isNaN(newValue)) {
      if (newValue.length > 3) {
      // $element.find('input')[0].selectionEnd  = 2;
      }
    }
  });
});

app.directive('setCaret', function() {

  return {
    restrict: 'A',
    link: function(scope,element,attrs) {
      var changed = false;
      element.bind('keypress', function() {
        if(element[0].selectionStart > 3 && !changed) {
          changed = true;
          element[0].selectionEnd = parseInt(attrs.position, 10);
        }
      })

    },
  }

})

You can see in the commented out part in the controller we can have access to this by using $element, but as this is DOM and controllers are not for DOM manipulation we need to make this into a directive.

回答3:

I also had the same problem.

I thought to solve it creating an appropriate directive. You can find it here. Enjoy it!

Usage

Include directive, declare it by caret-aware attribute

<script src="https://cdn.rawgit.com/leodido/ng-caret-aware/master/caretaware.min.js"></script>
<script type="text/javascript">
  var app = angular.module('myModule', ['leodido.caretAware']);
</script>
...
<div data-ng-app="app">
    <input type="text" name="myname" caret-aware="cursor"/>
</div>

Then on the scope you'll have a variable cursor containing the position of the caret in the input named myname.

Nevertheless, this directive's controller exposes an API

• getPosition
• setPosition

For other usage examples see example directory of the above linked github repository.

回答4:

I believe you could do it by using .setSelectionRange() on your input. I updated your example - see if this is what you wanted: http://plnkr.co/edit/bIJAPPAzkzqLIDUxVlIy?p=preview

Note: setSelectionRange is not supported by IE8 (see https://developer.mozilla.org/en-US/docs/Web/API/HTMLInputElement.setSelectionRange), so if you need to support IE < 9, you'll need to look for shims.

回答5:

I jsfiddled a working solution. So basically, you have to create a directive :

app.directive('keypressdetector', function($compile){
    return {
    restrict:'AEC',
    link: function(scope, element, attrs){
        element.bind("keypress", function (event) {
            if(event.which === 13) {
                            var selectionStart = element[0].selectionStart;
              var value = element.val();
              var valueLength = value.length;
              var newValue= '';
              if (selectionStart == valueLength){
                newValue = value;
              } else {
                newValue = value.substring(selectionStart, valueLength);
              }
              var newElement = angular.element('<input type="text" value="' + newValue +'"/>')
              angular.element(document.body).append(newElement);
            }
        });
    }
  };
});

Your controller would be useless in that situation. You can invoke the directive like this (see : keypressdetector) :

<div ng-app="myapp">
<div ng-controller="LoginController">
    <div>Hello {{ user.firstName }}</div>
    <input ng-model="user.firstName" keypressdetector />
    <input type="submit" ng-click="login()" value="Login"/>
    <div ng-repeat="login in logins">{{ login }}</div>
</div>
</div>

See demo : https://jsfiddle.net/Lt7aP/3468/