Question

我希望在ng-mousedown上开始并以mouseup结束。如果鼠标离开元素，我还希望鼠标按钮保持按下状态继续发生。在vanilla javascript中实现此功能的一种非常常见的方法是在元素mousedown事件like so中绑定文档mouseup事件：

HTML：

<button onMouseDown='onMouseDown()'>Click Me</button>
<div id="val"></div>

JS：

function onMouseDown() {
  var el = document.querySelector('#val'),
      changeValue = function() {
        el.innerHTML = 'done!';
        document.removeEventListener('mouseup', changeValue);
      };

  el.innerHTML = 'waiting for mouseup...';

  document.addEventListener('mouseup', changeValue);
}

我在使用jQuery's one()，angular.element.one和addEventListener / removeEventListener的Angular中实现此行为时遇到了问题：

HTML：

<div ng-app="MyApp" ng-controller="AppCtrl">
  <div>Note that 'done!' is not rendered, despite 'mouseup' being logged to the console</div>
  <button ng-mousedown='changeValue()'>Click Me</button>
  <div>{{value}}</div>   
</div>

JS（jQuery＆＃39; s one()）：

angular
  .module('MyApp', [])
  .controller('AppCtrl', function($scope) {
    $scope.changeValue = function() {
      console.log('mousedown');
      $scope.value = 'waiting for mouseup...';  

      $(document).one('mouseup', function() {
        console.log('mouseup');
        $scope.value = 'done!';
      });
    }
  });

JS（angular.element.one）：

angular
  .module('MyApp', [])
  .controller('AppCtrl', function($scope) {
    $scope.changeValue = function() {
      console.log('mousedown');
      $scope.value = 'waiting for mouseup...';  

      angular.element(document).one('mouseup', function() {
        console.log('mouseup');
        $scope.value = 'done!';
      });
    }
  });

JS（addEventListener / removeEventListener）：

angular
  .module('MyApp', [])
  .controller('AppCtrl', function($scope) {
    $scope.changeValue = function() {
      var changeValue = function() {
        console.log('mouseup');
        $scope.value = 'done!';
        document.removeEventListener('mouseup', changeValue);
      };

      console.log('mousedown');
      $scope.value = 'waiting for mouseup...';  

      document.addEventListener('mouseup', changeValue);
    }
  });

我还尝试利用ng-mouseup和ng-mouseleave like this：

HTML：

<div ng-app="MyApp" ng-controller="AppCtrl">
  <div>While clicking the button, move the mouse off of the button and release the mouse button. Note that 'done!' is not rendered, despite 'mouseup' being logged to the console</div>
  <button ng-mousedown='mouseDown()' ng-mouseup="mouseUp()" ng-mouseleave="mouseLeave()">Click Me</button>
  <div>{{value}}</div>  
</div>

JS：

angular
  .module('MyApp', [])
  .controller('AppCtrl', function($scope) {
    $scope.mouseDown = function() {
      console.log('mousedown');
      $scope.value = 'waiting for mouseup...';  
    }
    $scope.mouseUp = function() {
      console.log('mouseup');
      $scope.value = 'done!';
    }
    $scope.mouseLeave = function() {
      if ($scope.value && $scope.value.indexOf('waiting') > -1) {
        console.log('mouseleave, binding mouseup'); 
        $(document).one('mouseup', function() {
           $scope.mouseUp();
        });
      }
    }
  });

结果是一样的。 $scope.mouseUp已执行，但永远不会呈现'done!'。 This creates additional problems with $scope.$watch：

HTML：

<div ng-app="MyApp" ng-controller="AppCtrl">
  <div>value never === 'done!' in $scope.$watch</div>
  <button ng-mousedown='changeValue()'>Click Me</button>
  <div>{{value}}</div>   
</div>

JS：

angular
  .module('MyApp', [])
  .controller('AppCtrl', function($scope) {
    $scope.changeValue = function() {
      console.log('mousedown');
      $scope.value = 'waiting for mouseup...';  

      $(document).one('mouseup', function() {
        console.log('mouseup');
        $scope.value = 'done!';
      });
    }
    $scope.$watch('value', function(value) {
      if (value === 'done!') {
        console.log('value set to "done!"'); 
      }
    });
  });

Answer 1

不知道为什么这个问题在一个多月没有答案的情况下就已经存在了。

这里的主要问题很简单 - 更新$scope.value的代码在AngularJS之外执行。为了使您的数据绑定工作，您应该使用$scope.$apply这样包装它：

$scope.$apply(function () {
  $scope.value = 'done!';                
});

请注意，ng-mouseup工作正常，您可以在按钮上方触发mouseup时看到它。但是，如果您将鼠标移到按钮$(document).one('mouseup'..)之外，则会发生事件。

请记住，如果需要，必须用$scope.$apply包装所有外部回调（JQuery HTTP回调，不与ng- *指令捆绑的DOM事件，setTimeout等）使用AngularJS绑定或观察者。但请三思而后行 - 在另一个$scope.$apply内调用$scope.$apply会导致错误。

您可以浏览documentation或阅读更多here。

在ng-mousedown中绑定文档mouseup

1 个答案: