Fallback (default) image using Angular JS ng-src

问题

I'm trying to set an image source using data returned from a modal. This is inside an ng-repeat loop:

<div id="divNetworkGrid">
    <div id="{{network.id}}" ng-repeat="network in networks">
        <span>
            <table>
                <tr>
                    <td class="imgContainer">
                        <img ng-src="{{ ('assets/img/networkicons/'+ network.actual + '.png') || 
                                         'assets/img/networkicons/default.png' }}"/>
                    </td>
                </tr>
            </table>
        </span>
    </div>
</div>

As is apparent, I want to populate default.png when the network.actual model property is returned as null. But my code is not picking up the default image, though the first image is coming up fine when available.

I'm sure this is some syntax issue, but cant figure out what's wrong.

回答1:

Interesting way to use ng-src. I haven't tested how that expression would be handled but I would suggest doing it a more stable way:

<img ng-src="{{ networkIcon }}" />

And in your controller:

$scope.networkIcon = network.actual ? 'assets/img/networkicons/' + network.actual + '.png' : 'assets/img/networkicons/default.png';

Edit: Just to clarify, I'm not suggesting the best way to do this is to bind the image source directly to the scope but rather to move the image fallback logic outside of the view. In my applications I often do it in the services that retrieve the data or on the server itself and send an image URL so the client only has to worry about a single property.

Edit to address repeater:

angular.forEach($scope.networks, function(network) {
  network.icon = network.actual ? 'assets/img/networkicons/' + network.actual + '.png' : 'assets/img/networkicons/default.png';
});

<tr ng-repeat="network in networks">
  <td><img ng-src="{{ network.icon }}" /></td>
</tr>

回答2:

I have just found out, that you can use both ng-src and src on an img tag and if ng-src fails (variable used does not exists etc.), it will automatically fallback to src attribute.

回答3:

What I imagine is happening is the src is returning a 404 even if network.actual is null. For example, first value:

('assets/img/networkicons/'+network.actual+'.png')

is evaluating to a 404 src URL, something like ('assets/img/networkicons/null.png'). So in the OR selection, it's truth-y, but the resource is 404. In that case, you can set the fallback via onError with something like:

<img ng-src="{{('assets/img/networkicons/'+network.actual+'.png')}}" onerror="this.src='assets/img/networkicons/default.png'" />

CodePen to demo use cases - http://codepen.io/jpost-vlocity/pen/zqqerL

回答4:

angular.module('fallback',[]).directive('fallbackSrc', function () {
    return{
        link: function postLink(scope, element, attrs) {
            element.bind('error', function () {
                angular.element(this).attr("src", attrs.fallbackSrc);
            });
        }
    }
});

<img ng-src="{{url}}" fallback-src="default-image.jpg"/>

angular.module('fallback', []).directive('actualSrc', function () {
    return{
        link: function postLink(scope, element, attrs) {
            attrs.$observe('actualSrc', function(newVal, oldVal){
                 if(newVal != undefined){
                     var img = new Image();
                     img.src = attrs.actualSrc;
                     angular.element(img).bind('load', function () {
                         element.attr("src", attrs.actualSrc);
                     });
                 }
            });

        }
    }
});

<img actual-src="{{url}}" ng-src="default.jpg"/>

link

回答5:

<div id="divNetworkGrid">
                <div id="{{network.id}}" ng-repeat="network in networks">
                    <span>
                        <table>
                            <tr>
                                <td class="imgContainer">
                                    <img ng-src="{{'assets/img/networkicons/'+(network.actual || 'default' )+'.png'}}"/>
                                </td>
                            </tr>
                        </table>
                    </span>
                </div>
            </div>

The inline or will work if the the queried variable is undefined. The above will fix your issue

回答6:

You can supply the alternative image after OR operator like this:

{{ book.images.url || 'Images/default.gif' }}

来源：https://stackoverflow.com/questions/24614570/fallback-default-image-using-angular-js-ng-src