angularjs不会触发验证

Question

我在验证时遇到问题，提交时不会触发验证消息。

html看起来像：

<div class="inputContainer" ng-class="{'error' : thisForm.keywords.$invalid && !thisForm.keywords.$pristine}">
    <div class="infoLabel">Keywords:</div>
    <input type="text" ui-select2="keywordsSelect2Options" ng-model="thesis.keywords" name="tags" required data-placeholder="Enter keywords">

    <div class="editIcon"><i class="icon glyphicon glyphicon-pencil"></i></div>
    <div class="errorIcon">
        <div class="icon"> <span>!</span> </div>
    </div>
    <div class="validationMessage"><span animated-show="thisForm.keywords.$invalid && !thisForm.keywords.$pristine">You need to enter a keyword</span></div>
</div>

javascript文件：

$scope.thesis = {
    keywords: [],
};

我错过了什么，找不到错误？