Javascript Angularjs和google图表api:未定义图表类型

我正在开发一个web应用程序（Angularjs-J2EE）。在主页上，我展示了一个图表。 当我在启动服务器（Tomcat）后第一次访问此主页时，我遇到以下错误：

由于错误，图表未显示：未定义图表类型。。满满的 错误对象如下。ng google chart.js:197对象{id: “google-visualization-errors-0”，消息：“图表类型不是 已定义。“}

如果我刷新主页，我就不会再有这个错误了。图表显示良好。
如果有人知道为什么

谢谢

控制器：

$scope.chartObject = {type:"PieChart"};
var datas = CaNetPieChart.query(function(){
  $scope.chartObject.data = {"cols": [
          {id: "t", label: "Article", type: "string"},
          {id: "s", label: "Colis", type: "number"}
      ], "rows": [
          {c: [
              {v: "CA Net"},
              {v: datas[0].valeur},
          ]},
          {c: [
              {v: "CA Net N-1"},
              {v: datas[1].valeur}
          ]}
      ]};
      $scope.chartObject.type = "PieChart";
      $scope.chartObject.options = {
          'backgroundColor': '#f5f5f5',
          'title': "Comparaison CA et CA N-1" ,'height':"200"  
      }
});

和HTML：

<div class="col-md-6" >
    <div google-chart chart="chartObject" style="{{chart.cssStyle}}"/>
</div>

---

让我们试试这段代码

$scope.loanchart = function(){
    $scope.chartObject = {};

    $scope.chartObject.data = {"cols": [
        {id: "t", label: "Topping", type: "string"},
        {id: "s", label: "Slices", type: "number"}
    ], "rows": [
        {c: [
            {v: "Mushrooms"},
            {v: 3},
        ]},
        {c: [
            {v: "Olives"},
            {v: 31}
        ]},
        {c: [
            {v: "Zucchini"},
            {v: 5},
        ]}
    ]};
    $scope.chartObject.type = "PieChart";
    $scope.chartObject.options = {
        'title': 'How Much Pizza I Ate Last Night'
    };
  };

---

让我们试试这段代码

$scope.loanchart = function(){
    $scope.chartObject = {};

    $scope.chartObject.data = {"cols": [
        {id: "t", label: "Topping", type: "string"},
        {id: "s", label: "Slices", type: "number"}
    ], "rows": [
        {c: [
            {v: "Mushrooms"},
            {v: 3},
        ]},
        {c: [
            {v: "Olives"},
            {v: 31}
        ]},
        {c: [
            {v: "Zucchini"},
            {v: 5},
        ]}
    ]};
    $scope.chartObject.type = "PieChart";
    $scope.chartObject.options = {
        'title': 'How Much Pizza I Ate Last Night'
    };
  };