SAP UI5: Fill XML-Dropdown dynamically using Lifecycle Hook Function

I've done the Tutorial for building Fiori-like UIs with SAPUI5 and tried adding a sort-function.

The Dropdown-Box is filled with the Names of the JSON-Model-Data:

{
"SalesOrderCollection": [
    {
        "SoId": "300000097",
        "ApprovalStatus": "",
        "Status": "Initial",
        "ConfirmationStatus": "",
        "BillingStatus": "Initial",
        ...
        } ...

I implemented this function in my View Controller to fill the dropdown:

    fillDropdown : function(evt) {

    // Get current view and dropdownbox
    var oView = this.getView();
    var oDropdown = oView.byId("ddbox");

    // Get names of nodes in model
    var metaArray = Object.getOwnPropertyNames(oView.getModel()
            .getProperty("/SalesOrderCollection/0"));

    // Add every name to dropdownbox
    var arrayLength = metaArray.length;
    for ( var i = 0; i < arrayLength; i++) {
        oDropdown.addItem(new sap.ui.core.ListItem("item" + i)
                .setText(metaArray[i]));
    }
}

Finally, here comes my problem:

How can I run this function automatically when the View gets rendered? I know the lifecycle hook functions onInit & onBeforeRendering but I can't use them in my XML-View:

I can register the eventhandler for UI-Elements like here:

<uicom:DropdownBox id="ddbox" editable="true" change="handleListSort">

But not for the View or the Page like I tried here:

<Page title="myPage" onBeforeRendering="fillDropdown">

<core:View controllerName="sap.ui.demo.myFiori.view.Master" (...) onBeforeRendering="fillDropdown">

Possible dirty workaround: Call the function when clicking on the Sort-Button in the IconTabBar

<IconTabBar select="fillDropdown">

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Thanks for your help!