how to bind asynchronous data to control in alloy

when i asynchronously get data and bind the data to control in alloy , the control can not display my data. below is my code:

view:

<Collection src="tasklog"/>
<ScrollView layout="vertical">
    <TableView backgroundColor="yellow" id="taskLogList" dataCollection="tasklog"       dataTransform="transformTaskLog">
        <TableViewRow title="{taskLogSummary}" ></TableViewRow>
    </TableView>
</ScrollView>

controller:

//this function will get data asynchronously
logs.getTaskLogs(taskId, function(success) {
    var arrLog = success.responseText['taskLogs'];
    for(var i = 0; i < arrLog.length; i++)
    {
        logs.add({
            tasklogId : arrLog[i].taskLogId,
            taskLogSummary : arrLog[i].taskLogSummary
        });
    }
 
}, function(failed) {
 
});
 
function transformTaskLog(model){
    var transform = model.toJSON();
    return transform;
}

when I modify controller code to below?synchronously? ,my control can display the data:

//get data synchronously
  logs.add({
            tasklogId : 111,
            taskLogSummary : "ddddddddddddd"
        });
         logs.add({
            tasklogId : 222,
            taskLogSummary : "fffffffffffffffffff"
        });
function transformTaskLog(model){
    var transform = model.toJSON();
    return transform;
}

but I must get data from web service ,the opration is asynchronous.How do I resolve the problem???can Titanium.Network.HTTPClient be used synchronously?