Put document contents in a textBox - google-apps-script

Question

I'm looking to get the contents of a Google word document and put it in a textBox. The following code is spitting out an error:
function listBoxClick(e) {
var tapp = UiApp.getActiveApplication();
var docName = DocsList.find(e.parameter.doclist); //find the document with the same name as what the user clicked on
var docContents = docName[0].getContentAsString(); //get contents of document
tapp.getElementById("songboxID").setValue(songfile2); //set the value of the textBox to the contents of the document
return tapp;
}
This returns the following error:
Unsupported conversion requested.
I read somewhere that we can't do this for Google Documents but we can for other non-google documents that we upload. Is that right?
Here's the answer that I can't post for 5 more hours since I'm new and have no reputation:
With Serge's assistance, here's what worked for me:
function listBoxClick(e) {
var tapp = UiApp.getActiveApplication();
var docName = DocsList.find(e.parameter.doclist); //get document name based on what user clicked on in listBox
var docId = docName[0].getId(); //get document ID
var content = DocumentApp.openById(docId).getText(); //get contents of document
tapp.getElementById("songboxID").setValue(content); //set web app's textBox (called songboxID) to match the contents of the document the user clicked on
return tapp;
}

Answer 1

You have to use DocumentApp.getText(); to get the text content of your document.
in you code it would become :
function listBoxClick(e) {
var tapp = UiApp.getActiveApplication();
Logger.log(e.parameter.doclist)
var docName = DocsList.find(e.parameter.doclist); //find the document with the same name as what the user clicked on
var docId = docName[0].getId();
Logger.log(docName[0].getName()+' = '+docId)
var textContent = DocumentApp.openById(docId).getText();
Logger.log(textContent)
tapp.getElementById("songboxID").setValue(textContent); //set the value of the textBox to the contents of the document
return tapp;
}
EDIT : as you noticed with your experiments DocsList.find(e.parameter.doclist) returns results that you didn't expect... that's simply because the find operator searches not only on doc's names but also on docs content.
To solve that , you should add a smal routine that checks the results of the find query against the documents name, something like this :
var docName = DocsList.find(e.parameter.doclist); //find the document with the same name as what the user clicked on
for(var d in docName){{
if(docName[d].getName()==e.parameter.doclist){
var docId = docName[d].getId();
}
}
This will ensure that the document you are looking for is actually the right one.
PS: sorry for not having mentioned that immediately... it just slipped out of my mind ;-)