Protractor use sendKeys() to upload a file in a <div> - angularjs

Question

As you can see in the title, I am trying to upload a file using protractor.
In my project, I have a webpage where I can drag & drop a file, using resumable.js assigned to a div representing the drop area.
The fact is, when doing e2e testing, I obviously can't drag & drop a file, so I chose to upload it using sendKeys() with the absolute path of my file path.resolve('./tests', 'test.csv').
Until here, everything works (path is good and I can find my element with element(by.id(...)) but when I use sendKeys() it throws an error saying "unknown error: cannot focus element".
I tried to upload on an <input type="file"></input>, it works, but since it's on what I use I can't upload this on my original div.
I think I have to specify that this is a file, I saw the setFileDetector(detector) function but I am not sure this is the right way to proceed, and it doesn't seem to work with it anyway.
Here is the HTML drag & drop :
<p translate>Drag & Drop your file below</p>
<div class="drop" ng-class="dropClass" id="import-drop-area" data-ng-init="init()" translate> </div>
And here is the test that works on an but not on my div :
it('Should begin the import wizard by dropping a file', function(done) {
// Begin the wizard
var nextButton = element(by.id('next'));
nextButton.click();
// Upload a file
var uploadArea = element(by.id('import-drop-area'));
var file = path.resolve('./tests/import', 'test.csv');
uploadArea.sendKeys(file);
setTimeout(done, 1000);
});
I hope someone could help me, thank you by advance !
Best regards.