Detecting Google Drive changes - api

Question

I'm quite confused by how to operate the changes API.
At the moment, I'm just making get requests:
https://www.googleapis.com/drive/v3/changes?access_token=**my_token**&pageToken=68485 **Last few additions to the list
I get:
{
"kind": "drive#changeList",
"newStartPageToken": "68489",
"changes": [
{
"kind": "drive#change",
"type": "file",
"time": "2017-04-08T00:40:36.141Z",
"removed": false,
"fileId": "***ID",
"file": {
"kind": "drive#file",
"id": "***ID",
"name": "***NAME",
"mimeType": "application/vnd.google-apps.folder"
}
},
{
"kind": "drive#change",
"type": "file",
"time": "2017-04-08T00:41:00.171Z",
"removed": false,
"fileId": "***ID2",
"file": {
"kind": "drive#file",
"id": "***ID2",
"name": "***NAME2",
"mimeType": "application/vnd.openxmlformats-officedocument.wordprocessingml.document"
}
}
]
I'm not aware of making changes to the first item in the changes array.
After playing around, I realised that every time a folder is opened it's added to the changes, why? Is it because the meta-data is being changes, i.e. last-accessed?
Does the same thing happen when files are previewed/opened/downloaded?
I trashed the second item in the array, yet it shows nothing about this.
How exactly am I to tell what is being changed. I'm trying to retrieve events such as file updates, creations, deletions etc.

Answer 1

The official properties that Changes uses which are found in the Changes resource representations:
{
"kind": "drive#change",
"type": string,
"time": datetime,
"removed": boolean,
"fileId": string,
"file": files Resource,
"teamDriveId": string,
"teamDrive": teamdrives Resource
}

Answer 2

Now this might not make a complete answer but I'd like to share some points.
Is it because the meta-data is being changes, i.e. last-accessed?
Yes, it is. It's a bit strange but yes, even previewing the file counts as a change. If you've closely watched the Drive's Android App, you can see that just viewing a photo will populate it under the "Recents" tab.
In API v2, there was even a files.touch() method, just for updating the last accessed time of a file!
How exactly am I to tell what is being changed?
There is a property named changes[] returned by changes.list() which is a list containing the changes. You could use this to determine if the change was relevant to you (like updation, creation, deletion) or ignore if it was just a preview.
To add to this, instead of continuously checking for changes, a more efficient way to detect changes is by using the changes.watch() method to subscribe for updates to the changes, which I hope you are already aware of.
And about trashing. Trashing doesn't really "change" a file in Drive. A trashed file is treated just like an ordinary file with the exception of having "Trashed" flag, which makes it directly invisible. Note that shared files are still accessible by collaborators, even if it's trashed. However, change should fire if the file is permanently deleted.