Check if the folder and all data already exist

My Android application downloads data only the first lunch. the data is ~50 mb with ~2500 files.

开发者_如何学编程 1. Is it a good idea to store if the files got downloaded in SharedSettings? The problem is that if a user clears the data application (maybe by mistake), he has to redownload everything. I manually copy a prepacked database to /data/data/../databases/, is it a good idea to check if the db exists, and if no then download everything?:

if(new File(/data/data/../databases/myDB.db).exists){//dont download}

2.Is getting the folder size and checking if its the same a good way to see if the folder+data are good? or is there a better way to check if 2 folders are the same?

Thanks.

No, do not put 50MB of data into SharedSettings. That will fall over and die. A set of SharedSettings is stored in XML on disk and entirely loaded into RAM when opened. This also won't keep the user from clearing this data.

For determining whether the data has been downloaded, I would suggest just having a file you make once the download is complete indicating it is done. The user can't selectively remove files. They can clear your data, but that will also clear the sentinel file and you will know you need to re-download. (Also keep in mind you will need to deal with restarting the download if it gets interrupting in the middle.)

Also be sure you correctly handle filesystem operations as described here: http://android-developers.blogspot.com/2010/12/saving-data-safely.html

An alternate idea if you're worried about missing data files... If at any point your app looks for a file and it doesn't exist, throw an exception, pass it to a handler that shows a dialog and 'verifies' your data. You can keep a list of all needed data files, and then only download ones that don't exist. Something like a system check, if you will.

That way they don't end up downloading 50MB if they were only missing a couple files they accidentally deleted in root explorer ;-)