Saving Images on your Device

Hello all, I am using App Inventor 2, which I like very much, and I am working on a picture game app.

I used the principles in the old WebPrefetch, with some slight variations for the output file names, to try an keep the app size minimal.

The app is working beautifully for my Android tablet, but I have run into a slight snag.

When I pull the images off of my webserver i save them to the store directory of:

STORE DIRECTORY = "/data/nisi/"

To recover the images to view the Load directory for my tablet is actually

LOAD DIRECTORY" = "/storage/sdcard0/data/nisi/"

I noticed that the Webprefetch example's load directory was different and upon trying this on my wife's Galaxy S4 found that the path is yet again different.

So in a word, I am assuming every android device has a different storage path unique to the model of the the device. This is not entirely unexpected, but I I am now at a stand still.

So a couple of questions here.

1. Is there a way to auto detect the full path name and update my Load Directory variable once an image is saved.

2. Is there a way to download images off the web and save the images within the app directory so you do not need any of the prefixes to access the images.

Any ideas or suggestions would be gratefully appreciated.

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do you use Shival Wolf's web prefetch?

1. Is there a way to auto detect the full path name and update my Load Directory variable once an image is saved.

try file:///mnt/sdcard and check, if that path to the sd card works with all devices

2. Is there a way to download images off the web and save the images within the app directory so you do not need any of the prefixes to access the images.

no

well, probably possible with a rooted device?

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Thanks for the quick response Taifun.

Yes I did use the basic Webprefetch from Shival Wolf.

I was trying to add a screen shot, but this seems to be turned off, or is not showing anyway of doing this on my screen.

I have the prefetch downloading 6 images at a time.  Each set copies over the previous set so you do not eat up the device memory. The /mnt/sdcard/is it... I couldn't remember what Shival Wolf's had, for some reason his site is not working ... looks like some kind of server error.

I tried this first, /mnt/sdcard/data/nisi/, and couldn't get it to work, however Shival's is not exactly how you have it listed.

Mine is currently set as "/storage/sdcard0/data/nisi/"

So you are suggesting I try  "file:///mnt/sdcard/data/nisi/" this of course followed by the file name itself?

I will play around with it.  I'm not really a programmer so I am assuming the number of /// is the difference here. 

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Shival Wolf's tutorial is here http://ai.kittywolf.net/index.php/Webprefetch

try /data/nisi/ as storeddirectory 

and file:///mnt/sdcard/data/nisi/ as loaddirectory

Taifun

PS: another webprefetch version you can find here http://puravidaapps.com/filebyfile.php

That version avoids problems which can occur with larger files...

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Thanks very much, I will try later this weekend and let you know.

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Hello Taifun, thanks again.

That worked beautifully.  I have tried it on several devices and they all seem to work perfectly.

Also what I was saying about Shival's website. This is the message I am getting.

Error 418

I'm a Teapot
Kambrook/2.1.4 (Electric) Kettle Server at ai.kittywolf.net Port 80 

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Sorry the "Thanks Agin" is not in the error page :)

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Android Apps Break the 50MB Barrier

Android applications have historically been limited to a maximum size of 50MB. This works for most apps, and smaller is usually better — every megabyte you add makes it harder for your users to download and get started. However, some types of apps, like high-quality 3D interactive games, require more local resources.
So today, we’re expanding the Android app size limit to 4GB.
The size of your APK file will still be limited to 50MB to ensure secure on-device storage, but you can now attach expansion files to your APK.

⦁ Each app can have two expansion files, each one up to 2GB, in whatever format you choose.
⦁ Android Market will host the files to save you the hassle and cost of file serving.
⦁ Users will see the total size of your app and all of the downloads before they install/purchase.

On most newer devices, when users download your app from Android Market, the expansion files will be downloaded automatically, and the refund period won’t start until the expansion files are downloaded. On older devices, your app will download the expansion files the first time it runs, via a downloader library which we’ve provided below.
While you can use the two expansion files any way you wish, we recommend that one serve as the initial download and be rarely if ever updated; the second can be smaller and serve as a “patch carrier,” getting versioned with each major release.

Helpful Resources

In order to make expansion file downloading as easy as possible for developers, we're providing sample code and libraries in the Android SDK Manager.

⦁ In the Google Market Licensing package, an updated License Verification Library (LVL). This minor update mostly adds the ability to obtain expansion file details from the licensing server.
⦁ From the Google Market APK Expansion package, the downloader service example. The library makes it relatively simple to implement a downloader service in your application that follows many of our best practices, including resuming downloads and displaying a progress notification.
Because many developers may not be used to working with one or two large files for all of their secondary content, the example code also includes support for using a Zip file as the secondary file. The Zip example implements a reasonable patching strategy that allows for the main expansion file to “patch” the APK and the patch file to “patch” both the APK and the main expansion file by searching for asset files in all three places, in the order patch->main->APK.

Expansion File Basics

Expansion files have a specific naming convention and are located in a specific place for each app. As expansion files are uploaded to the publisher site, they are assigned a version code based upon the version of the APK that they are associated with. The naming convention and location are as follows:

⦁ Location: <shared-storage>/Android/obb/<package-name>/
⦁ Filename: [main|patch].<expansion-version>.<package-name>.obb
⦁ Example: /sdcard/Android/obb/com.example.myapp/main.5.com.example.myapp.obb

Expansion files are stored in shared storage. Unlike APK files, they can be read by any application.

Downloading and Using the Expansion Files

When the primary activity for the app is created, it should check to make sure the expansion files are available. The downloader library provides helper functions (for example the “Helpers” class in the code below) to make this easy.

boolean expansionFilesDelivered() {
    // get filename where main == true and version == 3
    String fileName = Helpers.getExpansionAPKFileName(this, true, 3);
    // does the file exist with FILE_SIZE?
    if (!Helpers.doesFileExist(this, fileName, FILE_SIZE, false)) {
        return false;
    }
    return true;
}

If the file does not exist, fire up the downloader service DownloaderClientMarshaller.startDownloadServiceIfRequired(). The downloader will perform an LVL check against the server. This check will deliver the names of the files, file sizes, and the file URLs.

with
Once that check has been completed, it will begin downloading the files. You don’t have to use our download solution, but you might want to because we:

⦁ Include a notification UI that provides progress and estimated completion time in layouts customized for ICS and pre-ICS devices
⦁ Resume large files safely
⦁ Handle redirection with appropriate limits
⦁ Run in the background as a service
⦁ Pause and resume downloads when WiFi is not available

Enjoy! We can’t wait to see what kinds of things developers do with this! For more information about how to use expansion files with your app, read the APK Expansion Files developer guide.
[This post wasn’t actually written by anyone, but bashed out by a posse of engineering and product-management people. Heavy bashers included Dan Galpin, Ilya Firman, Andy Stadler, Michael Siliski, and Ellie Powers.]

Posted by Unknown at 5:00 PM
Labels: APK Expansion Files