i am developing an application where i need to capture the pictures from camera and save them with in application like in this location "/data/data/com...../images" - what i want to know is this the right approach . if not please suggest but my images should not be available to other app's.
Thanks and Regards,
puneeth
I think every approach have their drawbacks. If the picture should always be there (unless delete through app), I feel it may not be best approach. Otherwise it is Ok to use this approach (which is what I am doing too). Only caution I took was, if picture was deleted by someone, always have a default picture to display there (which saves application crash and other alignment issues).
You’re talking about the Context.getFilesDir() directory. Note that, on older phones with separate SD card storage, this area is likely to be quite limited in size, so be careful about saving lots of images here. You may want to use getExternalCacheDir() or getExternalFilesDir() instead.
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I am new to Android Studio. While working on front end its sometimes easy to take some parts as png file and place it on the particular position instead of recreating it in xml file. I am confused can we use png all the time ? I am worried about memory space . Like the app contains 50 pages and in each page I use 1-2 assets . I don't want my app to have more than 40mb. What will be the best way to do? Can we store the image as a URL and retrieve it whenever we use. What's the drawback in that way?
So many questions :)
I am confused can we use png all the time ?
Use what's best for your picture. For a photo, a JPEG will probably do better. But if you wish, you can use PNG all the time, yes.
I don't want my app to have more than 40mb.
Check and see. Depends on how big your images are; we can't tell.
What will be the best way to do?
Not enough information to tell you that. In general, there's nothing wrong with using images in assets.
Can we store the image as a URL and retrieve it whenever we use.
Yes.
What's the drawback in that way?
You'll need to get some server space somewhere. Also, there will be a loading latency. Also, your app won't be usable while disconnected from the Internet.
While working on front end its sometimes easy to take some parts as png file and place it on the particular position instead of recreating it in xml file.
That's the part that is confusing to me. Android XML layouts usually contain interactive elements, ones that the user can interact with. Images, on the other hand, tend to be static. What kind of XML is there out there that you think you can replace by an image?
I'm making an android app, here the images are getting from Cloud, is it good idea to download images and save it & use it further. Or download images every-time user uses the app, what idea you prefer is the best?
Because downloading images always is slow & its bad i know but at some point if the images are updated then how to get to know about it?
You should definitely cache your downloaded files!
Do it in your internal app directory where only you do have access to (or otherwise external storage, thats still ok).
Bandwidth and connections are always expensive and should kept low as much as possible.
So your user can see images fast even on a bad connection and your app doesn't waste his valuable bandwidth of a users data plan.
Maybe this could also help you:
https://github.com/novoda/ImageLoader
http://www.androidhive.info/2012/07/android-loading-image-from-url-http/
Make it easy on yourself and use something like Android Smart Image View. It takes care of loading and caching, and it's just about a drop-in replacement for Android's ImageView. Universal Image Loader is another alternative, more configurable, but not as quick to implement.
I used https://github.com/nostra13/Android-Universal-Image-Loader
but I think you not want only download and cache.
these no trick ,if you want check weather the image update or not, you can add metadata for image, just like md5 .
in html and browser, you can set expires header for a image:
enter link description here
but in android app, you control all yourself.
Downloading images and saving them is probably the best way to do it because you don't want to download the same images over and over. If the images are updated you can delete the older one and download the new ones. Just make sure you don't download/save a million images. Take a look at this library. It has a built-in cache on sdcard/external sd.
Downloading images from the net for display, with possible requirement of caching is a very common problem that many people have solved, you can try these solutions to see which fits you:
Ion (https://github.com/koush/ion) - very flexible and feature complete, plus it can download more than images but JSON, Strings, Files, and Java types as well. The part that I really like about this is that it can automatically cancel operations when the calling Activity finishes, so users don't waste time & bandwidth downloading images that will no longer be displayed
Universal Image Loader (https://github.com/nostra13/Android-Universal-Image-Loader) - equally capable for most use cases but for downloading/caching images only
Good day, I have a requirement to create a kind of book app with pdfs, images and videos worth up to 10gb and more on a tablet locally. Now there is no intention to sell it on the android market or any other store, its completely in house, so i think issue with apk size has been clarified. What am asking is, where is the best place to put all this contents so that i can readily load them up and use them accordingly?
Should i be using the raw folder and create sub-folders for each images, videos and pdfs?
Should i create folders on an sdcard(assuming there is one in place)? or
Please if you have any other solution or ideas on how to implement this, I would gladly like to hear this. Thanks for your responses in advance.
P.S by the way, since its a tablet specific app, is there any need to have a multi-pane layout fragment or ii can just use all the space. thank you
I suppose you can use a RAW folder, but it would also make the APK size huge from what I understand because all the files in the RAW folder need to be packaged with the application.
From what I've seen in the past, most applications, actually most games, that have lots of extra data will download the additional data on first launch. Basically:
The application launches
It checks whether or not you have all the additional data (Books, pdfs, images)
If not, it starts downloading that data to the SDCARD.
It may not make sense in your situation, but doing it this way gives you more finite control over how much data needs to be downloaded. If function A only requires package A of additional data, then you only need to download package A, you don't need to download everything. Or perhaps you could let the user choose what packages of additional data they want to download, which would also save bandwidth, time and resources.
Can an android app read the memory (the RAM meory) of another app that is running?
Appreciate any pointers.
Do you mean the part of the memory that another app is using for code? Then No.
I assume that someone might find a way, but that would be a security issue, a bug in the system and something that would be adressed in an update. You should stay out of 'other' pieces of RAM.
Or do you mean something like internal memory where you can store a file? An app can save a file in several ways, including some that let other apps read them (example: if you take a picture with a cam-app, you can read it with any gallery app).
I currently have my app caching image files in the cache sub-directory for the application. The images are used in a ListView and stored in a HashMap of SoftReferences to Bitmaps.
So my question is this, what is the best way to cache these image files without inflating the space my application uses AND remains responsive from a user standpoint.
Things I am concerned about:
I know the user can clear the cache and that it is done automatically when space is low on internal memory, but I feel most users will see a several MB app and uninstall it. Also if the space is constantly low, my app will just keep downloading the images, making it appear slower.
Most devices have an SD card pre-installed, but what should I do when it is not inserted? The SD card may also be slower compared to internal storage, affecting my app's performance.
Should I include an option to choose the location of the cache?
Should I attempt to manage the size of my cache (be it in the /cache or /sdcard) or just forget about it?
Thank you for your time (its a long one I know) and please post any relevant experience.
I can't offer you a comprehensive set of best practices, but I can offer what I've learned so far:
Managing your cache is a good idea. My app's cache is such that I know that I'll never need more than a certain number of cached files, so whenever I insert a new file into the cache, I delete the oldest files until I'm under the limit I have set. You could do something similar based on size, or simply age.
Caching to the SD card, if it's available, is a good idea if your cache needs to take up a lot of space. You'll need to manage that space just as carefully, since it won't automatically clear that space for you. If you're caching image files, be sure to put them in a directory that begins with a dot, like "/yourAppHere/.cache". This will keep the images from showing up in the gallery, which is really annoying.
Letting the user choose the location of the cache seems like overkill to me, but if your audience is very geeky, it might be appreciated.
I haven't noticed a much of a penalty when caching to the SD, but I don't know how your app uses that information.
Everyone has good ideas. I like the idea of using SoftReference's, although I'm not sure how often those get cleaned up, as this varies so much from VM to VM. You might want to combine that with regular HashMap to prevent you entire cache getting cleared every few minutes.
EclipseLink has a few different cache implementations and pretty good documentation on them. You could probably take advantage of a few ideas from the implementation (e.g., LRU, MRU, etc.). e.g.,
hard cache
soft cache
combined hard/soft cache
Since you're tuning a cache down to the nitty-gritty, I would recommend tuning it to different devices based on the hard specs. This is normally bad design, but the scope of the hardware that your software runs on mandates it, IMHO. e.g.,
Detect the amount of available memory on the SD card. Most new smart phones come with multi-GB SD cards, and those are pretty hard to fill up with regular usage for most users. Use away! You can also detect the amount of space available on the SD card on startup, and increase/decrease the size of your cache on startup.
Detect the amount of available memory and configure your caches with that in mind. If a user is using a hardware-intensive application, I don't think they'll mind that it makes up 200MB of RAM and provides a very fast user experience, especially since they spent a lot of money to have a phone that has 1-2GB RAM.
Good luck!
Should I include an option to choose the location of the cache?
IMO: No, let make it more simplest as possible (Except you can include advance setting for expert user)
Should I attempt to manage the size of my cache (be it in the /cache
or /sdcard) or just forget about it?
IMO: This is optional, it is double sword: your more work on background will help user more convenience but also more bug prone
Use 3rd libs:
IMO using 3rd library as Picasso is better, it handle cache automatically by order: Memory cache -> Disk cache -> Network