So, largely for debugging purposes, I want to be able to write an image at arbitrary points in my code, and look at it later. I figured this would be easiest if I just wrote a my bitmap to a file and read it back later, but I cannot seem to figure out where to find the file after I write it, or how to open an image that is not in res/drawable with a corresponding handle in R.
You can use openFileOutput() and openFileInput(). These pull up data streams that point to files in your app's directory, and are (as far as I know), the suggested way to handle files that your app makes.
Related
I need to read binary file from asset folder in my app, and the way I'm trying to do it is by obtaining Channel:
AssetFileDescriptor assetFd = context.getAssets().openFd("file.db");
FileChannel fileChan = assetFd.createInputStream().getChannel();
The problem is that AssetManager, AssetFileDescriptor are very poorly documented classes and behave in unpredicted manner (as it seems to me). For example, if you will try to obtain fileChan.position() immediately after code above you won't get 0, in my case it'll be 976. After digging through StackOverflow I found out that it's normal behaviour and you need to be aware that assets are compressed into some internal binary form and AssetFileDescriptor isn't real file descriptor.
In my case I have a file structure with absolute byte positions stored in a header, so it seems like to read it properly I also need take into account assetFd.getStartOffset().
Also I've got zero clue about method AssetFileDescriptor.createInputStream behaviour after reading its doc:
This will either return a full asset AssetFileDescriptor.AutoCloseInputStream, or an underlying ParcelFileDescriptor.AutoCloseInputStream depending on whether the the object represents a complete file or sub-section of a file.
Lack of understanding whole picture and documentation makes me nervous about using this approach.
Should I be worried about AssetFileDescriptor.createInputStream behaviour when reading big files (over 1mb)? Is it safe to use Channels when reading asset files?
Thank you in advance!
The best way to deal with assets is to copy them to the internal or external storage and then read them with whatever method you want.
Thanks to #pskink for help!
Been having a little bit of trouble with this. Googled about and I can't really find anything. Saw a few things about setting text but I don't think that affects the string resource file or at least I can't make it affect the resource file. Help please!
No, you can't modify apk at the runtime. If you don't own source code, you can pull apk file to the computer and decompile it by using APKTool, for example. If you are working with data you get from internet/user, it should be kept inside DBs, files, whatever. In other words in internal or external storage. Please take a look on storage options you can use http://developer.android.com/guide/topics/data/data-storage.html
I am loading a GPX file into my emulator.
THE PROBLEM
The file has 7226 points (it says so in the Point Count column) so the file is being loaded in correctly. However, the problem happens when I press the play button it only reads in about 4 points before it then pauses itself. This is not the functionality I want.
THE QUESTION
How do I make it run through the entire file without it pausing itself?
Thanks in advance
Just for the sake of answering the question from my research and for those of you looking for a solution yourself.
I couldn't manage to get the entire GPX file loaded in via the DDMS even when using different types of converters that you can find online.
The solution in the end was to have a set of classes which decode a GPX file into a set of locations and then do whatever you want with those.
I hope this helps even it is just confirming your thoughts that it wont work (well i couldn't work it out!) :)
I'm developing for Android 2.2.
Things put to res and assets are compressed in the APK by default unless their extension indicates that they're already compressed (mp3, png). Moreover, before Android 2.3, to assets, you could only put uncompressed files of size less than 1 MB.
Question 1:
if I put a 1.5MB binary file to res/raw, and my program refers to it with its standard Android ID (R.raw.....), then will the system pull the whole file into memory? Since the 1.5MB is stored in a compressed way, I suppose it must. This is unpleasant because it is possible that the program only needs 1KB of data to be loaded from a given file offset. This can have a serious impact on app performance/speed.
I see two solutions:
(hack) Use mp3 or png extensions; but I am not sure this allows memory-efficient access after all (i.e. inputstream.skipbytes, etc.)
After the installation, at the first start of the app, the app will copy the files to its own writable working folder (in SD card). Since this point, it will always access the files from there instead of the R.raw... way. Therefore, the sequential read will work for sure, i.e. the memory usage will be no more than the actual data read from the specified file offset (apart from temporary read buffers used by inputstream.seek implementation, which are well-optimized i.e. small I suppose).
Question 2:
what is the best way of reading binary data memory-efficiently, from big files? I don't want to split my big files into many small ones unless that's the only way.
I'd go with #2 solution and then would use RandomAccessFile to avoid linear access.
I also would to opt for solution #2, but instead of using random access file, I would use java.nio.MappedByteBuffer - this way you will get fast random access with byte buffer semantic.
I have a text file within my raw folder of my app that I intend to use as a simple way to save settings and then read them back when needed. I can read from this file with using the BufferedReader and what comes with it, but I've tried a few different ways to be able to write to this file and none seem to work.
It seems to me that the problem is I never actually get the file, and I assume this is simply because I don't exactly know how I am supposed to give it the correct directory and file name. I've tried all I could come up with, and I tend to get errors like "No such file or directory exists" or "Read-only file system".
This seems to be a very simple problem relating to me just giving the wrong information, so if anybody could point me in the right direction it would be much appreciated.
Thank you,
Raphy
For saving settings you should use SharedPreferences rather than coming up with a custom solution.
SharedPreferences documentation
Data Storage
I'm not entirely sure you can do that with stuff in the "raw" folder.
One approach would be to use the SharedPreference storage in the API. See in the datastorage section of the docs. It's perfect from what you describe neededing. Another approach would be to put the file on the SDCard and read and write it from there.