In my application , downloading lot of files from server. I want to cache them in sdcard.
for that am using fallowing api..
context.getExternalCacheDir();
But problem is that, not able to save them in internal sdcard(i.e; non removable external storage).They are saving in to "/mnt/sdcard/external_sd/Android/data/".
Please gimme a way to save may files in to non removable android cache.
Regards,
Srinivas
From intellisense for Environment.getExternalStorageDirectory:
"Gets the Android external storage directory. This directory may not currently be accessible if it has been mounted by the user on their computer, has been removed from the device, or some other problem has happened. You can determine its current state with getExternalStorageState().
Note: don't be confused by the word "external" here. This directory can better be thought as media/shared storage. It is a filesystem that can hold a relatively large amount of data and that is shared across all applications (does not enforce permissions). Traditionally this is an SD card, but it may also be implemented as built-in storage in a device that is distinct from the protected internal storage and can be mounted as a filesystem on a computer.
In devices with multiple "external" storage directories (such as both secure app storage and mountable shared storage), this directory represents the "primary" external storage that the user will interact with.
Applications should not directly use this top-level directory, in order to avoid polluting the user's root namespace. Any files that are private to the application should be placed in a directory returned by Context.getExternalFilesDir, which the system will take care of deleting if the application is uninstalled. Other shared files should be placed in one of the directories returned by getExternalStoragePublicDirectory(String)."
Related
I want to store some media files(mp3) in either external storage (if available) or internal storage.
I've done some reading on the Android developer page and it says that by default only folders stored in internal storage are app-specific and cannot be accessed by other apps or the user.
However, since it may storage space might be limited on some devices, one may want to consider external storage. The issue with this is that other apps can access you folder and read its contents.
Is there a proper way of the files such that they are completely accessible only from my app regardless of whether they are in internal or external storage, preferably a method that doesn't involve encrypting the folder?
I have some downloadable content (e.g.:game character image) in a app, in iOS they are saved to path NSCachesDirectory, which I follows the guidelines of iOS that downloadable content should be saved in NSCachesDirectory, which is a cache directory. I am struggling if I should save the files to getCacheDir() in android side.
At first I think the cache folder in iOS should be equivalent (or similar) to the one in android, but after looking at some doc I doubt if they are functionally identical:
1.iOS suggest some downloadable content to save in cache folder, such content is more persist temporary file in tmp. But in android, the doc says getCacheDir() should store cache files rather than persist files, it makes me suspect android cache folder works more like the tmp folder in iOS
2.I cannot find any size limit guideline on iOS cache file, but android side says it should have reasonable size limit, say 1 MB (and I think my content would be far more than 1 MB, say 50 to 100 MB).
So my question is, are iOS cache folder works functionally equivalent to cache folder in android? Is it correct to use getCacheDir() at android side at the place that I use NSCachesDirectory in iOS side? if not,which path should I use at android side when I use NSCachesDirectory at iOS side?
No, iOS cache folder doesn't works functionally equivalent to cache
folder in android.
For more details of all the data-storage options of Android have a look at official docs here.
In Android for storing large amount of data you can go with either Internal or external data-storage options, Also you can make your data private on Internal or external data-storage options if you need so.
Internal storage
Each application has its own private internal storage to save files. This is the kind of storage to use if the user shouldn’t be able to modify the file from outside your application, and if other application shouldn’t be able to access those files. Since the internal storage is private to your application, the files will be deleted if your application is uninstalled. The internal storage is also where your application is installed by default, so your files will always be available. On some older or cheaper devices the internal storage is quite limited, so you need to be careful about the size of the data you save if you need to support those devices.
You should never hardcode the path to the storage directories, since the directory may changes depending on the version of the Android OS used. Also, Android 4.4 introduces the concept of multiple users : in that case, the internal and external storage depend on the user logged in and the files of the other users will be invisible. Here are some of the methods used to get the paths to the internal storage:
android.content.Context.getFilesDir(): returns a java.io.File object representing the root directory of the internal storage for your application from the current context.
android.content.Context.getDir(String name, Context.MODE_PRIVATE): returns a java.io.File object representing the directory name in the internal storage, creating the directory if it does not exists. The second parameter can also be used to set the directory to MODE_WORLD_READABLE or MODE_WORLD_WRITABLE so it is visible by all the other applications, but this is is risky security-wise and was deprecated in API level 17 (Android 4.2).
android.content.Context.getCacheDir(): returns a java.io.File object representing the internal cache directory for the application. This is mean for small files (the documentation suggests no more that 1MB total) that can be deleted at any time when the system needs more storage. There is no guarantee that the cache will be cleared, so you must also clear those files manually when they are not needed anymore.
As you can see, the files are represented by the File object from the java.io namepace: there is no file object specific to the Android SDK and the standard Java APIs for reading and writing files are used. Also, there is no specific application permission to set in the Android manifest to use the internal storage since it is already private to the application.
External storage
In addition of the internal storage, there is an external storage space shared by all the applications that is kept when your application is uninstalled. This is the storage that is shown when using a file explorer application and when the device is plugged in your computer. It may be implemented as a SD card that can be removed or as a partition of the built-in storage in the device, so your application should be able to work even if the card is removed or changed. To check the current state of the external storage, you can call the getExternalStorageState() method.
On device with many users (starting with Android 4.4), the external storage is specific to the current user and files for other users can’t be accessed. Also, there may be more than one external storage if the device has a built-in external storage which is a partition on the internal memory and a SD card: in that case, the built-in storage is the primary external storage. Reading files from the external storage requires the READ_EXTERNAL_STORAGE permission and writing or reading files requires the WRITE_EXTERNAL_STORAGE permission.
Here are the methods you should use to call to get the directories of the primary external storage:
android.os.Environment.getExternalStorageDirectory(): returns a java.io.File object representing the root directory of the primary external storage of the device that is shared by all applications.
android.os.Environment.getExternalStoragePublicDirectory(): returns a java.io.File object representing a public directory for files of a particular type on the primary external storage of the device. For example, you can get the path to the public music directory by calling Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MUSIC) or the public pictures directory by calling Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES).
android.content.Context.getExternalFilesDir(): returns a java.io.File representing the root directory of the primary external storage specific to your application, which is under the directory returned by getExternalStorageDirectory(). Unlike the other directories of the external storage, the files you store in that folder will be deleted when your application is uninstalled. So, if you need to store files that are only needed by your application you should use this folder. Also, there is no specific permission needed for the application to read or write to its own external storage starting with Android 4.4, but with older versions your application needs the READ_EXTERNAL_STORAGE or WRITE_EXTERNAL_STORAGE permission.
android.content.Context.getExternalFilesDirs(): returns an array of java.io.File representing the root directories of all the external storage directories that can be used by your application with the primary external storage as the first directory in the array. All those directories works the same as the primary storage returned by the getExternalFilesDir() method. If the device has a built-in storage as the primary external storage and a SD card as a secondary external storage, this is the only way to get the path to the SD card. This method was introduced in Android 4.4, before that it was impossible to get the path to the secondary storage.
android.content.Context.getExternalCacheDir(): returns a java.io.File object representing the cache of the application on the primary external storage. This cache is not visible to the user and is deleted when the application is uninstalled. There is no mechanism in the Android SDK to delete files in the cache directory, so you need to manage your cache to keep it to a reasonable maximum size. Starting with Android 4.4, the application does not need permission to access its own cache, but with older versions your application needs the READ_EXTERNAL_STORAGE or WRITE_EXTERNAL_STORAGE permission.
how can I get the path for the folder where my app can save large JPG files?. getExternalStorageDirectory() works fine only when SD Card is present, but what happens when SD is removed or the harware don't have SD Card slot.
thanks
You can use the getFilesDir() method of a Context. From a context you can also use methods to get the cache directory, external cache directory, and the external files directory. An Activity is also a context, so you can use these methods from inside one.
The getFilesDir() method gives you the folder where your files will be accessible only from your application and will be always available. However, you should use the cache directory instead, when possible. This way you will avoid making the system run out of space.
EDIT:
My answer: Almost always a device will either have an SD card or built-in external storage. When it's built-in, it's still called external storage. To check whether the external storage is removable (SD card) or built-in you can use isExternalStorageRemovable() in Environment.
Basically, you shouldn't place large files on the internal memory. There is no public folder in the internal memory. If a device doesn't have external storage, it's simply not capable of doing certain things. Simple as that. So one option you have when there is no external storage is to inform the user about it and ask them to insert a card. You don't have to handle this case, let the user handle it.
The answer you asked for: Try using getDir(String name, int mode) and/or openFileOutput(String name, int mode) of a Context object, and for mode use MODE_WORLD_READABLE or MODE_WORLD_WRITEABLE. Also check Using the Internal Storage.
You are facing intended limitations of the platform that are there for the good of everyone.
You could either require external directory to exist, or you can store to the internal directory. If you choose to permit both, I suggest you store a flag in internal space to indicate that you've stored something externally, so that if external storage is not present you can take appropriate action.
As you are Saving Large JPG files, its is better to save it in external storage because Phone has very small internal memory and its all effect the performance of phone.
I currently use Environment.getExternalStorageDirectory() to obtain a location where I can store some data temporarily and then after being used gets deleted. This data can range from 1-100MB.
This works fine but on some cases the state of the external storage is removed or unmounted etc... and I can't access to store my data...
My question is what could be a good fallback solution when this storage is not available?
I'm targeting Android 1.6 and greater.
Note that you should not use the path returned by Environment.getExternalStorageDirectory() directly:
Applications should not directly use this top-level directory, in
order to avoid polluting the user's root namespace. Any files that are
private to the application should be placed in a directory returned by
Context.getExternalFilesDir, which the system will take care of
deleting if the application is uninstalled. Other shared files should
be placed in one of the directories returned by
getExternalStoragePublicDirectory(String).
Use the path returned by getFilesDir() to store files private to your app on the internal storage, or getExternalFilesDir() to store on the external storage.
If you're storing data temporarily, consider using the cache directories.
These files will be ones that get deleted first when the device runs
low on storage.
Use the methods: getCacheDir() or getExternalCacheDir() on the external filesystem. Read the documentation for important differences between them.
If the size of the data to be stored is not large, you'd be better off using the internal storage. Otherwise, you'll have to managing the complexity of detecting if external storage is available, falling backing to internal storage if not.
From the official documentation:
Using the External Storage
Every Android-compatible device supports a shared "external storage"
that you can use to save files. This can be a removable storage
media (such as an SD card) or an internal (non-removable)
storage ...
I'm really confused about this subject. From what I understand, using external storage doesn't necessarily mean to use a removable card, am I right? However, when talking about external storage, it's always referred as "sd card".
I'm developing an app that downloads .mp3 files from the internet. I want to save those files in the phone memory (don't want to use any removable device) but for what I have learned, those files have to be saved in external memory.However, I would like to offer the possibility of importing a file from a removable device. Where and how should I save those files?
Thanks
Difference between Internal Storage, External Storage (aka primary external storage) and Secondary External Storage?
Internal Storage: is storage that is not accessible by the user, except via installed apps (or by rooting their device). Example: data/data/app_packageName
External Storage has two types:
Primary External Storage: In built shared storage which is "accessible by the user by plugging in a USB cable and mounting it as a drive on a host computer". Example: When we say Nexus 5 32 GB.
Secondary External Storage: Removable storage. Example: SD Card.
When building an app that uses the internal storage, the Android OS creates a unique folder, which will only be accessible from the app, so no other app, or even the user, can see what's in the folder.
The external storage is more like a public storage, so for now, it's the sdcard, but could become any other type of storage (remote hard drive, or anything else).
The internal storage should only be used for application data, (preferences files and settings, sound or image media for the app to work).
If you intent to download many mp3s, i'd reccomend saving them to external storage, as the external storage is often bigger. Besides, storing data on the internal storage may prevent the user to install other applications.
The Internal and External Storage terminology according to Google/official Android docs is quite different from what we think.
According to official Android docs:-
Internal Storage: By default, files saved to the internal storage are private to your application and other applications cannot access them. When the user uninstalls your application, these files are removed/deleted. Your app user also can't access them using file manager; even after enabling "show hidden files" option in file manager. To access files in Internal Storage, you have to root your Android phone. So, this is NOT what we think as internal memory of the phone - Nexus 5's 32 GB internal memory.
External Storage:
This can be a removable storage media (such as an SD card) or an
internal (non-removable) storage
That means, both storage types like Nexus 6P's 64 GB internal memory and removable microSD card which we insert in phone's card slot are considered as External Storage.
Removable Storage means just microSD card storage, not the internal memory.
To store your app files in SD card, you may use File[] getExternalFilesDirs (String type) method in Context class. Generally, second returned path would be the storage path for microSD card (if any).
Note: I have edited - made my answer more useful after #Tunaki's comment.
From the Developer docs
All Android devices have two file storage areas: "internal" and "external" storage. These names come from the early days of Android, when most devices offered built-in non-volatile memory (internal storage), plus a removable storage medium such as a micro SD card (external storage). Some devices divide the permanent storage space into "internal" and "external" partitions, so even without a removable storage medium, there are always two storage spaces and the API behavior is the same whether the external storage is removable or not.
I think in the operating system, it defines external storage as anything not related to the actual OS filestructure. If you recall, when you write to 'internal storage', Android will make a folder privately for your application. So basically, if this is a hidden folder of some kind, it would mean that external storage could qualify as anything not being automatically hidden or managed directly by the OS. So this would mean that it would be up to the phone manufacturer about the definition of internal storage, as they could have 1 main piece of internal flash memory with two partitions on it. One partition meant to hold the os and the other meant to let you store everything on the phone.
Basically what I'm saying is: That's more a hardware related thing, and that the concept of 'external storage' could extend even to extra internal storage (flash memory) that the manufacturer added in. You could even consider storage options defined by the user as external storage as well.
Here's an updated answer for the latest Android (currently Android 13).
Internal storage used to mean the phone's internal memory and external storage used to mean, among other things, any inserted SD cards. Nowadays, this is not really the case because phones don't have SD cards any more. Phones without SD card slots still have "external storage" from the point of view of an app (eg Environment.getExternalStorageDirectory() still returns a valid location), but it's emulated - meaning it's actually a slice of internal storage.
This means one of the big differences between external and internal storage - which was that external was slower but bigger and internal fast and small - is no longer true.
Since Android 11, external storage has been scoped. This means apps get a folder of their own which is readable to them and unreadable to any other app (though see below). They can access this folder without permissions. Again, this brings external storage in line with internal. (Note scoped storage actually appeared in Android 10 but has only been enforced since Android 11).
But there are remaining differences between internal and external.
One big difference is that apps can still get a permission to read/write across all of external storage (MANAGE_EXTERNAL_STORAGE). This is hard to come by - users need to manually enable it by going into Settings, and apps which implement it are severely limited on the Play Store.
But it does mean that data written to external storage is less secure than that written to internal. Other apps may be able to eavesdrop on external.
The above is the TL;DR but there's a bit more to it. Here's a good article: https://medium.com/#tdcolvin/demystifying-internal-vs-external-storage-in-modern-android-c9c31cb8eeec