Hope This Might Help You !!!
use this code to Checking media availability in **inbuilt external storage.**
boolean mExternalStorageAvailable = false; boolean mExternalStorageWriteable = false; String state = Environment.getExternalStorageState(); if (Environment.MEDIA_MOUNTED.equals(state)) { // We can read and write the media mExternalStorageAvailable = mExternalStorageWriteable = true; } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) { // We can only read the media mExternalStorageAvailable = true; mExternalStorageWriteable = false; } else { // Something else is wrong. It may be one of many other states, but all we need // to know is we can neither read nor write mExternalStorageAvailable = mExternalStorageWriteable = false; }
do your code depend on that

I'd recommend reading [storage options][1] on developer.android.com.
To check external memory is available (taken from developer.android.com):
boolean mExternalStorageAvailable = false; boolean mExternalStorageWriteable = false; String state = Environment.getExternalStorageState(); if (Environment.MEDIA_MOUNTED.equals(state)) { // We can read and write the media mExternalStorageAvailable = mExternalStorageWriteable = true; } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) { // We can only read the media mExternalStorageAvailable = true; mExternalStorageWriteable = false; } else { // Something else is wrong. It may be one of many other states, but all we need // to know is we can neither read nor write mExternalStorageAvailable = mExternalStorageWriteable = false; }
To read internal files use `context.fileList();` see more [here][2].
**Edit**
I'm not sure what you want with 2 and 3. You can use mediascan to many things but using it just for using it sounds unproductive. For that I'd recommend @Singularity advice. There is a post [here about using mediascan for pdfs][3].

[1]: http://developer.android.com/guide/topics/data/data-storage.html [2]: http://developer.android.com/reference/android/content/Context.html#fileList%28%29 [3]: https://stackoverflow.com/q/10384080/969325