How to delete internal storage file in android?

I know this is a bit of an oldie, but the docs say to use:

deleteFile("filename");

rather than:

File.delete();

Which if you are already using:

getFilesDir();

kind of makes sense.

If you want to delete all files from a folder then use the following function:

private void deleteTempFolder(String dir) {
        File myDir = new File(Environment.getExternalStorageDirectory() + "/"+dir);
        if (myDir.isDirectory()) {
            String[] children = myDir.list();
            for (int i = 0; i < children.length; i++) {
                new File(myDir, children[i]).delete();
            }
        }
    }

Folder must be present on storage. If not we can check one more codition for it.

  if (myDir.exists() && myDir.isDirectory()) {
//write same defination for it.
}

File dir = getFilesDir();
File file = new File(dir, "my_filename");
boolean deleted = file.delete();

You should always delete files that you no longer need. The most straightforward way to delete a file is to have the opened file reference call delete() on itself.

myFile.delete();

If the file is saved on internal storage, you can also ask the Context to locate and delete a file by calling deleteFile():

myContext.deleteFile(fileName);

Note: When the user uninstalls your app, the Android system deletes the following: All files you saved on internal storage All files you saved on external storage using getExternalFilesDir(). However, you should manually delete all cached files created with getCacheDir() on a regular basis and also regularly delete other files you no longer need.

Source : http://developer.android.com/training/basics/data-storage/files.html