Create a folder and write into it in the root of android

问题

I'm not trying to write into the external sd at /mnt/sdcard. I'm trying to create a folder for may app files and have them accesible by others.

I have an app called Libra that generates .csv files when exporting data and all af it goes to /Libra/ folder. I want my app to do the same.

As far as I've seen there's external storage which is the sd and internal which is a non public place for the app.

How can I make a dir at the root of the android file system as Libra does ?

If I ask for the external storage I get the following non desired locations :

Environment.getExternalStorageDirectory()

/storage/emulated/0/ (in my Nexus)
/mnt/sdcard          (in the emulator)

If I try to make the folder in an absolute path /MyDiary It returns Error creating folder

File folder = new File("/MyDiary");
boolean success = true;
if (!folder.exists()) {
        success = folder.mkdir();
}
if (success) {
        Toast.makeText(getBaseContext(), "Already exists", Toast.LENGTH_LONG).show();
} else {
        Toast.makeText(getBaseContext(), "Error creating directory", Toast.LENGTH_LONG).show();
        return;
}

If I try to check if the Libra folder does exists, it says it doesn't exist:

File folder = new File("/Libra");
boolean success = true;
if (!folder.exists()) {
        success = folder.mkdir();
}
if (success) {
        Toast.makeText(getBaseContext(), "Libra exists", Toast.LENGTH_LONG).show();
}

Note: I've got the manifest permissions to write in external storage.

回答1:

The root is a ramdisk. And the folder in it some are created by init.rc. Only init.rc have permission to create the folder in the ramdisk. If you create the folder by init.rc, you still need init.rc help to mount a true stroage device on the new folder.

Repack like The init.rc file regenerated on restart

回答2:

First of all you need root access Permissions to write. You can see whether it has created folder there or not using rootexplorer app. Try this after getting root access.

回答3:

I don't think that's the right way to create a File in the Android OS. From http://developer.android.com/training/basics/data-storage/files.html:

If you want to save public files on the external storage [I've read your advice, but I think this way you can access files from multiple apps, if that's what you want], use the getExternalStoragePublicDirectory() method to get a File representing the appropriate directory on the external storage. The method takes an argument specifying the type of file you want to save so that they can be logically organized with other public files, such as DIRECTORY_MUSIC or DIRECTORY_PICTURES. For example:

public File getAlbumStorageDir(String albumName) {
    // Get the directory for the user's public pictures directory. 
    File file = new File(Environment.getExternalStoragePublicDirectory(
        Environment.DIRECTORY_PICTURES), albumName);
    if (!file.mkdirs()) {
        Log.e(LOG_TAG, "Directory not created");
    }
    return file;
}

回答4:

try first getting superuser permission to your app.Run linux commands for making folder and files into which you want to write data(You can do this with only linux commands)just at 1st run of your app.Then you can write data to files by getting FileOutputStream("filename") object.Leave ur remarks if it worked or not. partial code for above procedures is

    Process p=Runtime.getRuntime().exec("su");
    OutputStream o=p.getOutputStream();
    o.write("mkdir foldername\n".getBytes());
    o.write("cd foldername\n".getBytes());
    o.write("cat > filename\n".getBytes());
    o.write("exit\n".getBytes());
    o.flush();
    p.waitFor();

来源：https://stackoverflow.com/questions/15587458/create-a-folder-and-write-into-it-in-the-root-of-android

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android

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