android - Turn on Unknown Sources setting programmatically

Question

I want to turn on Unknown Sources setting programmatically on non rooted device. I have checked with this code:

boolean success;
int result = Settings.Secure.getInt(getContentResolver(),
Settings.Secure.INSTALL_NON_MARKET_APPS, 0);
if (result == 0) {
    success = Settings.Secure.putString(getContentResolver(), Settings.Secure.INSTALL_NON_MARKET_APPS, "1");    
}

and with following permissions:

<uses-permission android:name="android.permission.WRITE_SETTINGS" />
<uses-permission android:name="android.permission.WRITE_SECURE_SETTINGS"/>

but on executing, it says permission denied: writing to secure settings requires android.permission.WRITE_SECURE_SETTINGS which I already have given.

I have made this application with device admin permission.

Answer 1

but on executing, it says permission denied: writing to secure settings requires android.permission.WRITE_SECURE_SETTINGS which I already have given.

You cannot hold that permission, unless you are signed by the same signing key that signed the firmware or if you were installed on the system partition (e.g., by a rooted device user).

I have made this application with device admin permission.

That has nothing to do with modifying secure settings programmatically.