Get Android application signature

android_application_signature.java

PackageInfo info;

try {
	info = getPackageManager().getPackageInfo("ecentinela.mercadotes", PackageManager.GET_SIGNATURES);

	for (Signature signature : info.signatures) {
		MessageDigest md;
		md = MessageDigest.getInstance("SHA");

		md.update(signature.toByteArray());
		String something = new String(Base64.encode(md.digest(), 0));
		//String something = new String(Base64.encodeBytes(md.digest()));
		Log.e("hash key", something);
	} 
}
catch (NameNotFoundException e1) {
	Log.e("name not found", e1.toString());
}
catch (NoSuchAlgorithmException e) {
	Log.e("no such an algorithm", e.toString());
}
catch (Exception e){
	Log.e("exception", e.toString());
}

You can follow this example: https://stackoverflow.com/questions/52041805/how-to-use-packageinfo-get-signing-certificates-in-api-28

If it helps, please vote UP my post.

I added and update to that question.