Able To Open The App In Emulator, But Unable To Start The Activity For Google Signin

MainActivity.java @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initialize

Solution 1:

You have a NullPointerException on this line:

sign.setOnClickListener(this);

This is presumably because sign is not found when you call this line:

sign = (SignInButton) findViewById(R.id.sign_in_button);

Make sure the XML id is correct (R.id.sign_in_button).