Remove ConstraintLayout, fix crash

app/src/main/java/in/ac/iitb/gymkhana/iitbapp/LoginActivity.java

@@ -122,6 +122,7 @@ public class LoginActivity extends AppCompatActivity {
                     "AuthCode: " + response.authorizationCode, Toast.LENGTH_SHORT)
                     .show();
 
+//            TODO: Replace gcmId
             login(response.authorizationCode, "xyz");
         } else {
             Log.i(TAG, "Authorization failed: " + error.getMessage());
@@ -174,6 +175,7 @@ public class LoginActivity extends AppCompatActivity {
             @Override
             public void onResponse(Call<LoginResponse> call, Response<LoginResponse> response) {
                 if (response.isSuccessful()) {
+                    //Save credentials in AccountManager to keep user logged in
                     //Go to MainActivity
                 }
                 //Server error

app/src/main/java/in/ac/iitb/gymkhana/iitbapp/MainActivity.java

@@ -140,7 +140,7 @@ public class MainActivity extends AppCompatActivity
     private void updateFragment(Fragment fragment) {
         FragmentManager manager = getSupportFragmentManager();
         FragmentTransaction transaction = manager.beginTransaction();
-        transaction.replace(R.id.constraintlayout_for_fragment, fragment, fragment.getTag());
+        transaction.replace(R.id.framelayout_for_fragment, fragment, fragment.getTag());
         transaction.commit();
     }
 }

app/src/main/res/layout/content_main.xml

 <?xml version="1.0" encoding="utf-8"?>
-<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
-    android:id="@+id/constraintlayout_for_fragment"
+    android:id="@+id/framelayout_for_fragment"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     app:layout_behavior="@string/appbar_scrolling_view_behavior"

build.gradle

@@ -7,7 +7,7 @@ buildscript {
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.0.0-alpha5'
+        classpath 'com.android.tools.build:gradle:3.0.0-alpha6'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files