fragment - navigation drawer - app stopped error - android-fragments

Question

Greeting
When I click on the camera text, the app shows an error said "The application has stopped". How it can be fixed?
MaingActivity.java
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
CameraFragment cameraFragment = new CameraFragment();
FragmentManager manager= getSupportFragmentManager();
manager.beginTransaction().replace(
R.id.relativelayout_for_fragment,
cameraFragment,
cameraFragment.getTag()
).commit();
} else if (id == R.id.nav_gallery) {
Toast.makeText(this,"Gallary",Toast.LENGTH_SHORT).show();
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}

Answer 1

I have found it
Select contant_main.xml => click on icon refer Constrains
The code will be as the following
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:context="com.example.shakeralmoosa.nav1.MainActivity"
tools:showIn="#layout/app_bar_main"
android:id="#+id/mainLayout">
<RelativeLayout
android:layout_width="0dp"
android:layout_height="0dp"
tools:layout_constraintTop_creator="1"
tools:layout_constraintRight_creator="1"
tools:layout_constraintBottom_creator="1"
android:layout_marginStart="5dp"
app:layout_constraintBottom_toBottomOf="parent"
android:layout_marginEnd="5dp"
app:layout_constraintRight_toRightOf="parent"
android:layout_marginTop="4dp"
tools:layout_constraintLeft_creator="1"
android:layout_marginBottom="4dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp">
</RelativeLayout>
</android.support.constraint.ConstraintLayout>