NavigationView covers the activity

Question

I tried to add drawer to one of the activities in my app. However the Navigation View covers all other layouts and it's the only thing I can see when I open the Activity.I can not slide it back,or do anything with it. Other objects seem to be placed behind that drawer somehow. Sorry if it's something simple, it's my first time doing it. Does anybody know why that may happen?

Here is my XML code:

<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    tools:context=".CategoryActivity"
    android:id="@+id/drawer_layout"
    android:fitsSystemWindows="true"
    android:background="@color/dark_blue"
    tools:openDrawer="start">

<com.google.android.material.navigation.NavigationView
    android:layout_marginTop="50dp"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:headerLayout="@layout/nav_header"
    app:menu="@menu/drawer_menu"
    android:foregroundGravity="right"
    >

</com.google.android.material.navigation.NavigationView>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/dark_blue">


    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        android:popupTheme="@style/ThemeOverlay.AppCompat.Light"
        android:elevation="4dp"/>

    <FrameLayout
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>


<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Categories"
    android:textColor="#ffffff"
    android:textSize="30sp"
    android:textStyle="bold"
    android:layout_marginStart="130dp"
    />

<RelativeLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:src="@drawable/hist_bg" />

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="25dp"
        android:layout_marginTop="75dp"
        android:layout_marginEnd="40dp"
        android:gravity="end"
        android:text="History"
        android:textColor="@color/white"
        android:textSize="25sp"
        android:textStyle="bold" />

    <Button
        android:id="@+id/bt_hist_start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="270dp"
        android:layout_marginTop="100dp"
        android:background="@drawable/his_btn" />

</RelativeLayout>



<RelativeLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:src="@drawable/android_bg" />

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"

        android:layout_marginTop="75dp"
        android:gravity="start"
        android:text="Programming"
        android:textColor="@color/white"
        android:textSize="25sp"
        android:textStyle="bold"
        android:layout_marginStart="20dp"/>

    <Button
        android:id="@+id/bt_prog_start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="15dp"
        android:layout_marginTop="100dp"
        android:background="@drawable/an_btn" />

</RelativeLayout>

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_gravity="center">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginTop="10dp"
        android:src="@drawable/allknow_bg" />

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="25dp"
        android:layout_marginTop="75dp"
        android:layout_marginEnd="40dp"
        android:gravity="end"
        android:text="Technology"
        android:textColor="@color/white"
        android:textSize="25sp"
        android:textStyle="bold" />

    <Button
        android:id="@+id/bt_tech_start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="270dp"
        android:layout_marginTop="100dp"
        android:background="@drawable/allknow_btn" />

</RelativeLayout>

</LinearLayout>

</androidx.drawerlayout.widget.DrawerLayout>

Here is the Activity code:

Toolbar toolbar  = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        drawer = findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawer, toolbar,
                R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.addDrawerListener(toggle);
        toggle.syncState();

Answer 1

I can see few missing things in your xml code.

1. There is no parent <AppBarLayout tag for your <Toolbar tag
2. What is the purpose of NavigationView? You haven't given it any ID and not using it?
3. The NavigationView height should be match_parent
4. Remove foregroundGravity in NavigationView and add android:layout_gravity="start", also add android:fitsSystemWindows="true"

You should initialize your NavigationView in your Main Activity and use it to setup NavController. I am not giving you the code for everything so you can search a little bit yourself but if you don't find the solutions let me know.