I am trying to make an app where you can toggle the drawer using by clicking onto an imageview, however it seems I get a nasty error everytime I set an onClickListener in the OnCreate of the main activity

E/AndroidRuntime: FATAL EXCEPTION: main     Process: com.example.myapplication, PID: 7921     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapplication/com.example.myapplication.activities.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3356)         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3500)         at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)         at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)         at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2049)         at android.os.Handler.dispatchMessage(Handler.java:106)         at android.os.Looper.loop(Looper.java:223)         at android.app.ActivityThread.main(ActivityThread.java:7523)         at java.lang.reflect.Method.invoke(Native Method)         at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:941)      Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference         at com.example.myapplication.activities.MainActivity.onCreate(MainActivity.kt:43)         at android.app.Activity.performCreate(Activity.java:7984)         at android.app.Activity.performCreate(Activity.java:7973)         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3329)         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3500)          at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)          at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)          at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2049)          at android.os.Handler.dispatchMessage(Handler.java:106)          at android.os.Looper.loop(Looper.java:223)          at android.app.ActivityThread.main(ActivityThread.java:7523)          at java.lang.reflect.Method.invoke(Native Method)          at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:941)  

Been digging around for half an hour with no results, any tips on how to do this?

Everything else works except this. Just in case your wondering, here are the important bits of code:

    override fun onCreate(savedInstanceState: Bundle?) {         super.onCreate(savedInstanceState)         setContentView(R.layout.activity_main)          setUpActionBar()          showProgressDialog(resources.getString(R.string.please_wait))         FirestoreClass().loadUserData(this)                  nav_view_main.setNavigationItemSelectedListener(this)          iv_cancel_icon.setOnClickListener {             toggleDrawer()         }     }      private fun toggleDrawer(){         if(drawer_layout_main.isDrawerOpen(GravityCompat.START)){             drawer_layout_main.closeDrawer(GravityCompat.START)         } else {             drawer_layout_main.openDrawer(GravityCompat.START)         }     }      private fun setUpActionBar(){          setSupportActionBar(toolbar_main_activity)          toolbar_main_activity.setNavigationIcon(R.drawable.ic_action_navigation_menu)          toolbar_main_activity.setNavigationOnClickListener {             toggleDrawer()         }          getSupportActionBar()!!.setDisplayShowTitleEnabled(false)      }