How to add an activity to the side menu?

Question

Android

activity:

package com.example.admin.myapplication;

import android.app.ProgressDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.activity_main);
        WebView webView = new WebView(MainActivity.this);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.getSettings().setPluginState(WebSettings.PluginState.ON);

        //---you need this to prevent the webview from
        // launching another browser when a url
        // redirection occurs---
        webView.setWebViewClient(new Callback());

        String pdfURL = "http://www.uoipd.by/files/files/studentu/raspisanie/dnevnoe/3kurs.pdf";
        webView.loadUrl(
                "http://docs.google.com/gview?embedded=true&url=" + pdfURL);

        setContentView(webView);
    }

    private class Callback extends WebViewClient {
        @Override
        public boolean shouldOverrideUrlLoading(
                WebView view, String url) {
            return (false);
        }
    }


}

in another activity to launch this window. where is the side menu itself (more precisely, the items) navigation drawer.

if (id == R.id.kurs1) {

            startActivity(new Intent(this, kurs1.class));

this code is responsible for opening the pdf in the application window.
How can I make my schedule window pop up when I click in the navigation drawer, let's say course 3?
if I add everything as I want, then the error is:

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.admin.ulmxsd, PID: 23242
                  android.content.ActivityNotFoundException: Unable to find explicit activity class {com.example.admin.ulmxsd/com.example.admin.ulmxsd.kurs1}; have you declared this activity in your AndroidManifest.xml?
                      at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1794)
                      at android.app.Instrumentation.execStartActivity(Instrumentation.java:1512)
                      at android.app.Activity.startActivityForResult(Activity.java:3930)
                      at android.support.v4.app.BaseFragmentActivityJB.startActivityForResult(BaseFragmentActivityJB.java:48)
                      at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:77)
                      at android.app.Activity.startActivityForResult(Activity.java:3890)
                      at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:859)
                      at android.app.Activity.startActivity(Activity.java:4213)
                      at android.app.Activity.startActivity(Activity.java:4181)
                      at com.example.admin.ulmxsd.MainActivity.onNavigationItemSelected(MainActivity.java:85)
                      at android.support.design.widget.NavigationView$1.onMenuItemSelected(NavigationView.java:156)
                      at android.support.v7.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:817)
                      at android.support.v7.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:156)
                      at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:964)
                      at android.support.design.internal.NavigationMenuPresenter$1.onClick(NavigationMenuPresenter.java:332)
                      at android.view.View.performClick(View.java:5204)
                      at android.view.View$PerformClick.run(View.java:21153)
                      at android.os.Handler.handleCallback(Handler.java:739)
                      at android.os.Handler.dispatchMessage(Handler.java:95)
                      at android.os.Looper.loop(Looper.java:148)
                      at android.app.ActivityThread.main(ActivityThread.java:5417)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Answer 1

Well, what's wrong is written

android.content.ActivityNotFoundException: Unable to find explicit activity class {com.example.admin.ulmxsd/com.example.admin.ulmxsd.kurs1}; have you declared this activity in your AndroidManifest.xml?