public class MainActivity extends AppCompatActivity {
    private WebView webView;
    public ValueCallback<Uri[]> uploadMessage;
    public static final int REQUEST_SELECTED_FILE = 100;
    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent intent) {
        super.onActivityResult(requestCode, resultCode, intent);
        if (requestCode == REQUEST_SELECTED_FILE) {
            if (uploadMessage == null) return;
            uploadMessage.onReceiveValue(WebChromeClient.FileChooserParams.parseResult(resultCode, intent));
            uploadMessage = null;
        }
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        webView.setWebChromeClient(new WebChromeClient(){
            public boolean onShowFileChooser(WebView view, ValueCallback<Uri[]> filePathCallback,WebChromeClient.FileChooserParams fileChooserParams){
                if(uploadMessage != null){
                    uploadMessage.onReceiveValue(null);
                }
                uploadMessage = filePathCallback;
                Intent intent;
                intent = fileChooserParams.createIntent();
                try{
                    startActivityForResult(intent,REQUEST_SELECTED_FILE);
                } catch (ActivityNotFoundException e){
                    uploadMessage = null;
                    return false;
                }
                return true;
            }
        });
    }
}

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        webView = findViewById(R.id.webView);
        if(isNetworkConnected(this)){
            webView.loadUrl("https://site.ru/");
        }
        else{
            webView.loadUrl("file:///android_asset/lost.html");
        }
    }
    private boolean isNetworkConnected(Context context) {
        ConnectivityManager cm =
                (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
        return activeNetwork != null && activeNetwork.isConnectedOrConnecting();
    }
}

public class MainActivity extends AppCompatActivity {
    private WebView webView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        webView = findViewById(R.id.webView);
        webView.setWebViewClient(new CustomWebViewClient());
    }
    private class CustomWebViewClient extends WebViewClient{
        @Override
        public void onPageFinished(WebView view, String url) {
            String username = "";
            String cookies_all = CookieManager.getInstance().getCookie(url);
            if (cookies_all != null) {
                String[] cookies_array = cookies_all.split(";");
                for (String cookie : cookies_array) {
                    String[] cookie_array = cookie.split("=");
                    if (cookie_array[0].contains("users")){
                        String[] user_data = cookie_array[1].split("%");
                        username=user_data[0];
                        if (!Objects.equals(username, "")) {
                            Toast.makeText(view.getContext(), username, Toast.LENGTH_LONG).show();
                        }
                    }
                }
            }
            super.onPageFinished(view, url);
        }
    }
}

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        setTheme(R.style.Theme_Test);
        super.onCreate(savedInstanceState);
    }
}

public class MainActivity extends AppCompatActivity {
    private WebView webView;
    private ProgressBar spinner;
    String ShowOrHideWebViewInitialUse = "show";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        webView = findViewById(R.id.webView);
        spinner = findViewById(R.id.progress);
        webView.setWebViewClient(new CustomWebViewClient());
    }
    private class CustomWebViewClient extends WebViewClient{
        @Override
        public void onPageStarted(WebView view, String url, Bitmap favicon){
            spinner.setVisibility(View.VISIBLE);
            if(ShowOrHideWebViewInitialUse.equals("show")){
                view.setVisibility(View.INVISIBLE);
            }
        }
        @Override
        public void onPageFinished(WebView view, String url){
            ShowOrHideWebViewInitialUse = "hide";
            spinner.setVisibility(View.GONE);
            view.setVisibility(View.VISIBLE);
            super.onPageFinished(view, url);
        }
     }
}

public class MainActivity extends AppCompatActivity {
    private WebView webView;
    private SwipeRefreshLayout swipeRefreshLayout;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        webView = findViewById(R.id.webView);
        swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                swipeRefreshLayout.setRefreshing(true);
                new Handler().postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        swipeRefreshLayout.setRefreshing(false);
                        webView.reload();
                    }
                },3000);
            }
        });
        swipeRefreshLayout.setColorSchemeColors(
                getResources().getColor(R.color.orange)
        );
    }
}

public class MainActivity extends AppCompatActivity {
    private WebView webView;
    @Override
    public void onBackPressed(){
        if(webView.canGoBack()){
            webView.goBack();
        }
        else{
            super.onBackPressed();
        }
    }
}