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

public class MainActivity extends AppCompatActivity {

    private  WebView web;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        web = (WebView) findViewById(R.id.web);
        web.setWebViewClient(new WebViewClient());
        web.loadUrl("https://site.com");
        web.getSettings().setJavaScriptEnabled(true);
    }

    @Override
    public void onBackPressed() {
        if (web.canGoBack()) {
            web.goBack();
        } else {
            super.onBackPressed();
        }
    }
}

// В этой переменной у нас хранится адрес сайта
String site = "http://site.com/";

Uri siteUri = Uri.parse(site);

// Создаём интент
Intent openLinkIntent = new Intent(Intent.ACTION_VIEW, siteUri);

// Открываем в браузере
startActivity(openLinkIntent);

private class MyWebViewClient extends WebViewClient {
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        if (Uri.parse(url).getHost().equals("www.example.com")) {
            // This is my web site, so do not override; let my WebView load the page
            return false;
        }
        // Otherwise, the link is not for a page on my site, so launch another Activity that handles URLs
        Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
        startActivity(intent);
        return true;
    }
}

WebView myWebView = (WebView) findViewById(R.id.webview);
myWebView.setWebViewClient(new MyWebViewClient());