如何使用Jsoup监听WebView中的元素更改？

Question

I'm trying to retrieve a value of a hidden input HTML element using Jsoup, the value is "none" when the user isn't logged in and when the user is logged in (in the WebView app) it gives their username, i successfuly was able to fetch the element i want using Jsoup but i'm trying to listen on the WebView to fetch the value of the element when they're actually logged in and the element's value is different from "none", i used the onPageStarted and onPageFinished with no avail as they keep sending me the original value (none) when the user isn't logged in yet, this is my MainActivity

MainActivity.java

package com.gci.gestioncapteursincendie;

import android.graphics.Bitmap;
import android.os.AsyncTask;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.webkit.WebSettings;
import android.webkit.WebView;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.iid.FirebaseInstanceId;
import com.google.firebase.iid.InstanceIdResult;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

import java.io.IOException;

public class MainActivity extends AppCompatActivity {
    WebView webView;
    String webView_url;

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

       //storing webView defined in activity_main.xml inside a WebView instance webView
        webView = (WebView) findViewById(R.id.webview);

        //enabling js in the WebView
        WebSettings webSettings = webView.getSettings();
        webSettings.setJavaScriptEnabled(true);


        webView.setWebViewClient( new WebViewClientImpl(this){

            @Override
            public void onPageStarted(WebView view, String url, Bitmap favicon) {
                super.onPageStarted(view, url, favicon);
                new MyTask().execute();

            }
        });

        //defining the website the webView loads when the app is launched
        webView.loadUrl("http://gestioncapteursincendie.herokuapp.com");
        webView_url = webView.getUrl();




        FirebaseInstanceId.getInstance().getInstanceId()
                .addOnCompleteListener(new OnCompleteListener<InstanceIdResult>() {
                    @Override
                    public void onComplete(@NonNull Task<InstanceIdResult> task) {
                      if(task.isSuccessful()){
                          String token = task.getResult().getToken();
                          System.out.println("token: "+token);
                        }
                        else
                      {
                          System.out.println("Token Not Generated");
                      }
                    }
                });

        }
    private class MyTask extends AsyncTask<Void, Void, String> {

        @Override
        protected String doInBackground(Void... params) {
            Document doc = null;
            Element x = null;
            try {
                doc = Jsoup.connect(webView_url).get();
                x = doc.getElementById("loggedin");
            } catch (IOException e) {
                e.printStackTrace();
            }

            System.out.println("Webview url= " +webView_url);
            System.out.println("loggedin= " + x);
            return x.val();
        }


        @Override
        protected void onPostExecute(String result) {
            System.out.println("RESULT: "+result);
        }
    }
        }

Answer 1

Jsoup is not a browser and it is not synchronized with the WebView (which is basically a browser!)

So you would only get the same content of the the WebView, if the full state of the site is reflected in the URL, which I very much doubt, because this would be very insecure for the website.

So here is what happens in your code I think (I did not carefully analyze it):

1. You create a WebView
2. In that Webview you log in. For that usually form POST requests are sent to the web server and the web server responds with setting a couple of cookies in the browser so that you maintain the logged in state for the next requests. The URL of the page however does not change in a way that would let you in to take over that session.
3. You create a new session with the web server by connecting to it with JSoup's http connection feature. The web server responds with a site that of course has no logged in user.
4. You parse that page -> not logged in

What you need to do:

1. same as above
2. same as above
3. find the WebView function that retrieves the HTML of the currently loaded page and use it to put all content into a string
4. parse the string using JSoup. Do not use the JSoup connect method.
5. Find what you were looking for