CODEWITHSUNDEEP
javascriptjavaandroidweb-crawler
Abhishek Aggarwal
Abhishek Aggarwal

Reputation: 89

Extract text from a Webview

I basically want to extract text from inside a webpage that is already loaded into the Webview of the app.

Just as a trial, I built an app to count the occurrence of the Rupee symbol(₹) with the help of method from this post.

See the screenshot: App's Screenshot

But I am not able to make it work. The TextView should show the number of '₹' symbols on the webpage but it stays unchanged.

I am a noob at Android and would highly appritiate any help :)

This is my code: (MainActivity)

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

public class MainActivity extends AppCompatActivity {

    static TextView count;

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

        count = (TextView) findViewById(R.id.textView);

    /* An instance of this class will be registered as a JavaScript interface */
        class MyJavaScriptInterface {
            @JavascriptInterface
            @SuppressWarnings("unused")
            public void processHTML(String html) {
                // process the html as needed by the app

                int occ = 0;

                for(int i = 0 ; i < html.length() ; i++)
                    if(html.charAt(i) == '₹')
                        occ++;

                MainActivity.count.setText(occ);
            }
        }

        final WebView browser = (WebView) findViewById(R.id.browser);

        /* JavaScript must be enabled if you want it to work, obviously */
        browser.getSettings().setJavaScriptEnabled(true);

        /* Register a new JavaScript interface called HTMLOUT */
        browser.addJavascriptInterface(new MyJavaScriptInterface(), "HTMLOUT");

        /* WebViewClient must be set BEFORE calling loadUrl! */
        browser.setWebViewClient(new WebViewClient() {
            @Override
            public void onPageFinished(WebView view, String url) {

                /* This call inject JavaScript into the page which just finished loading. */
                browser.loadUrl("javascript:HTMLOUT.processHTML(document.documentElement.outerHTML);");

            }
        });

        /* load a web page */
        browser.loadUrl("https://www.google.co.in/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=buy+chocolate");
    }
}

Upvotes: 0

Views: 1721

Answers (2)

RatherBeSailing
RatherBeSailing

Reputation: 311

While the provided code is correct Kotlin supports a simpler version

val webView = findViewById<WebView>(R.id.webView)
webView.getSettings().setJavaScriptEnabled(true)
webView.webViewClient = object : WebViewClient() {
    override fun onPageFinished(view: WebView?, url: String?) {
        super.onPageFinished(view, url)
        webView.evaluateJavascript("document.body.textContent") { text ->
            var count = 0
            for (ch in text) if (ch == 'a') count++
            Log.d(TAG, "Webpage contains $count a's")
        }
    }
}
webView.loadUrl(downloadURL)

The single line evaluateJavaScript replaces the (longer) MyJavaScriptInterface

Note: the provided code uses "document.body.textContent" rather than "document.documentElement.outerHTML". Other values are possible including document.body.innerHTML and document.body.outerHTML

Upvotes: 0

user5734311
user5734311

Reputation:

Got it to work. Two small problems:

  1. You're making a UI call in the function called by JavaScript. That's not allowed. Replace MainActivity.count.setText(occ); with 

    runOnUiThread(new Runnable() {
    @Override
    public void run() {
        count.setText(String.valueOf(occ));
    }
});
  2. This code already fixes the 2nd issue: calling setText(int) expects a resource ID, thus you need to convert to a String first.

(You need to also remove static from your declaration of count)

Upvotes: 1

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