Can data from HTML forms be extracted into an Android app when utilizing webView?

Creating a simple HTML form for collecting user input, which is then displayed in a paragraph using both HTML and JavaScript when a button is clicked. The form takes the user's name through a text box: This is the original HTML code:

<!DOCTYPE html>
<html>
<body>
<p> Enter your name to win a game console! Winners will be announced in 4 days.</p>
Type your name here: <input id="thebox" type="text" name="value" value=""><br>

    <button onclick="myFunction()">Try it</button>

    <p id="demo"></p>

    <script>
    function myFunction() {
        var x = document.getElementById("thebox").value;
        document.getElementById("demo").innerHTML = x;
    }
    </script>

    </body>
    </html>

UPDATED FORM

<form name="albert" action="" method="POST">

 <label for="firstname"> First Name </label>
 <br /><br />

 <input type="text" name="firstname" id="firstname" />

 <input type="submit" name="sbumit" value="Submit" />


</form>

I am attempting to retrieve the value of the input box "thebox" in Android on button click. I have tried various methods involving injecting a JS file, but my lack of expertise in JS has led to unsuccessful attempts. Here is the content of my inject.js file:

document.getElementsByTagName('form')[0].onsubmit = function () {
    var objAccount;
    var str = '';
    var inputs = document.getElementsByTagName('thebox');
    for (var i = 0; i < inputs.length; i++) {
        if (inputs[i].name.toLowerCase() === 'thebox') {
            objAccount = inputs[i];
        }
    }
    if(objAccount != null) {
        str += objAccount.value;
    }
    window.AndroidInterface.processHTML(str);
    return true;
};

Following the instructions, I attempted to modify my MainActivity in Android with the following code:

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        WebView webView = new WebView(this);
        this.setContentView(webView);

        // enable javascript
        WebSettings webSettings = webView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        webView.addJavascriptInterface(new JavaScriptInterface(), "AndroidInterface");

        // catch events
        webView.setWebViewClient(new WebViewClient(){
            @Override
            public void onPageFinished(WebView view, String url) {
                try {
                    view.loadUrl("javascript:" + buildInjection());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });

        webView.loadUrl("http://someurl.com");
    }

A nested class created inside the MainActivity:

class JavaScriptInterface {
        @JavascriptInterface
        public void processHTML(String formData) {
            Log.d("AWESOME_TAG", "form data: " + formData);
        }
    }

The method responsible for injecting the code:

private String buildInjection() throws IOException {
        StringBuilder buf = new StringBuilder();
        InputStream inject = getAssets().open("inject.js");// file from assets
        BufferedReader in = new BufferedReader(new InputStreamReader(inject, "UTF-8"));
        String str;
        while ((str = in.readLine()) != null) {
            buf.append(str);
        }
        in.close();

        return buf.toString();
    }

I am looking to extract values from an HTML form shown in a WebView on Android. Is this achievable? If so, how can I do it and in which variable will the value be stored? Your explanation would be greatly appreciated. Thank you.

Answer №1

    WebView myBrowser = (WebView) view.findViewById(R.id.webChart);
    myBrowser.getSettings().setJavaScriptEnabled(true);
    myBrowser.addJavascriptInterface(new WebAppInterface(getActivity()), "Android");
    myBrowser.loadUrl("file:///android_asset/yourHtmlFileName.html");

Include the following interface class, WebAppInterface

public class WebAppInterface {
 Context myContext;
 String myData;

 WebAppInterface(Context context){
    this.myContext = context;
 } 


 @JavascriptInterface
 public void sendData(String data) {
    //Get and process the string value
      this.myData = data;
 }
}

Your HTML code to handle data

 function loadChartData() {
  var x = document.getElementById("thebox").value;
   Android.sendData(x);
 }

Call this function when the HTML button is clicked in the Android WebView.

UPDATE

1) By default, JavaScript is disabled in the WebView. To enable it, access the settings of the WebView and setJavaScriptEnabled(true); to true.

2) To create the interface between your JavaScript code and your Android code, you must create a Javacript interface class.

3) Bind the interface between your JavaScript code and Android code by passing the reference of the interface class and an interface name that your JavaScript can call to access the class.

4) Pass the file path of the HTML file to be loaded into the WebView (myBrowser).

5) Create the interface class as shown above (WebAppInterface).

For more details, please refer to https://developer.android.com/guide/webapps/webview.html

6) In the HTML file, create a button and add a click listener to that button. Call the sendData("your value") function with the interface name (in this case, Android).

That's all! You can now pass values from HTML to your Android code.

Answer №2

A great way to retrieve webpage content is by using JavaScript in conjunction with the webview jsInterface to transfer the content back to your Java code.

Check out this Github project, alongside this helpful answer and this informative article.

final Context myApp = this;

/* An instance of this class will be registered as a JavaScript interface */
class MyJavaScriptInterface
{
    @JavascriptInterface
    @SuppressWarnings("unused")
    public void processHTML(String html)
    {
        // Perform necessary processing on the retrieved HTML
    }
}

final WebView browser = (WebView)findViewById(R.id.browser);
/* Enable JavaScript for functionality */
browser.getSettings().setJavaScriptEnabled(true);

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

/* Set the WebViewClient BEFORE loading the URL */
browser.setWebViewClient(new WebViewClient() {
    @Override
    public void onPageFinished(WebView view, String url)
    {
        /* Inject JavaScript into the loaded page */
        browser.loadUrl("javascript:window.HTMLOUT.processHTML('<head>'+document.getElementsByTagName('html')[0].innerHTML+'</head>');");
    }
});

/* Load the desired webpage */
browser.loadUrl("http://lexandera.com/files/jsexamples/gethtml.html");

I hope this information proves useful.

Answer №3

To achieve the desired functionality for forms with method "GET," one can simply override the shouldOverrideUrlLoading method. This solution is effective when the URL was loaded using the webview.loadUrl() method.

private class CustomWebViewClient extends WebViewClient {
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) { 
        // Handling form submission URL like "data:,?firstname=SomeInput&sbumit=Submit"
        if (URLUtil.isDataUrl(url)) {
            url = url.replace(":,?", ":/?"); // Adjusting URL for proper parsing
            Uri uri = Uri.parse(url);

            // Extracting parameters by field name
            String firstname = uri.getQueryParameter("firstname");

            // Taking control of handling this URL ourselves 
            return true;
        }

        return super.shouldOverrideUrlLoading(view, url);
    }
}

Answer №4

For seamless communication between a webView and native Android, here's a straightforward approach: Within your JavaScript code, initiate an onClick event on the button to trigger a URL call that includes your required text, for example, myPrefix://myData. In the Android side of things,

webView.setWebViewClient(new WebViewClient()
{
   @Override
   public boolean shouldOverrideUrlLoading(final WebView view, final String url) 
    {
     if(url.startsWith("myPrefix://")) 
      {
       //Retrieve your data by parsing the URL
       return true;
      }
 return false;

});

Answer №5

@Shariq While many individuals have already provided answers to this question, I believe you are seeking further clarification on how data flows from a webview to Android within the code. To save space and avoid redundancy, I will skip reiterating information that has already been covered:

(Referring to your existing code for clarity) To enhance your understanding, follow these steps within the code:

Step 1:

We must define a method on the Android side capable of receiving data from the webview

@JavascriptInterface
//The 'formData' variable receives data from the webview 
public void processHTML(String formData) {
    Log.d("AWESOME_TAG", "form data: " + formData);
}

Now, the value is accessible in the Java Android context.

Step 2:

Below are your HTML code snippets (for the webview). If the URL being accessed in the webview belongs to you, you can insert these codes into the HTML page. Even if accessing a third-party URL, you can inject this JS code into the webview with a simple line of code:

...
//Partial code
webView.load("javascript:function myFunction() { var x = document.getElementById('thebox').value; Android.processHTML(x); } myFunction();";
... 

Here's what's happening: Variable 'x' in JS holds the necessary value, which is then sent to the Android context through the method call Android.processHTML(x)

This explanation should provide you with a clearer insight into the process

Answer №6

Absolutely! You can achieve that. Here's a code snippet for you to try:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.web_view_layout);
    WebView webView = (WebView) findViewById(R.id.webView);
    webView.getSettings().setPluginState(WebSettings.PluginState.ON);
    WebSettings webSettings = webView.getSettings();
    webSettings.setJavaScriptEnabled(true);
    try {
        progressDialog = new ProgressDialog(ActivityName);
        progressDialog.setMessage("Loading.."); 
        progressDialog.setCancelable(false);
        webView.setWebViewClient(new MyWebViewClient());
        webView.loadUrl(YOUR_URL);
    } catch (Exception e) {
        e.toString();
    }
}

private class MyWebViewClient extends WebViewClient {

    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
       view.loadUrl(url);
       progressDialog.dismissProgress();
       return true;
    }

    @Override
    public void onPageFinished(WebView view, String url) {
        progressDialog.dismissProgress();
    }
}

Answer №7

To extract data from a WebView, you can intercept alert messages using WebChromeClient.

Implement the following code snippet:

mWebview = (WebView)findViewById(R.id.yourwebviewlayout);
final class YourWebChromeClient extends WebChromeClient {
                @Override
                public boolean onJsAlert(WebView view, String url, String message, JsResult result) {
                    Toast.makeText(getApplicationContext(),
                            "alert message =  " + message,
                            Toast.LENGTH_SHORT).show();
                    result.confirm();
                    return true;
                }
            }
mWebview.setWebChromeClient(new YourWebChromeClient());

Answer №8

This code snippet features the best JavaScript injection method I have come across, as it effectively captures data from all forms upon submission.

document.getElementsByTagName("form")[0].addEventListener("submit", myFunction);
function myFunction()
{
    var data="";
    var inputs = document.forms[0].getElementsByTagName('input');
    for (var i = 0; i < inputs.length; i++) {
        var field = inputs[i];
        if (field.type != 'submit' && field.type != 'reset' && field.type != 'button')
        data += '' + field.name + '=' + field.value+'\n';
    }
    window.AndroidInterface.processHTML(data);
    return true;
}

Answer №9

These are the two essential steps:

1- Locate the specific element by its ID or Class

 getElement = "(function() { " +
                        "return document.getElementById('content').innerHTML;" +
                        "})()"

2- Insert the following code inside onPageLoaded:

view.executeScript(getElement) { 
                        console.log("Content loaded: $data")}

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