Adding a Listener to a HTMLBrowserPanel Component

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H.A. Camp
H.A. Camp il 19 Apr 2018
Modificato: H.A. Camp il 27 Feb 2020
I've recently come across the need to provide users with HTML/Javascript pages and conduct calculations based on user responses. Currently, I'm displaying HTML content in a HTMLBrowserPanel component, then parsing HTML fields after the user clicks a form button. (Let's presume this is a rational design choice -- I recognize I could use MATLAB uicontrol objects, but in this case it's more feasible to display HTML content for reasons I don't want to get into.)
In order to parse the form's contents, I'm periodically polling a hidden field on the form to see if it changes values. This is functional, but not ideal -- I'd rather attach a listener object to the form field that triggers a MATLAB response (like we would for any uicontrol object). However, I cannot seem to figure out how to attach a listener to the HTML field object. Is this even possible?
Here's a simplified code example showing how I'm capturing information. Users are presented with a form field and a submit button. When 'submit' is clicked, the 'Monitoring Flag' field flips from 0 to 1. MATLAB is polling the flag field every 1/4 second and when it changes, it knows to parse the form data. Again, the question is: can I attach a listener object to the HTML form field rather than polling the field every so often?
% Create figure
hFig = figure('Pos', [0 0 1420 1024], 'Name', 'Test Window', 'NumberTitle', 'off', 'Units', 'norm', 'Menu', 'none');
movegui(hFig, 'center');
% Add Browser object
[browserPanel, bContainer] = javacomponent(com.mathworks.mlwidgets.html.HTMLBrowserPanel, [], hFig);
set(bContainer, 'Units', 'norm', 'Pos', [0 0 1 1]);
% Navigate to a URL...
% htmlAddress = 'C:\Code\test.html';
% browserPanel.setCurrentLocation(htmlAddress);
% ...Or load html data directly
htmlData = {
'<!DOCTYPE html>'
'<html lang="en">'
' <head>'
' <meta charset="utf-8">'
' <meta http-equiv="X-UA-Compatible" content="IE=Edge" />'
' <title>Test Window</title>'
' </head>'
' <body>'
' <form name="testForm">'
' MATLAB Input Test: <input id="testField" name="testVar"></input>'
' <button type="button" onClick="matlab()">'
' Submit'
' </button>'
' </form>'
' <form name="matForm">'
' Monitoring Flag: <input id="matlab" name="matVar" value="0"></input>'
' <button>Reset</button>'
' </form>'
' </body>'
' <script type = "text/JavaScript">'
' function matlab() {'
' document.matForm.matVar.value = 1;'
' }'
' </script>'
'</html>'
};
browserPanel.setHtmlText(strjoin(htmlData));
% Get JxBrowser BrowserView and Browser objects
if verLessThan('matlab', '8.6')
error('JxBrowser BrowserView is not available in MATLAB R2015a or earlier');
elseif verLessThan('matlab', '9.1')
browserView = browserPanel.getComponent(0).getComponent(0).getComponent(0).getComponent(0);
else
browserView = browserPanel.getComponent(0).getComponent(0).getComponent(0);
end
browser = browserView.getBrowser();
% Wait until browser finishes loading
while browser.isLoading
pause(0.1);
end
% Check Browser
interrupt = false;
tic; % Just so the demo ends nicely
while ~(interrupt) || (toc > 60)
pause(0.25);
if ~(browser.isLoading)
matObj = browser.getDocument(1).findElement(com.teamdev.jxbrowser.chromium.dom.By.id('matlab'));
if ~isempty(matObj)
matVal = matObj.getValue;
matVal = matVal.toCharArray.';
if ~isequal(matVal, '0')
testObj = browser.getDocument(1).findElement(com.teamdev.jxbrowser.chromium.dom.By.id('testField'));
testVal = testObj.getValue;
testVal = testVal.toCharArray.';
fprintf('MATLAB value detected: %s\n', testVal);
interrupt = true;
end
end
end
end

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