I am not sure how Java's regexp is implemented. If it's implemented in Java
code, that would be quite slow.
Regexp in WebView's JavaScript is implemented in native code. I have some
complicated regexps to parse 600K ~100K HTML files, and they usually finish
in 100ms or less (or at least not long enough for me to notice)
Actually, using JavaScript in WebView is not so hard. Here's how to do it
(1) Create a file called asset/foo.html like this:
-----------------------------------------------------------------
<html>
<head>
<META HTTP-EQUIV="content-type" CONTENT="text/html; charset=utf-8">
</head>
<body>
<script language="javascript">
var string = window.js.getInput() + ""; // Note: you need the + ""
// to make it into
a JavaScript string
string=string.replace(/A/, "a");
window.js.output(string);
</script>
</body>
</body></html>
-----------------------------------------------------------------
(2) In Java:
mWebView = (WebView)findViewById(R.id.foo);
WebSettings webSettings = mWebView .getSettings();
webSettings.setSavePassword(false);
webSettings.setSaveFormData(false);
webSettings.setJavaScriptEnabled(true);
webSettings.setSupportZoom(false);
Object js = new Object() {
public String getInput() { return "AAbbAA";}
public void output(String s) { /* s == "aabbaa" */ }
};
mWevView.addJavascriptInterface(js, "js");
mWebView.loadUrl("file:///android_asset/foo.html");
If you're activity is in BG, I think you can just "new" a WebView and use it
without displaying it. Actually I do the same in my app -- I have two
WebViews -- one for parsing the HTML files, the other for displaying them
On Wed, Feb 18, 2009 at 2:45 PM, Mariano Kamp <mariano.k...@gmail.com>wrote:
>
> That sounds interesting. I subscribed to your blog and look forward to
> the results.
>
> I am doing the processing as a background activity and don't feel that
> WebView is a good fit for me here.
>
> I just use the regular Java 1.4+ regexps. And I have to say that I
> wouldn't recommend that. I will very likely build my own parser for
> image, stylesheet and background-image tags in the future.
> I use Matcher.find() to iterate over the html/stylesheet file.
> Unfortunately this can lead to 100% CPU indefinitely
> (http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4771934).
>
> Cheers,
> Mariano
>
> On Wed, Feb 18, 2009 at 10:18 PM, Mattaku Betsujin
> <mattaku.betsu...@gmail.com> wrote:
> > Hi Mariano,
> >
> > Not directly related to your question, but how do you use regexp? Do you
> use
> > the Java API?
> >
> > I am doing a hobby project that's similar to your app. I use regexp to
> strip
> > all the ads from web pages and reformat them for better display. I
> actually
> > use a WebView to run the regexp using JavaScript. It's a lot easier to
> code
> > than Java. I could add support for a new site (such as yahoo news) in a
> > couple of hours.
> >
> > I have posted some screen shots at
> >
> > http://nubinewsblog.blogspot.com/
> >
> > I will upload to Android Market after a few more days of testing. Source
> > will be available on SourceForge under Apache 2.
> >
> >
> > On Wed, Feb 18, 2009 at 11:32 AM, Mariano Kamp <mariano.k...@gmail.com>
> > wrote:
> >>
> >> Hi,
> >>
> >> I wrote an app that acts as a Google Reader client. It downloads an
> XML
> >> from Google, parses it and afterward analyzes web pages with regular
> >> expressions to find image and stylesheet tags to make the pages
> available
> >> offline.
> >>
> >> So far so good. The problem is the above mentioned tasks are pretty
> CPU
> >> intensive and I also use gesture to mark items as read etc. The gesture
> >> detection gets really bad when done during the synchronization phase
> (see
> >> above).
> >>
> >> Those tasks from the synchronization phase are not time critical. I
> >> would like to tell the OS that the UI thread is far more important than
> my
> >> background thread. I just don't know how to do that efficiently.
> >>
> >> In an ideal world the OS would take care of that for me, so I started
> out
> >> with "Thread.currentThread().setPriority(Thread.MIN_PRIORITY);". That
> didn't
> >> have any obvious effect. Then I sprinkled "Thread.yield()" in all major
> >> areas, in particular in the loops. But that also didn't seem to have
> much of
> >> an effect. Before I know start to to all kind of silly stuff, I'd like
> to
> >> pick your brains on how this is done properly?
> >>
> >> I am absolutely willing to use Thread.sleep(20) in some of the places I
> >> use Thread.yield. A little bit of a pause might be a good thing for the
> >> battery heat and power consumption, but I can't let the pause get really
> >> long, e.g. 250ms, because I wouldn't get any work done and would keep
> the
> >> phone awake unnecessarily (I am holding a partial wake lock). On the
> other
> >> hand I am not sure if a small pause now and then, like a 20ms pause,
> then
> >> 50ms work, won't take too much a toll on the CPU for switching tasks and
> in
> >> the end burn the battery too fast.
> >> Also, what seems like a good pause for the G1 might be not so much of a
> >> good idea on different hardware, like a Netbook.
> >>
> >> I could try to set the Priority of the UI thread to MAX_PRIORITY, but
> as
> >> I didn't start the thread, I feel that it's not my business to change
> its
> >> priority.
> >>
> >> I could check if the screen is off. If that is the case high
> resolution
> >> touch events are not so likely so I could revert all the measurement
> from
> >> above until the screen comes on again.
> >>
> >> So what do you think? I guess I am not the only one with the problem,
> or
> >> am I?
> >>
> >> Cheers,
> >> Mariano
> >>
> >>
> >
> >
> > >
> >
>
> >
>
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