RemoteDroid

So I was trying to implement a ListView in Android the other day where the items would have varying levels of alpha transparency in the background. For some reason, every item’s background would go black whenever the ListView scrolled. (presumably for performance reasons.) Googling around yielded not much, but a co-worker had solved this problem in a previous app. Looking through the layout file, I saw that the android:cacheColorHint was set in his layout, but not mine. Adding it solved the problem.

Basically, just adding android:cacheColorHint=”#00000000″ to the ListView enabled transparency while scrolling.

Since I’ve been banging my head against this for the last 12 hours, I thought I’d post a solution here, so other people might stumble across it and benefit.

I ran into two memory leaks in Android itself in WebView, and Typeface. Both are because of bugs in the OS, so if you’re encountering memory leaks, and all your code looks pretty watertight, (Meaning you never pass Activities as a Context to a View, and you use WeakReferences for static inner classes) you might be hitting one of these.

The first bug for WebView is described here.

The solution is just to call destroy() on your webview in the onDestroy() method of the containing activity, then set any references to that WebView to null, just in case. The app I’m working on is webview heavy, so this was causing some grief.

The second bug for Typeface is described here.

The issue was that I was creating a new Typeface from assets in the onCreate method of my activity. Every time I did this, it was allocating around 700k of memory, which then never got released. Big, big problems. The solution in this case is to initialize the typeface object in a static class (You can subclass Application and stick it there if you want, but be aware that you can’t call getAssets() before the first activity gets it’s onCreate method called.) and then use that one instance for any TextViews you may have.

The only way I managed to figure out what was causing the leaks was to go into adb shell, and then use dumpsys meminfo. That showed me a whole lot of bad.

Android + Arduino wireless from Guus Baggermans on Vimeo.

Well damn!

Thanks to Nicolas Frenay, RemoteDroid now has some cool multitouch gestures. You can now use two fingers to scroll, just like a macbook, as well as clicking the onscreen mouse buttons, and dragging using the touchpad, just like you always wanted. He’s using reflection to find out if your phone supports multitouch, which means that 1.6 devices aren’t left totally out in the cold, and I don’t have to worry about maintaining two different branches.

One note for Nexus One users, the Nexus One apparently has some pretty serious multitouch problems, making click and drag a bit wonky. I’d advise sticking to tap-to-click and hold for dragging items around.

Another change is that I’ve removed the trackball as mouse functionality. Now clicking the trackball acts as a CTRL key, and moving the trackball acts as a scrollwhell, making it more like ConnectBot, and making the user experience a little bit more consistent.

Lastly, I’ve added better support for the soft keyboard. All keys, except for the ones that don’t have direct analogues on your regular keyboard now work. (long-press keys still aren’t supported) In the future, because of differing physical keyboard layouts between devices, I’m going to try to get RemoteDroid to recognize which device you’re using, and change what it sends depending on that, but for now, at least the soft keyboard should be pretty consistent.

One of the things I’ve always wanted to see in Flash has been support for UDP sockets. As anyone whose tried to write a real-time networked game knows, TCP/IP is just too slow for the sorts of fast-twitch reactions used for first-person shooters, or anything real-time at all.

Apparently, Adobe AIR 2.0 has now added support for UDP, and this post by Jeff Winder shows how he’s added accelerometer support to RemoteDroid, and is using it to control an Adobe AIR application. Check out the video below:

I’ve finally gotten around to open-sourcing RemoteDroid, and putting it up on Google code. You can get to it at:

http://code.google.com/p/remotedroid/

You’ll also always be able to find the latest .apk and server files there.

Part of my reason for open-sourcing it is that I’m just one person, with just one phone. Like or not, Android has already fragmented, and will probably fragment even more in the future, so support for every Android device out there will become increasingly difficult. That’s where open-source comes in.

I’m looking for contributors to help debug on platforms other than the G1. There are several issues that I simply can’t fix because I have no way of replicating them. Additionally, other people might think of features that I haven’t or haven’t had time to implement. If nothing else, people might be curious about how RemoteDroid works, and open-source is a great way of dealing with these issues.

If you’d like to help, feel free to email me at admin@remotedroid.net, or use the feedback form.

I just wanted to get this out there, Android’s browser caches like a madman. It completely ignores POST variables. This is particularly relevant when doing AJAX calls. You can’t simply add a timestamp to POST and expect the Android browser to give you new page data. You have to append to timestamp to the GET query string.

Pragma: no-cache, and all the other server-side headers also have no effect as far as I can tell.

It makes sense though. Since the browser’s on a mobile network, and since they want to minimize network traffic as much as possible, caching is going to be extremely aggressive.

One of the head-scrathers about Android for me has been that when you open the keyboard on a device with a slide-out keyboard, the current activity is totally destroyed, then rebuilt again. I understand why it’s done, since all of a sudden, you’ve got a new resolution, and a new set of capabilities, but I never knew how to differentiate an orientation change from an Activity being destroyed because you’re going to a new Activity.

An example of this might be if you have a game thread, or some process going that you don’t want to have to shut down and restart just because you suddenly have to deal with a keyboard. The solution to this is Activity’s onRetainNonConfigurationInstance() method, as described here:

http://android-developers.blogspot.com/2009/02/faster-screen-orientation-change.html

Now you know!

It’s called a Toast.

Here’s a quick little tutorial on how to use it.
quick alert tutorial

A quick list of 3rd party apps that really make the Android experience for me:

OI File Manager

There are several good file browsers out there, but I like the philosophy behind this one. I prefer the directories and folders metaphor over the idea of every app keeping it’s own list of files, a la iTunes, or the iPhone’s big list o’ apps home screen. This means access to the filesystem. At the moment, there isn’t a native file picker widget/view/whatever, so OpenIntents designed their file browser to provide that.

With that in mind, the next app is

Download Crutch

This just allows the Android browser to download any file type. Currently, it only downloads files that have corresponding apps. This is by design. Since Android doesn’t have a native file browser, if you were to download something without an app to manage it, you’d never be able to delete it. People will make new apps, and those apps will be able to deal with different files, therefore they need a way to tell the browser what the new file types are. I guess Download Crutch just tells the browser that it’ll handle everything.

Terminal Emulator

Because every computer needs a command line.

Connectbot

An SSH program for Android. If you have a Linux box running somewhere, you can just SSH into it, then use IRC, or any command line program you want. I think you can even use SSH tunneling, but I’m not sure.

Tetherbot

It takes some configuring, and it’s really only good for browsing the web, but when I happen to have my laptop with me, and there’s no wifi available, this app is indispensable. T-Mobile isn’t keen on tethering, so this app can’t be released on the market, but lucky for us, Google lets us install whatever the heck we want on our phones. Eventually, Google will allow us to write native apps, and we’ll hopefully start to see true tethering apps, (You can already do this if you’ve rooted your phone) but until then, this app works pretty well.

So basically, what I really want is a very small computer that also happens to be able to make phone calls. Netbooks won’t fit in my pocket, and don’t serve as phones. The iPhone’s soft keyboard bugs me, I don’t like it’s overly managed interface, and the fact that it’s completely tied to iTunes. Windows Mobile just blows, and Palm is somewhat outdated, so we’re left with Android.

At it’s heart, a mobile phone is just a computer, and computers at their heart, are supposed to be able to do just about anything that you can figure out how to tell them to do. These apps aren’t everyday use programs, but they go a long way towards providing the kind of flexibility that you should have out of these devices.