Task Killers have their purpose, but for the average person a task killer is not needed and can cause the phone to actually work worse than it would otherwise. They were needed back in the day when Android was in it's infancy but with the latest Android releases (2.1 and 2.2) they are not needed. If you need some sort of multitasking capability, simply holding the HOME button for a second will pull up a list of the last 6 applications you used.
If anyone wants a more in depth explanation in common terms (for the layman) of how Android manages tasks I can try and explain it. The above 4 links should explain it, but some may find it a bit more complex and won't be able to get their head around it to understand it.
When you close an application in Android (pressing the HOME button) the process is put into a suspended mode. If it is something that streams (like radio) then it will stay active but otherwise it is going to go to sleep essentially. If it is an app that requires syncing, it will wake up whenever that sync cycle comes up, otherwise it uses very little to no processor time. The app is still in memory, but if you were to load up something that needed more memory than what was available (a game for example) then Android would remove suspended applications from memory automatically until enough memory was available, no data is lost. Having items loaded in memory offers nothing but benefits as far as speed and resource usage is concerned. Unused memory is wasted memory.
This means that if you close an app and then 30 minutes open it up again it will open up much quicker than it did the first time (in many cases almost instantly) because it is already loaded into memory (unless something else pushed it out). When you use a Task Killer it kills he app and no matter what the next time you open it the app will have to load all of it's dependent services, images, caching data, etc. to load up again versus just reusing what is in memory already. These actions all require using active processor time and therefore require much more battery power to perform. So by constantly having to reload apps from scratch you are actually causing your battery to drain faster.
A much better solution to short battery life is to ensure you are turning off GPS, Wi-Fi, Bluetooth and 4G (if applicable) when you aren't using them. In addition, set email, news, stocks, Twitter, Facebook, etc. syncing to a longer update interval. By having them check for updates less often they will stay in that sleep mode longer and ultimately use less power being inactive. Live Wallpapers use more power when displayed, but when your wallpaper is not visible (like when you are in an Application, or the screen is off) the image is static and does not use more power. Instant Messaging applications like AIM, MSN, Yahoo, Google Talk, etc. all require a constant data connection and will not go to sleep like other apps. These will drain the battery quickly because they also prevent the Android System itself from going to sleep. Make sure you sign out of these applications when not using them. You can see how long the phone has been awake by going to Settings > About Phone > Battery, It will show your total uptime since it was turned on, and the time it has been awake and active. You can also see which applications have been using the battery the most.
TL;DR (too long; didn't read) - Don't use a task killer on Android just because someone told you to. Manage your app update intervals. Turn off GPS, WiFi, Bluetooth, and 4G when not in use. Avoid instant messaging applications like AIM, MSN, Yahoo and Google Talk.
Thanks for the post. I'll keep it bookmarked for all the times people argue with me on how Task killers are a gift from God. Ever since I read the Geekfor.me post when I first got my Hero and tried it for my self, I have been trying to tell people not to use them. Battery drainers and could sometimes cause the famous force closes.
I have my task killer set to kill applications that I never use, but somehow they are open (like Moxier Mail). It kills the tasks when the screen goes to sleep. I agree that managing radio connection is huge for improving the battery life. I use "Setting Profiles" to turn on Autosync for 5 minutes every hour and go into Airplane mode when at church. I also have a profile to control Wifi.
I'm not certain whether turning off the GPS will save battery. On my phone, it appears that the GPS is inactive unless the green GPS signal indicates otherwise. Does the GPS receiver use battery when it's not active? If the GPS indicator keeps flashing while you aren't using it (eg for navigation), perhaps it would be easier to manage the application that is calling for GPS (eg the Weather app). Setting the weather app so that it does not follow your location will help reduce GPS usage.
Message was edited by: beliving (saw a spelling error)
Task killers won't work properly in Android 2.2. This is because the team at Google decided the only way to stop the mistreatment of the kill command was to remove it. You can still stop tasks, but its more like a restart, which means you'll get worse battery life if you do it, since the app immediately needs to use processor power to get back to its original state. Don't use a task killer in 2.2. You'll only hurt your battery life. They really never did all that much for battery and were actually battery drainers in most cases. Its all placebo. Anyways, read the OP for more info on how they work and why they are bad.
As for GPS, from the way I understand it, you are correct in your assumptions. When not in use, it appears to have no effect. The main thing turning it off would do is prevent it from activating while using an app that wants to use it. A lot of ad supported apps have access to GPS for ad location targeting. This would drain your battery for no good reason. I personally don't turn it off for convenience reasons, but if I really needed more battery, I probably would just to prevent an unintentional activation.
That's a great write up on the task killer, Halcyion Commander. Thanks for the education. I've been using it as a matter of habit just to try to extend the battery life on my HTC Hero. If it makes no difference, then you just saved me a ton of time over the long haul.
I use the Task Killer, mainly being new and researching apps it was listed as one of the ones to have, so I have it and use it quite often on my Samsung Intercept. In having it, I found one app (that I didn't install) keeps running all the time. Amazon MP3, it came pre-loaded and I can't get rid of it. How do I uninstall this? I've tried upgrading and then uninstalling but it will only uninstall the upgrade. I don't like it, won't use it and really want it gone. Its like they are trying to force me to use it. If not for the Advanced Task Killer, I would not have ever known it was running as often as it does. If anyone has any suggestion as to how I can delete it or at least make it not run ever, I'd much appreciate.
Amazon MP3 is preinstalled on every Android phone I've seen. This is built in software, and the only way to remove it is to get root access on your phone and delete it manually. I wouldn't worry about it running in the background, as all its doing is keeping a service open to make sure you don't have any downloads pending. While it may not completely remove the service, there is a setting in the newer version that let's you stop it from automatically checking for downloads. It won't use any resources except for a small amount of memory either way. Read the above post and links if you want to know why programs running in the background aren't actively consuming anything more than memory, and how Android handles memory to ensure that that resource is well utilized. Don't worry about built in apps running in the background, it happens on every Android phone and without rooting it, you can't do anything about it. Killing it will use more resources than letting it stay there. If you have third party apps constantly running on startup that you don't think should be, you can try their settings, and if you are really worried, you can uninstall those. Hopefully in the future, Google will allow removal of any extra apps that aren't tied into the phone.
Before you complain about it being unfair, realize that virtually all phones have these kinds of built in software, including the iPhone. It doesn't have third party software built in, but you can't remove the music store from it either.
I really don't mind it being on the phone, as other things are on it that I will never use but its just that it keeps popping in the task that need to be turned off is whats bugging me. I did find and turn off the automatic download setting with help of technical support. I don't know if I'll go to that extreme of rooting the phone just to get rid of it just yet. It shouldn't have to be that way and knowing they paid some serious money to force advertize this way makes me not use their product more. So thanks Amazon.
This seems interesting. I saw something in Android Market a few weeks ago about "uninstalling task manager". I will try this out as well. There are a lot of applications (kindly pre-set on the Samsung Moment) that I thought I was using the task manager for. Lately my phone has been randomly freezing and shutting down. I do not know if this has to do with the Task Manager or the Update to 2.1 or Phone or even the Applications I am running/have installed (which are not many) but it is beyond annoying... especially since the phone takes about 3minutes to start-up.
Again, I'll be giving this a try. Maybe it will also solve my text/voice messages arriving several hours to a couple days late?!