[Tutorial] How to get a Logcat -example - check for Battery drain

**munchy_cool** · 10-01-2010, 05:21 PM

Well I always read on the forum about logcat, and being in the computer field I knew it was about getting logs or system activity, thought it was a very difficult thing to do and then I read about it and realized it is so simple.

In the below explanation I will show you an app which is running even when it should not and hence draining the battery.

So, here we go.

What is logcat?

Logcat is the command to view the internal logs of the Android system. Viewing logs is often the best way to diagnose a problem, and is required for many issues. This way you'll find out what apps are doing in the background without you noticing.

Advantages of Logcat

Debugging
You can see what processes are running, if a process is running after a certain interval of time, it will eat battery. So you can also find out what is draining your battery.

How do I install it?

Make sure you've enabled on USB debugging on your phone in Settings -> Application -> Development
2. Get the Android SDK here: Android SDK | Android Developers
Extract the SDK to any folder say C:\Android
Make sure that you have installed the drivers for your phone and the operating system recognizes your phone.

Everything installed? Continuing...

Now how to actually access the log, everything in italic are commands you need to enter.

Open the 'run' dialog by pressing the 'Windows' + 'r' buttons on your keyboard (minimize the browser & other non-windows programs)
cmd (this will open a DOS prompt)
cd c:\Android\tools (go to the directory where you extracted the SDK)
adb shell
Now you'll see just a '$'
logcat

You can now just press the power button on your phone to see what happens. It displays everything the device is doing.

So the thing is: leave your device connected for a while and see what is actually going on when you're not using it.

An Example

Twidroid auto refreshing my Tweets

Code:

=> again nothing special  
D/dalvikvm(   75): GC freed 40165 objects / 1974768 bytes in 91ms 
D/dalvikvm( 1560): GC freed 25 objects / 1800 bytes in 53ms 
D/dalvikvm( 1687): GC freed 7551 objects / 330032 bytes in 102ms   

=> Twidroid doing it's thing  

I/ActivityManager(   75): Start proc com.twidroidpro:remote for service com.twidroid ...

   => back to freeing up the objects  

D/dalvikvm( 1287): GC freed 3 objects / 72 bytes in 95ms 
D/dalvikvm( 1253): GC freed 281 objects / 12688 bytes in 91ms

If you're seeing apps that are constantly busy when they shouldn't that means they're draining battery because of bugs in the app/ bad coding/ ...

Example of a buggy app:

Code:

D/dalvikvm( 1287): GC freed 3 objects / 72 bytes in 92ms 
D/dalvikvm( 2216): GC freed 6646 objects / 313032 bytes in 104ms 
D/NetworkLocationProvider(   75): onCellLocationChanged [***] 
D/LocationManager( 2216): removeUpdates: listener = com.levelup.beautifulwidgets .UpdateWeather$2@447843d8 
D/dalvikvm( 1253): GC freed 281 objects / 12688 bytes in 93ms 
D/NetworkLocationProvider(   75): onCellLocationChanged [***] 
D/LocationManager( 2216): removeUpdates: listener = com.levelup.beautifulwidgets .UpdateWeather$2@447843d8 
D/dalvikvm(   75): GC freed 41839 objects / 1963448 bytes in 88ms
D/dalvikvm( 1287): GC freed 3 objects / 72 bytes in 94ms 
D/NetworkLocationProvider(   75): onCellLocationChanged [***] 
D/LocationManager( 2216): removeUpdates: listener = com.levelup.beautifulwidgets .UpdateWeather$2@447843d8
D/dalvikvm( 2216): GC freed 6657 objects / 314648 bytes in 35ms D/NetworkLocationProvider(   75): onCellLocationChanged [***] 
D/LocationManager( 2216): removeUpdates: listener = com.levelup.beautifulwidgets .UpdateWeather$2@447843d8 
D/dalvikvm( 1253): GC freed 279 objects / 12640 bytes in 94ms 
D/NetworkLocationProvider(   75): onCellLocationChanged [***] 
D/LocationManager( 2216): removeUpdates: listener = com.levelup.beautifulwidgets .UpdateWeather$2@447843d8 
D/dalvikvm( 1287): GC freed 3 objects / 72 bytes in 60ms 
D/dalvikvm( 2216): GC freed 6661 objects / 314192 bytes in 104ms 
D/NetworkLocationProvider(   75): onCellLocationChanged [***] 
D/LocationManager( 2216): removeUpdates: listener = com.levelup.beautifulwidgets .UpdateWeather$2@447843d8

As you can see the app (BeautifulWidgets) was constantly trying to remove the same updates and thus draining my battery for no reason. This was happening every 10seconds (!!).

Uninstalling those crappy apps should help your battery life (and hope a future update of that app fixes it)

The less you see in the logcat the better

Starting with a fresh log

If you want to clear the log and only see what's happening on your phone from now on, go to adb shell (step 4) and then type logcat -c. This clears the log and then type logcat.

So all those of you having battery drains, please get a logcat to see whats eating your battery. Hope this helps

Source-HOW TO: troubleshoot bad battery life with logcat - Android Forums

EDIT-Leshak if you find this appropriate can we add it to wiki?

**bboylalu** · 10-01-2010, 05:44 PM

You must be s!%#@ me... is Beautiful Widgets the reason of my battery's extremely short life? I know I have Wi-Fi always turned on at home, but I'm going to see what happens without Beautiful Widgets. If it's because of it... I'm going to go berserk

) (as I had some biiig problems with the battery when I needed it). Thanks for the tip.

**munchy_cool** · 10-01-2010, 05:47 PM

Originally Posted by bboylalu

You must be s!%#@ me... is Beautiful Widgets the reason of my battery's extremely short life? I know I have Wi-Fi always turned on at home, but I'm going to see what happens without Beautiful Widgets. If it's because of it... I'm going to go berserk

) (as I had some biiig problems with the battery when I needed it). Thanks for the tip.

this was just an example man, am not pointing fingers at any app, maybe there was a bug in the version which may have been fixed...

anyways you can go and check it out and give us the feedback.

**bboylalu** · 10-01-2010, 08:49 PM

This is unbelievable man... It's been unplugged for 3 hours, wi-fi on, moderate usage and only 5% is gone :|. So Beautiful Widgets was the problem. I was really concerned about my battery's life, but it seems it's fine now. Thank you very much for the tip. I'll get back with more feedback after playing some games

.

Besides, the phone seems snapier all of a sudden :|.

**munchy_cool** · 10-01-2010, 08:55 PM

Originally Posted by bboylalu

This is unbelievable man... It's been unplugged for 3 hours, wi-fi on, moderate usage and only 5% is gone :|. So Beautiful Widgets was the problem. I was really concerned about my battery's life, but it seems it's fine now. Thank you very much for the tip. I'll get back with more feedback after playing some games

.

Besides, the phone seems snapier all of a sudden :|.

thanks man , glad to help you.

**markus75** · 10-01-2010, 09:17 PM

nice explained munchy !

**munchy_cool** · 10-01-2010, 09:23 PM

Originally Posted by markus75

nice explained munchy !

dude, check the original link at the bottom.actually a lot of people complain about battery life on spica so i went about looking to find out whats eating ur battery and i found this out. hope we now have less people complaining about battery life.

**kevinkoh** · 10-02-2010, 04:09 AM

or just use alogcat?

im sorry, but i saw something dont understand in my logcat.

Code:

D:/dalvikvm(11061): GetFieldID: unable to find field L java/util/HashMap;/loadFactor :F

occationally it keeps spamming my screen, but i am unable to trace back which app caused this, Im assuming this has something to do with antibyte's FE8b7?