Monday, March 17, 2014

Python Android App Debugging Tip: adb and python print statements

With the phone connected to the USB cable and in debug mode, open a new terminal window and type:

  $ adb logcat |grep python

Update 10/11/2014. Windows users, see below. An alternative to using grep:

$ adb  logcat python *:s

You can now view standard python output from applications running on your android phone with python print statements. Output of logcat
I/python  ( 2392): play sounds
I/python  ( 2392): play sounds
I/python  ( 2392): play sounds

The most common problems with Python Subset for Android Apps dying on the Android phone at startup:
  1. you didn't import the sound mixer module properly
  2. your fonts are not in the main program directory
  3. your sound files are not in the main program directory
  4. your graphic files or map files are not in the main program directory
  5. you are using a python module that is not in your main program directory
Note that there's a common theme here of a desktop program working because the assets exist somewhere on your desktop machine, but those assets don't get transferred to your phone.  Look at your sound, graphic, and font files to make sure they are in your main directory.

In the problems above, the adb logcat command will usually show you what asset the program fails to load.

You'll save time in the debugging process if you open up two terminals at once.  In one terminal, run the adb output.  In the other terminal, build and install your program onto your phone.  With the USB cable connected, run your application on your phone.

Check to make sure you are initializing the android library.

Make sure you are importing the mixer module as shown below. In previous versions of pgs4a, I had problems with audio files that weren't in *.wav format. I only use wav files now.

Another common problem is that your application is not named

Make sure you have called the application and that you are building the application with the name of the directory that contains your application.

if you are using the sgc gui toolkit with android, you need to make sure that the fonts are loaded prior to setting up the sgc screen. I've had several occasions when I got the order wrong the my application worked on the desktop and crashed on the phone. This code below is only relevant if you use sgc, which is definitely not needed to make games on android. However, if you do use sgc to make your buttons and sliders, it can be a bit tricky to use on android.

Update: 10/11/2014 As my son is starting to do some development on Windows 8.1, I realized that he didn't have grep installed and didn't really need to go through the hassle of installing grep with cygwin. I looked at the filter options for adb logcat. The key is to set everything to silent except for strings containing python. Here's some docs built into adb that are somewhat difficult to understand. The only one that you need to use is the -s or *:s
Usage: logcat [options] [filterspecs]
options include:
  -s              Set default filter to silent.
                  Like specifying filterspec '*:s'
  -f    Log to file. Default to stdout
  -r []   Rotate log every kbytes. (16 if unspecified). Requires -f
  -n       Sets max number of rotated logs to , default 4
  -v      Sets the log print format, where  is one of:

                  brief process tag thread raw time threadtime long

  -c              clear (flush) the entire log and exit
  -d              dump the log and then exit (don't block)
  -t       print only the most recent  lines (implies -d)
  -g              get the size of the log's ring buffer and exit
  -b      Request alternate ring buffer, 'main', 'system', 'radio'
                  or 'events'. Multiple -b parameters are allowed and the
                  results are interleaved. The default is -b main -b system.
  -B              output the log in binary
filterspecs are a series of

where  is a log component tag (or * for all) and priority is:
  V    Verbose
  D    Debug
  I    Info
  W    Warn
  E    Error
  F    Fatal
  S    Silent (supress all output)

'*' means '*:d' and  by itself means :v

If not specified on the commandline, filterspec is set from ANDROID_LOG_TAGS.
If no filterspec is found, filter defaults to '*:I'

If not specified with -v, format is set from ANDROID_PRINTF_LOG
or defaults to "brief"

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