Pygame on Android App Crashes on Start: FIXED

A good tileset in the wrong place at the wrong time

After catching Jack smelt in Capitola and seeing an amazing display of seals, dolphins, and school of tens of thousands of fish, my son worked on his 2D tile map game, Maze.  The Android app consistently crashed on start.  It would display the initial splash screen and then die, leaving no error message.

This has happened in the past with other games.  We usually solve the problem with adb, the Android debugger.  Today, the fix was easy.  However, since I know that it can be daunting to wade through the adb logcat, I'll provide a few tips specific to Python / Pygame Subset for Android debugging.

My son's game uses Python and pgs4a.  He also uses Tiled to export JSON map files. 

First, find adb on your system.  It's not something that python developers normally use from the command line.  adb is in the platform-tools sub-directory of the android-sdk main SDK directory.

  pgs4a/android-sdk/platform-tools$
 From the Linux command line, you can either just run adb logcat or you can run it through grep and look for references to python.

  platform-tools$ ./adb logcat *:D |grep python

 A larger snippet of the log file is shown below. I/ActivityManager( 1465): Start proc com.kaiyotesof.maze:python for activity com.kaiyotesof.maze/org.renpy.android.PythonActivity: pid=5088 uid=10062 gids={1015, 3003} I/python ( 5088): Private directory is /data/data/com.kaiyotesof.maze/files I/python ( 5088): Argument is /data/data/com.kaiyotesof.maze/files I/python ( 5088): Handing off to main. I/python ( 5088): /data/data/com.kaiyotesof.maze/files/main.py:1: RuntimeWarning: import cdrom: No module named cdrom I/python ( 5088): (ImportError: No module named cdrom) I/python ( 5088): 1600 I/python ( 5088): 1600 I/python ( 5088): Traceback (most recent call last): I/python ( 5088): File "start.pyx", line 52, in start (jni/../jni/application/src//start.c:1313) I/python ( 5088): File "KaiGames/Maze/main.py", line 55, in <module> I/python ( 5088): error: Couldn't open ../../../pgs4a/KaiGames/Maze/tilesets/grass_water_terrain.png I/ActivityManager( 1465): Process com.kaiyotesof.maze:python (pid 5088) has died.


 In this case, the error was an incorrect reference to the tileset graphic.
   I/python ( 5088): error: Couldn't open ../../../pgs4a/KaiGames/Maze/tilesets/grass_water_terrain.png I/ActivityManager( 1465): Process com.kaiyotesof.maze:python (pid 5088) has died.

The error is caused by a relative reference to a non-existent file.  Although the program works on the desktop, it doesn't work on the phone.  The fix is to place the tileset files in the same directory or sub-directory of your main.py program and create a new map and tileset with tiled.  If you've already created an extensive map, you can also edit the json file with a text editor to have it reference the correct location.

In this example, the file is called grass_water_terrain.png.

In a previous game, my son had a similar problem with the app crashing when it tried to load a font file that was in the wrong location.  Fonts and graphics are the two most common problems.  If you have all your fonts and graphic files in the same directory and your program still doesn't work on Android, but works on your desktop, you may be trying to import a library another directory.  Everything needs to be in the directory where main.py is or in a sub-directory.

If the application works on your desktop and it builds and then loads onto your phone fine, but crashes on start, think through what files the application is trying to load on the Android phone.  Then, work backwards and think through the differences between the phone directory structure and your desktop.  Also, think about the obvious things.  Check that you imported the android library and you've initialized it android.init().

If the problem is not immediately obvious, fire up adb and look for references to python.

Checklist:

• import android library
• initialize android library
• main game file is called, main.py
• graphic files are in the main or sub-directory
• font files are in the main or sub-directory
• custom libraries that you wrote are in the main or sub-directory

Update: March 3, 2014
One of the viewers of my pychildren YouTube channel had a problem with sound.  The important section is to map pygame.mixer and android.mixer to mixer.

try:    
    import pygame.mixer as mixer
except ImportError:    
    import android.mixer as mixer

The other problem with sound is that there may be problems with different types of sound formats.  I suggest you use .wav files.  Since sound is handled differently on Android and the desktop, a few problems occur.