Android: When do classes get unloaded by the system? 
This is a very weird problem. My app that runs just fine but somehow if I leave my phone for an hour or two while my app is running, I get the following error when I come back to it later:


<code>
java.lang.NoClassDefFoundError: yoga.database.Manager
at
yoga.YogaActivity.openDatabase(YogaActivity.java:294)
at
yoga.YogaActivity.initData(YogaActivity.java:275)
at
yoga.YogaActivity.onCreate(YogaActivity.java:102)
at
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)
at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2417)
at android.app.ActivityThread.access$2100(ActivityThread.java:116)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:4203)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
at dalvik.system.NativeStart.main(Native Method)
</code>

I know for a fact that my yoga.database.Manager class was loaded at the time when the app was launched, but somehow the class must have been unloaded by the system as I left the phone. 

Does Android unload classes automatically after certain periods? What can I do when my class gets unloaded? 

The above error causes my app to crash, but I can easily re-launch it and it runs just fine. 

The problem occurs mostly on my HTC Magic phone running Android 1.6. 

Any insight is highly appreciated. 

Thank you,
Android: When do classes get unloaded by the system? 
===

This is a very weird problem. My app that runs just fine but somehow if I leave my phone for an hour or two while my app is running, I get the following error when I come back to it later:


<code>
java.lang.NoClassDefFoundError: yoga.database.Manager
at
yoga.YogaActivity.openDatabase(YogaActivity.java:294)
at
yoga.YogaActivity.initData(YogaActivity.java:275)
at
yoga.YogaActivity.onCreate(YogaActivity.java:102)
at
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)
at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2417)
at android.app.ActivityThread.access$2100(ActivityThread.java:116)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:4203)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
at dalvik.system.NativeStart.main(Native Method)
</code>

I know for a fact that my yoga.database.Manager class was loaded at the time when the app was launched, but somehow the class must have been unloaded by the system as I left the phone. 

Does Android unload classes automatically after certain periods? What can I do when my class gets unloaded? 

The above error causes my app to crash, but I can easily re-launch it and it runs just fine. 

The problem occurs mostly on my HTC Magic phone running Android 1.6. 

Any insight is highly appreciated. 

Thank you,