Finding what violated StrictMode policy

I've enabled StrictMode in my app and it's causing a few crashes as expected. How can I find out where in my code I'm violating these policies?

This is the stack trace:

E/AndroidRuntime(19523): FATAL EXCEPTION: main
E/AndroidRuntime(19523): android.os.StrictMode$StrictModeViolation: policy=95 violation=2
E/AndroidRuntime(19523):        at android.os.StrictMode.executeDeathPenalty(StrictMode.java:1326)
E/AndroidRuntime(19523):        at android.os.StrictMode.access$1300(StrictMode.java:111)
E/AndroidRuntime(19523):        at android.os.StrictMode$AndroidBlockGuardPolicy.handleViolation(StrictMode.java:1319)
E/AndroidRuntime(19523):        at android.os.StrictMode$AndroidBlockGuardPolicy$1.run(StrictMode.java:1206)
E/AndroidRuntime(19523):        at android.os.Handler.handleCallback(Handler.java:605)
E/AndroidRuntime(19523):        at android.os.Handler.dispatchMessage(Handler.java:92)
E/AndroidRuntime(19523):        at android.os.Looper.loop(Looper.java:137)
E/AndroidRuntime(19523):        at android.app.ActivityThread.main(ActivityThread.java:4424)
E/AndroidRuntime(19523):        at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(19523):        at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime(19523):        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787)
E/AndroidRuntime(19523):        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554)
E/AndroidRuntime(19523):        at dalvik.system.NativeStart.main(Native Method)

but as you can see ... it's not very useful ... I know who killed my app, I need to know why!

Thanks.

Solution

You need to call penaltyLog() on your StrictMode.ThreadPolicy.Builder, so that it will show you the underlying reason as well as stopping your app.

Here's what you probably have currently:

StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
.detectDiskReads()
.detectDiskWrites()
.detectNetwork()
.penaltyDeath()
.build());

If you call the network on the main thread, you'll get this exception which is hard to understand:

E/AndroidRuntime(8752): android.os.StrictMode$StrictModeViolation: policy=71 violation=4
E/AndroidRuntime(8752):     at android.os.StrictMode.executeDeathPenalty(StrictMode.java:1311)

If you then add penaltyLog() to your policy...

StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
.detectDiskReads()
.detectDiskWrites()
.detectNetwork()
.penaltyLog()
.penaltyDeath()
.build());

then you will see a much more helpful message like the one below. This will be in the LogCat output.

D/StrictMode(8810): StrictMode policy violation; ~duration=2956 ms: android.os.StrictMode$StrictModeNetworkViolation: policy=87 violation=4
D/StrictMode(8810):     at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1090)

If you look closely, you'll see that this stack trace will lead you to the code which is causing the StrictMode violation.