Crashlytics Android SDK – custom UncaughtExceptionHandler

UPDATE

Please see @kmityak answer as Crashlytics/Fabric initialization is now asynchronous and my solution below is no longer valid.

ORIGINAL ANSWER

You can set your custom UncaughtExceptionHandler providing that it will pass exception to default UncaughtExceptionHandler to be handled later via Crashlytics.

Below code is implemented inside Application subclass:

private static Thread.UncaughtExceptionHandler mDefaultUEH;
private static Thread.UncaughtExceptionHandler mCaughtExceptionHandler = new Thread.UncaughtExceptionHandler() {
    @Override 
    public void uncaughtException(Thread thread, Throwable ex) {
        // Custom logic goes here

        // This will make Crashlytics do its job
        mDefaultUEH.uncaughtException(thread, ex);
    }
};

@Override
public void onCreate() {
    super.onCreate();

    // Order is important!
    // First, start Crashlytics
    Crashlytics.start(this);

    // Second, set custom UncaughtExceptionHandler
    mDefaultUEH = Thread.getDefaultUncaughtExceptionHandler();
    Thread.setDefaultUncaughtExceptionHandler(mCaughtExceptionHandler);
}

Second option is to register Crashlytics after setting your custom UncaughtExceptionHandler – then all uncaught exceptions will be reported by Crashlytics as fatals, and after that passed to your custom handler.