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Please see @kmityak answer as Crashlytics/Fabric initialization is now asynchronous and my solution below is no longer valid.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

Yes, it is possible.

In your Application class:

@Override
public void onCreate() {
    super.onCreate();
    Crashlytics.start(this);
    initUncaughtExceptionHandler();
}

private void initUncaughtExceptionHandler() {
    final ScheduledThreadPoolExecutor c = new ScheduledThreadPoolExecutor(1);
    c.schedule(new Runnable() {
        @Override
        public void run() {
            final UncaughtExceptionHandler defaultHandler = Thread.getDefaultUncaughtExceptionHandler();
            Thread.setDefaultUncaughtExceptionHandler(new UncaughtExceptionHandler() {
                @Override
                public void uncaughtException(Thread paramThread, Throwable paramThrowable) {
                    // do my amazing stuff here 
                    System.err.println("Error!");
                    //then pass the job to the previous handler
                    defaultHandler.uncaughtException(paramThread, paramThrowable);
                }
            });
        }
    }, 5, TimeUnit.SECONDS);
}

The reason I'm scheduling this after 5 seconds is because Crashlytics needs some time to set up his stuff. I'm using this code and it works perfectly. Of course if your app crashes on start, sorry but no custom handler ;)

Since recent versions of Crashlytics perform initialization asynchronously, it's better to use Fabric's initialization callback:

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);
    }
};

CrashlyticsCore core = new CrashlyticsCore.Builder()
            .disabled(BuildConfig.DEBUG)
            .build();
Fabric.with(new Fabric.Builder(this).kits(new Crashlytics.Builder()
            .core(core)
            .build())
            .initializationCallback(new InitializationCallback<Fabric>() {
                @Override
                public void success(Fabric fabric) {
                    mDefaultUEH = Thread.getDefaultUncaughtExceptionHandler();
                    Thread.setDefaultUncaughtExceptionHandler(mCaughtExceptionHandler);
                }

                @Override
                public void failure(Exception e) {

                }
            })
            .build());

None if those solutions worked for me. I did it like following:

// Setup handler for uncaught exceptions.
Thread.setDefaultUncaughtExceptionHandler (new Thread.UncaughtExceptionHandler()
{
    @Override
    public void uncaughtException (Thread thread, Throwable e)
    {
        //Send Report to Crashlytics. Crashlytics will send it as soon as it starts to work
        Crashlytics.logException(e);

        //Your custom codes to Restart the app or handle this crash
        HandleCrashes(thread, e);
    }
});

And here is my Custom Method to restart the APP:

private void HandleCrashes(Thread t, Throwable e) {

    Intent i = new Intent(mContext, frmLogin.class);
    i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
    i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    i.putExtra("JustLogin", true);
    startActivity(i);

    System.exit(1);
}