Crash reporting

Custom crash handler

By default, your application will be crashed by the OS if some exception is not caught by anbody at the moment this exception was thrown. This results in a system dialog which notifies the user that the app has crashed, and app is force stopped.

This can be avoided if we define custom Uncaught excpetion handler:

public class AppCrashHandler implements Thread.UncaughtExceptionHandler {

    private Activity liveActivity;

    public AppCrashHandler(Application application) {
        application.registerActivityLifecycleCallbacks(new Application.ActivityLifecycleCallbacks() {
            public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
            public void onActivityStarted(Activity activity) {
            public void onActivityResumed(Activity activity) {
                liveActivity = activity;
            public void onActivityPaused(Activity activity) {
                liveActivity = null;
            public void onActivityStopped(Activity activity) {
            public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
            public void onActivityDestroyed(Activity activity) {
    public void uncaughtException(Thread thread, Throwable ex) {
        if(liveActivity != null){
            Intent intent = WelcomeActivity.startFromCrash(liveActivity);


When an uncaught application has been detected by the OS, uncaughtException(Thread thread, Throwable ex) method is called. At first, we check if the activity where this exception was caused is still alive - if it is, this means that our app is in foreground and we have to define some crash fallback. The safest fallback is to simply start the application once again, and finish the current activity. If activity is null, this means that app is in background and we can simply force stop the application.

AppCrashHandler has to be registered as default uncaught exception handler in your application class (in onCreate() method)

  Thread.setDefaultUncaughtExceptionHandler(new AppCrashHandler(this));


Crashlytics, part of Fabric, is crash reporting tool. It provides simple API for reporting crashes and annotating them with user information and other details. Crashes and logged exceptions will be notified to you via email if you decide to use it. More information about the issues is available, like the whole stack trace, Android versions that caused the issue, device models and even more details you want to add.

To get access to Crashlytics you should ask your team leader.

To add Crashlytics to project, you have to edit your build.gradle: ```gradle // top-level build.gradle buildscript { repositories { maven { url '' } } dependencies { classpath '' } }

apply plugin: 'io.fabric'

repositories { maven { url '' } }

// app/build.gradle

dependencies { compile('') { transitive = true; } } ```

Then, in application’s onCreate() add: java Fabric.with(this, new Crashlytics());

And if you want, you can also disable Crashlytics reporting in debug mode. Then, instead of line above, you should put:

CrashlyticsCore crashlyticsCore = new CrashlyticsCore.Builder().disabled(BuildConfig.DEBUG).build();
Fabric.with(this, new Crashlytics.Builder().core(crashlyticsCore).build());

At this point, any exception that caused app crash will be reported to Crashlytics automatically. Also, you can simply use Crashlytics.logException(e) and Crashlytics.log(message) to log caught exception and messages to Crashlytics. What we usually want to do is to have all the crashes and errors form release version of our app reported to Crashlytics. This way we can easily see how often is our app crashing and why and what is causing problems to users. On the other hand, while we use debug version of our app, we want all those exceptions and messages printed to logcat (and not to Crashlytics). That's why Timber is great. It enables us to print errors and messages to logcat while we are developing and to report that same errors and messages to Crashlytics when app is in production, simply by calling Timber.e(exception, “Message”). Here’s how to do it:

First we have to define new Tree we will use for release version. We can use something like this:

private static class CrashReportingTree extends Timber.Tree {

    protected void log(int priority, String tag, String message, Throwable t) {
        if (priority == Log.VERBOSE || priority == Log.DEBUG) {
            // avoid reporting

        // will write to the crash report but NOT to logcat

        if (t != null) {

The other thing we have to do is to plant that Tree for release version:

if (BuildConfig.DEBUG) {
    Timber.plant(new Timber.DebugTree());
} else {
    Timber.plant(new CrashReportingTree());

And that’s all the magic we need for successful logging!

Crashlytics, remote source control and CI server

In some cases, we don't want to store Crashlytics apiKey and apiSecret on remote source control (I.E. GitHub or Bitbucket). We need to make the following changes to our code in order to properly configure our enviroment:

  1. Remove all Crashlytics meta-tags from AndroidManifest
  2. Add apiKey and apiSecret to file
  3. Add file to .gitignore

If you are using CI server for running tests and static code analysis, further modification are needed. As is not included on remote source control, we need to manually create it after our build has been assembled on CI server. Paste the following code snippet to your build.gradle file:

afterEvaluate {

def initFabricPropertiesIfNeeded() {
    def propertiesFile = file('')
    if (!propertiesFile.exists()) {
        if(System.env.crashlyticsApiSecret == null){
            throw new GradleException('Required ORG_GRADLE_PROJECT_crashlyticsApiSecret environment variable not set.')
        else if(System.env.crashlyticsApiKey == null){
            throw new GradleException('Required ORG_GRADLE_PROJECT_crashlyticsApiKey environment variable not set.')
            def commentMessage = "This is autogenerated fabric property from system environment to prevent key to be committed to source control."
            ant.propertyfile(file: "", comment: commentMessage) {
                entry(key: "apiSecret", value: crashlyticsApiSecret)
                entry(key: "apiKey", value: crashlyticsApiKey)

We also nees to generate 2 enviroment variables on our CI server (ORG_GRADLE_PROJECT_crashlyticsApiKey and ORG_GRADLE_PROJECT_crashlyticsApiSecret), which will store Crashlytics apiKey and apiSecret. Variable name must start with "ORG_GRADLE_PROJECT_" prefix, so that they can be used inside build.gradle file as enviromental variables.

Useful links