Scratch That Itch

21 Nov 2019 | tags: android studio tools

One of the most useful things for me whilst I was learning Kotlin was TryKotlin. It gave me a quick way to test concepts, try new APIs, or just to get familiar with the syntax.

Sometimes though I want to see if something would work with my own data classes, and it’s a bit too much trying to cram them all into that page. Other times I don’t want to use my own app either, cause that means adding logs or TextViews then recompiling and rerunning the whole app just to see if something would work as I expect it to.

It is during these times that scratch files really come in handy. Scratch files are super lightweight, runnable, and debuggable files.

Creating scratch files

To create a new scratch file, press ⌘ + SHIFT + N (or File > New > Scratch File). There are a whole bunch of file types available, including Kotlin, Java, and JSON.

Some of the available file types

Since scratch files are fully functional, make sure to choose the correct file type so you get syntax highlighting, auto-completion, and all the other file type-specific features of IntelliJ.

:information_desk_person: When choosing Java, IntelliJ automatically creates the main() function for you; when choosing Kotlin, there is no need to declare a main function – everything in the file is executed as if they are inside main().

Locating scratch files

You can access all of your scratch files inside Project > Scratches and Consoles > Scratches.

:information_desk_person: Open Project View by default in Android Studio by going to Help > Edit Custom Properties and adding studio.projectview=true.

All of the scratches

The first file of any particular type is named scratch by default, and any subsequent ones have an increasing integer attached to it.

Scratches are not attached to any one project, which means that we can try something out in project and have that scratch file viewable in other projects as well!

Using scratch files

You can use and navigate around scratch files the same way you would any other file in Android Studio.

When you’re ready to run your file, click on the green play button on the upper left of the editor. The output of the scratch would be displayed on the right hand side of the screen.

Output of scratch file

For added fun, enabling Interactive Mode runs your code automatically when you stop typing!

If we are logging too much text and it won’t fit the side panel, Android Studio would automatically open the Scratch Output panel.

That's a lot of text

Accessing Your Own Stuff

Let’s say I want to play around with the User data class in the about module of Plaid. With scratch files, we do not have to copy-paste the data class.

To access this existing class, we need to import them into the file like normal. And since scratch files are fully functional, auto-import is supported too!


Make sure to choose the correct option in the “Use classpath of module” dropdown before running your scratch file. Remember that if the underlying source code changes, the scratch files pick up those changes too (as soon as you rebuild the module that is!)!

You can read more about scratch files here and here. Get scratching! :dash:

On-Device Debugging Part V: Strut Your Stuff

20 Jul 2019 | tags: android

Over the past year, my team have been steadily building a Developer Options screen for our app. It is a simple PreferenceScreen available on debug builds that help us:

In this series of posts, I will share what these various options are and how we made them.

Read the other posts in this series:

(If you are not familiar with PreferenceFragmentCompat, I highly suggest to read about that first before proceeding. You can start with this AndroidX guide on Settings.)

Working on an app means we are constantly tweaking how things look. Change this shade of green, use this widget instead of that, move this thing to there.

In the last part of our on-device debugging series, we look at some of the ways we showcase how things should look in our app.

Design Playground and Shortcuts

Design Playground

A few weeks ago, we went all in and switched our whole app to use the new Material Design Components theme. (Nick Rout has an awesome article showing you more details on how to do this for your app.)

We fully expected that some widgets might look strange and we might have to tweak some things a bit. Taking inspiration from the MDC Catalog app, we came up with a Theme Showcase page.

This page has all the widgets as well as the custom components we use throughout the app.

Widget showcase

This has been really useful in helping us figure out how things look as we go through adapting MDC. This page has also been handy when we are tweaking something with our design team, and as a reference page for when we are visually testing a new feature.

Since we also have multiple themes in the app, we included a theme switcher that allows us to see how everything looks in each of the themes.

Dynamically switch themes

This switcher is accessed through the overflow menu. When the user chooses a theme, we save the value to a SharedPreferences file.

For simplicity, we only save the position of the chosen theme:

We then need to make sure that we get back the chosen theme:

And set it on our Activity’s onCreate via setTheme().


Some parts of the app are a bit cumbersome to get to.

When we were building our app’s order confirmation page, it was getting annoying having to complete an order each time to see how it looks whenever we change something in the layout.

As we saw in my previous post about app shortcuts, we can put in a targetPackage and a targetClass in our Intents:

Having these shortcuts available helped us skip having to navigate through multiple steps to get to a particular screen.

And with that, we wrap up this series on on-device debugging options. We have seen how we can make feature toggles more user-friendly, how we can surface stacktraces for quicker debugging, and how we can retrieve Logcat traces out of our testers’ devices.

Thank you for sticking with the series, and massive thanks to everyone who has given me their time helping get these posts through! :green_heart:

On-Device Debugging Part IV: Log All The Things!

08 Jul 2019 | tags: android

Over the past year, my team have been steadily building a Developer Options screen for our app. It is a simple PreferenceScreen available on debug builds that help us:

In this series of posts, I will share what these various options are and how we made them.

Read the other posts in this series:

(If you are not familiar with PreferenceFragmentCompat, I highly suggest to read about that first before proceeding. You can start with this AndroidX guide on Settings.)

As I mentioned in part II, we leverage Timber a lot. Those stacktrace log screens have been really useful when the app misbehaves, but what about those times when we just want to have checkpoints whilst using the app?

Enter our next set of developer options:

More debugging!

Show Debug Toasts

Toasts are a great way of setting visual checkpoints in an app. They are relatively unobtrusive and easy to create.

Enabling “Show debug Toasts” in our developer settings allows us to surface these checkpoints when we are testing something unpredictable:

I previously talked about a geofencing feature we had to implement, and we have that feature to thank for spurning the idea for this debugging feature.

In this feature, we want the app to notify the user when they enter a geofence. Testing geofences in the middle of the city can be tricky, and having visual cues that let us know if we have entered or exited a geofence has been super helpful for us.

This function lives in our DebugExtensions class:

(In this case, SettingsInteractor takes care of exposing some of the debug options that our main source set needs access to.)

Having a developer option toggle to control this means we can turn the Toasts off when it gets too annoying, and we lower the risk of leaving a debugging Toast when we release to production as well.

Enable Leak Canary

We have some really old Activities in the app that drive Leak Canary crazy. Until we get around to cleaning them up, it also drives our QAs crazy. This toggle gives them the power to turn the tool off so they can test in peace.

As a rule, developers keep this toggle on during active development. As for those old Activities, we are in the process of reworking them to make them perform better.

Show Debug Notification

When enabled, the app shows a persistent notification that serves as the shortcut to this Developer Settings screen (we also provided an entry to this screen in our app’s junk drawer aka the “More” menu for debug builds). Pretty straightforward.


When connected to our development computers, we have a wide array of debugging tools at our disposal. We can use Timber, or System.out, or Toasts, or breakpoints, etc.

But going back to our geofencing feature, all of these options are not really viable to us during testing. Sure we can walk around Surry Hills with a laptop and keep an eye on Logcat whilst debugging. But we really can’t expect everyone who is testing the app to do this.

When this option is turned on, we send all the Logcat information from our app into a text file:

Getting those logs out of a particular device can be fiddly, dealing with multiple OEMs and USB variations. And those logs are pretty useless just sitting there, so we put in the option to send those files to us:

Using ACTION_SEND_MULTIPLE with the Intent allows us to automatically attach all the log files we can find in the user’s debug file storage.

Gimme those logs!

Depending on the email client they choose to send the files with, they can remove or add more files as they please.

To be good citizens, we have also provided the option to clear all existing logs so that users can reclaim their precious storage space.

Out of all the debugging features that we have, this one is probably my favourite. :green_heart:

(Massive thanks go out to @ataul for all his patience reviewing my crazy ramblings :laughing: )

In the next post, we will look at how our developer settings help us work better with the designers in our team. Stay tuned! :radio: