Android Object LifeCycle / BackStack Flipper Plugin

What you get ?

This library is an app introspection plugin for the Flipper tool. It does focus on Android Sdk mains objects and their life cycle inspection.

It enables to see the big internal picture of your running app in a side tool. Meaning that :

• trough running the app as a user
• you can keep an eye on internals as a developer
• see the dynamic of objects evolution
• without struggling with debugger

Status :

• The plugin is under development
• The plugin name is not sealed (ideas are welcome)
• The private Api is not sealed at all (it will change in the future)
• The public Api is simple : future breaking change will be easy to handle

Availability :

You can get the Android plugin with the Gradle dependency from Jitpack :

• 

Current version is 5.0.2

Vision

The idea behind this plugin is to enable understanding of what is happening during the usage of an Android Application by :

• seeing logs about object life cycle changes
• seeing internal Android object structure (limited to a set of specific architecture)
• seeing objects stacks (FragmentManager BackStack, Jetpack Navigation Stack)
• seeing current running objects
• seeing objects destroyed (in Trash)

Show me a ScreenShot !

What is in the Left part ?

You can see the app object structure :

• Application
• Activities
• Fragments
• ViewModels (with reflexion)
• ViewModel members (LiveDatas) (with reflexion)
• Jobs (not yet available)
• Services (not yet available)
• Trash (objects destroyed)
• FragmentManager BackStack (legacy, only for activity)
• JetPack Navigation BackStack

The object structure is viewed as a tree, where each instance of an object has is dedicated object category.

• HomeFragment parent is fragments
• HomeFragment children are running instances of HomeFragment

What is in the Right part ?

You can see the object lifeCycle events for :

• activities
• fragments

You can filter those event categories :

• created / destroyed
• started / stopped
• paused / resumed
• attached / detached
• view-created / view-destroyed
• SaveInstanceState

Installation

Step 1 : Add the JitPack repository to your build file

Add it in your root build.gradle at the end of repositories:

allprojects {
	repositories {
		...
		maven { url 'https://jitpack.io' }
	}
}

Step 2 : Add the dependency

dependencies {
	debugImplementation 'com.github.afaucogney:flipper-backstack:-SNAPSHOT'
}

Step 3 : Add Flipper to your app

Follow the Getting Started section of the Flipper documentation

Step 4 : Add the Android-Object-LifeCycle plugin to Flipper

In your application, register the plugin the Flipper configuration.

val client: FlipperClient = AndroidFlipperClient.getInstance(this)
with(client) {
    addPlugin(
        InspectorFlipperPlugin(
            this@App,
            DescriptorMapping.withDefaults()
        )
    )
    ... 
    addPlugin(BackStackFlipperPlugin(this@App))
    start()
}	

Be careful, to not embed this library in production !

Step 5 : Add the Android-Object-LifeCycle plugin to Flipper-Desktop

Install the plgin in Flipper, it is called lifecycle Npm page

What can you achieve with the plugin ?

• identify runtime object instances and structure
• identify leaks (remaining objects)
• identify bug instantiations (recreation Vs preservation)
• understand architecture in a breeze
• see object instantiation in real time
• lifeCycle issues
• backStack issues

Consideration

• This plugin (as Flipper) must not be shipped in Production
• This plugin may doing lot of work, so please consider disabling it if you are not using it. I have not yet done measurement to evalute it resource requirement. But from the 5.0.0 version
• It should run on Background tread thank to Rx
• However, data structure of the app is kept in memory, so it may be a problem for some App or some low memory devices
• The Plugin uses Reflection for accessing privage properties or functions

TODO

• Be able to filter object in structure
• Impact event filtering from object
• Evaluate saving data in db / shareprefs
• Handle clean versioning / release
• Generate docs
• Impl Jobs support
• Impl Services support
• See bundle / saveinstance state
• See App lifecycle
• Evaluated StateFlow support (on going PR)
• Imp BlackStack for ChildFragmentManager
• Highligh duplicate object in the tree if you click on it (see link between framgnet in stack...)

ISSUES

• At first start, the tree is not updated ! You need to change screen to update the plugin.