StartActivityForResult is the Core/OG Component of the Android Activity Ecosystem of how we used to start an activity & get results from it with this getting deprecated we have got a new & better way RegisterActivityForResult.
Why was StartActivityForResult deprecated?
StartActivityForResult is the most fundamental component of the Android ecosystem but with its simple-to-use advantage it had many disadvantages like
- Hard to find from where a certain request is being made
- Had to send a unique request code in case there is a duplicate used. that can lead to buggy results sometimes
- The result is missed if the component is recreated
- onActivityResult callback doesn’t work well with fragments
Why new Activity Result is better?
- Simple, easy & clean
- Inbuilt & Custom Contract-based Support
- Separate callback for each activity (earlier for each we used to have a common activity Result)
How to use Activity Result API
Step 1: Declare the launcher
lateinit var launcher : ActivityResultLauncher
Step 2: Register it
launcher = registerForActivityResult
(ActivityResultContracts.StartActivityForResult()) { result ->
useTheResult(result)
}
Note: You must call registerForActivityResult() before the fragment or activity is created; you cannot launch the ActivityResultLauncher until the fragment or activity’s Lifecycle has reached CREATED.
Step 3: Use the launcher
launcher.launch(Intent(context, ResultActivity::class.java) .putExtra(ResultActivity.PARAM_DATA,id))
Now in this way whenever we can easily & efficiently refactor all the old startActivityForResult()
Some of the Built-in ActivityResultContracts are :
- StartActivityForResult
- RequestPermission
- TakePicture
- CaptureVideo
- OpenDocument
You can find more here: https://developer.android.com/reference/androidx/activity
Along with these inbuilt result type contracts, there is also support for custom contracts i.e
| class CustomContract : ActivityResultContract<String, String?>() { | |
| const val DATA = "data" | |
| const val INPUT_DATA = "input_data" | |
| override fun createIntent(context: Context, input: String?): Intent { | |
| val intent = Intent(context, DummyResultActivity::class.java) | |
| intent.putExtra(INPUT_DATA, input) | |
| return intent | |
| } | |
| override fun parseResult(resultCode: Int, intent: Intent?): String? { | |
| return when (resultCode) { | |
| //Transforming our result to required format before returning it | |
| Activity.RESULT_OK -> intent?.getStringExtra(DATA) | |
| else -> null | |
| } | |
| } | |
| } |
Some Additional thoughts?
With Custom Contract we can separate all the logic to the Contract Class
Though this is a much better way as compared to what we have earlier still this is coupled with our activity.
In order to decouple it a bit, we can make use of customization with live data & lifecycle observer.
Further reading
⨭ Getting a result from an activity | Official Documentation
⨭ Introducing the Activity Results APIs | Adam Bennett
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This article was originally published on proandroiddev.com on September 27, 2022
