is it necessary to unRegisterForActivityResult when start activity for result in android ? how manage different request codes?

Question

I have two questions about registerForActivityResult call back in android. is it necessary to un register this call back when the activity is going to destroy? or this call back is lifeCycle aware and safe when it is going to use ? and the other question when you use

ActivityResultContracts.StartActivityForResult()

it will bring you a result data. how to manage request codes like the onActivityResult before? assume that you want to start two activities with different request codes for different results and so on. so what is the best approach for handling different request codes from one activity

registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result -> if (result.resultCode == Activity.RESULT_OK) {

} }

Answer 1

Q1: is it necessary to unregister this call back when the activity is going to destroy?

Ans: NO

Q2: this call back is lifeCycle aware?

Ans: Yes

Q3: When you use it ActivityResultContracts.StartActivityForResult()?

Ans: it will be used when you creating a custom contract, more info: https://developer.android.com/training/basics/intents/result#custom

Q4:What is the best approach for handling different request codes from one activity?

Ans:

Example: for one activity

->launch the second activity from the first activity:

val intent =  Intent(this, SecondActivity::class.java)
    startActivityForResult(intent,101)

->in the first activity you must override onActivityResult():

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)

    when (requestCode) {
        101 -> {
            when (resultCode) {
                Activity.RESULT_OK -> {
                    data!!.getStringExtra("keySecond")
                }
                Activity.RESULT_CANCELED -> {
                    //if there's no result
                }
            }
        }
    }

-> in second activity send the result back to the first activity as follow:

 val intent = Intent()
    intent.putExtra("keySecond","dataFromSecondActivity")
    setResult(Activity.RESULT_OK,intent)
    finish()

Example: for multiple activities

-> if you handling different request codes from one activity:

   val intent =  Intent(this, ThirdActivity::class.java)
    startActivityForResult(intent,210)

-> in third activity send the result back

 val intent = Intent()
    intent.putExtra("keyThird","dataFromThirdActivity")
    setResult(Activity.RESULT_OK,intent)
    finish()

->then your onActivityResult() function in first activity should look like:

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)

    when (requestCode) {
        101 -> { //result from second activity
            when (resultCode) {
                Activity.RESULT_OK -> {
                    data!!.getStringExtra("keySecond")
                }
                Activity.RESULT_CANCELED -> {
                    //if there's no result
                }
            }
        }
        210 -> { //result from third activity
            when (resultCode) {
                Activity.RESULT_OK -> {
                    data!!.getStringExtra("keyThird")
                }
                Activity.RESULT_CANCELED -> {
                    //if there's no result
                }
            }
        }

    }
}