[android] Android: how to make an activity return results to the activity which calls it?

I have a Location activity that can be called from many activities, such as Sign up and Order. In the Location activity the user enters his location, so the activity Location will return this new location to that activity which called it.

So when the Sign up activity calls the Location activity, it has to return the data to the Sign up activity. Another time the Order activity will do the same thing.

Note

I know you will tell me that I should post the code, but I am not asking you to give me the code; I just want some tips, links or good threads.

Your error is in resultCode = Activity.RESULT_CANCELED, you should instance like resultCode == Activity.RESULT_CANCELED ==

UPDATE Feb. 2021

As in Activity v1.2.0 and Fragment v1.3.0, the new Activity Result APIs have been introduced.

The Activity Result APIs provide components for registering for a result, launching the result, and handling the result once it is dispatched by the system.

So there is no need of using startActivityForResult and onActivityResult anymore.

In order to use the new API, you need to create an ActivityResultLauncher in your origin Activity, specifying the callback that will be run when the destination Activity finishes and returns the desired data:

private val intentLauncher =
    registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result ->

        if (result.resultCode == Activity.RESULT_OK) {
            result.data?.getStringExtra("streetkey")
            result.data?.getStringExtra("citykey")
            result.data?.getStringExtra("homekey")
        }
    }

and then, launching your intent whenever you need to:

intentLauncher.launch(Intent(this, YourActivity::class.java))

And to return data from the destination Activity, you just have to add an intent with the values to return to the setResult() method:

val data = Intent()
data.putExtra("streetkey", "streetname")
data.putExtra("citykey", "cityname")
data.putExtra("homekey", "homename")

setResult(Activity.RESULT_OK, data)
finish()

For any additional information, please refer to Android Documentation

If you want to finish and just add a resultCode (without data), you can call setResult(int resultCode) before finish().

For example:

...
if (everything_OK) {
    setResult(Activity.RESULT_OK); // OK! (use whatever code you want)
    finish();
}
else {
   setResult(Activity.RESULT_CANCELED); // some error ...
   finish();
}
...

Then in your calling activity, check the resultCode, to see if we're OK.

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == someCustomRequestCode) {
        if (resultCode == Activity.RESULT_OK) {
            // OK!
        }
        else if (resultCode = Activity.RESULT_CANCELED) {
            // something went wrong :-(
        }
    }
}

Don't forget to call the activity with startActivityForResult(intent, someCustomRequestCode).