从第二个应用程序返回后，在第一个应用程序上打印“ toast”消息

Question

I am trying to so the following on android studio : Sending the user to another app (ie a second app like Facebook or or Twitter ) from my android app that I developed.then , if the user closes the second app, I need to go back to the first app (ie my app) and show a "toast message " on it.

After some search, I have found some way of sending the user from my app to the second app if the user a presses a button on my app.

However, I did not know how to print a "a toast message " if the user closes the second ?

Any help would be really apprecaitd

Answer 1

There is a activity lifecycle callback called onResume() ( onStart() also works), this callback is called when the user comes back to your app, so you can make a toast message in this method

void onResume(){
    super.onResume();
    Toast.makeText(...).show();
}

But this method is also called when the app starts, so maybe you need a boolean flag to distinguish those situations

void onResume(){
    super.onResume();
    if(isBack){
        Toast.makeText(...).show();
        isBack = false;
    }
}

Answer 2

I would suggest to use startActivityForResult when you start second activity. Then in onActivityResult , you can do whatever you want (eg: show Toast message ) when second activity finish.

Assume first activity class is called FirstActivity , & second activity is SecondActivity .

In FirstActivity , do this when you want to start SecondActivity :

// use "startActivityForResult" instaed of "startActivity"
Intent intent = new Intent(this, SecondActivity.class);
startActivityForResult(intent, "START_SECOND_ACTIVITY");

To detect finish of second activity , add this in first activity :

@Override
protected void onActivityResult (int requestCode, int resultCode, Intent data) {
    if (requestCode == "START_SECOND_ACTIVITY") {
        // show Toast message
        Toast toast = Toast.makeText(this, "SecondActivity finish", Toast.LENGTH_SHORT);
        toast.show();
    }
}