startActivityForResult. When second activity is finish, it will send back result (some data) to main activity.How main activity get the result ?
From your
FirstActivity call the SecondActivity using startActivityForResult() method Intent i = new Intent(this, SecondActivity.class);  
 startActivityForResult(i, 1);  
In your 
SecondActivity set the data which you want to return back to FirstActivity. If you don't want to return back, don't set any.
For example: In secondActivity if you want to send back data:
If you don't want to return data:
Now in your FirstActivity class override
reference : http://stackoverflow.com/questions/10407159/how-to-manage-start-activity-for-result-on-android
 Intent returnIntent = new Intent();  
 returnIntent.putExtra("result",result);  
 setResult(RESULT_OK,returnIntent);  
 finish();  
If you don't want to return data:
 Intent returnIntent = new Intent();  
 setResult(RESULT_CANCELED, returnIntent);  
 finish();  
Now in your FirstActivity class override
onActivityResult() method. And process intent data by resultCode. protected void onActivityResult(int requestCode, int resultCode, Intent data) {  
   if (requestCode == 1) {  
     if(resultCode == RESULT_OK){  
       String result=data.getStringExtra("result");  
     }  
     if (resultCode == RESULT_CANCELED) {  
       //Write your code if there's no result  
     }  
   }  
 }
reference : http://stackoverflow.com/questions/10407159/how-to-manage-start-activity-for-result-on-android
 




