android on a return data to the activity, it can be used to echo data

(A) who
Description: Yes, that is startActivityForResult () method, which is used to return data in the event is destroyed when given on a method.
Parameters:
the startActivityForResult (Intent,. 1) The first argument is the Intent, the second parameter is the request code, for determining the source of the data.
(B) what
are now two activity, activityA and activityB, activityA activityB want to send request to have actiivtyB return data.
code show as below:

public class ActivityA extends AppCompatActivity {
    private Button sendBtn;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_a);
        sendBtn = findViewById(R.id.send_btn);
        sendBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(ActivityA.this, ActivityB.class );
                 // first parameter is the Intent, the second parameter is the request code, randomly defined, guaranteed to be unique on the line 
                the startActivityForResult (Intent,. 1 ); 
            } 
        }); 
    } 

    @Override 
    protected  void the onActivityResult ( int requestCode, int the resultCode, the Intent data) {
         Super .onActivityResult (requestCode, the resultCode, data);
         // here to determine the source of the data for a request code via 
        Switch (requestCode) {
             Case . 1 :
             // result of the determination request is successful, resultCode == RESULT_OK , on behalf of the success of the 
                IF (resultCode == RESULT_OK) {
                    String getData = data.getStringExtra("data");
                    Toast.makeText(ActivityA.this, getData, Toast.LENGTH_LONG).show();
                }
                break;
            /**这里可以有多个requestcode**/    
                default:
        }
    }
}

Here is activityB

public class ActivityB extends AppCompatActivity{
    private Button returnData;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_b);
        returnData = findViewById(R.id.return_data);
        returnData.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent();
                //To be passed to the data stored in the intent activityA in 
                intent.putExtra ( "data", "Hello, Time" );
                 // upwardly activity returns a result of the first parameter, and in general there are two values RESULT_OK RESULT_CANCEL, first two parameters with the intent to pass the data back 
                setResult (RESULT_OK, intent); 
                Finish (); 
            } 
        }); 
    } 
}

Note: When the user points back key, the data does not return back, this time we should rewrite onBackPressed () method of

@Override
    public void onBackPressed() {
        Intent intent = new Intent();
        intent.putExtra("data", "你好，time");
        setResult(RESULT_OK, intent);
        finish();
    }