SecondActivity.java

package com.example.asus.myapplication;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

/**
 * SecondActivity defines the second activity in the app.  It is launched from an intent
 * with a message, and sends an intent back with a second message.
 */
public class SecondActivity extends AppCompatActivity {
    /* Unique tag for the intent reply. */
    public static final String EXTRA_REPLY =
            "com.example.android.twoactivities.REPLY";

    /* EditText for the reply  */
    private EditText mReply = null;

    /**
     * Initialize the activity.
     * @param savedInstanceState The current state data
     */
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);

        /* initialize view variables */
        mReply = (EditText) findViewById(R.id.editText_second);

        /* Get the intent that launched this activity, and the message in
        the intent extra. */
        Intent intent = getIntent();
        String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

        /* Put that message into the text_message TextView */
        TextView textView = (TextView) findViewById(R.id.text_message);
        if (textView != null) {
            textView.setText(message);
        }
    }

    /**
     * Handle the onClick for the "Reply" button.  Gets the message
     * from the second EditText, creates an intent, and returns
     * that message back to the main activity.
     *
     * @param view The view (Button) that was clicked.
     */
    public void returnReply(View view) {
        /* Get the reply message from the edit text */
        String reply = "";
        if (mReply != null) {
            reply = mReply.getText().toString();
        }

        /* Create a new intent for the reply, add the reply message to it as an extra,
        set the intent result, and close the activity. */
        Intent replyIntent = new Intent();
        replyIntent.putExtra(EXTRA_REPLY, reply);
        setResult(RESULT_OK, replyIntent);
        finish();
    }
}