[Android Studio] Intent

create_message_activity.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <EditText
        android:id="@+id/message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        android:hint="@string/hint"
        android:ems="10" />
    <Button
        android:id="@+id/send"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        android:onClick="onSendMessage" 
        android:text="@string/send" />
</LinearLayout>

activity_receive_message.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp"
    android:orientation="vertical"
    tools:context=".ReceiveMessageActivity">

    <TextView
        android:id="@+id/message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

CreateMessageActivity.java

package com.example.exampleandroid;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;

import androidx.annotation.Nullable;

public class CreateMessageActivity  extends Activity {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.create_message_activity);
    }

    public void onSendMessage(View view) {
        EditText messageView = (EditText) findViewById(R.id.message);
        String messageText = messageView.getText().toString();
        Intent intent = new Intent(this, ReceiveMessageActivity.class);
        intent.putExtra(ReceiveMessageActivity.EXTRA_MESSAGE, messageText);
        startActivity(intent);
    }
}

ReceiveMessageActivity.java

package com.example.exampleandroid;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;

public class ReceiveMessageActivity extends AppCompatActivity {

    public static final String EXTRA_MESSAGE = "message"; // 인텐트로 전달한 문자열의 이름

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_receive_message);
        Intent intent = getIntent();
        String messageText = intent.getStringExtra(EXTRA_MESSAGE); // 인텐트를 가져온 다음 getStringExtra()로 메세지를 얻음
        TextView messageView = (TextView) findViewById(R.id.message);
        messageView.setText(messageText); // 메세지 텍스트 뷰에 텍스트를 추가
    }
}