[Android] 액티비티 간의 단방향 데이터 전달 방법. Serializable, putExtra(), getSerializableExtra()

Intent.putExtra() 

key, value 형식으로 데이터를 다음 액티비티로 보낼 수 있다.

 

getIntent()

보낸 intent 객체를 반환한다.

 

getIntent().getStringExtra(name);

String 형식의 name의 값을 반환한다.

 

getIntent().getIntExtra(name, default);

Int 형식의 name 값을 반환한다.

값이 존재하지 안으면 default값을 반환한다.

 

(ClassType) getIntent().getSerializableExtra(name);

ClassType의 객체가 넘어오면 이 객체를 받아온다.

 

예제

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.fullspringwater.data">

    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.Data"
        tools:targetApi="31">
        <activity
            android:name=".SecondActivity"
            android:exported="false" />
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

 

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".MainActivity">


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <EditText
            android:id="@+id/editEmail"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="text"
            android:hint="이메일"
            android:textSize="30sp" />

        <EditText
            android:id="@+id/editName"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="text"
            android:hint="이름"
            android:textSize="30sp" />

        <EditText
            android:id="@+id/editAge"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number"
            android:hint="나이"
            android:textSize="30sp" />

        <Button
            android:id="@+id/button"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Button" />

    </LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

activity_second.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".SecondActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <TextView
            android:id="@+id/txtEmail"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="TextView"
            android:textSize="30sp" />

        <TextView
            android:id="@+id/txtName"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="TextView"
            android:textSize="30sp" />

        <EditText
            android:id="@+id/editAge"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number"
            android:hint="나이"
            android:textSize="30sp" />

        <Button
            android:id="@+id/button"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Button"
            android:textSize="30sp" />
    </LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

방법 1. 객체의 변수를 하나씩 보내는 방법

User.java

package com.fullspringwater.data;

public class User {
    public String email;
    public String name;
    public int ageStr;

    public User(String email, String name, int age){
        this.email = email;
        this.name = name;
        this.ageStr = age;
    }



}

MainActivity.java

package com.fullspringwater.data;

import androidx.activity.result.ActivityResult;
import androidx.activity.result.ActivityResultCallback;
import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

    EditText editEmail;
    EditText editName;
    EditText editAge;
    Button button;
	User user;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editEmail = findViewById(R.id.editEmail);
        editName = findViewById(R.id.editName);
        editAge = findViewById(R.id.editAge);
        button = findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                String email = editEmail.getText().toString().trim();
                String name = editName.getText().toString().trim();
                String ageStr = editAge.getText().toString().trim();

                int age = Integer.parseInt(ageStr);
				
                user = new User(email, name, age);

                // 새로운 액티비티를 띄우고,
                // 데이터를 전달한다.

                Intent intent = new Intent(MainActivity.this, SecondActivity.class);
                // 데이터를 key, value 형식으로 보낸다.
                intent.putExtra("email", user.email);
                intent.putExtra("name", user.name);
                intent.putExtra("age", user.age);

                // 데이터만 전달하는 경우
                startActivity(intent);

            }
        });
    }
}

 

 

SecondActivity.java

package com.fullspringwater.data;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class SecondActivity extends AppCompatActivity {

    TextView txtEmail;
    TextView txtName;
    EditText editAge;
    Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);

        // 넘어오는 데이터가 있으면 처리 해준다.
        String email = getIntent().getStringExtra("email");
        String name = getIntent().getStringExtra("name");
        int age =getIntent().getIntExtra("age", 0);

        // 화면과 연결
        txtEmail = findViewById(R.id.txtEmail);
        txtName = findViewById(R.id.txtName);
        editAge = findViewById(R.id.editAge);
        button = findViewById(R.id.button);

        // 데이터를 화면에 셋팅
        txtEmail.setText(email);
        txtName.setText(name);
        editAge.setText(""+age);



    }
}

 

실행화면

 

버튼 누른 후

 

방법 2.  객체 전체를 보내는 방법

User.java

implements Serializable 코드를 추가해줍니다.

package com.fullspringwater.data;

import java.io.Serializable;

public class User implements Serializable {
    public String email;
    public String name;
    public int age;

    public User(String email, String name, int age){
        this.email = email;
        this.name = name;
        this.age = age;
    }



}

 

MainActivity.java

package com.fullspringwater.data;

import androidx.activity.result.ActivityResult;
import androidx.activity.result.ActivityResultCallback;
import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

    EditText editEmail;
    EditText editName;
    EditText editAge;
    Button button;
	User user;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editEmail = findViewById(R.id.editEmail);
        editName = findViewById(R.id.editName);
        editAge = findViewById(R.id.editAge);
        button = findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                String email = editEmail.getText().toString().trim();
                String name = editName.getText().toString().trim();
                String ageStr = editAge.getText().toString().trim();

                int age = Integer.parseInt(ageStr);
				
                user = new User(email, name, age);

                // 새로운 액티비티를 띄우고,
                // 데이터를 전달한다.

                Intent intent = new Intent(MainActivity.this, SecondActivity.class);
                // 데이터를 key, value 형식으로 보낸다.
                intent.putExtra("user", user);

                // 데이터만 전달하는 경우
                startActivity(intent);

            }
        });
    }
}

 

SecondActivity.java

package com.fullspringwater.data;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class SecondActivity extends AppCompatActivity {

    TextView txtEmail;
    TextView txtName;
    EditText editAge;
    Button button;
    User user;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);

        // 넘어오는 데이터가 있으면 처리 해준다.
        // 다른 액티비티로부터 넘겨받은 데이터가 있으면, 이 데이터를 먼저 처리하자.
        user = (User) getIntent().getSerializableExtra("user");

        // 화면과 연결
        txtEmail = findViewById(R.id.txtEmail);
        txtName = findViewById(R.id.txtName);
        editAge = findViewById(R.id.editAge);
        button = findViewById(R.id.button);

        // 데이터를 화면에 셋팅
        txtEmail.setText(user.email);
        txtName.setText(user.name);
        editAge.setText(""+user.age);


        // 버튼 이벤트 처리
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                // 1. 수정한 나이 데이터를 가져온다.
                int age = Integer.parseInt(editAge.getText().toString().trim());
                // 이 나이 데이터를 MainActivity에 전달한다.
                Intent intent = new Intent();
                intent.putExtra("age", age);
                setResult(0, intent);
                // 3. 이 액티비티는 종료한다.
                finish();

            }
        });
    }
}

실행화면

 

버튼 누른 후