ที่ MainActivity ให้เรียก SecondActivity ด้วย startActivityForResult() และรอรับข้อมูลกลับมาด้วย onActivityResult()

ไฟล์ที่เกี่ยวข้อง

• AndroidManifest.xml
• activity_main.xml
• MainActivity.java
• activity_second.xml
• SecondActivity.java

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:dist="http://schemas.android.com/apk/distribution"
    package="com.phaisarn.myapplication">

    <dist:module dist:instant="true" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".SecondActivity"
            android:parentActivityName=".MainActivity"></activity>
        <activity android:name=".MainActivity">
            <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"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

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

</LinearLayout>

MainActivity.java

package com.phaisarn.myapplication;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

    public final static String MESSAGE2 = "Message2";
    public static final int CODE = 1;

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

        Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(getApplicationContext(), SecondActivity.class);
                startActivityForResult(intent, CODE);
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == CODE) {
            if (resultCode == RESULT_OK) {
                String msg = data.getStringExtra(MESSAGE2);
                Toast.makeText(this, msg, Toast.LENGTH_SHORT).show();
            }
        }
    }
}

activity_second.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    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="horizontal">

        <EditText
            android:id="@+id/editText"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:hint="Text Me"
            android:text="Hello MainActivity" />

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

</LinearLayout>

SecondActivity.java

package com.phaisarn.myapplication;

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 SecondActivity extends AppCompatActivity {

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

        final EditText editText = findViewById(R.id.editText);

        Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String msg = editText.getText().toString();

                Intent intent = new Intent();
                intent.putExtra(MainActivity.MESSAGE2, msg);
                setResult(RESULT_OK, intent);
                finish();
            }
        });
    }
}

บรรทัดที่ 29: finish() เป็นการกำหนดให้ SecondActivity นี้ทำงานเสร็จสิ้น ให้ปิดทันที