Cách truyền dữ liệu giữa các Activity trong Android

Hướng dẫn này minh họa cách truyền dữ liệu đơn giản (String, int) giữa hai Activity bằng Intent và Bundle.

Bước 1: Tạo dự án mới

Mở Android Studio, chọn File → New Project.

Bước 2: Giao diện màn hình 1 (res/layout/activity_first.xml)

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:tools="https://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/activity_first"
    android:paddingTop="60dp"
    tools:context=".FirstActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:padding="16dp">

        <EditText
            android:id="@+id/editTxtName"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Nhập tên"
            android:ems="10" />

        <Spinner
            android:id="@+id/ageGroupSpinner"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp" />

        <Button
            android:id="@+id/btnSubmit"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:layout_gravity="center_horizontal"
            android:text="Gửi" />

    </LinearLayout>
</RelativeLayout>

Bước 3: Giao diện màn hình 2 (res/layout/activity_second.xml)

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/activity_second"
    android:paddingTop="60dp">

    <TextView
        android:id="@+id/displayMsg"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textSize="20sp"
        android:layout_centerInParent="true" />

</RelativeLayout>

Bước 4: FirstActivity - Gửi (src/FirstActivity.java)

package com.example.sample;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;

public class FirstActivity extends AppCompatActivity {
    private EditText editTxtName;
    private Spinner ageGroupSpinner;
    private Button btnSubmit;
    private int selectedAgeGroup = 0;

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

        editTxtName = findViewById(R.id.editTxtName);
        ageGroupSpinner = findViewById(R.id.ageGroupSpinner);
        btnSubmit = findViewById(R.id.btnSubmit);

        // Setup Spinner
        String[] ageGroups = {"Dưới 18", "18-30", "Trên 30"};
        ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, ageGroups);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        ageGroupSpinner.setAdapter(adapter);

        ageGroupSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                selectedAgeGroup = position;
            }
            @Override
            public void onNothingSelected(AdapterView<?> parent) {}
        });

        btnSubmit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = editTxtName.getText().toString().trim();
                if (name.isEmpty()) {
                    Toast.makeText(FirstActivity.this, "Tên không được để trống!", Toast.LENGTH_LONG).show();
                    return;
                }

                Intent intent = new Intent(FirstActivity.this, SecondActivity.class);
                Bundle bundle = new Bundle();
                bundle.putString("name", name);
                bundle.putInt("ageGroup", selectedAgeGroup);
                intent.putExtra("userBundle", bundle);
                startActivity(intent);
            }
        });
    }
}

Bước 5: SecondActivity - Nhận (src/SecondActivity.java)

package com.example.sample;

import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;

public class SecondActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);

        TextView displayMsg = findViewById(R.id.displayMsg);
        Intent intent = getIntent();
        Bundle bundle = intent.getBundleExtra("userBundle");

        if (bundle != null) {
            String name = bundle.getString("name", "");
            int ageGroup = bundle.getInt("ageGroup", 0);

            String message = "Xin chào, " + name + "! ";
            switch (ageGroup) {
                case 0: message += "Hãy tận hưởng cuộc sống!"; break;
                case 1: message += "Đừng quá nghiêm trọng, hãy vui lên!"; break;
                case 2: message += "Hãy kỷ niệm những kỉ niệm đẹp!"; break;
            }
            displayMsg.setText(message);
        }
    }
}

Bước 6: Manifest (AndroidManifest.xml)

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="https://schemas.android.com/apk/res/android" package="com.example.sample">
    <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=".FirstActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".SecondActivity" />
    </application>
</manifest>

Chạy ứng dụng

Kết nối thiết bị, nhấn Run. Nhập tên, chọn nhóm tuổi, nhấn "Gửi" để xem thông điệp tùy chỉnh trên màn hình 2.