Gửi Email với file đính kèm Android Kotlin

Hướng dẫn này minh họa cách gửi email kèm file đính kèm (attachment) trong Android sử dụng Kotlin.

Bước 1: Tạo dự án mới

Mở Android Studio, chọn File → New Project và điền thông tin cần thiết.

Bước 2: Thiết kế giao diện (activity_main.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:tools="https://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="4dp"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/etTo"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="5dp"
        android:hint="Email người nhận"
        android:inputType="textEmailAddress"
        android:singleLine="true" />

    <EditText
        android:id="@+id/etSubject"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="5dp"
        android:hint="Tiêu đề"
        android:singleLine="true" />

    <EditText
        android:id="@+id/etMessage"
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:layout_margin="5dp"
        android:gravity="top|start"
        android:hint="Nội dung email"
        android:inputType="textMultiLine" />

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <Button
            android:id="@+id/btSend"
            android:layout_width="80dp"
            android:layout_height="50dp"
            android:layout_margin="5dp"
            android:text="Gửi" />

        <Button
            android:id="@+id/btAttachment"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentEnd="true"
            android:text="Đính kèm" />

    </RelativeLayout>

    <TextView
        android:id="@+id/tvAttachment"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:drawableStart="@drawable/ic_baseline_attach_file_24"
        android:visibility="gone" />

</LinearLayout>

Bước 3: Viết code MainActivity.kt

import android.content.Intent
import android.net.Uri
import android.os.Bundle
import android.view.View
import android.widget.Button
import android.widget.EditText
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {
    lateinit var etEmail: EditText
    lateinit var etSubject: EditText
    lateinit var etMessage: EditText
    lateinit var send: Button
    lateinit var attachment: Button
    lateinit var tvAttachment: TextView
    lateinit var email: String
    lateinit var subject: String
    lateinit var message: String
    var uri: Uri? = null
    private val PICK_FROM_GALLERY = 101

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        title = "KotlinApp"

        etEmail = findViewById(R.id.etTo)
        etSubject = findViewById(R.id.etSubject)
        etMessage = findViewById(R.id.etMessage)
        attachment = findViewById(R.id.btAttachment)
        tvAttachment = findViewById(R.id.tvAttachment)
        send = findViewById(R.id.btSend)

        send.setOnClickListener { sendEmail() }
        attachment.setOnClickListener { openFilePicker() }
    }

    private fun openFilePicker() {
        val intent = Intent().apply {
            type = "image/*"
            action = Intent.ACTION_GET_CONTENT
            putExtra("return-data", true)
        }
        startActivityForResult(Intent.createChooser(intent, "Chọn ứng dụng"), PICK_FROM_GALLERY)
    }

    private fun sendEmail() {
        try {
            email = etEmail.text.toString()
            subject = etSubject.text.toString()
            message = etMessage.text.toString()

            val emailIntent = Intent(Intent.ACTION_SEND).apply {
                type = "plain/text"
                putExtra(Intent.EXTRA_EMAIL, arrayOf(email))
                putExtra(Intent.EXTRA_SUBJECT, subject)
                putExtra(Intent.EXTRA_TEXT, message)
                uri?.let { putExtra(Intent.EXTRA_STREAM, it) }
            }

            startActivity(Intent.createChooser(emailIntent, "Gửi email qua..."))
        } catch (t: Throwable) {
            Toast.makeText(this, "Gửi thất bại: $t", Toast.LENGTH_LONG).show()
        }
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if (requestCode == PICK_FROM_GALLERY && resultCode == RESULT_OK) {
            data?.data?.let {
                uri = it
                tvAttachment.text = uri?.lastPathSegment
                tvAttachment.visibility = View.VISIBLE
            }
        }
    }
}

Bước 4: Cấu hình AndroidManifest.xml (cần quyền)

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="https://schemas.android.com/apk/res/android"
    package="com.example.q11">

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

    <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=".MainActivity">
            <intent-filter>
                
                
            </intent-filter>
        </activity>

    </application>
</manifest>

Chạy ứng dụng

Kết nối thiết bị, nhấn Run. Nhập email, subject, nội dung. Nhấn "Đính kèm" chọn ảnh từ gallery. Nhấn "Gửi" → Mở chooser chọn app email (Gmail, Outlook...).

Giải thích Intent.ACTION_SEND

Gửi nhiều file đính kèm

val uris: ArrayList = arrayListOf(uri1, uri2, uri3)
val emailIntent = Intent(Intent.ACTION_SEND_MULTIPLE).apply {
    type = "*/*"
    putParcelableArrayListExtra(Intent.EXTRA_STREAM, uris)
    // ... other extras
}

Lưu ý Android 10+ (Scoped Storage)

• Không cần READ_EXTERNAL_STORAGE khi dùng ACTION_GET_CONTENT/ACTION_OPEN_DOCUMENT
• Uri trả về là content:// (không phải file://)
• Email app cần hỗ trợ content Uri (Gmail, Outlook hỗ trợ tốt)