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Creating an Android app to send SMS text messages
Use Empty Views Activity
Creating an Android app to send SMS messages involves several key components:
Let's go through each step to build a simple SMS messaging app using Kotlin in Android Studio.
activity_main.xml: Design the UL
To implement View Binding in your Android Kotlin app for sending SMS messages, you'll first need to enable View Binding in your project's `build.gradle` file.
Then code `MainActivity.kt` and `activity_main.xml` accordingly.
Step 1: Enable View Binding
In your module-level (`app`) `build.gradle` file, add the following inside the `android` block:
```gradle
android {
...
viewBinding {
enabled = true
}
}
```
After adding this, click "Sync Now" in the bar that appears at the top of Android Studio.
### Step 2: activity_main.xml
Your `activity_main.xml` stays the same as before. Here's a reminder of what it looks like:
```xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="16dp">
<EditText
android:id="@+id/phoneNumberEditText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Phone Number"
android:inputType="phone" />
<EditText
android:id="@+id/messageEditText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Message"
android:inputType="textShortMessage" />
<Button
android:id="@+id/sendButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Send SMS" />
</LinearLayout>
```
Step 3: MainActivity.kt with View Binding
Now, modify your `MainActivity.kt` to use View Binding:
```kotlin
package com.example.smsmessenger
import android.Manifest
import android.content.Intent
import android.content.pm.PackageManager
import android.net.Uri
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import com.example.smsmessenger.databinding.ActivityMainBinding
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
binding.sendButton.setOnClickListener {
val phone = binding.phoneNumberEditText.text.toString()
val message = binding.messageEditText.text.toString()
sendSMS(phone, message)
}
}
private fun sendSMS(phone: String, message: String) {
if (ContextCompat.checkSelfPermission(this, Manifest.permission.SEND_SMS) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.SEND_SMS), REQUEST_SEND_SMS)
} else {
val intent = Intent(Intent.ACTION_SENDTO).apply {
data = Uri.parse("smsto:$phone")
putExtra("sms_body", message)
}
startActivity(intent)
}
}
companion object {
private const val REQUEST_SEND_SMS = 1
}
}
In this ViewBindings code formulation, `ActivityMainBinding` is a generated binding class that corresponds to the `activity_main.xml` layout.
This class holds direct references to all views that have an ID in the corresponding layout.
By using `binding`, you access these views directly, which is more efficient and null-safe compared to using `findViewById`.
### Important Steps to Remember:
1. **Enable View Binding**: Ensure it's enabled in your `build.gradle` file.
2. **Inflate the Binding**: Use `ActivityMainBinding.inflate()` to inflate the view binding.
3. **Access Views through Binding**: Use the `binding` variable to access your layout's views directly.
4. **Set Content View**: Set the content view to `binding.root` in `onCreate`.
5. **Build the Project**: After making these changes, build your project to generate the binding classes.
This setup provides a more robust, concise, and safer way to handle views in your Kotlin Android app than the old school findViewByID way.
Problem determination practices:
To use SMS functionality in your Android app, you need to declare the necessary permission in your `AndroidManifest.xml` file.
This is required because sending SMS is a protected action that can impact user privacy and costs.
Here's how you declare the SMS permission in `AndroidManifest.xml`:
```xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.yourapplication">
<!-- Add this line inside the manifest tag for SMS permission -->
<uses-permission android:name="android.permission.SEND_SMS"/>
<application
...
<!-- Your application components like activities go here -->
</application>
</manifest>
```
Replace `"com.example.yourapplication"` with your actual package name.
### Explanation:
- The `<uses-permission>` tag is used to request a specific permission. In this case, `android.permission.SEND_SMS` is the permission to send SMS messages.
- This permission is essential for the app to legally access the SMS functionality of the device. Without it, attempts to send SMS messages will fail.
- This declaration does not automatically grant the permission. When the app is installed, the user will be informed that the app requires this permission and will have to grant it manually, usually upon first use of the SMS feature.
- For Android 6.0 (API level 23) and higher, you must also request permissions at runtime within your application code. The static declaration in the manifest file is not sufficient on its own.
Remember, always respect the user's privacy and handle permissions responsibly in your applications.
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