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Introduction to SMS in Android

  • SMS (Short Message Service) ek popular feature hai mobile devices mein, jo text messages send aur receive karne ki facility deta hai. Android mein, SmsManager class ka use karke aap programmatically SMS bhej sakte ho apne application se.
  • Kyunki SMS ek sensitive operation hai (ye unwanted costs ya spam create kar sakta hai), Android strict permission checks enforce karta hai taaki users ko clearly pata ho ki unhone app ko SMS functionality use karne ki permission di hai.

Permission Model in Android

Android permissions 2 categories mein divide ki gayi hain:

  • Static Permissions: Ye AndroidManifest.xml file mein define hoti hain. Ye system ko batati hain ki aapke app ko kaun kaun si permissions chahiye. Jaise, SMS bhejne ke liye aapko ye permission add karni hoti hai:
                                        
    <uses-permission android:name="android.permission.SEND_SMS" />
                                        
                                    

    Is permission ko add karne ka matlab hai ki aapka app SMS bhejne ka intention declare kar raha hai. Ye permission tab check hoti hai jab app install ki ja rahi hoti hai.

  • Dynamic Permissions: Android 6.0 (API level 23) aur uske baad introduce ki gayi, ye sensitive permissions (jaise SMS) ke liye runtime par user se consent maangti hain. Iska purpose hai ki user aware ho ki app kya kar rahi hai aur user ko ye control mile ki wo isse allow kare ya nahi.

Steps for Implementing SMS in Android

To implement SMS functionality in Android, the following steps are required:

  • AndroidManifest.xml file mein static permission android.permission.SEND_SMS add karein.
  • Runtime par check karein ki SEND_SMS permission granted hai ya nahi, checkSelfPermission method ka use karke.
  • Agar permission nahi di gayi hai, to requestPermissions method ka use karke dynamically permission maangein.
  • Jab permission mil jaye, tab SmsManager class ka use karke SMS programmatically bhejein.

SmsManager Class

SmsManager Android ka primary class hai jo SMS bhejne ke liye use hota hai. Ye developers ko text messages (SMS) aur multimedia messages (MMS) dono bhejne ki facility deta hai. Iske kuch important points hain:

  • Ye programmatically messages bhej sakta hai bina default messaging app ko open kiye.
  • Ye single-part aur multi-part messages dono ko support karta hai. Multi-part messages ka use long texts ke liye hota hai jo single SMS ke character limit (generally 160 characters) se zyada ho jate hain.
  • Ye data messages bhejne ki bhi facility deta hai, jo binary data wale SMS hote hain.

An example usage of SmsManager to send a simple SMS:

                            
SmsManager smsManager = SmsManager.getDefault();
smsManager.sendTextMessage(
    "1234567890",  // Destination phone number
    null,          // SMS Center number (null for default)
    "Hello, this is a test message!", // Message content
    null,          // Sent intent (for sent notification)
    null           // Delivery intent (for delivery notification)
);
                            
                        

Is class ko use karne ke liye AndroidManifest.xml file mein appropriate permission declare karni hoti hai, jaise:

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

Introduction to SMS in Android

  • SMS (Short Message Service) is a widely used feature in mobile devices, enabling the sending and receiving of text messages. In Android, the SmsManager class provides the functionality to send SMS programmatically from your application.
  • Since SMS is a sensitive operation (it can lead to unwanted costs or spam), Android enforces strict permission checks to ensure that users have explicitly allowed apps to use SMS functionality.

Permission Model in Android

Android permissions can be divided into two categories:

  • Static Permissions: These are defined in the AndroidManifest.xml file. They inform the system about the permissions your app requires. For example, to send SMS, the following permission must be added:
                                        
    <uses-permission android:name="android.permission.SEND_SMS" />
                                        
                                    

    Adding this permission means your app declares its intention to send SMS. This permission will be checked when the app is installed.

  • Dynamic Permissions: Introduced in Android 6.0 (API level 23) and above, these require you to ask for the user's consent at runtime for sensitive permissions like SMS. This ensures that users are aware of what the app is doing and gives them control over whether to allow it or not.

Steps for Implementing SMS in Android

To implement SMS functionality in Android, the following steps are required:

  • Add the static permission android.permission.SEND_SMS in the AndroidManifest.xml file.
  • Check dynamically at runtime if the SEND_SMS permission is granted using the method checkSelfPermission.
  • Request the permission dynamically using requestPermissions if it hasn't been granted.
  • Use the SmsManager class to send the SMS programmatically once the permission is granted.

SmsManager Class

SmsManager is the primary class in Android used for sending SMS messages. It allows developers to send both text messages (SMS) and multimedia messages (MMS). It provides various methods to customize the message-sending process. Some key points about SmsManager are:

  • It can send messages programmatically without opening the default messaging app.
  • It supports both single-part and multi-part messages. Multi-part messages are useful for long texts that exceed the character limit of a single SMS (usually 160 characters).
  • It also enables sending data messages, which are SMS messages containing binary data.

An example usage of SmsManager to send a simple SMS:

                            
SmsManager smsManager = SmsManager.getDefault();
smsManager.sendTextMessage(
    "1234567890",  // Destination phone number
    null,          // SMS Center number (null for default)
    "Hello, this is a test message!", // Message content
    null,          // Sent intent (for sent notification)
    null           // Delivery intent (for delivery notification)
);
                            
                        

This class requires the appropriate permissions in the AndroidManifest file, such as:

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

Complete Example Program

                            
package com.example.mybcaapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.telephony.SmsManager;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

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

    // Method to handle SMS sending
    public void sendSMS(View view) {
        // Check if the SEND_SMS permission is granted
        if (checkSelfPermission(Manifest.permission.SEND_SMS) == PackageManager.PERMISSION_GRANTED) {
            sendMySMS();
        } else {
            // Request the SEND_SMS permission
            requestPermissions(new String[]{Manifest.permission.SEND_SMS}, 1);
        }
    }

    // Method to send SMS
    public void sendMySMS() {
        String number = "xxxxxxxx89"; // Recipient's phone number
        String message = "Hello from Android"; // SMS content

        try {
            SmsManager smsManager = SmsManager.getDefault();
            smsManager.sendTextMessage(number, null, message, null, null);

            Toast.makeText(this, "SMS sent", Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            Toast.makeText(this, "SMS not Sent", Toast.LENGTH_SHORT).show();
        }
    }
}
                        
                        
                            <?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">

    <Button
        android:id="@+id/sendButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Send SMS"
        android:onClick="sendSMS"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintBottom_toBottomOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>
                        
                    
                            <manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.mybcaapplication">

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

    <application
        android:allowBackup="true"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.MyBCAApplication">

        <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>
                        
                    

Explanation of Key Functions and Classes

  • SmsManager: This is the main class used to send SMS messages. It provides methods to send text messages or even multimedia messages.
  • checkSelfPermission(String permission): This method checks if a specific permission has been granted. It takes a permission string, such as Manifest.permission.SEND_SMS, and returns:
    • PackageManager.PERMISSION_GRANTED: If the permission is granted.
    • PackageManager.PERMISSION_DENIED: If the permission is denied.
  • requestPermissions(String[] permissions, int requestCode): This method requests permissions at runtime. It displays a system dialog to the user asking for consent. Parameters include:
    • permissions: An array of permissions (e.g., {Manifest.permission.SEND_SMS}).
    • requestCode: A unique code to identify the permission request.
  • sendTextMessage: This is the main method of SmsManager for sending SMS. Key parameters:
    • Destination Address: Recipient's phone number.
    • SC Address: Service center address (can be null to use the default).
    • Text: The SMS content.
    • SentIntent: Pending intent triggered when the SMS is sent (can be null).
    • DeliveryIntent: Pending intent triggered when the SMS is delivered (can be null).

Introduction to Sensor Devices

What is a Sensor?

Sensor ek aisi device hai jo kisi physical quantity ko detect ya measure karke usse ek signal me convert karti hai jo machine ya system samajh sake.
Simple words me, sensors machines ke liye senses ki tarah kaam karte hain, jise wo apne environment ko perceive kar sakein, bilkul waise hi jaise humans apni eyes, ears, aur senses ka use karte hain.
For example, ek temperature sensor heat measure kar sakta hai aur ek light sensor brightness detect kar sakta hai.

How Do Sensors Work?

Sensors kaam karte hain kuch steps me, jahan wo physical phenomena ko useful information me convert karte hain:

  1. Physical Phenomenon: Sensor kisi physical quantity ke sath interact karta hai, jaise temperature, light, pressure, ya motion.
    Example: Ek thermometer heat ke sath interact karke temperature measure karta hai.
  2. Transduction: Sensor detect ki gayi physical quantity ko ek electrical signal me convert karta hai. Ye kisi bhi sensor ki core functionality hoti hai.
    Example: Ek photoresistor apni resistance ko light ki intensity ke basis par change karta hai.
  3. Signal Processing: Raw electrical signal ko process kiya jata hai, jisse noise hatayi jaye ya desired information ko enhance kiya jaye better accuracy ke liye.
    Example: Ek temperature sensor ke paas ek circuit ho sakta hai jo readings me sudden environmental changes ki wajah se hone wali fluctuations ko smooth kare.
  4. Output: Processed signal ya to display hota hai, store hota hai, ya phir kisi system ko control karne ya event trigger karne ke liye use hota hai.
    Example: Car ke tire ka pressure sensor pressure ko screen pe display kar sakta hai ya low pressure hone par alarm trigger kar sakta hai.

Sensors kaam karte hain physical quantities jaise temperature, light, ya pressure ke saath interact karke aur unhe electrical signals mein convert karke. Is process ko transduction kaha jata hai. Ye signals phir process kiye jate hain taaki noise remove kiya ja sake aur accuracy badh sake, jo reliable data ensure karta hai. Processed signals ka use information display karne, store karne, ya actions trigger karne ke liye hota hai, jaise tire pressure screen par dikhana ya alarm activate karna.

Types of Sensors

Sensors alag-alag types ke hote hain, har ek specific physical phenomena detect karne ke liye design kiye gaye hai. Following are some common types of sensors:

1. Temperature Sensors

Yeh sensors temperature measure karte hain. Common types include:

  • Thermistors: Temperature ke basis par apni resistance change karte hain.
    Example: Thermostats me use hote hain room temperature regulate karne ke liye.
  • Thermocouples: Jab do points ke beech temperature difference hota hai to ek chhota voltage generate karte hain.
    Example: Industrial machinery me high temperatures monitor karne ke liye commonly use hote hain.
  • RTDs (Resistance Temperature Detectors): Inki resistance temperature ke sath linearly change hoti hai, jo accurate readings deti hai.
    Example: Laboratories me precise temperature measurement ke liye use hote hain.

2. Light Sensors

Yeh sensors light intensity detect karte hain. Types include:

  • Photoresistors: Light intensity ke basis par apni resistance change karte hain.
    Example: Streetlights me use hote hain jo raat me automatically on ho jate hain.
  • Photodiodes: Light ko electrical current me convert karte hain.
    Example: Solar panels me use hote hain sunlight se electricity generate karne ke liye.
  • Phototransistors: Light ke generate kiye gaye electrical current ko amplify karte hain.
    Example: TV remotes aur light-sensitive alarms me use hote hain.

3. Pressure Sensors

Yeh sensors pressure measure karte hain aur zyada tar industrial aur automotive applications me milte hain. Types include:

  • Piezoresistive Sensors: Applied pressure ke sath apni resistance change karte hain.
    Example: Digital weighing scales me use hote hain.
  • Capacitive Sensors: Capacitance me changes detect karke pressure measure karte hain.
    Example: Touch-sensitive elevator buttons me use hote hain.
  • Strain Gauge Sensors: Jab strain apply hoti hai to resistance change karte hain.
    Example: Bridges me structural integrity monitor karne ke liye use hote hain.

4. Motion Sensors

Yeh sensors motion ya movement detect karte hain. Examples include:

  • Accelerometers: Alag-alag axes me acceleration measure karte hain.
    Example: Smartphones me use hote hain screen rotation enable karne ke liye jab phone tilt hota hai.
  • Gyroscopes: Angular velocity ya orientation measure karte hain.
    Example: Drones me flight stabilize karne ke liye use hote hain.
  • Magnetometers: Magnetic fields detect karte hain.
    Example: Smartphones ke digital compasses me use hote hain.

5. Chemical Sensors

Yeh sensors chemical properties detect karte hain. Types include:

  • Gas Sensors: Specific gases ki presence detect karte hain.
    Example: Homes me carbon monoxide detectors safety ke liye use hote hain.
  • pH Sensors: Solution ki acidity ya alkalinity measure karte hain.
    Example: Agriculture me soil quality test karne ke liye use hote hain.

Applications of Sensors

Sensors kaafi important role play karte hain different fields me, aur inka use almost endless hai. Following are some common applications:

  • Smartphones: Sensors jaise accelerometers, gyroscopes aur proximity sensors features enable karte hain, jaise auto-rotation, gesture control, aur adaptive brightness.
    Example: Jab aap phone ko call ke time apne ear ke paas le jaate ho, screen automatically off ho jati hai (proximity sensor).
  • Automotive Industry: Sensors safety aur performance improve karte hain, jaise airbag systems, tire pressure monitoring, aur anti-lock brakes.
    Example: Rear-view camera sensor parking me help karta hai obstacles detect karke.
  • Healthcare: Medical devices sensors ka use karke vital signs monitor karte hain, jaise heart rate, blood pressure, aur glucose levels.
    Example: Fitness trackers motion sensors ka use karke steps count karte hain aur activity monitor karte hain.
  • Industrial Automation: Sensors machinery control karte hain aur manufacturing processes monitor karte hain for quality aur efficiency.
    Example: Assembly lines temperature aur pressure sensors ka use karte hain product standards maintain karne ke liye.
  • Home Automation: Sensors homes ko smarter banate hain by enabling automatic lighting, climate control, aur security systems.
    Example: Motion sensor lights on kar deta hai jab aap room me enter karte ho.
1

Introduction to Sensor Devices

What is a Sensor?

A sensor is a device that detects or measures a physical quantity and converts it into a signal that can be understood by a machine or a system. In simpler terms, sensors act as the senses of machines, helping them to perceive the environment just as humans do with their eyes, ears, and other senses. For example, a temperature sensor can measure heat, and a light sensor can detect brightness.

How Do Sensors Work?

Sensors operate in several steps, converting physical phenomena into useful information:

  1. Physical Phenomenon: The sensor interacts with a physical quantity such as temperature, light, pressure, or motion.
    Example: A thermometer interacts with heat to measure temperature.
  2. Transduction: The sensor converts the detected physical quantity into an electrical signal. This is the core functionality of any sensor.
    Example: A photoresistor changes its resistance based on the intensity of light.
  3. Signal Processing: The raw electrical signal is processed to remove noise or enhance the desired information for better accuracy.
    Example: A temperature sensor may have a circuit to smooth fluctuations in readings caused by sudden environmental changes.
  4. Output: The processed signal is either displayed, stored, or used to control a system or trigger an event.
    Example: A pressure sensor in a car's tires might display the pressure on a screen or trigger an alarm if the pressure is too low.

Sensors work by interacting with physical quantities like temperature, light, or pressure and converting them into electrical signals through a process called transduction. These signals are then processed to remove noise and enhance accuracy, ensuring reliable data. Finally, the processed signals are used to display information, store it, or trigger actions, like showing tire pressure on a screen or activating an alarm.

Types of Sensors

Sensors come in many types, each designed to detect specific physical phenomena. Below are some commonly used types:

1. Temperature Sensors

These sensors measure temperature. Common types include:

  • Thermistors: Change resistance based on temperature.
    Example: Used in thermostats to regulate room temperature.
  • Thermocouples: Generate a small voltage when there is a temperature difference between two points.
    Example: Commonly used in industrial machinery to monitor high temperatures.
  • RTDs (Resistance Temperature Detectors): Their resistance changes linearly with temperature, offering accurate readings.
    Example: Used in laboratories for precise temperature measurement.

2. Light Sensors

These sensors detect light intensity. Types include:

  • Photoresistors: Change resistance with light intensity.
    Example: Used in streetlights that turn on automatically at night.
  • Photodiodes: Convert light into electrical current.
    Example: Found in solar panels to generate electricity from sunlight.
  • Phototransistors: Amplify the electrical current generated by light.
    Example: Used in devices like TV remotes and light-sensitive alarms.

3. Pressure Sensors

These sensors measure pressure and are often found in industrial and automotive applications. Types include:

  • Piezoresistive Sensors: Change resistance with applied pressure.
    Example: Used in digital weighing scales.
  • Capacitive Sensors: Measure pressure by detecting changes in capacitance.
    Example: Used in touch-sensitive elevator buttons.
  • Strain Gauge Sensors: Change resistance when strained.
    Example: Used in bridges to monitor structural integrity.

4. Motion Sensors

These sensors detect motion or movement. Examples include:

  • Accelerometers: Measure acceleration in various axes.
    Example: Found in smartphones to enable screen rotation when the phone is tilted.
  • Gyroscopes: Measure angular velocity or orientation.
    Example: Used in drones to stabilize flight.
  • Magnetometers: Detect magnetic fields.
    Example: Found in digital compasses in smartphones.

5. Chemical Sensors

These sensors detect chemical properties. Types include:

  • Gas Sensors: Detect the presence of specific gases.
    Example: Carbon monoxide detectors in homes for safety.
  • pH Sensors: Measure the acidity or alkalinity of a solution.
    Example: Used in agriculture to test soil quality.

Applications of Sensors

Sensors play a vital role in various fields, and their applications are nearly endless. Here are some common uses:

  • Smartphones: Sensors like accelerometers, gyroscopes, and proximity sensors enable features such as auto-rotation, gesture control, and adaptive brightness.
    Example: Your phone screen turns off automatically when you hold it near your ear during a call (proximity sensor).
  • Automotive Industry: Sensors improve safety and performance, such as airbag systems, tire pressure monitoring, and anti-lock brakes.
    Example: A rear-view camera sensor assists in parking by detecting obstacles.
  • Healthcare: Medical devices use sensors to monitor vital signs like heart rate, blood pressure, and glucose levels.
    Example: Fitness trackers use motion sensors to count steps and monitor activity.
  • Industrial Automation: Sensors control machinery and monitor manufacturing processes for quality and efficiency.
    Example: Assembly lines use temperature and pressure sensors to maintain product standards.
  • Home Automation: Sensors make homes smarter by enabling automatic lighting, climate control, and security systems.
    Example: A motion sensor can turn lights on when you enter a room.