How to Build a SOS Mobile Application in Android Studio?

Last Updated : 30 May, 2026

An SOS mobile application is an emergency assistance app designed to help users quickly contact trusted people during dangerous or critical situations. These apps provide fast communication and safety features that can be triggered without manually operating the phone for a long time.

  • Sends emergency alerts and live location to saved contacts instantly
  • Provides quick access to help during accidents, attacks, or medical emergencies
  • Uses accessibility features like shake detection or emergency buttons for faster response

Pre-requisites:

Step by Step Implementation

Follow these steps to create a Mobile Application in Androide Studio.

Step 1: Create a New Project

  • Open Android Studio
  • Click New Project
  • Select Empty Activity
  • Language: Java or Kotlin
  • Minimum SDK: Android 6.0 or above
  • Finish project setup

Step 2: Creating the Contacts Module

Create a Contacts folder to manage all contact-related files used for storing and displaying emergency contacts in the ListView.

Step 2.1: Creating model class for Contact

We create this class to store contact details like name and phone number in a structured format. It also ensures the phone number is properly validated before use.

Java 
public class ContactModel {
    private int id;
    private String phoneNo;
    private String name;

    // constructor
    public ContactModel(int id, String name, String phoneNo) {
        this.id = id;
        this.phoneNo = validate(phoneNo);
        this.name = name;
    }

    // validate the phone number, and reformat is necessary
    private String validate(String phone) {
        
        // creating StringBuilder for both the cases
        StringBuilder case1 = new StringBuilder("+91");
        StringBuilder case2 = new StringBuilder("");

        // check if the string already has a "+"
        if (phone.charAt(0) != '+') {
            for (int i = 0; i < phone.length(); i++) {
                // remove any spaces or "-"
                if (phone.charAt(i) != '-' && phone.charAt(i) != ' ') {
                    case1.append(phone.charAt(i));
                }
            }
            return case1.toString();
        } else {
            for (int i = 0; i < phone.length(); i++) {
                // remove any spaces or "-"
                if (phone.charAt(i) != '-' || phone.charAt(i) != ' ') {
                    case2.append(phone.charAt(i));
                }
            }
            return case2.toString();
        }

    }

    public String getPhoneNo() {
        return phoneNo;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

 Step 2.2: Creating a Database Helper class

We use this class to store and manage emergency contacts using SQLite database. It ensures contacts remain saved permanently even after app restart.

Java 
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import java.util.ArrayList;
import java.util.List;

public class DbHelper extends SQLiteOpenHelper {
    
    // Database Version
    private static final int DATABASE_VERSION = 1;

    // Database Name
    private static final String DATABASE_NAME = "contactdata";

    // Country table name
    private static final String TABLE_NAME= "contacts";

    // Country Table Columns names
    private static final String KEY_ID = "id";
    private static final String NAME = "Name";
    private static final String PHONENO = "PhoneNo";


    public DbHelper(Context context){
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        // create the table for the first time
        String CREATE_COUNTRY_TABLE = "CREATE TABLE " + TABLE_NAME + "("
                + KEY_ID + " INTEGER PRIMARY KEY," + NAME + " TEXT,"
                + PHONENO + " TEXT" + ")";
        db.execSQL(CREATE_COUNTRY_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {

    }

    // method to add the contact
    public void addcontact(ContactModel contact){
        SQLiteDatabase db=this.getWritableDatabase();
        ContentValues c=new ContentValues();
        c.put(NAME,contact.getName());
        c.put(PHONENO,contact.getPhoneNo());
        db.insert(TABLE_NAME,null,c);
        db.close();
    }

    // method to retrieve all the contacts in List
    public List<ContactModel> getAllContacts(){
        List<ContactModel> list=new ArrayList<>();
        String query="SELECT * FROM "+TABLE_NAME;
        SQLiteDatabase db=this.getReadableDatabase();
        Cursor c=db.rawQuery(query,null);
        if(c.moveToFirst()) {
            do {

                list.add(new ContactModel(c.getInt(0),c.getString(1),c.getString(2)));

            } while (c.moveToNext());
        }
        return list;
    }

    // get the count of data, this will allow user
    // to not add more that five contacts in database
    public int count(){
        int count=0;
        String query="SELECT COUNT(*) FROM "+TABLE_NAME;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor c=db.rawQuery(query,null);
        if(c.getCount()>0){
            c.moveToFirst();
            count=c.getInt(0);
        }
        c.close();
        return count;
    }

    // Deleting single country
    public void deleteContact(ContactModel contact) {
        SQLiteDatabase db = this.getWritableDatabase();
        int i=db.delete(TABLE_NAME,KEY_ID + " = ?",
                new String[] { String.valueOf(contact.getId()) });

        db.close();
    }
}

Step 2.3: Creating a CustomAdapter.java

We create this to connect contact data with ListView for proper display. It also handles actions like showing and deleting contacts from the list.

Java 
import android.content.Context;
import android.content.DialogInterface;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;

import com.google.android.material.dialog.MaterialAlertDialogBuilder;
import com.raghav.sos.R;

import java.util.List;

public class CustomAdapter extends ArrayAdapter<ContactModel> {

    Context context;
    List<ContactModel> contacts;

    public CustomAdapter(@NonNull Context context, List<ContactModel> contacts) {
        super(context, 0, contacts);
        this.context = context;
        this.contacts = contacts;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        // create a database helper object 
        // to handle the database manipulations
        DbHelper db = new DbHelper(context);

        // Get the data item for this position
        ContactModel c = getItem(position);
        
        // Check if an existing view is being reused, otherwise inflate the view
        if (convertView == null) {
            convertView = LayoutInflater.from(getContext()).inflate(R.layout.item_user, parent, false);
        }

        LinearLayout linearLayout = (LinearLayout) convertView.findViewById(R.id.linear);

        // Lookup view for data population
        TextView tvName = (TextView) convertView.findViewById(R.id.tvName);
        TextView tvPhone = (TextView) convertView.findViewById(R.id.tvPhone);
        
        // Populate the data into the template
        // view using the data object
        tvName.setText(c.getName());
        tvPhone.setText(c.getPhoneNo());

        linearLayout.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View view) {
                // generate an MaterialAlertDialog Box
                new MaterialAlertDialogBuilder(context)
                        .setTitle("Remove Contact")
                        .setMessage("Are you sure want to remove this contact?")
                        .setPositiveButton("YES", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialogInterface, int i) {
                                // delete the specified contact from the database
                                db.deleteContact(c);
                                // remove the item from the list
                                contacts.remove(c);
                                // notify the listview that dataset has been changed
                                notifyDataSetChanged();
                                Toast.makeText(context, "Contact removed!", Toast.LENGTH_SHORT).show();
                            }
                        })
                        .setNegativeButton("NO", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialogInterface, int i) {

                            }
                        })
                        .show();
                return false;
            }
        });
        // Return the completed view to render on screen
        return convertView;
    }

    // this method will update the ListView
    public void refresh(List<ContactModel> list) {
        contacts.clear();
        contacts.addAll(list);
        notifyDataSetChanged();
    }
}

 Step 2.4: item_user.xml

We design this layout to define how each contact will look in the ListView. It improves UI by showing name and phone number in a structured format.

XML 
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/linear"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="4dp">

    <androidx.cardview.widget.CardView
        android:id="@+id/cardview"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <TextView
                android:id="@+id/tvName"
                style="@style/TextAppearance.AppCompat.Medium"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Name"
                android:textColor="@color/design_default_color_secondary" />

            <TextView
                android:id="@+id/tvPhone"
                style="@style/TextAppearance.AppCompat.Large"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Phone"
                android:textColor="@color/design_default_color_secondary_variant"
                android:textStyle="bold" />
            
        </LinearLayout>
        
    </androidx.cardview.widget.CardView>
    
</LinearLayout>

Step 3: Creating the Service Module

We create this module to handle background tasks like shake detection and SOS alerts. It ensures the app works even when it is not open.

Step 3.1: Creating ShakeDetector class

We use this to detect device shaking using accelerometer sensor. It triggers SOS only when a specific shake pattern is detected.

Java 
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;

public class ShakeDetector implements SensorEventListener {

    /*
     * The gForce that is necessary to register as shake.
     * Must be greater than 1G (one earth gravity unit).
     * You can install "G-Force", by Blake La Pierre
     * from the Google Play Store and run it to see how
     *  many G's it takes to register a shake
     */
    private static final float SHAKE_THRESHOLD_GRAVITY = 2.7F;
    private static final int SHAKE_SLOP_TIME_MS = 500;
    private static final int SHAKE_COUNT_RESET_TIME_MS = 3000;

    private OnShakeListener mListener;
    private long mShakeTimestamp;
    private int mShakeCount;

    public void setOnShakeListener(OnShakeListener listener) {
        this.mListener = listener;
    }

    public interface OnShakeListener {
        public void onShake(int count);
    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {
        // ignore
    }

    @Override
    public void onSensorChanged(SensorEvent event) {

        if (mListener != null) {
            float x = event.values[0];
            float y = event.values[1];
            float z = event.values[2];

            float gX = x / SensorManager.GRAVITY_EARTH;
            float gY = y / SensorManager.GRAVITY_EARTH;
            float gZ = z / SensorManager.GRAVITY_EARTH;

            // gForce will be close to 1 when there is no movement.
            Float f = new Float(gX * gX + gY * gY + gZ * gZ);
            Double d = Math.sqrt(f.doubleValue());
            float gForce = d.floatValue();

            if (gForce > SHAKE_THRESHOLD_GRAVITY) {
                final long now = System.currentTimeMillis();
                // ignore shake events too close to each other (500ms)
                if (mShakeTimestamp + SHAKE_SLOP_TIME_MS > now) {
                    return;
                }

                // reset the shake count after 3 seconds of no shakes
                if (mShakeTimestamp + SHAKE_COUNT_RESET_TIME_MS < now) {
                    mShakeCount = 0;
                }

                mShakeTimestamp = now;
                mShakeCount++;

                mListener.onShake(mShakeCount);
            }
        }
    }
}

 Step 3.2: Creating the SensorService

We create this to run continuous background monitoring of shake events. It sends emergency SMS with location even if the app is closed.

Java 
@RequiresApi(Build.VERSION_CODES.O)
private void startMyOwnForeground()
{
    String NOTIFICATION_CHANNEL_ID = "example.permanence";
    String channelName = "Background Service";
    NotificationChannel chan = new NotificationChannel(
        NOTIFICATION_CHANNEL_ID, channelName,
        NotificationManager.IMPORTANCE_MIN);

    NotificationManager manager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
    assert manager != null;
    manager.createNotificationChannel(chan);

    NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID);
    Notification notification = notificationBuilder.setOngoing(true)
              .setContentTitle("You are protected.")
              .setContentText("We are there for you")

              // this is important, otherwise the
              // notification will show the way you want i.e.
              // it will show some default notification
              .setSmallIcon(R.drawable.ic_launcher_foreground)
              .setPriority(NotificationManager.IMPORTANCE_MIN)
              .setCategory(Notification.CATEGORY_SERVICE)
              .build();
    startForeground(2, notification);
}

 If you start a service starts with the START STICKY return type, it will run in the background even if the host activity is not running in the foreground. If Android has to forcibly close a program due to a memory error or other reasons, the service will be restarted without the user's intervention.

Java 
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        super.onStartCommand(intent, flags, startId);

        return START_STICKY;
    }

In order to make the user aware that the Shake event has been registered or say the messages have been delivered, we create a vibrate() method. This will make the phone vibrate in a defined wave format.

Java 
// method to vibrate the phone
public void vibrate()
{
    final Vibrator vibrator = (Vibrator)getSystemService(Context.VIBRATOR_SERVICE);
  
    VibrationEffect vibEff;
    // Android Q and above have some predefined vibrating
    // patterns
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
        vibEff = VibrationEffect.createPredefined(VibrationEffect.EFFECT_DOUBLE_CLICK);
        vibrator.cancel();
        vibrator.vibrate(vibEff);
    }
    else {
        vibrator.vibrate(500);
    }
}

 We use FusedLocationProviderClient to get the user’s current location using getCurrentLocation(). It requires GPS/location services to be ON, otherwise it returns null. From Android O onwards, location access only works when the user explicitly enables location for privacy and awareness.

Java 
FusedLocationProviderClient fusedLocationClient = LocationServices.getFusedLocationProviderClient(getApplicationContext());

fusedLocationClient.getCurrentLocation(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY, new CancellationToken() {
            @Override
            public boolean isCancellationRequested()
            {
                return false;
            }
            @NonNull
            @Override
            public CancellationToken onCanceledRequested(
                @NonNull OnTokenCanceledListener
                    onTokenCanceledListener)
            {
                return null;
            }
        })
    .addOnSuccessListener(
        new OnSuccessListener<Location>() {
            @Override
            public void onSuccess(Location location)
            {
                // check if location is null
                // for both the cases we will create
                // different messages
                if (location != null) {
                    ...
                }
                else {
                    ...
                }
            }
        })
    .addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception e)
        {
            ...
        }
    });

After getting the location successfully, we use SmsManager to send emergency messages to all saved contacts from the database. If location is not available, we send a fallback message without coordinates so receivers still get alert and can contact help or authorities for assistance.

Java 
SmsManager smsManager = SmsManager.getDefault();
DbHelper db = new DbHelper(SensorService.this);
List<ContactModel> list = db.getAllContacts();
for (ContactModel c : list) {
    String message
        = "Hey, " + c.getName()
          + "I am in DANGER, i need help. Please urgently reach me out. Here are my coordinates.\n "
          + "http://maps.google.com/maps?q="
          + location.getLatitude() + ","
          + location.getLongitude();
    smsManager.sendTextMessage(c.getPhoneNo(), null,
                               message, null, null);
}

Till now whatever we have done will work until the activity is in Foreground or Running. But what when the user kills the application? Or locks the phone? For this, we create a BroadcastReceiver.

Java 
import android.annotation.SuppressLint;
import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.hardware.Sensor;
import android.hardware.SensorManager;
import android.location.Location;
import android.os.Build;
import android.os.IBinder;
import android.os.VibrationEffect;
import android.os.Vibrator;
import android.telephony.SmsManager;
import android.util.Log;

import androidx.annotation.NonNull;
import androidx.annotation.RequiresApi;
import androidx.core.app.NotificationCompat;

import com.google.android.gms.location.FusedLocationProviderClient;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.tasks.CancellationToken;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.OnTokenCanceledListener;
import com.raghav.sos.Contacts.ContactModel;
import com.raghav.sos.Contacts.DbHelper;
import com.raghav.sos.R;

import java.util.List;

public class SensorService extends Service {

    private SensorManager mSensorManager;
    private Sensor mAccelerometer;
    private ShakeDetector mShakeDetector;

    public SensorService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        super.onStartCommand(intent, flags, startId);

        return START_STICKY;
    }

    @Override
    public void onCreate() {
        
        super.onCreate();

        // start the foreground service
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O)
            startMyOwnForeground();
        else
            startForeground(1, new Notification());

        // ShakeDetector initialization
        mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
        mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        mShakeDetector = new ShakeDetector();
        mShakeDetector.setOnShakeListener(new ShakeDetector.OnShakeListener() {

            @SuppressLint("MissingPermission")
            @Override
            public void onShake(int count) {
                // check if the user has shacked
                // the phone for 3 time in a row
                if (count == 3) {
                    
                    // vibrate the phone
                    vibrate();

                    // create FusedLocationProviderClient to get the user location
                    FusedLocationProviderClient fusedLocationClient = LocationServices.getFusedLocationProviderClient(getApplicationContext());
                    
                    // use the PRIORITY_BALANCED_POWER_ACCURACY
                    // so that the service doesn't use unnecessary power via GPS
                    // it will only use GPS at this very moment
                    fusedLocationClient.getCurrentLocation(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY, new CancellationToken() {
                        @Override
                        public boolean isCancellationRequested() {
                            return false;
                        }

                        @NonNull
                        @Override
                        public CancellationToken onCanceledRequested(@NonNull OnTokenCanceledListener onTokenCanceledListener) {
                            return null;
                        }
                    }).addOnSuccessListener(new OnSuccessListener<Location>() {
                        @Override
                        public void onSuccess(Location location) {
                            // check if location is null
                            // for both the cases we will
                            // create different messages
                            if (location != null) {
                                
                                // get the SMSManager
                                SmsManager smsManager = SmsManager.getDefault();
                                
                                // get the list of all the contacts in Database
                                DbHelper db = new DbHelper(SensorService.this);
                                List<ContactModel> list = db.getAllContacts();
                                
                                // send SMS to each contact
                                for (ContactModel c : list) {
                                    String message = "Hey, " + c.getName() + "I am in DANGER, i need help. Please urgently reach me out. Here are my coordinates.\n " + "http://maps.google.com/maps?q=" + location.getLatitude() + "," + location.getLongitude();
                                    smsManager.sendTextMessage(c.getPhoneNo(), null, message, null, null);
                                }
                            } else {
                                String message = "I am in DANGER, i need help. Please urgently reach me out.\n" + "GPS was turned off.Couldn't find location. Call your nearest Police Station.";
                                SmsManager smsManager = SmsManager.getDefault();
                                DbHelper db = new DbHelper(SensorService.this);
                                List<ContactModel> list = db.getAllContacts();
                                for (ContactModel c : list) {
                                    smsManager.sendTextMessage(c.getPhoneNo(), null, message, null, null);
                                }
                            }
                        }
                    }).addOnFailureListener(new OnFailureListener() {
                        @Override
                        public void onFailure(@NonNull Exception e) {
                            Log.d("Check: ", "OnFailure");
                            String message = "I am in DANGER, i need help. Please urgently reach me out.\n" + "GPS was turned off.Couldn't find location. Call your nearest Police Station.";
                            SmsManager smsManager = SmsManager.getDefault();
                            DbHelper db = new DbHelper(SensorService.this);
                            List<ContactModel> list = db.getAllContacts();
                            for (ContactModel c : list) {
                                smsManager.sendTextMessage(c.getPhoneNo(), null, message, null, null);
                            }
                        }
                    });

                }
            }
        });

        // register the listener
        mSensorManager.registerListener(mShakeDetector, mAccelerometer, SensorManager.SENSOR_DELAY_UI);
    }

    // method to vibrate the phone
    public void vibrate() {
        
        final Vibrator vibrator = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
        VibrationEffect vibEff;
        
        // Android Q and above have some predefined vibrating patterns
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
            vibEff = VibrationEffect.createPredefined(VibrationEffect.EFFECT_DOUBLE_CLICK);
            vibrator.cancel();
            vibrator.vibrate(vibEff);
        } else {
            vibrator.vibrate(500);
        }


    }

    // For Build versions higher than Android Oreo, we launch
    // a foreground service in a different way. This is due to the newly
    // implemented strict notification rules, which require us to identify
    // our own notification channel in order to view them correctly.
    @RequiresApi(Build.VERSION_CODES.O)
    private void startMyOwnForeground() {
        String NOTIFICATION_CHANNEL_ID = "example.permanence";
        String channelName = "Background Service";
        NotificationChannel chan = new NotificationChannel(NOTIFICATION_CHANNEL_ID, channelName, NotificationManager.IMPORTANCE_MIN);

        NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        assert manager != null;
        manager.createNotificationChannel(chan);

        NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID);
        Notification notification = notificationBuilder.setOngoing(true)
                .setContentTitle("You are protected.")
                .setContentText("We are there for you")

                // this is important, otherwise the notification will show the way
                // you want i.e. it will show some default notification
                .setSmallIcon(R.drawable.ic_launcher_foreground)

                .setPriority(NotificationManager.IMPORTANCE_MIN)
                .setCategory(Notification.CATEGORY_SERVICE)
                .build();
        startForeground(2, notification);
    }

    @Override
    public void onDestroy() {
        // create an Intent to call the Broadcast receiver
        Intent broadcastIntent = new Intent();
        broadcastIntent.setAction("restartservice");
        broadcastIntent.setClass(this, ReactivateService.class);
        this.sendBroadcast(broadcastIntent);
        super.onDestroy();
    }

}

 Step 3.3: Creating the Broadcast Receiver

  • Whenever a service is destroyed, the onDestroy method is called, and we will use that method to call a broadcast receiver before the service is actually destroyed. 
  • The broadcast receiver in return again starts the service. And our problem is resolved!! The service now runs without the host activity in the background.e.
Java 
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Build;
import android.util.Log;

public class ReactivateService extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        Log.d("Check: ","Receiver Started");
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            context.startForegroundService(new Intent(context, SensorService.class));
        } else {
            context.startService(new Intent(context, SensorService.class));
        }
    }
}

Step 4: Working with the MainActivity

Go to the MainActivity.java file and refer to the following code. Below is the code for the MainActivity.java file. Comments are added inside the code to understand the code in more detail.

Java 
import android.Manifest;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.ActivityManager;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.os.PowerManager;
import android.provider.ContactsContract;
import android.provider.Settings;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;

import com.raghav.sos.Contacts.ContactModel;
import com.raghav.sos.Contacts.CustomAdapter;
import com.raghav.sos.Contacts.DbHelper;
import com.raghav.sos.ShakeServices.ReactivateService;
import com.raghav.sos.ShakeServices.SensorService;

import java.util.List;

public class MainActivity extends AppCompatActivity {

    private static final int IGNORE_BATTERY_OPTIMIZATION_REQUEST = 1002;
    private static final int PICK_CONTACT = 1;

    // create instances of various classes to be used
    Button button1;
    ListView listView;
    DbHelper db;
    List<ContactModel> list;
    CustomAdapter customAdapter;

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

        // check for runtime permissions
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_DENIED) {
                requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.SEND_SMS, Manifest.permission.READ_CONTACTS}, 100);
            }
        }

        // this is a special permission required only by devices using
        // Android Q and above. The Access Background Permission is responsible
        // for populating the dialog with "ALLOW ALL THE TIME" option
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
            requestPermissions(new String[]{Manifest.permission.ACCESS_BACKGROUND_LOCATION}, 100);
        }

        // check for BatteryOptimization,
        PowerManager pm = (PowerManager) getSystemService(POWER_SERVICE);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (pm != null && !pm.isIgnoringBatteryOptimizations(getPackageName())) {
                askIgnoreOptimization();
            }
        }

        // start the service
        SensorService sensorService = new SensorService();
        Intent intent = new Intent(this, sensorService.getClass());
        if (!isMyServiceRunning(sensorService.getClass())) {
            startService(intent);
        }


        button1 = findViewById(R.id.Button1);
        listView = (ListView) findViewById(R.id.ListView);
        db = new DbHelper(this);
        list = db.getAllContacts();
        customAdapter = new CustomAdapter(this, list);
        listView.setAdapter(customAdapter);

        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // calling of getContacts()
                if (db.count() != 5) {
                    Intent intent = new Intent(Intent.ACTION_PICK, ContactsContract.Contacts.CONTENT_URI);
                    startActivityForResult(intent, PICK_CONTACT);
                } else {
                    Toast.makeText(MainActivity.this, "Can't Add more than 5 Contacts", Toast.LENGTH_SHORT).show();
                }
            }
        });
    }

    // method to check if the service is running
    private boolean isMyServiceRunning(Class<?> serviceClass) {
        ActivityManager manager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
        for (ActivityManager.RunningServiceInfo service : manager.getRunningServices(Integer.MAX_VALUE)) {
            if (serviceClass.getName().equals(service.service.getClassName())) {
                Log.i("Service status", "Running");
                return true;
            }
        }
        Log.i("Service status", "Not running");
        return false;
    }

    @Override
    protected void onDestroy() {
        Intent broadcastIntent = new Intent();
        broadcastIntent.setAction("restartservice");
        broadcastIntent.setClass(this, ReactivateService.class);
        this.sendBroadcast(broadcastIntent);
        super.onDestroy();
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == 100) {
            if (grantResults[0] == PackageManager.PERMISSION_DENIED) {
                Toast.makeText(this, "Permissions Denied!\n Can't use the App!", Toast.LENGTH_SHORT).show();
            }
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        
        // get the contact from the PhoneBook of device
        switch (requestCode) {
            case (PICK_CONTACT):
                if (resultCode == Activity.RESULT_OK) {

                    Uri contactData = data.getData();
                    Cursor c = managedQuery(contactData, null, null, null, null);
                    if (c.moveToFirst()) {

                        String id = c.getString(c.getColumnIndexOrThrow(ContactsContract.Contacts._ID));
                        String hasPhone = c.getString(c.getColumnIndex(ContactsContract.Contacts.HAS_PHONE_NUMBER));
                        String phone = null;
                        try {
                            if (hasPhone.equalsIgnoreCase("1")) {
                                Cursor phones = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, ContactsContract.CommonDataKinds.Phone.CONTACT_ID + " = " + id, null, null);
                                phones.moveToFirst();
                                phone = phones.getString(phones.getColumnIndex("data1"));
                            }
                            String name = c.getString(c.getColumnIndex(ContactsContract.Contacts.DISPLAY_NAME));
                            db.addcontact(new ContactModel(0, name, phone));
                            list = db.getAllContacts();
                            customAdapter.refresh(list);
                        } catch (Exception ex) {
                        }
                    }
                }
                break;
        }
    }

    // this method prompts the user to remove any 
    // battery optimisation constraints from the App
    private void askIgnoreOptimization() {

        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
            @SuppressLint("BatteryLife") Intent intent = new Intent(Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS);
            intent.setData(Uri.parse("package:" + getPackageName()));
            startActivityForResult(intent, IGNORE_BATTERY_OPTIMIZATION_REQUEST);
        }

    }

}

Navigate to the app > res > layout > activity_main.xml and add the below code to that file. Below is the code for the activity_main.xml file. 

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/Button1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="12dp"
        android:background="#0F9D58"
        android:text="Add Emergency Contact "
        android:textColor="#FFFFFF" />

    <ListView
        android:id="@+id/ListView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

 Step 5: Working with AndroidManifest.xml

XML 
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.raghav.sos">

    <uses-permission android:name="android.permission.READ_CONTACTS"/>
    <uses-permission android:name="android.permission.VIBRATE"/>
    <uses-permission android:name="android.permission.SEND_SMS"/>
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.FOREGROUND_SERVICE"/>
  
    <!--This permission is necessary for devices 
      with Android O and above, so that 
      we can use the location ALL THE TIME-->
    <uses-permission android:name="android.permission.ACCESS_BACKGROUND_LOCATION"/>
 
    <!-- We also ask user to remove any battery optimization constraints during runtime -->
    <uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS"/>

    <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/Theme.SOS">
      
        <!-- register the receiver -->
        <receiver
            android:name=".ShakeServices.ReactivateService"
            android:enabled="true"
            android:exported="true"/>
      
        <!-- register the service -->
        <service
            android:name=".ShakeServices.SensorService"
            android:enabled="true"
            android:exported="true" />

        <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>

Steps To Run SOS App in Android Studio (Final Execution Steps)

Step 1: Open Project

  • Open Android Studio
  • Click File -> Open
  • Select your SOS project folder and Wait for Gradle Sync to complete

Step 2: Build Project

  • Click Build -> Make Project
  • Ensure no errors appear in bottom window If error comes, first resolve dependencies

Step 3: Connect Device / Emulator

You can run app in 2 ways:

1. Emulator

  • Open Device Manager
  • Start virtual device

2. Real Device (Recommended)

  • Enable Developer Options
  • Turn ON USB Debugging
  • Connect mobile via USB cable

Step 4: Install & Run App

  • Click Run button (Green Play icon)
  • Select device and Wait for installation

Step 5: First Launch Setup (Very Important)

When app opens first time:

Allow all permissions:

  • Location -> “Allow all the time”
  • SMS permission -> Allow
  • Contacts -> Allow

Go to Settings if asked:

  • Disable Battery Optimization for this app
  • Enable Background Location

Output:

Future Scope

  • We can add options for personal assistance emergencies like a map that indicates nearby police stations, hospitals, cabs, etc.
  • We create a logic that sends the user location every 1 or 2 minutes without the user shaking the device again.
  • We can add voice or/and video recording functionality.
  • Also, you can add a call to multiple or a single person at the time of shake.
  • We can try to add OpenCellId, this will allow you to fetch the location of the nearest mobile tower. But again remember that in order to calculate the location you would require some device information(no GPS) and that would require your GPS or location services to be turned ON.
  • Doors to changes in the UI are always open.

Notes:

1. Allow the app to autostart, in order to use the app while the screen is off.

2. Remove any battery optimization constraints on the app. This might make Android kill the service.

3. Allow all the permissions, especially allow location permissions by Allowing the app to use the device location all the time. This would allow the service to use the device location when the shake event is registered.
 

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