build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.example.tinej.iota3"
        minSdkVersion 27
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0-alpha1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.0'
    implementation 'org.altbeacon:android-beacon-library:2+'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

MainActivity.java

package com.example.tinej.iota3;

import android.Manifest;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.RemoteException;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import org.altbeacon.beacon.Beacon;
import org.altbeacon.beacon.BeaconConsumer;
import org.altbeacon.beacon.BeaconManager;
import org.altbeacon.beacon.BeaconParser;
import org.altbeacon.beacon.Identifier;
import org.altbeacon.beacon.MonitorNotifier;
import org.altbeacon.beacon.RangeNotifier;
import org.altbeacon.beacon.Region;

import java.util.Collection;

public class MainActivity extends AppCompatActivity implements BeaconConsumer, MonitorNotifier {


    protected static final String TAG = "MonitoringActivity";
    private static final int PERMISSION_REQUEST_COARSE_LOCATION = 1;

    private BeaconManager mBeaconManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            // Android M Permission check
            if (this.checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, PERMISSION_REQUEST_COARSE_LOCATION);
            } else {
                Log.d(TAG, "Location permission already granted.");
            }
        }
    }

    @Override
    public void onResume() {
        super.onResume();
        mBeaconManager = BeaconManager.getInstanceForApplication(this.getApplicationContext());

        mBeaconManager.getBeaconParsers().add(new BeaconParser().setBeaconLayout(BeaconParser.ALTBEACON_LAYOUT));
        mBeaconManager.getBeaconParsers().add(new BeaconParser().setBeaconLayout(BeaconParser.EDDYSTONE_TLM_LAYOUT));
        mBeaconManager.getBeaconParsers().add(new BeaconParser().setBeaconLayout(BeaconParser.EDDYSTONE_UID_LAYOUT));
        mBeaconManager.getBeaconParsers().add(new BeaconParser().setBeaconLayout(BeaconParser.EDDYSTONE_URL_LAYOUT));
        mBeaconManager.getBeaconParsers().add(new BeaconParser().setBeaconLayout(BeaconParser.URI_BEACON_LAYOUT));

        mBeaconManager.setDebug(true);

        mBeaconManager.bind(this);
    }

    @Override
    public void onBeaconServiceConnect() {
        Region region = new Region("all-beacons-region", null, null, null);
        mBeaconManager.addMonitorNotifier(this);
        try {
            mBeaconManager.startMonitoringBeaconsInRegion(region);
        } catch (RemoteException e) {
            e.printStackTrace();
        }

        mBeaconManager.addRangeNotifier(new RangeNotifier() {
            @Override
            public void didRangeBeaconsInRegion(Collection<Beacon> beacons, Region region) {
                Log.d(TAG, beacons.toString());
                if (beacons.size() > 0) {
                    Log.i(TAG, "The first beacon I see is about "+beacons.iterator().next().getDistance()+" meters away.");
                }
            }
        });

        try {
            mBeaconManager.startRangingBeaconsInRegion(region);
        } catch (RemoteException e) {    }
    }

    public void didEnterRegion(Region region) {
        Log.d(TAG, "I detected a beacon in the region with namespace id " + region.getId1() +
                " and instance id: " + region.getId2() + "; unique id: " + region.getUniqueId());
    }

    public void didExitRegion(Region region) {
        Log.d(TAG, "Exited region?: " + region.getUniqueId() + " - " + region);
    }

    public void didDetermineStateForRegion(int state, Region region) {
        Log.d(TAG, "Something something: " + state + " : " + region);
    }

    @Override
    public void onPause() {
        super.onPause();
        mBeaconManager.unbind(this);
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
        switch (requestCode) {
            case PERMISSION_REQUEST_COARSE_LOCATION: {
                if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    Log.d(TAG, "coarse location permission granted");
                } else {
                    final AlertDialog.Builder builder = new AlertDialog.Builder(this);
                    builder.setTitle("Functionality limited");
                    builder.setMessage("Since location access has not been granted, this app will not be able to discover beacons when in the background.");
                    builder.setPositiveButton(android.R.string.ok, null);
                    builder.setOnDismissListener(new DialogInterface.OnDismissListener() {
                        @Override
                        public void onDismiss(DialogInterface dialog) {
                        }

                    });
                    builder.show();
                }
                return;
            }
        }
    }

}

Manifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.tinej.iota3">


    <uses-permission android:name="android.permission.BLUETOOTH"/>
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

    <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>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>