IMEI

Every GSM phone, be it a basic, dirt-cheap handset or a pricey, powerful smartphone, has its own International Mobile Equipment Identity number, commonly known as IMEI. This is usually a string of 15 or 16 digits, and carriers use it to identify the devices registered on their networks. Being unique and hard to modify, the IMEI can also be used to blacklist stolen phones from a given network. In some cases, the number can even be used to track down a certain device in order to return it to its rightful owner

Programatically we will get IMEI number like below

Activity_main.xml

<RelativeLayout 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"  >
    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView1"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="24dp"
        android:text="Click here to get imei number in android programmatically" />
    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="170dp"
        android:gravity="center"
        android:text="Your IMEI Number Display Here"
        android:textAppearance="?android:attr/textAppearanceLarge" />
</RelativeLayout>

MainActivity.Java

package androiindians.helloworld;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.telephony.TelephonyManager;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity {
    TextView imei_number;
    Button get_imei;
    String IMEI_Number_Holder;
    TelephonyManager telephonyManager;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imei_number = (TextView)findViewById(R.id.textView1);
        get_imei = (Button)findViewById(R.id.button1);
        telephonyManager = (TelephonyManager) this.getSystemService(Context.TELEPHONY_SERVICE);
        get_imei.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                IMEI_Number_Holder = telephonyManager.getDeviceId();
                imei_number.setText(IMEI_Number_Holder);
            }
        });
    }
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="androiindians.helloworld">
    <uses-permission android:name="android.permission.READ_PHONE_STATE"></uses-permission>
    <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>
        <activity android:name=".Second"></activity>
    </application>
</manifest>