How can detact incoming call in android using code ?

Step. 1 : Create android project by selecting file > new > new android application. Now name your app whatever you like. When done hit finish.

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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
</RelativeLayout>

Step.2 :

MainActivity.java

package com.example.detectincomingcall;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}

Step.3 : Create a service class that extends BraodcastReciever class
MyCallReciever.java

package com.example.detectincomingcall;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.telephony.TelephonyManager;
import android.widget.Toast;
public class MyCallReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
// TODO Auto-generated method stub
if (intent.getStringExtra(TelephonyManager.EXTRA_STATE).equals(TelephonyManager.EXTRA_STATE_RINGING)) {
// This code will execute when the phone has an incoming call
// get the phone number
String incomingNumber = intent.getStringExtra(TelephonyManager.EXTRA_INCOMING_NUMBER);
Toast.makeText(context, "Call from:" +incomingNumber, Toast.LENGTH_LONG).show();
} else if (intent.getStringExtra(TelephonyManager.EXTRA_STATE).equals(
TelephonyManager.EXTRA_STATE_IDLE)
|| intent.getStringExtra(TelephonyManager.EXTRA_STATE).equals(
TelephonyManager.EXTRA_STATE_OFFHOOK)) {
// This code will execute when the call is disconnected
Toast.makeText(context, "Detected call hangup event", Toast.LENGTH_LONG).show();
}
}
}

Step.4

Add following code in AndroidManifest.xml

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