How to open dial-pad and press extension number during a call in my android calling application.

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Android

I am developing an apps for my organization which will connect to any employee desk phone after dialing his/her extension after main organization number. and this extension is saved in application db. suppose main contact number is "123456789" and then ext "234#" is required to connect an employee.

In Main Activity we have code like this:

Intent newIntent=new Intent();
newIntent.setAction(Intent.ACTION_CALL);
newIntent.setData(Uri.parse("tel: 123456789"));

As per above lines of code application is able to start call activity to specified number. but after this I want to know how to implement to enter extension number programmatically in background.

What I have tried:

Tried to create new Intent to parse extension number in broadCastReceiver class as below:
if(stateStr.equals(TelephonyManager.EXTRA_STATE_OFFHOOK)){
state = TelephonyManager.CALL_STATE_OFFHOOK;
callReceived=true;
Intent newIntent=new Intent();
newIntent.setAction(Intent.ACTION_DIAL);
newIntent.setData(Uri.parse("tel: 234#"));

}

But this code snippet is not working.

Then I tried with PAUSE/WAIT number in MainActivity as below:

Intent newIntent=new Intent();
newIntent.setAction(Intent.ACTION_CALL);
newIntent.setData(Uri.parse("tel: 123456789;234#"));
}
But this ask user to click 'ok' with a message to send tune.