Android Plugin Help

Hello

Im making an App for android phones and i want if i push a GUI button, that it will start an other application on my phone (like Calculator ,Whatsapp, Sms).

But i have a few problems and i've searched everywhere on the internet the last 3 days but i cant find a good awnser. I only know (the things i read) I need a program to write the plugin and export it to a .Jar file. But i cant find a good program or tutorial.

So can someone give a good program to make the plugins because i think its the Main problem right now.

thanks in advance,