UPDATE
Please refer to https://faq.whatsapp.com/en/android/26000030/?category=5245251
WhatsApp’s Click to Chat feature allows you to begin a chat with
someone without having their phone number saved in your phone’s
address book. As long as you know this person’s phone number, you can
create a link that will allow you to start a chat with them.Use: https://wa.me/15551234567
Don’t use: https://wa.me/+001-(555)1234567
Example: https://wa.me/15551234567?text=I’m%20interested%20in%20your%20car%20for%20sale
Original answer
Here is the solution
public void onClickWhatsApp(View view) {
PackageManager pm=getPackageManager();
try {
Intent waIntent = new Intent(Intent.ACTION_SEND);
waIntent.setType("text/plain");
String text = "YOUR TEXT HERE";
PackageInfo info=pm.getPackageInfo("com.whatsapp", PackageManager.GET_META_DATA);
//Check if package exists or not. If not then code
//in catch block will be called
waIntent.setPackage("com.whatsapp");
waIntent.putExtra(Intent.EXTRA_TEXT, text);
startActivity(Intent.createChooser(waIntent, "Share with"));
} catch (NameNotFoundException e) {
Toast.makeText(this, "WhatsApp not Installed", Toast.LENGTH_SHORT)
.show();
}
}