You need to use an Intent to open "Compose new email" with required data filled in.
Intent intent = new Intent(Intent.ACTION_SEND);
intent.setType("message/rfc822");
intent.putExtra(Intent.EXTRA_EMAIL , new String[]{emailAddressEditText.getText().toString()});
intent.putExtra(Intent.EXTRA_SUBJECT, emailSubjectEditText.getText().toString());
intent.putExtra(Intent.EXTRA_TEXT , emailBodyEditText.getText().toString());
try {
startActivity(Intent.createChooser(intent, "Leave feedback..."));
} catch (android.content.ActivityNotFoundException ex) {
Toast.makeText(MyActivity.this, "No email clients installed.", Toast.LENGTH_SHORT).show();
}