TextInput prompt does not appear in soft keyboard

I want the TextInput prompt to appear in the soft keyboard. When an Android device is held in the landscape orientation, the soft keyboard occupies the entire screen, and the user has no hint what they are entering. Native Android does allow the prompt in the soft keyboard; in this example, the prompt is "Compose Mail".

Is there a feature that does this for Air? I have tried the prompt and toolTip but have not been successful. The prompt appears in the regular view, but not in the soft keyboard.