LongToastMessageShower.java

class LongToastMessageShower implements MessageShower{
    private Toast toast;

    public LongToastMessageShower(Context appContext){
         this.toast = Toast.makeText(appContext,"",Toast.LENGTH_LONG);
    }

    @Override
    public void showMessage(String message){
        toast.cancel();
        toast.setText(message);
        toast.show(); 
    }

}

MessageShower.java

interface MessageShower{
    void showMessage(String message);
}