Vaadin 7 UI Design By Example Beginner's Guide

Time for action – validating user input

We can run a TestSet instance only if the user selects one. Follow these steps to add a proper validation:

1. Implement your initButton method to match this code:

   private void initButton() {
     button.addClickListener(new ClickListener() {
       @Override
       public void buttonClick(ClickEvent event) {
         if(isValid()) {
           runSelectedTest();
         }
       }
     });
   }

2. Now implement your validate method. Here is how we validate:

   public boolean isValid() { combo.setComponentError(null); textField.setComponentError(null); boolean isValid = true; if(combo.getValue() == null) { combo.setComponentError( new UserError("Select a test from the list.")); isValid = false; } if(textField.getValue().toString().isEmpty()) { textField.setComponentError(new UserError( ...