java - 如何烘烤验证错误消息显示未选择微调器中的任何项目？

Question

如何显示验证错误消息显示未选择微调器中的任何项目？下面的编码有效，但是当我选择其中一项时，也会显示 toast 消息。有人可以帮我吗，我错过了哪一部分？

    if(RegisterUserType.getSelectedItemPosition() == 0)
    {
        Toast.makeText(RegistrationActivity.this, "Select the options listed, either parents or tuition provider.", Toast.LENGTH_SHORT).show();
    }

微调器设置适配器的编码:-

    List<String> categories = new ArrayList<>();
    categories.add(0, "Choose Category");
    categories.add("Parents");
    categories.add("Tuition Provider");

    ArrayAdapter<String> dataAdapter;
    dataAdapter = new ArrayAdapter(this,android.R.layout.simple_spinner_item, categories);

    dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

    RegisterUserType.setAdapter(dataAdapter);

    RegisterUserType.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener()
    {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id)
        {
            if (parent.getItemAtPosition(position).equals("Chooose Category"))
            {
                //Do Nothing
            }

            else
            {
                String item = parent.getItemAtPosition(position).toString();

                Toast.makeText(parent.getContext(), item +" selected.", Toast.LENGTH_SHORT).show();
            }
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent)
        {
            // TODO Auto-generated method stub
        }
    });

Answer 1

我认为您可以满足您的要求，例如在您的 Activity 的 Oncreate() 中，

    ArrayList<String> countries=new ArrayList<>();
        countries.add("Select Country");
        countries.add("India");
        countries.add("China");
        countries.add("USA");
        countries.add("Africa");
        countries.add("Russia");

    ArrayAdapter<String> adapter=new ArrayAdapter<>(this,android.R.layout.simple_list_item_1, countries);
    RegisterUserType.setAdapter(adapter);

    RegisterUserType.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            if(position==0){
                Toast.makeText(getApplicationContext(),"No Item Selected",Toast.LENGTH_LONG).show();
            }else {
                Toast.makeText(getApplicationContext(),"Item Selected = "+parent.getItemAtPosition(position),Toast.LENGTH_LONG).show();
            }
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {

        }
    });