How to put hint in a spinner?

Complementing @CaiqueOliveira's answer: To achieve the desired effect you can do the following

final ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(
        this,R.layout.spinner_item,plantsList){

    @Override
    public boolean isEnabled(int position){

        if(position == 0){

            // Disabilita a primeira posição (hint)
            return false;

        } else {
            return true;
        }
    }

    @Override
    public View getDropDownView(int position, View convertView,
                                ViewGroup parent) {

        View view = super.getDropDownView(position, convertView, parent);
        TextView tv = (TextView) view;

        if(position == 0){

            // Deixa o hint com a cor cinza ( efeito de desabilitado)
            tv.setTextColor(Color.GRAY);

        }else {
            tv.setTextColor(Color.BLACK);
        }

        return view;
    }
});

spinnerArrayAdapter.setDropDownViewResource(R.layout.spinner_item);
spinner.setAdapter(spinnerArrayAdapter);

spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

        String selectedItemText = (String) parent.getItemAtPosition(position);

        if(position > 0){

            // Ação realizada quando um elemento diferente
           // do hint é selecionado
        }
    }

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

    }
});

Note: Retired and adapted from link link

The simplest way I found was this:

Creates a TextView or LinearLayout and places it along with Spinner in a RelativeLayout. Initially the textview will have the text as if it were the "Select one ..." tip, after the first click this TextView becomes invisible, disabled and calls the Spinner that is right behind it.

Step 1:

In the activity.xml that finds the spinner, put:

 <RelativeLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
    <Spinner
        android:id="@+id/sp_main"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:spinnerMode="dropdown" />
    <LinearLayout
        android:id="@+id/ll_hint_spinner"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:gravity="center">
        <TextView

            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="center"
            android:text="Select..."/>

    </LinearLayout>
</RelativeLayout>

Step 2:

In your Activity.java:

  public class MainActivity extends AppCompatActivity {

    private LinearLayout ll_hint_spinner;
    private Spinner sp_main;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ll_hint_spinner = findViewById(R.id.ll_hint_spinner);
        sp_main = findViewById(R.id.sp_main);
        //Action after clicking LinearLayout / Spinner;
        ll_hint_spinner.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //By clicking "Select ..." the Spinner is requested;
                sp_main.performClick();
                //Make LinearLayout invisible
                setLinearVisibility(false);
                //Disable LinearLayout
                ll_hint_spinner.setEnabled(false);
                //After LinearLayout is off, Spinner will function normally;
                sp_main.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                    @Override
                    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                        sp_main.setSelection(position);
                    }
                    @Override
                    public void onNothingSelected(AdapterView<?> parent) {
                        setLinearVisibility(true);
                    }
                });
            }
        });
    }
    //Method to make LinearLayout invisible or visible;
    public void setLinearVisibility(boolean visible) {
        if (visible) {
            ll_hint_spinner.setVisibility(View.VISIBLE);
        } else {
            ll_hint_spinner.setVisibility(View.INVISIBLE);
        }
    }
}

The image examples I used a custom Spinner, but the result of the last example will be the same.

Note: I hope I have helped.

Hello

Just add in the first row of your spinner what you want and this line of items will be visible.