How to create a drop-down list?

simple / elegant / how I do it:

Preview:

XML:

<Spinner
    android:id="@+id/spinner1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@android:drawable/btn_dropdown"
    android:spinnerMode="dropdown"/>

spinnerMode set to dropdown is androids way to make a dropdown. (https://developer.android.com/reference/android/widget/Spinner#attr_android:spinnerMode)

Java:

//get the spinner from the xml.
Spinner dropdown = findViewById(R.id.spinner1);
//create a list of items for the spinner.
String[] items = new String[]{"1", "2", "three"};
//create an adapter to describe how the items are displayed, adapters are used in several places in android.
//There are multiple variations of this, but this is the basic variant.
ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_dropdown_item, items);
//set the spinners adapter to the previously created one.
dropdown.setAdapter(adapter);

Documentation:

This is the basics but there is more to be self taught with experimentation. https://developer.android.com/guide/topics/ui/controls/spinner.html

1. You can use a setOnItemSelectedListener with this. (https://developer.android.com/guide/topics/ui/controls/spinner.html#SelectListener)
2. You can add a strings list from xml. (https://developer.android.com/guide/topics/ui/controls/spinner.html#Populate)
3. There is an appCompat version of this view. (https://developer.android.com/reference/androidx/appcompat/widget/AppCompatSpinner)

Spinner xml:

<Spinner
      android:id="@+id/spinner"
      android:layout_width="wrap_content"
      android:layout_height="match_parent" />

java:

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener{

    private Spinner spinner;
    private static final String[] paths = {"item 1", "item 2", "item 3"};

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);

        spinner = (Spinner)findViewById(R.id.spinner);
        ArrayAdapter<String>adapter = new ArrayAdapter<String>(MainActivity.this,
                android.R.layout.simple_spinner_item,paths);

        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(adapter);
        spinner.setOnItemSelectedListener(this);

    }

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

        switch (position) {
            case 0:
                // Whatever you want to happen when the first item gets selected
                break;
            case 1:
                // Whatever you want to happen when the second item gets selected
                break;
            case 2:
                // Whatever you want to happen when the thrid item gets selected
                break;

        }
    }

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

}

Here is the code for it.

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<Spinner
    android:id="@+id/static_spinner"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_marginBottom="20dp"
    android:layout_marginTop="20dp" />

<Spinner
    android:id="@+id/dynamic_spinner"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content" />

strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">Ahotbrew.com - Dropdown</string> 
<string-array name="brew_array">
    <item>Cappuccino</item>
    <item>Espresso</item>
    <item>Mocha</item>
    <item>Caffè Americano</item>
    <item>Cafe Zorro</item>
</string-array> 

MainActivity

Spinner staticSpinner = (Spinner) findViewById(R.id.static_spinner);

    // Create an ArrayAdapter using the string array and a default spinner
    ArrayAdapter<CharSequence> staticAdapter = ArrayAdapter
            .createFromResource(this, R.array.brew_array,
                    android.R.layout.simple_spinner_item);

    // Specify the layout to use when the list of choices appears
    staticAdapter
            .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

    // Apply the adapter to the spinner
    staticSpinner.setAdapter(staticAdapter);

    Spinner dynamicSpinner = (Spinner) findViewById(R.id.dynamic_spinner);

    String[] items = new String[] { "Chai Latte", "Green Tea", "Black Tea" };

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

    dynamicSpinner.setAdapter(adapter);

    dynamicSpinner.setOnItemSelectedListener(new OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view,
                int position, long id) {
            Log.v("item", (String) parent.getItemAtPosition(position));
        }

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

This example is from http://www.ahotbrew.com/android-dropdown-spinner-example/

This code is workig fine for me, hope it will help you too.

item.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="1dip" >
    <TextView
        android:id="@+id/spinnerItem"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="2dp"
        android:textSize="12sp" >
    </TextView>
</RelativeLayout>

details.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:layout_marginBottom="20dp"
        android:background="#FF00FF">   
    <Spinner
            android:id="@+id/dropStatus"
            android:layout_width="250dp"
            android:layout_height="30dp"
            android:layout_marginBottom="7dp"
            android:drawSelectorOnTop="true"/> 
</LinearLayout>

Adapter class:

import java.util.ArrayList;

import android.content.Context;
import android.content.res.Resources;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

public class StatusAdapter extends ArrayAdapter<StatusBean> {

    private Context context;
    private ArrayList<StatusBean> statuses;
    public Resources res;
    StatusBean currRowVal = null;
    LayoutInflater inflater;

    public StatusAdapter(Context context,
            int textViewResourceId, ArrayList<StatusBean> statuses,
            Resources resLocal) {
        super(context, textViewResourceId, statuses);
        this.context = context;
        this.statuses = statuses;
        this.res = resLocal;        
        inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    @Override
    public View getDropDownView(int position, View convertView, ViewGroup parent) {
        return getCustomView(position, convertView, parent);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        return getCustomView(position, convertView, parent);
    }

    public View getCustomView(int position, View convertView, ViewGroup parent) {
        View row = inflater.inflate(R.layout.status_item, parent, false);
        currRowVal = null;
        currRowVal = (StatusBean) statuses.get(position);
        TextView label = (TextView) row.findViewById(R.id.spinnerItem);
        if (position == 0) {
            label.setText("Please select status");
        } else {
            label.setText(currRowVal.getStatus());
        }

        return row;
    }
}

StatusBean class:

public class StatusBean {

    private String status;
    private String statusCode;

    public StatusBean() {
    }

    public StatusBean(String status,
            String statusCode) {
        this.status = status;
        this.statusCode = statusCode;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status =  status;
    }

    public String getStatusCode() {
        return statusCode;
    }

    public void setStatusCode(String statusCode) {
        this.statusCode = statusCode;
    }
}

Activity class :

Inside onCreate methos:

static ArrayList<StatusBean> STATUS_LIST = new ArrayList<StatusBean>();

for(int i=0;i<=10;i++) {
STATUS_LIST.add(new StatusBean(“Status ”+i, “Stattus ”+i));
}

final Spinner  dropStatus = (Spinner)findViewById(R.id.dropStatus);
            Resources res = getResources(); 
            StatusAdapter adapter = new StatusAdapter(this, R.layout.item, SessionData. STATUS_LIST, res);
            dropStatus.setAdapter(adapter);