Spinner

MainActivity.java

private Spinner spinner;
private TextView tv_result;

spinner = (Spinner)findViewById(R.id.spinner);
tv_result = (TextView)findViewById(R.id.tv_result);

spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        tv_result.setText(parent.getItemAtPosition(position).toString());
    }

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

    }
});

values/arrays.xml

<resources>
    <string-array name="string_array">
        <item>월요일</item>
        <item>화요일</item>
        <item>수요일</item>
        <item>목요일</item>
    </string-array>
</resources>

activity_main.xml

<Spinner
    android:layout_width="150dp"
    android:layout_height="40dp"
    android:id="@+id/spinner"
    android:entries="@array/string_array"
    />
<TextView
    android:id="@+id/tv_result"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    />

arrays.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    
    <string-array name="string_array">
        <item>월요일</item>
        <item>화요일</item>
        <item>@string/wednesday</item>
        <item>@string/thursday</item>
    </string-array>
    
    <integer-array name="integer_array">
        <item>1</item>
        <item>2</item>
        <item>3</item>
        <item>4</item>
    </integer-array>
    
    <array name="icon_array">
        <item>@drawable/home</item>
        <item>@drawable/settings</item>
    </array>
    
    <array name="color_array">
        <item>#FFFF0000</item>
        <item>#FF00FF00</item>
        <item>@color/blue</item>
    </array>
    
</resources>

동적으로 할당하기

Resources res = getResources();

// String arrays
String[] strings = res.getStringArray(R.array.string_array);

// Integer arrays
int[] integers = getResources().getIntArray(R.array.integer_array);
List<Integer> integerList = Arrays.asList(ArrayUtils.toObject(integers));

// Drawable arrays
TypedArray icons = res.obtainTypedArray(R.array.icon_array);
Drawable drawable = icons.getDrawable(0);

// Color arrays
TypedArray colors = res.obtainTypedArray(R.array.color_array);
int color = colors.getColor(0, 0);

Resource 배열 활용하기
https://parkho79.tistory.com/33

안드로이드 앱 만들기 #20 (Spinner 드롭다운) – 홍드로이드

홍드로이드 깃헙
https://github.com/hongdroid94