0. 실행 예

1.setInfoWindowAdapter()

public class MapsActivity extends AppCompatActivity implements OnMapReadyCallback {
    private GoogleMap mMap;
//〜略〜
    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        mMap.setInfoWindowAdapter(new GoogleMap.InfoWindowAdapter() {
            @Override
            public View getInfoWindow(Marker marker) {
                return null;    //どちらかに処理を記述
            }

            @Override
            public View getInfoContents(Marker marker) {
                return null;    //どちらかに処理を記述
            }

2.InfoWindow 레이아웃 작성

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/tv_1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/iw_1"/>
    <TextView
        android:id="@+id/tv_2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/iw_2"/>
    <TextView
        android:id="@+id/tv_3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/iw_3"/>
    <Button
        android:id="@+id/bt_1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/bt_1"/>

</LinearLayout>

<resources>
<!-- 〜略〜 -->
    <string name="iw_1">1行目の情報</string>
    <string name="iw_2">2行目の情報</string>
    <string name="iw_3">3行目の情報</string>
    <string name="bt_1">ボタンも置ける</string>
</resources>

3.getInfoContents() 구현

            @Override
            public View getInfoContents(Marker marker) {
                View view = getLayoutInflater().inflate(R.layout.info_window_layout,null);
                return view;
            }

참고