ApiClient.java

public class ApiClient {
  
  public static final String BASE_URL = "enter api base url here";
  //Insert retrofit dependency in build.gradle
  public static Retrofit retrofit;
  
  public static Retrofit getApiClient() {
    if (retrofit == null) {
      
      retrofit = new Retrofit.Builder().baseurl(BASE_URL)
        .client(getUnsafeOkHttpClient().build())
        .addConverterFactory(GsonConverterFactory.create())
        .build();
      
    }
    
    return retrofit;
  }
  
  public static OkHttpClient.builder getUnsafeOkHttpClient(){
    try {
            // Create a trust manager that does not validate certificate chains
            final TrustManager[] trustAllCerts = new TrustManager[]{
                    new X509TrustManager() {
                        @Override
                        public void checkClientTrusted(java.security.cert.X509Certificate[] chain, String authType) throws CertificateException {
                        }

                        @Override
                        public void checkServerTrusted(java.security.cert.X509Certificate[] chain, String authType) throws CertificateException {
                        }

                        @Override
                        public java.security.cert.X509Certificate[] getAcceptedIssuers() {
                            return new java.security.cert.X509Certificate[]{};
                        }
                    }
            };

            // Install the all-trusting trust manager
            final SSLContext sslContext = SSLContext.getInstance("SSL");
            sslContext.init(null, trustAllCerts, new java.security.SecureRandom());

            // Create an ssl socket factory with our all-trusting manager
            final SSLSocketFactory sslSocketFactory = sslContext.getSocketFactory();

            OkHttpClient.Builder builder = new OkHttpClient.Builder();
            builder.sslSocketFactory(sslSocketFactory, (X509TrustManager) trustAllCerts[0]);
            builder.hostnameVerifier(new HostnameVerifier() {
                @Override
                public boolean verify(String hostname, SSLSession session) {
                    return true;
                }
            });
            return builder;
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
  }
}