I faced a complex coding challenge while implementing MSAL for secure user authentication, and I would like to share my detailed approach. 

First, I integrated the MSAL library into the Android project and configured the authentication parameters in the Azure portal, obtaining the Client ID and redirect URI from Azure. 

Next, I initialized the PublicClientApplication object within the application, which I used to handle authentication requests. To facilitate user login, I called the acquireToken method and managed the result in the callback to ensure successful authentication. 

To secure token acquisition and renewal, I implemented token caching and made sure that tokens were refreshed before they expired. I also securely stored the tokens using encrypted shared preferences. 

After thoroughly testing the implementation, I confirmed that it provided secure and seamless user authentication. This complex problem was successfully solved through careful planning and execution.