only set pkce verifier on android pkce activity launch

Author: adamint

src/androidMain/kotlin/com/adamratzman/spotify/auth/SpotifyDefaultCredentialStore.kt

@@ -53,6 +53,11 @@ public class SpotifyDefaultCredentialStore(
          */
         public const val SpotifyRefreshTokenKey: String = "spotifyRefreshToken"
 
+        /**
+         * The PKCE code verifier key currently being used in [EncryptedSharedPreferences]
+         */
+        public const val SpotifyCurrentPkceCodeVerifierKey: String = "spotifyCurrentPkceCodeVerifier"
+
         /**
          * The activity to return to if re-authentication is necessary on implicit authentication. Null except during authentication when using [guardValidImplicitSpotifyApi]
          */
@@ -101,6 +106,13 @@ public class SpotifyDefaultCredentialStore(
         get() = encryptedPreferences.getString(SpotifyRefreshTokenKey, null)
         set(value) = encryptedPreferences.edit().putString(SpotifyRefreshTokenKey, value).apply()
 
+    /**
+     * Get/set the current Spotify PKCE code verifier.
+     */
+    public var currentSpotifyPkceCodeVerifier: String?
+        get() = encryptedPreferences.getString(SpotifyCurrentPkceCodeVerifierKey, null)
+        set(value) = encryptedPreferences.edit().putString(SpotifyCurrentPkceCodeVerifierKey, value).apply()
+
     /**
      * Get/set the Spotify [Token] obtained from [spotifyToken].
      * If the token has expired according to [spotifyTokenExpiresAt], this will return null.

src/androidMain/kotlin/com/adamratzman/spotify/auth/pkce/AbstractSpotifyPkceLoginActivity.kt

@@ -92,6 +92,7 @@ public abstract class AbstractSpotifyPkceLoginActivity : AppCompatActivity() {
         // launch the activity when a Spotify intent result has been received
         if (intent?.isSpotifyPkceAuthIntent(redirectUri) == false) {
             authorizationIntent = Intent(Intent.ACTION_VIEW, getAuthorizationUrl())
+            credentialStore.currentSpotifyPkceCodeVerifier = pkceCodeVerifier
             startActivity(authorizationIntent)
             finish()
         }
@@ -150,7 +151,7 @@ public abstract class AbstractSpotifyPkceLoginActivity : AppCompatActivity() {
                         redirectUri = redirectUri,
                         authorization = SpotifyUserAuthorization(
                             authorizationCode = authorizationCode,
-                            pkceCodeVerifier = pkceCodeVerifier
+                            pkceCodeVerifier = credentialStore.currentSpotifyPkceCodeVerifier
                         ),
                         options ?: {}
                     ).build()