Require DownloadRequest#Builder to have mandatory Source URI

This change modifies the API to require that the
DownloadRequest#Builder includes the Source URI as a mandatory,
non-null parameter.

Test: Manual, Telephony Test MBMS app
Bug: 67640102
Merged-In: I25b39008317e333d422cd32a0c6348c010ca280f
Change-Id: I7d44e977314a57fdf063aa233bfb978b48ebf1db
diff --git a/telephony/java/android/telephony/mbms/DownloadRequest.java b/telephony/java/android/telephony/mbms/DownloadRequest.java
index a5f256e..95c6590 100644
--- a/telephony/java/android/telephony/mbms/DownloadRequest.java
+++ b/telephony/java/android/telephony/mbms/DownloadRequest.java
@@ -16,6 +16,7 @@
 
 package android.telephony.mbms;
 
+import android.annotation.NonNull;
 import android.annotation.SystemApi;
 import android.content.Intent;
 import android.net.Uri;
@@ -26,7 +27,6 @@
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
-import java.io.File;
 import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
@@ -72,6 +72,19 @@
         private String appIntent;
         private int version = CURRENT_VERSION;
 
+
+        /**
+         * Builds a new DownloadRequest.
+         * @param sourceUri the source URI for the DownloadRequest to be built. This URI should
+         *     never be null.
+         */
+        public Builder(@NonNull Uri sourceUri) {
+            if (sourceUri == null) {
+                throw new IllegalArgumentException("Source URI must be non-null.");
+            }
+            source = sourceUri;
+        }
+
         /**
          * Sets the service from which the download request to be built will download from.
          * @param serviceInfo
@@ -93,15 +106,6 @@
         }
 
         /**
-         * Sets the source URI for the download request to be built.
-         * @param source
-         */
-        public Builder setSource(Uri source) {
-            this.source = source;
-            return this;
-        }
-
-        /**
          * Set the subscription ID on which the file(s) should be downloaded.
          * @param subscriptionId
          */
@@ -317,9 +321,11 @@
             throw new RuntimeException("Could not get sha256 hash object");
         }
         if (version >= 1) {
-            // Hash the source URI, destination URI, and the app intent
+            // Hash the source URI and the app intent
             digest.update(sourceUri.toString().getBytes(StandardCharsets.UTF_8));
-            digest.update(serializedResultIntentForApp.getBytes(StandardCharsets.UTF_8));
+            if (serializedResultIntentForApp != null) {
+                digest.update(serializedResultIntentForApp.getBytes(StandardCharsets.UTF_8));
+            }
         }
         // Add updates for future versions here
         return Base64.encodeToString(digest.digest(), Base64.URL_SAFE | Base64.NO_WRAP);