[Downloads] Expose basic download history to UI

chrome/browser/android/download/download_manager_service.cc

Index: chrome/browser/android/download/download_manager_service.cc
diff --git a/chrome/browser/android/download/download_manager_service.cc b/chrome/browser/android/download/download_manager_service.cc
index 3c410a414ef7fe62c03ad89b921406593510e8ad..177047ec791e5d49ed239941daff291394b66fb9 100644
--- a/chrome/browser/android/download/download_manager_service.cc
+++ b/chrome/browser/android/download/download_manager_service.cc
@@ -23,6 +23,8 @@ using base::android::JavaParamRef;
 using base::android::ConvertJavaStringToUTF8;
 using base::android::ConvertUTF8ToJavaString;
 
+using DownloadVector = content::DownloadManager::DownloadVector;
+
 // static
 bool DownloadManagerService::RegisterDownloadManagerService(JNIEnv* env) {
   return RegisterNativesImpl(env);
@@ -73,6 +75,56 @@ void DownloadManagerService::PauseDownload(
     EnqueueDownloadAction(download_guid, PAUSE);
 }
 
+void DownloadManagerService::GetAllDownloads(JNIEnv* env,
+                                             const JavaParamRef<jobject>& obj) {
+  if (is_history_query_complete_)
+    GetAllDownloadsInternal();
+  else
+    EnqueueDownloadAction(std::string(), INITIALIZE_UI);
+}
+
+void DownloadManagerService::GetAllDownloadsInternal() {
+  content::DownloadManager* manager = GetDownloadManager(false);
+  if (java_ref_.is_null() || !manager)
+    return;
+
+  DownloadVector all_items;
+  manager->GetAllDownloads(&all_items);
+
+  // Create a list in Java-land and then add information about all the
+  // downloads to it.
+  JNIEnv* env = base::android::AttachCurrentThread();

[qinmin, 2016/07/14 17:08:05]

Since we always call onAllDownloadsRetrieved, can we just skipping creating the
empty list and pass an array of objects from native to java, and create the list
in java at that time?

[gone, 2016/07/14 17:11:08]

This is actually what the DownloadsBridge does, so we're just mimicking what's
going on there.

But how would you actually pass the objects?  Would we create 4 jstring arrays
and 2 jlong arrays?  Is that a thing we can do?

[qinmin, 2016/07/14 18:06:54]

You can call a jni call to pack the fields into a jobject and return it, so at
the end, just an array of jobjects

[Ian Wen, 2016/07/14 18:16:26]

Aha! I found a trick that BookmarkBridge did to simplify the code by a tiny
margin: in GetAllDownloas(), java side passes a java list directly to native and
let it cache it for returning.

This is a nit though. orz

[gone, 2016/07/14 19:11:56]

Changed it around to create the jobjectarray like Min suggested; lmk if this
looks right.

+  ScopedJavaLocalRef<jobject> jdownload_item_list =
+      Java_DownloadManagerService_createDownloadItemList(
+          env, java_ref_.obj());
+
+  for (size_t i = 0; i < all_items.size(); i++) {
+    content::DownloadItem* item = all_items[i];
+    if (item->IsTemporary() ||
+        item->GetFileNameToReportUser().empty() ||
+        item->GetTargetFilePath().empty()) {
+      continue;
+    }
+
+    Java_DownloadManagerService_addItemToDownloadItemList(
+        env,
+        java_ref_.obj(),
+        jdownload_item_list.obj(),
+        ConvertUTF8ToJavaString(env, item->GetGuid()).obj(),
+        ConvertUTF8ToJavaString(
+            env,
+            item->GetFileNameToReportUser().BaseName().value()).obj(),
+        ConvertUTF8ToJavaString(env, item->GetTabUrl().spec()).obj(),
+        ConvertUTF8ToJavaString(env, item->GetMimeType()).obj(),
+        item->GetStartTime().ToJavaTime(),
+        item->GetTotalBytes());
+  }
+
+  Java_DownloadManagerService_onAllDownloadsRetrieved(
+      env, java_ref_.obj(), jdownload_item_list.obj());
+}
+
+
 void DownloadManagerService::CancelDownload(
     JNIEnv* env,
     jobject obj,
@@ -114,6 +166,9 @@ void DownloadManagerService::OnHistoryQueryComplete() {
       case CANCEL:
         CancelDownloadInternal(download_guid, false);
         break;
+      case INITIALIZE_UI:
+        GetAllDownloadsInternal();
+        break;
       default:
         NOTREACHED();
         break;
@@ -188,6 +243,9 @@ void DownloadManagerService::EnqueueDownloadAction(
     case CANCEL:
       iter->second = action;
       break;
+    case INITIALIZE_UI:
+      iter->second = action;
+      break;
     default:
       NOTREACHED();
       break;