Seriously improve error reporting in DownloadThread.

My old error reporting strategy for DownloadThread was to log the
stack trace for the exception, so we'd know exactly what conditions
caused the StopRequest.  hackbod suggested that we shouldn't log
tracebacks as they clutter the log.  Instead, we should just always
include a little string tag explaining why the request is being
stopped -- this is more concise and more useful to developers.

There are three main changes here to acheive this goal:
* make StopRequest require a short, log-friendly error message upon
  construction, and add such a message to all construction sites
* make a similar change to GenerateSaveFileError, so that the variety
  of errors that originate with Helpers.generateSaveFile() get
  similarly fine-grained and concise error reporting
* make network usable checking code return a distinct error code for
  each distinct negative condition, and add a utility to return a
  log-friendly error message for each such code.

Finally, I cleaned up some of the ways errors/exceptions are handled
in the process.

Change-Id: Ie70cbf3f2960e260e97f8449258e25218d0f900f

1 files changed, 41 insertions, 5 deletions

diff --git a/src/com/android/providers/downloads/DownloadInfo.java b/src/com/android/providers/downloads/DownloadInfo.java
index b6f478c8..3327e80b 100644
--- a/src/com/android/providers/downloads/DownloadInfo.java
+++ b/src/com/android/providers/downloads/DownloadInfo.java
@@ -175,9 +175,9 @@ public class DownloadInfo {
     public static final int NETWORK_OK = 1;
 
     /**
-     * The network is unusuable for some unspecified reason.
+     * There is no network connectivity.
      */
-    public static final int NETWORK_UNUSABLE_GENERIC = 2;
+    public static final int NETWORK_NO_CONNECTION = 2;
 
     /**
      * The download exceeds the maximum size for this network.
@@ -191,6 +191,16 @@ public class DownloadInfo {
     public static final int NETWORK_RECOMMENDED_UNUSABLE_DUE_TO_SIZE = 4;
 
     /**
+     * The current connection is roaming, and the download can't proceed over a roaming connection.
+     */
+    public static final int NETWORK_CANNOT_USE_ROAMING = 5;
+
+    /**
+     * The app requesting the download specific that it can't use the current network connection.
+     */
+    public static final int NETWORK_TYPE_DISALLOWED_BY_REQUESTOR = 6;
+
+    /**
      * For intents used to notify the user that a download exceeds a size threshold, if this extra
      * is true, WiFi is required for this download size; otherwise, it is only recommended.
      */
@@ -340,10 +350,10 @@ public class DownloadInfo {
     public int checkCanUseNetwork() {
         Integer networkType = mSystemFacade.getActiveNetworkType();
         if (networkType == null) {
-            return NETWORK_UNUSABLE_GENERIC;
+            return NETWORK_NO_CONNECTION;
         }
         if (!isRoamingAllowed() && mSystemFacade.isNetworkRoaming()) {
-            return NETWORK_UNUSABLE_GENERIC;
+            return NETWORK_CANNOT_USE_ROAMING;
         }
         return checkIsNetworkTypeAllowed(networkType);
     }
@@ -357,6 +367,32 @@ public class DownloadInfo {
     }
 
     /**
+     * @return a non-localized string appropriate for logging corresponding to one of the
+     * NETWORK_* constants.
+     */
+    public String getLogMessageForNetworkError(int networkError) {
+        switch (networkError) {
+            case NETWORK_RECOMMENDED_UNUSABLE_DUE_TO_SIZE:
+                return "download size exceeds recommended limit for mobile network";
+
+            case NETWORK_UNUSABLE_DUE_TO_SIZE:
+                return "download size exceeds limit for mobile network";
+
+            case NETWORK_NO_CONNECTION:
+                return "no network connection available";
+
+            case NETWORK_CANNOT_USE_ROAMING:
+                return "download cannot use the current network connection because it is roaming";
+
+            case NETWORK_TYPE_DISALLOWED_BY_REQUESTOR:
+                return "download was requested to not use the current network type";
+
+            default:
+                return "unknown error with network connectivity";
+        }
+    }
+
+    /**
      * Check if this download can proceed over the given network type.
      * @param networkType a constant from ConnectivityManager.TYPE_*.
      * @return one of the NETWORK_* constants
@@ -365,7 +401,7 @@ public class DownloadInfo {
         if (mIsPublicApi) {
             int flag = translateNetworkTypeToApiFlag(networkType);
             if ((flag & mAllowedNetworkTypes) == 0) {
-                return NETWORK_UNUSABLE_GENERIC;
+                return NETWORK_TYPE_DISALLOWED_BY_REQUESTOR;
             }
         }
         return checkSizeAllowedForNetwork(networkType);