Tweaks to Activity up navigation

Be more explicit in docs about getParentActivityIntent and guard against
calls when a parent has not been declared in the manifest.

Move automatic up navigation to happen after dispatch of the menu
selection event of id android.R.id.home to fragments. (Last.)

Fixes bug 6305357

Change-Id: I944e5c40774121f9a28250d8d98da6aa646f9357

Author: adamp

core/java/android/app/Activity.java

@@ -2522,7 +2522,19 @@ public boolean onMenuItemSelected(int featureId, MenuItem item) {
                 if (onOptionsItemSelected(item)) {
                     return true;
                 }
-                return mFragments.dispatchOptionsItemSelected(item);
+                if (mFragments.dispatchOptionsItemSelected(item)) {
+                    return true;
+                }
+                if (item.getItemId() == android.R.id.home && mActionBar != null &&
+                        (mActionBar.getDisplayOptions() & ActionBar.DISPLAY_HOME_AS_UP) != 0) {
+                    if (mParent == null) {
+                        onNavigateUp();
+                    } else {
+                        mParent.onNavigateUpFromChild(this);
+                    }
+                    return true;
+                }
+                return false;
 
             case Window.FEATURE_CONTEXT_MENU:
                 EventLog.writeEvent(50000, 1, item.getTitleCondensed());
@@ -2654,15 +2666,6 @@ public boolean onOptionsItemSelected(MenuItem item) {
         if (mParent != null) {
             return mParent.onOptionsItemSelected(item);
         }
-        if (item.getItemId() == android.R.id.home && mActionBar != null &&
-                (mActionBar.getDisplayOptions() & ActionBar.DISPLAY_HOME_AS_UP) != 0) {
-            if (mParent == null) {
-                onNavigateUp();
-            } else {
-                mParent.onNavigateUpFromChild(this);
-            }
-            return true;
-        }
         return false;
     }
 
@@ -4865,11 +4868,19 @@ public boolean navigateUpToFromChild(Activity child, Intent upIntent) {
      * Obtain an {@link Intent} that will launch an explicit target activity specified by
      * this activity's logical parent. The logical parent is named in the application's manifest
      * by the {@link android.R.attr#parentActivityName parentActivityName} attribute.
+     * Activity subclasses may override this method to modify the Intent returned by
+     * super.getParentActivityIntent() or to implement a different mechanism of retrieving
+     * the parent intent entirely.
      *
-     * @return a new Intent targeting the defined parent of this activity
+     * @return a new Intent targeting the defined parent of this activity or null if
+     *         there is no valid parent.
      */
     public Intent getParentActivityIntent() {
-        return new Intent().setClassName(this, mActivityInfo.parentActivityName);
+        final String parentName = mActivityInfo.parentActivityName;
+        if (TextUtils.isEmpty(parentName)) {
+            return null;
+        }
+        return new Intent().setClassName(this, parentName);
     }
 
     // ------------------ Internal API ------------------