AAPT2: Workaround for findViewById with package ID > 0x7f

The entire View code base checks IDs against View.NO_ID except
findViewById(), which checks to see if the ID is negative.

Any package ID > 0x7f is interpreted as a negative number in Java
(no unsigned ints), so this check prevents the use of IDs > 0x7f.

findViewById is final, so support library workarounds are not possible.

Instead, IDs (@id/foo) are just sentinels, their values don't matter.
If building for pre-O devices, rewrite any references to these IDs of
the for 0xPPTTEEEE, where PP > 7f, to 0x7fPPEEEE.

The symbol table will check for potential collisions against the base
APK, so this should be safe.

Bug: 37498913
Test: manual
Change-Id: Ife3bbd29db287757ef8a2ffd83053d97f1db2613
diff --git a/tools/aapt2/java/JavaClassGenerator.cpp b/tools/aapt2/java/JavaClassGenerator.cpp
index a8226c0..2a23aa9 100644
--- a/tools/aapt2/java/JavaClassGenerator.cpp
+++ b/tools/aapt2/java/JavaClassGenerator.cpp
@@ -31,6 +31,7 @@
 #include "Resource.h"
 #include "ResourceTable.h"
 #include "ResourceValues.h"
+#include "SdkConstants.h"
 #include "ValueVisitor.h"
 #include "java/AnnotationProcessor.h"
 #include "java/ClassDefinition.h"
@@ -430,9 +431,15 @@
                                          const ResourceEntry& entry, ClassDefinition* out_class_def,
                                          MethodDefinition* out_rewrite_method,
                                          std::ostream* out_r_txt) {
+  ResourceId real_id = id;
+  if (context_->GetMinSdkVersion() < SDK_O && name.type == ResourceType::kId &&
+      id.package_id() > kAppPackageId) {
+    real_id = ResourceId(kAppPackageId, id.package_id(), id.entry_id());
+  }
+
   const std::string field_name = TransformToFieldName(name.entry);
   std::unique_ptr<ResourceMember> resource_member =
-      util::make_unique<ResourceMember>(field_name, id);
+      util::make_unique<ResourceMember>(field_name, real_id);
 
   // Build the comments and annotations for this entry.
   AnnotationProcessor* processor = resource_member->GetCommentBuilder();
@@ -458,7 +465,7 @@
   out_class_def->AddMember(std::move(resource_member));
 
   if (out_r_txt != nullptr) {
-    *out_r_txt << "int " << name.type << " " << field_name << " " << id << "\n";
+    *out_r_txt << "int " << name.type << " " << field_name << " " << real_id << "\n";
   }
 
   if (out_rewrite_method != nullptr) {