core: fix incorrect package for R class (#99)

jadx-core/src/main/java/jadx/core/codegen/ClassGen.java

@@ -501,6 +501,10 @@ public class ClassGen {
 		if (searchCollision(cls.dex(), useCls, extClsInfo)) {
 			return fullName;
 		}
+		// ignore classes from default package
+		if (extClsInfo.isDefaultPackage()) {
+			return shortName;
+		}
 		if (extClsInfo.getPackage().equals(useCls.getPackage())) {
 			fullName = extClsInfo.getNameWithoutPackage();
 		}

jadx-core/src/main/java/jadx/core/codegen/InsnGen.java

@@ -52,6 +52,8 @@ import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import static jadx.core.utils.android.AndroidResourcesUtils.handleAppResField;
+
 public class InsnGen {
 	private static final Logger LOG = LoggerFactory.getLogger(InsnGen.class);
 
@@ -169,12 +171,7 @@ public class InsnGen {
 		boolean fieldFromThisClass = clsGen.getClassNode().getClassInfo().equals(declClass);
 		if (!fieldFromThisClass) {
 			// Android specific resources class handler
-			ClassInfo parentClass = declClass.getParentClass();
-			if (parentClass != null && parentClass.getShortName().equals("R")) {
-				clsGen.useClass(code, parentClass);
-				code.add('.');
-				code.add(declClass.getAlias().getShortName());
-			} else {
+			if (!handleAppResField(code, clsGen, declClass)) {
 				clsGen.useClass(code, declClass);
 			}
 			code.add('.');

jadx-core/src/main/java/jadx/core/dex/info/ClassInfo.java

@@ -125,6 +125,10 @@ public final class ClassInfo {
 		return pkg;
 	}
 
+	public boolean isDefaultPackage() {
+		return pkg.isEmpty();
+	}
+
 	public String getRawName() {
 		return type.getObject();
 	}

jadx-core/src/main/java/jadx/core/dex/nodes/FieldNode.java

@@ -17,10 +17,8 @@ public class FieldNode extends LineAttrNode {
 	private ArgType type; // store signature
 
 	public FieldNode(ClassNode cls, Field field) {
-		this.parent = cls;
-		this.fieldInfo = FieldInfo.fromDex(cls.dex(), field.getFieldIndex());
-		this.type = fieldInfo.getType();
-		this.accFlags = new AccessInfo(field.getAccessFlags(), AFType.FIELD);
+		this(cls, FieldInfo.fromDex(cls.dex(), field.getFieldIndex()),
+				field.getAccessFlags());
 	}
 
 	public FieldNode(ClassNode cls, FieldInfo fieldInfo, int accessFlags) {

jadx-core/src/main/java/jadx/core/dex/nodes/RootNode.java

@@ -9,6 +9,7 @@ import jadx.core.dex.info.ClassInfo;
 import jadx.core.dex.info.ConstStorage;
 import jadx.core.utils.ErrorsCounter;
 import jadx.core.utils.StringUtils;
+import jadx.core.utils.android.AndroidResourcesUtils;
 import jadx.core.utils.exceptions.DecodeException;
 import jadx.core.utils.exceptions.JadxException;
 import jadx.core.utils.files.DexFile;
@@ -97,24 +98,7 @@ public class RootNode {
 	}
 
 	public void initAppResClass() {
-		ClassNode resCls;
-		if (appPackage == null) {
-			appResClass = makeClass("R");
-			return;
-		}
-		String fullName = appPackage + ".R";
-		resCls = searchClassByName(fullName);
-		if (resCls != null) {
-			appResClass = resCls;
-		} else {
-			appResClass = makeClass(fullName);
-		}
-	}
-
-	private ClassNode makeClass(String clsName) {
-		DexNode firstDex = dexNodes.get(0);
-		ClassInfo r = ClassInfo.fromName(firstDex, clsName);
-		return new ClassNode(firstDex, r);
+		appResClass = AndroidResourcesUtils.searchAppResClass(this);
 	}
 
 	public void initClassPath() throws DecodeException {
@@ -169,6 +153,18 @@ public class RootNode {
 		return null;
 	}
 
+	public List<ClassNode> searchClassByShortName(String shortName) {
+		List<ClassNode> list = new ArrayList<ClassNode>();
+		for (DexNode dexNode : dexNodes) {
+			for (ClassNode cls : dexNode.getClasses()) {
+				if (cls.getClassInfo().getShortName().equals(shortName)) {
+					list.add(cls);
+				}
+			}
+		}
+		return list;
+	}
+
 	public List<DexNode> getDexNodes() {
 		return dexNodes;
 	}

jadx-core/src/main/java/jadx/core/utils/android/AndroidResourcesUtils.java

+package jadx.core.utils.android;
+
+import jadx.core.codegen.ClassGen;
+import jadx.core.codegen.CodeWriter;
+import jadx.core.dex.info.ClassInfo;
+import jadx.core.dex.nodes.ClassNode;
+import jadx.core.dex.nodes.DexNode;
+import jadx.core.dex.nodes.RootNode;
+
+import java.util.List;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Android resources specific handlers
+ */
+public class AndroidResourcesUtils {
+	private static final Logger LOG = LoggerFactory.getLogger(AndroidResourcesUtils.class);
+
+	public static ClassNode searchAppResClass(RootNode root) {
+		String appPackage = root.getAppPackage();
+		String fullName = appPackage != null ? appPackage + ".R" : "R";
+		ClassNode resCls = root.searchClassByName(fullName);
+		if (resCls != null) {
+			return resCls;
+		}
+		List<ClassNode> candidates = root.searchClassByShortName("R");
+		if (candidates.size() == 1) {
+			return candidates.get(0);
+		}
+		if (!candidates.isEmpty()) {
+			LOG.info("Found several 'R' class candidates: {}", candidates);
+		}
+		LOG.warn("Unknown 'R' class, create references to '{}'", fullName);
+		return makeClass(root, fullName);
+	}
+
+	public static boolean handleAppResField(CodeWriter code, ClassGen clsGen, ClassInfo declClass) {
+		ClassInfo parentClass = declClass.getParentClass();
+		if (parentClass != null && parentClass.getShortName().equals("R")) {
+			clsGen.useClass(code, parentClass);
+			code.add('.');
+			code.add(declClass.getAlias().getShortName());
+			return true;
+		}
+		return false;
+	}
+
+	private static ClassNode makeClass(RootNode root, String clsName) {
+		DexNode firstDex = root.getDexNodes().get(0);
+		ClassInfo r = ClassInfo.fromName(firstDex, clsName);
+		return new ClassNode(firstDex, r);
+	}
+}

jadx-core/src/test/java/jadx/tests/integration/inner/TestRFieldRestore.java

@@ -9,6 +9,8 @@ import java.util.Map;
 import org.junit.Test;
 
 import static jadx.tests.api.utils.JadxMatchers.containsOne;
+import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.not;
 import static org.junit.Assert.assertThat;
 
 public class TestRFieldRestore extends IntegrationTest {
@@ -31,5 +33,6 @@ public class TestRFieldRestore extends IntegrationTest {
 		ClassNode cls = getClassNode(TestCls.class);
 		String code = cls.getCode().toString();
 		assertThat(code, containsOne("return R.id.Button;"));
+		assertThat(code, not(containsString("import R;")));
 	}
 }