fix: generates code of missing R class (#353)

jadx-core/src/main/java/jadx/api/JadxDecompiler.java

@@ -91,7 +91,6 @@ public final class JadxDecompiler {
 
 		root.initClassPath();
 		root.loadResources(getResources());
-		root.initAppResClass();
 
 		initVisitors();
 	}

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

@@ -94,10 +94,7 @@ public class RootNode {
 		ResourceStorage resStorage = parser.getResStorage();
 		constValues.setResourcesNames(resStorage.getResourcesNames());
 		appPackage = resStorage.getAppPackage();
-	}
-
-	public void initAppResClass() {
-		appResClass = AndroidResourcesUtils.searchAppResClass(this);
+		appResClass = AndroidResourcesUtils.searchAppResClass(this, resStorage);
 	}
 
 	public void initClassPath() {

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

 package jadx.core.utils.android;
 
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedList;
 import java.util.List;
+import java.util.Map;
+import java.util.Set;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -11,6 +16,8 @@ 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 jadx.core.xmlgen.ResourceStorage;
+import jadx.core.xmlgen.entry.ResourceEntry;
 
 /**
  * Android resources specific handlers
@@ -21,7 +28,7 @@ public class AndroidResourcesUtils {
 	private AndroidResourcesUtils() {
 	}
 
-	public static ClassNode searchAppResClass(RootNode root) {
+	public static ClassNode searchAppResClass(RootNode root, ResourceStorage resStorage) {
 		String appPackage = root.getAppPackage();
 		String fullName = appPackage != null ? appPackage + ".R" : "R";
 		ClassNode resCls = root.searchClassByName(fullName);
@@ -36,7 +43,7 @@ public class AndroidResourcesUtils {
 			LOG.info("Found several 'R' class candidates: {}", candidates);
 		}
 		LOG.warn("Unknown 'R' class, create references to '{}'", fullName);
-		return makeClass(root, fullName);
+		return makeClass(root, fullName, resStorage);
 	}
 
 	public static boolean handleAppResField(CodeWriter code, ClassGen clsGen, ClassInfo declClass) {
@@ -50,12 +57,48 @@ public class AndroidResourcesUtils {
 		return false;
 	}
 
-	private static ClassNode makeClass(RootNode root, String clsName) {
+	private static ClassNode makeClass(RootNode root, String clsName, ResourceStorage resStorage) {
 		List<DexNode> dexNodes = root.getDexNodes();
 		if (dexNodes.isEmpty()) {
 			return null;
 		}
 		ClassInfo r = ClassInfo.fromName(root, clsName);
-		return new ClassNode(dexNodes.get(0), r);
+		ClassNode classNode = new ClassNode(dexNodes.get(0), r);
+		generateMissingRCode(classNode, resStorage);
+		return classNode;
+	}
+	
+	private static void generateMissingRCode(ClassNode cls, ResourceStorage resStorage) {
+		Map<String, List<ResourceEntry>> sortedMap = new HashMap<>();
+		for(ResourceEntry ri : resStorage.getResources()) {
+			List<ResourceEntry> entries = sortedMap.get(ri.getTypeName());
+			if(entries == null) {
+				entries = new LinkedList<>();
+				sortedMap.put(ri.getTypeName(), entries);
+			}
+			entries.add(ri);
+		}
+		
+		Set<String> addedValues = new HashSet<>();
+		CodeWriter clsCode = new CodeWriter();
+		if (!"".equals(cls.getPackage())) {
+			clsCode.add("package ").add(cls.getPackage()).add(';').newLine();
+		}
+		clsCode.startLine("public final class ").add(cls.getShortName()).add(" {").incIndent();
+		for(String typeName : sortedMap.keySet()) {
+			clsCode.startLine("public static final class ").add(typeName).add(" {").incIndent();
+			for(ResourceEntry ri : sortedMap.get(typeName)) {
+				if(addedValues.add(ri.getTypeName() + "." + ri.getKeyName())) {
+					clsCode.startLine("public static final int ").add(ri.getKeyName()).add(" = ")
+						.add("" + ri.getId()).add(";");
+				}
+			}
+			clsCode.decIndent();
+			clsCode.add("}");
+		}
+		clsCode.decIndent();
+		clsCode.add("}");
+		
+		cls.setCode(clsCode);
 	}
 }