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Resolve @null drawable references due to resource overlays #94

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259 changes: 258 additions & 1 deletion src/main/java/com/reandroid/apk/ApkBundle.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,11 +15,20 @@
*/
package com.reandroid.apk;

import com.reandroid.archive.ByteInputSource;
import com.reandroid.archive.InputSource;
import com.reandroid.archive.ZipEntryMap;
import com.reandroid.archive.block.ApkSignatureBlock;
import com.reandroid.arsc.chunk.PackageBlock;
import com.reandroid.arsc.chunk.TableBlock;
import com.reandroid.arsc.chunk.xml.ResXmlAttribute;
import com.reandroid.arsc.chunk.xml.ResXmlDocument;
import com.reandroid.arsc.chunk.xml.ResXmlElement;
import com.reandroid.arsc.model.ResourceEntry;
import com.reandroid.arsc.value.ValueType;
import com.reandroid.utils.collection.ArrayCollection;

import java.io.ByteArrayOutputStream;
import java.io.Closeable;
import java.io.File;
import java.io.FileNotFoundException;
Expand Down Expand Up @@ -67,6 +76,9 @@ public ApkModule mergeModules(boolean force) throws IOException {

result.setApkSignatureBlock(signatureBlock);

// Resolve resource overlays (@null references) from split modules
resolveResourceOverlays(result, moduleList);

if(result.hasTableBlock()){
TableBlock tableBlock=result.getTableBlock();
tableBlock.sortPackages();
Expand Down Expand Up @@ -190,9 +202,254 @@ private void logError(String msg, Throwable tr) {
apkLogger.logError(msg, tr);
}
}
private void logVerbose(String msg) {
private void logVerbose(String msg){
if(apkLogger!=null){
apkLogger.logVerbose(msg);
}
}

/**
* Resolves @null drawable references in merged APK by updating binary XML attributes
* to point to actual PNG resources from density split modules.
*
* Modern App Bundles use resource overlays where base APK contains XML with @null
* references and density splits contain the actual PNG files. After merging, the PNGs
* are present but XMLs still reference @null, causing Resources$NotFoundException at runtime.
*
* This method:
* 1. Scans drawable XMLs for @null references (type=REFERENCE, data=0)
* 2. Finds corresponding PNG resources using fuzzy name matching
* 3. Looks up resource IDs from the resource table
* 4. Updates XML binary attributes with correct resource IDs
*/
private void resolveResourceOverlays(ApkModule merged, List<ApkModule> splits) {
try {
if (!merged.hasTableBlock()) {
return;
}

TableBlock tableBlock = merged.getTableBlock();
PackageBlock packageBlock = null;
Iterator<PackageBlock> packages = tableBlock.getPackages();
while (packages.hasNext()) {
PackageBlock pkg = packages.next();
if (pkg.getName() != null) {
packageBlock = pkg;
break;
}
}
if (packageBlock == null) {
return;
}

ZipEntryMap mergedZip = merged.getZipEntryMap();
int resolvedCount = 0;
int totalNullCount = 0;
List<String> unresolved = new ArrayList<>();

// Scan drawable XMLs for @null references
for (ResFile resFile : merged.listResFiles()) {
String path = resFile.getFilePath();
if (!path.startsWith("res/drawable/") || !path.endsWith(".xml")) {
continue;
}

InputSource source = resFile.getInputSource();
if (source == null) continue;

try {
ResXmlDocument xmlDoc = new ResXmlDocument();
xmlDoc.readBytes(source.openStream());

if (hasNullDrawableReferences(xmlDoc)) {
String baseName = getBaseName(path);
totalNullCount++;

// Find corresponding PNG resources
List<String> pngPaths = findOverlayPngs(baseName, mergedZip);

if (!pngPaths.isEmpty()) {
// Extract drawable names and look up resource IDs
Map<String, Integer> drawableIds = new HashMap<>();
for (String pngPath : pngPaths) {
String drawableName = extractDrawableName(pngPath);
ResourceEntry entry = packageBlock.getResource("drawable", drawableName);
if (entry != null) {
drawableIds.put(drawableName, entry.getResourceId());
}
}

if (!drawableIds.isEmpty()) {
// Update XML with resource IDs
if (updateNullReferences(xmlDoc, drawableIds, baseName)) {
// Write updated XML back to merged APK
ByteArrayOutputStream baos = new ByteArrayOutputStream();
xmlDoc.writeBytes(baos);
byte[] newBytes = baos.toByteArray();

mergedZip.remove(path);
mergedZip.add(new ByteInputSource(newBytes, path));
resolvedCount++;
}
} else {
unresolved.add(baseName);
}
} else {
unresolved.add(baseName);
}
}
} catch (Exception e) {
// Skip files that can't be parsed
}
}

if (totalNullCount > 0) {
logMessage("Resolved " + resolvedCount + "/" + totalNullCount + " resource overlays");
if (!unresolved.isEmpty() && unresolved.size() <= 5) {
logMessage("Unresolved: " + String.join(", ", unresolved));
}
}
} catch (Exception e) {
logError("Error resolving resource overlays", e);
}
}

/**
* Checks if XML document contains @null drawable references.
* In binary XML, null references are represented as type=REFERENCE with data=0.
*/
private boolean hasNullDrawableReferences(ResXmlDocument xmlDoc) {
ResXmlElement root = xmlDoc.getDocumentElement();
if (root == null) return false;

Iterator<ResXmlElement> items = root.recursiveElements();
while (items.hasNext()) {
ResXmlElement item = items.next();
if (!"item".equals(item.getName())) continue;

ResXmlAttribute drawable = item.searchAttributeByName("drawable");
if (drawable != null) {
ValueType vtype = drawable.getValueType();
int data = drawable.getData();
if (vtype == ValueType.REFERENCE && data == 0) {
return true;
}
}
}
return false;
}

/**
* Extracts base filename without extension.
* Example: "res/drawable/abc_switch.xml" -> "abc_switch"
*/
private String getBaseName(String path) {
String name = path.substring(path.lastIndexOf('/') + 1);
return name.substring(0, name.lastIndexOf('.'));
}

/**
* Extracts drawable name from PNG path.
* Example: "res/drawable-xxhdpi/abc_btn_switch.9.png" -> "abc_btn_switch"
*/
private String extractDrawableName(String pngPath) {
String fileName = pngPath.substring(pngPath.lastIndexOf('/') + 1);
return fileName.replaceAll("\\.9?\\.png$", "");
}

/**
* Finds PNG resources that match the XML base name using fuzzy keyword matching.
* Material Design resources often have different naming patterns between XML and PNG.
* Example: "abc_switch_thumb_material.xml" matches "abc_btn_switch_to_on_mtrl_*.png"
*/
private List<String> findOverlayPngs(String baseName, ZipEntryMap zip) {
List<String> pngs = new ArrayList<>();

// Extract keywords for fuzzy matching (skip short words)
String[] keywords = baseName.toLowerCase().split("_");

for (InputSource inputSource : zip.listInputSources()) {
String path = inputSource.getAlias();
if (!path.endsWith(".png") || !path.startsWith("res/drawable-")) {
continue;
}

String fileName = path.substring(path.lastIndexOf('/') + 1).toLowerCase();

// Count keyword matches
int matches = 0;
for (String keyword : keywords) {
if (keyword.length() > 3 && fileName.contains(keyword)) {
matches++;
}
}

// Require at least 1 keyword match for fuzzy matching
if (matches >= 1 && keywords.length > 2) {
pngs.add(path);
}
}

return pngs;
}

/**
* Updates @null drawable references with actual resource IDs.
* Uses heuristics to match states (checked/unchecked) based on drawable names.
*
* @return true if any references were updated, false otherwise
*/
private boolean updateNullReferences(ResXmlDocument xmlDoc, Map<String, Integer> drawableIds, String baseName) {
ResXmlElement root = xmlDoc.getDocumentElement();
if (root == null) return false;

boolean updated = false;
Map<String, Integer> stateToId = new HashMap<>();

// Map drawable names to states based on naming patterns
for (Map.Entry<String, Integer> entry : drawableIds.entrySet()) {
String name = entry.getKey();
Integer id = entry.getValue();

// Heuristic: "on" or "00012" in name = checked state
if (name.contains("_on_") || name.contains("00012")) {
stateToId.put("checked", id);
} else if (!stateToId.containsKey("default")) {
stateToId.put("default", id);
}
}

// Update @null references
Iterator<ResXmlElement> items = root.recursiveElements();
while (items.hasNext()) {
ResXmlElement item = items.next();
if (!"item".equals(item.getName())) continue;

ResXmlAttribute drawable = item.searchAttributeByName("drawable");
if (drawable != null && drawable.getValueType() == ValueType.REFERENCE && drawable.getData() == 0) {
// Determine which state this item represents
boolean isChecked = false;
Iterator<ResXmlAttribute> attrs = item.getAttributes();
while (attrs.hasNext()) {
ResXmlAttribute attr = attrs.next();
if ("state_checked".equals(attr.getName()) && attr.getValueAsBoolean()) {
isChecked = true;
break;
}
}

// Get appropriate resource ID
Integer newResId = isChecked ?
stateToId.getOrDefault("checked", stateToId.get("default")) :
stateToId.get("default");

if (newResId != null) {
drawable.setData(newResId);
updated = true;
}
}
}

return updated;
}
}