GitHub - woct0rdho/mathstudio-apk-modernized: MathStudio Android APK modernized for Android >= 7

5 min read Original article ↗

MathStudio is the best Android math app I've used. It's a pity that it's unmaintained on Android since 2016. I've modernized the APK and now it should support Android >= 7 with armeabi-v7a. I've tested it on Android 13 and 14. It may show some incompatibility warnings, but it actually works.

On some Android systems, you may need to manually grant storage permission.

Files in this repo

  • MathStudio_5.3_APKPure.apk: original 5.3 APK obtained from APKPure.
  • MathStudio_5.3_modern_signed.apk: modernized 5.3 APK.
  • MathStudioExpress_6.0.5_APK4Fun.apk: original 6.0.5 APK obtained from APK4Fun.
  • MathStudioExpress_6.0.5_modern_signed.apk: modernized 6.0.5 APK.
  • mathstudio_loader.c: loader shim for 5.3 .
  • mathstudio_express_loader.c: loader shim for 6.0.5 .
  • patch_mathstudio_apk.py: binary APK/manifest repack script.
  • patch_smali_modern_storage.py: smali patch script for 5.3 Java-side storage changes.
  • patch_smali_express_modern_storage.py: smali patch script for 6.0.5 Java-side storage changes.

What was patched

  1. Raised the app target SDK to 24.
  2. Replaced the native library entry with a loader shim.
  3. Patched storage routing so .math / .scripts notebooks are saved to /sdcard/Documents/MathStudio/, and internal files are saved in /sdcard/Android/.
  4. Added high aspect ratio support.
  5. Repacked and signed the APK.

Manifest patch

patch_mathstudio_apk.py edits the binary Android manifest directly. It does the following:

  1. Adds or updates android:targetSdkVersion on <uses-sdk>.
  2. Optionally adds android:debuggable="true" when --debuggable is passed.
  3. Adds android:resizeableActivity="true" and android:maxAspectRatio="3.0" to the application/activity entries.
  4. Adds android.max_aspect metadata with value 3.0 for vendor compatibility.
  5. Updates the binary XML string pool and resource map so the inserted attributes are valid.

Loader shim

The original MathStudio 5.3 libpomegranate.so is an armeabi-v7a library with text relocations. Android blocks text relocations for apps targeting API 23 or newer. The modernized app targets API 24, which is supported as of Android 17. The loader shim temporarily lowers the linker target SDK to 22 when loading the original library, then restores the linker target SDK to 24. The shim also registers the original JNI methods with GameNative, so Java continues calling the original engine functions.

MathStudio Express 6.0.5 uses a separate shim. Its native library did not contain text relocations, so this shim does not lower the linker target SDK. Instead, it loads the original library, registers the original JNI methods, and patches Pomegranate::GetStoragePath(...) in memory so the file picker root and .math / .scripts paths resolve under /sdcard/Documents/MathStudio/, while fonts and other resources stay under the app's internal files directory.

Native storage patch

The native engine builds resource paths through Pomegranate::GetStoragePath(...). That function prepends /sdcard/, uses the native window title as the folder name, and appends /.data/ for resource files.

To make native resource reads land in app-specific external storage, the shim assigns Pomegranate::WindowTitle to this relative folder:

Android/data/com.PomegranateSoftware.MathStudio/files/MathStudio

The native code then resolves resource files such as:

/sdcard/Android/data/com.PomegranateSoftware.MathStudio/files/MathStudio/.data/verdana18.font

Java storage patch

The MathStudio 5.3 Java code originally used /sdcard/ and GameNative.title() to build paths. After the native title was repurposed for storage routing, those Java title calls had to be separated from user-facing names. The 5.3 smali patch does the following:

  1. Adds GameActivity.getStorageRoot().
  2. Implements it with getExternalFilesDir(null).getAbsolutePath() + "/".
  3. Changes resource paths to use getStorageRoot().
  4. Uses literal MathStudio for the visible app folder/title where Java needs the real display name.

The MathStudio Express 6.0.5 Java code already has native setStoragePath(...), so it does not need the native-title shim trick. The 6.0.5 smali patch does the following:

  1. Adds GameActivity.getStorageRoot().
  2. Adds GameActivity.getInternalStorageRoot() and implements it with getFilesDir().getAbsolutePath().
  3. Adds GameActivity.getDocumentStorageRoot() for /sdcard/Documents/MathStudio/.
  4. Copies bundled .font files to internal Resources/, and bundled .math / .scripts files to /sdcard/Documents/MathStudio/.
  5. Requests WRITE_EXTERNAL_STORAGE at runtime when needed.

Aspect ratio patch

Before patching, there was a black area between the app UI and the Android navigation buttons. That is Android high-aspect-ratio compatibility letterboxing: the original app did not declare that it supports tall phone screens, so the system limited the app to a shorter viewport and filled the remaining area black. The patch fixes this in the manifest by declaring high-aspect support:

android:resizeableActivity="true"
android:maxAspectRatio="3.0"
<meta-data android:name="android.max_aspect" android:value="3.0" />

The default 3.0 ratio is intentionally higher than current tall phones, including 20:9 and similar displays. You can override it with --max-aspect-ratio <ratio> when running patch_mathstudio_apk.py.

Build steps

The commands below assume the required Android SDK build tools, Android NDK compiler, baksmali.jar, smali.jar, and a signing keystore are available.

MathStudio 5.3

  1. Disassemble the original DEX: 
    java -jar baksmali.jar disassemble MathStudio_5.3_APKPure.apk -o smali_modern_storage
  2. Apply the smali storage patch: 
    python patch_smali_modern_storage.py smali_modern_storage
  3. Reassemble the patched DEX: 
    java -jar smali.jar assemble smali_modern_storage -o classes_modern_storage.dex
  4. Build the loader shim with Android NDK clang: 
    clang --target=armv7a-linux-androideabi24 -shared -fPIC -O2 \
  -o libpomegranate_shim.so \
  mathstudio_loader.c \
  -llog -ldl
  5. Repack an unsigned APK: 
    python patch_mathstudio_apk.py \
  --apk MathStudio_5.3_APKPure.apk \
  --shim libpomegranate_shim.so \
  --classes-dex classes_modern_storage.dex \
  --out MathStudio_5.3_modern_unsigned.apk
  6. Align the APK: 
    zipalign -p -f 4 \
  MathStudio_5.3_modern_unsigned.apk \
  MathStudio_5.3_modern_aligned.apk
  7. Sign the APK: 
    apksigner sign \
  --ks <keystore> \
  --ks-key-alias <alias> \
  --out MathStudio_5.3_modern_signed.apk \
  MathStudio_5.3_modern_aligned.apk
  8. Verify the signature: 
    apksigner verify --verbose MathStudio_5.3_modern_signed.apk

MathStudio Express 6.0.5

  1. Disassemble the original DEX: 
    java -jar baksmali.jar disassemble MathStudioExpress_6.0.5_APK4Fun.apk -o smali_express_modern_storage
  2. Apply the smali storage patch: 
    python patch_smali_express_modern_storage.py smali_express_modern_storage
  3. Reassemble the patched DEX: 
    java -jar smali.jar assemble smali_express_modern_storage -o classes_express_modern_storage.dex
  4. Build the loader shim with Android NDK clang: 
    clang --target=armv7a-linux-androideabi24 -shared -fPIC -O2 \
  -o libpomegranate_express_shim.so \
  mathstudio_express_loader.c \
  -llog -ldl
  5. Repack an unsigned APK: 
    python patch_mathstudio_apk.py \
  --apk MathStudioExpress_6.0.5_APK4Fun.apk \
  --shim libpomegranate_express_shim.so \
  --classes-dex classes_express_modern_storage.dex \
  --out MathStudioExpress_6.0.5_modern_unsigned.apk
  6. Align the APK: 
    zipalign -p -f 4 \
  MathStudioExpress_6.0.5_modern_unsigned.apk \
  MathStudioExpress_6.0.5_modern_aligned.apk
  7. Sign the APK: 
    apksigner sign \
  --ks <keystore> \
  --ks-key-alias <alias> \
  --out MathStudioExpress_6.0.5_modern_signed.apk \
  MathStudioExpress_6.0.5_modern_aligned.apk
  8. Verify the signature: 
    apksigner verify --verbose MathStudioExpress_6.0.5_modern_signed.apk