Android build now works end-to-end: JDK pin, p4a venv fix, kivy recipe

- build.sh: pin JAVA_HOME to java-17-openjdk for the build only (Gradle
  8.14.3 can't parse this machine's default java-26 class files).
- build.sh: delete p4a's internal pymodules venv before every run — it
  re-runs `python -m venv` without --clear on each build and corrupts
  its own pip (confirmed two dist-info dirs coexisting).
- CLAUDE.md / android/README.md: document all three build-tooling fixes
  from this session (kivy python_depends, p4a venv corruption, JDK pin)
  so a future session/rebuild doesn't have to re-diagnose them.

Confirmed: full BUILD SUCCESSFUL Gradle run, APK produced at
android/bin/eventtracker-0.1-arm64-v8a-debug.apk.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

CLAUDE.md

@@ -9,14 +9,21 @@ Context for future Claude sessions working on this repo.
   relocatable data path, taskbar icon, "Time Since" column.
 - Repo is pushed to `repo.tas-tech.net/tas-tech.net/event-tracker`
   (private — will go public once there's a tagged release).
-- Android build (`android/`) is in progress. Native recipe compilation
-  (SDL2, OpenSSL, sqlite3, pyjnius, hostpython3) succeeds. The last
-  blocker was a p4a upstream bug in the `kivy` recipe's `python_depends`
-  — see "Android companion — design decisions" below for the fix
-  (`android/p4a-recipes/kivy`). Not yet confirmed working end-to-end —
-  next session should check whether the user has run
-  `./build.sh android debug` since that fix landed and, if not, ask for
-  the latest log tail before touching anything else Android-related.
+- **Android build (`android/`) works end-to-end** — `./build.sh android
+  debug` produces `android/bin/eventtracker-0.1-arm64-v8a-debug.apk`.
+  Confirmed via a full `BUILD SUCCESSFUL` Gradle run, not just "recipes
+  compiled." Three real, distinct bugs had to be fixed to get here (all
+  now baked into `build.sh`/`buildozer.spec`, nothing left to redo):
+  1. p4a's `kivy` recipe pulling in unused `requests`/`charset-normalizer`
+     that couldn't actually install — `android/p4a-recipes/kivy`.
+  2. p4a's own internal pymodules venv corrupting itself on every
+     re-build — `build.sh` deletes it before each run.
+  3. Gradle's build-script compiler rejecting this machine's default JDK
+     (java-26) — `build.sh` pins `JAVA_HOME` to `java-17-openjdk` for
+     just this build.
+  See "Android companion — design decisions" below for the full
+  root-cause writeup on each. Not yet installed/tested on an actual
+  phone — that's the next real checkpoint, not another build fix.
 - **Outstanding, agreed but not implemented**: split `config.json` into
   two files — event list (safe to sync between machines) vs. data file
   path (must stay local per-device, same principle as the Android app's
@@ -212,6 +219,38 @@ android/
   mode than the one it fixed. Don't reintroduce it as a quick fix for a
   future build error without checking whether it's actually leaking
   something first.
+- **`build.sh` deletes p4a's internal pymodules venv before every run** —
+  separate from `android/build/venv` (ours, for buildozer/cython) and
+  separate from the `p4a-recipes` bug above. p4a creates its own
+  throwaway venv per arch at
+  `.buildozer/android/platform/build-<arch>/build/venv` to pip-install
+  pure-Python deps, and unconditionally re-runs `python -m venv venv`
+  over it on *every* build without `--clear`. First build: ensurepip
+  bootstraps whatever pip version shipped with this system's Python
+  (25.3). p4a then runs `pip install -U pip` inside it (26.2.1). Next
+  build: `python -m venv` re-invokes ensurepip, which unpacks its older
+  bundled pip back over the newer one without removing the newer
+  version's now-orphaned files — confirmed by hand, both
+  `pip-25.3.dist-info` and `pip-26.2.1.dist-info` present in the same
+  site-packages afterward, producing exactly the kind of mismatched-file
+  crash you'd expect (`ImportError: cannot import name
+  'BuildDependencyInstallError' from 'pip._internal.exceptions'` — a
+  newer file expecting a class only the newer exceptions.py defines).
+  `build.sh` just deletes that venv before every buildozer invocation;
+  costs a few seconds (pip + Cython reinstall in a tiny throwaway venv),
+  leaves the expensive SDK/NDK/recipe build state untouched.
+- **`build.sh` pins `JAVA_HOME` to `java-17-openjdk` for the build only**
+  — this machine's `archlinux-java` default is java-26 (rolling
+  release), and Gradle 8.14.3 (pulled in by this p4a version) ships a
+  Groovy/ASM build-script compiler that can't parse that new a class
+  file: `BUG! ... Unsupported class file major version 70`. java-17 is
+  installed alongside the default (`archlinux-java status` lists both);
+  `JAVA_HOME_FOR_BUILD` at the top of `build.sh` points at it without
+  touching the system-wide default JDK used by everything else. If this
+  ever needs to change (different machine, JDK package renamed), that's
+  the one line to edit — `build.sh` fails loudly with a clear message if
+  the path doesn't exist rather than silently falling through to
+  whatever `java` resolves to on PATH.
 
 ## Conventions for changes
 

android/README.md

@@ -24,6 +24,7 @@ Run on the Linux machine you're building from (not the phone):
 ```sh
 command -v buildozer && buildozer version 2>&1
 command -v java && java -version 2>&1
+archlinux-java status 2>&1
 python3 -c "import cython; print('cython:', cython.__version__)" 2>&1
 ```
 
@@ -32,9 +33,19 @@ python3 -c "import cython; print('cython:', cython.__version__)" 2>&1
 **Arch / EndeavourOS:**
 
 ```sh
-sudo pacman -S --needed jdk-openjdk
+sudo pacman -S --needed jdk17-openjdk
 ```
 
+Gradle (pulled in by buildozer/p4a) needs a JDK it actually supports —
+`jdk-openjdk` on a rolling-release system tracks whatever's newest, and
+a too-new JDK breaks Gradle's build-script compiler with `Unsupported
+class file major version …`. `jdk17-openjdk` specifically, installed
+alongside whatever your system default is (`archlinux-java status`
+lists both — no need to switch the default). `build.sh` points this
+build at it via `JAVA_HOME` on its own; if `archlinux-java status` shows
+it under a different name on your machine, update
+`JAVA_HOME_FOR_BUILD` at the top of `build.sh` to match.
+
 buildozer and cython go in an isolated venv, not system Python — see
 next step. (No `pip install --break-system-packages`; that pollutes the
 system Python site-packages for no reason when a venv does the job.)

android/build.sh

@@ -3,6 +3,18 @@
 # buildozer through it directly. Usage: ./build.sh android debug
 set -euo pipefail
 
+# ---- Configuration ----
+# Gradle 8.14.3 (pulled in by this p4a/buildozer version) ships a
+# Groovy/ASM build-script compiler that doesn't understand class files
+# newer than it was built against. This system's `java` default is
+# java-26-openjdk (`archlinux-java status`), and Gradle chokes on it:
+#   BUG! ... Unsupported class file major version 70
+# java-17-openjdk is also installed on this machine and works — set only
+# for this build, via JAVA_HOME below, so the system-wide default JDK
+# (used by everything else) is untouched. If Arch's package layout ever
+# changes this path, `archlinux-java status` shows the current one.
+JAVA_HOME_FOR_BUILD="/usr/lib/jvm/java-17-openjdk"
+
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 VENV_BIN="$SCRIPT_DIR/build/venv/bin"
 BUILDOZER="$VENV_BIN/buildozer"
@@ -12,7 +24,14 @@ if [ ! -x "$BUILDOZER" ]; then
     exit 1
 fi
 
+if [ ! -d "$JAVA_HOME_FOR_BUILD" ]; then
+    echo "Expected JDK not found at $JAVA_HOME_FOR_BUILD — run 'archlinux-java status' and update JAVA_HOME_FOR_BUILD in this script." >&2
+    exit 1
+fi
+
 cd "$SCRIPT_DIR"
+export JAVA_HOME="$JAVA_HOME_FOR_BUILD"
+export PATH="$JAVA_HOME/bin:$PATH"
 # Running buildozer by absolute path skips everything `source venv/bin/activate`
 # normally sets up, so it's replicated by hand:
 #  - PATH: buildozer shells out to find tools like `cython`, which only
@@ -23,4 +42,26 @@ cd "$SCRIPT_DIR"
 #    a venv, uses --user, and pip refuses (no user site-packages in a venv).
 export PATH="$VENV_BIN:$PATH"
 export VIRTUAL_ENV="$SCRIPT_DIR/build/venv"
+
+# p4a creates its OWN throwaway venv per arch (.buildozer/.../build/venv,
+# distinct from our build/venv above) to pip-install pure-Python deps for
+# the app, and unconditionally re-runs `python -m venv venv` over it on
+# every single build — without --clear. The first time, ensurepip bundles
+# whatever pip version shipped with this system's Python (e.g. 25.3); if
+# a previous build then ran `pip install -U pip` inside it (p4a does this
+# every time too), the NEXT build's `python -m venv` re-invokes ensurepip,
+# which unpacks its older bundled pip back over the newer one WITHOUT
+# removing the newer version's now-orphaned files — two dist-info dirs
+# end up coexisting, and a newer file (e.g. build_env/installer.py,
+# importing a class only the newer pip's exceptions.py defines) can end
+# up paired with an older file that doesn't define it, e.g.:
+#   ImportError: cannot import name 'BuildDependencyInstallError' from
+#   'pip._internal.exceptions'
+# Confirmed by hand: pip-25.3.dist-info and pip-26.2.1.dist-info both
+# present in the same site-packages after a second build. Deleting that
+# venv before every build keeps it single-version and costs a few
+# seconds (pip + Cython reinstall) — cheap next to the SDK/NDK/recipe
+# build state, which this leaves untouched.
+rm -rf "$SCRIPT_DIR"/.buildozer/android/platform/build-*/build/venv
+
 exec "$BUILDOZER" "$@"