Android compatibility matrix

Picodroid’s goal is that Android code and intuition transfer directly: class names, method signatures, and semantics track android.*. Embedded constraints force some divergences, and a few Android subsystems are intentionally absent. This page is the authoritative list of what’s full, partial, renamed-only, or unsupported — and the picodroid alternative for every gap.

The SDK is imported as picodroid.* — every class below mirrors its android.* counterpart’s name, so the API reads the same; you just import picodroid.* (e.g. import picodroid.view.View;). Apps always use picodroid.* imports.

Status legend

Status	Meaning
Full	API surface and semantics match Android closely enough to port unchanged.
Partial	Present, but a subset of methods/overloads or a documented behavior difference.
Renamed	Same shape, but only reachable as picodroid.* (or via the android alias) — not a real Android class.
Unsupported	No equivalent; use the listed alternative.

By package

android.app

API	Status	Notes / alternative
Activity	Full	Lifecycle (onCreate/onStart/onResume/onPause/onStop/onRestart/onDestroy), startActivity, startActivityForResult + onActivityResult, setResult, getIntent, finish.
Application	Full	onCreate entry point.
Service	Partial	Started + bound services, onRebind, stopSelfResult. No IntentService, no foreground-service notification contract.
AlertDialog / AlertDialog.Builder	Partial	Positive/negative/neutral buttons, setItems, single- and multi-choice. List variants cap at ~12 rows (LVGL renderer limit) and a message set alongside items wins (items are dropped, with a Log.w) — matching Android’s message-vs-items precedence.
Notification / NotificationManager	Partial	Basic post/cancel. No channels, styles, or actions.
Fragment, Loader, PendingIntent	Unsupported	No Fragment system — compose with Activities + Views.

android.view

API	Status	Notes / alternative
View	Partial	Geometry/visibility/enabled/tag/id, setTranslationX/Y, setRotation, setScaleX/Y + getters (getX() == getLeft() + getTranslationX()), OnClickListener, OnLongClickListener + performLongClick, OnTouchListener, OnKeyListener. No findViewById (no resource IDs — keep references or use setTag/getTag); no post/postDelayed (use Executors.mainExecutor() or animation timers).
ViewGroup / ViewPropertyAnimator	Partial	animate() with alpha, x/y, translationX/Y, rotation, scaleX/Y, setDuration, setStartDelay, setInterpolator (the four built-in curves), withEndAction — to-only, as on Android. Rotation/scale render through an off-screen layer of the view’s size; keep transformed views small.
MotionEvent	Partial	getX/getY are view-relative, getRawX/getRawY are screen-absolute, matching Android. Coordinates are int, not float (no FPU).
GestureDetector	Partial	OnGestureListener + SimpleOnGestureListener; slop/fling use raw coordinates.
KeyEvent	Partial	D-pad / button codes for button-only boards.
LayoutInflater, XML layouts, Menu	Unsupported	No resource/XML layout system — build View trees programmatically.

android.widget

API	Status	Notes / alternative
TextView, Button, LinearLayout, ImageView, Switch, CheckBox, ToggleButton, RadioButton/RadioGroup, ProgressBar, SeekBar, Toast, Spinner, NumberPicker, EditText, ListView	Partial–Full	Core widgets present. See specific divergences below.
ProgressBar	Partial	indeterminate() is creation-time only — setIndeterminate(boolean) after construction is unsupported (LVGL can’t morph bar↔spinner).
Spinner.OnItemSelectedListener	Partial	Full 4-arg onItemSelected(parent, view, position, id); view is always null (LVGL rows have no Java wrapper) and parent is the Spinner (no AdapterView).
ImageView	Partial	SCALE_FIT_CENTER, SCALE_CENTER. Source is a bundled asset name (see assets).
EditText + TextWatcher	Partial	TextWatcher takes String (no CharSequence/Editable); only afterTextChanged fires in v1.

android.util

API	Status	Notes / alternative
Log (v/d/i/w/e)	Full	Maps to defmt levels on device; the simulator prints every level as [Tag] msg. Filter by tag/level with pdb logcat --stdin.

android.graphics

API	Status	Notes / alternative
Color	Full	Named constants + ARGB ints.
drawable.GradientDrawable	Partial	Solid/gradient fills, corner radius.
Canvas, Paint, Bitmap	Unsupported	Drawing is via LVGL widgets, not an immediate-mode Canvas.

android.content

API	Status	Notes / alternative
Intent	Partial	Explicit (class-targeted) intents + extras. No implicit intents / IntentFilter resolution.
Context	Partial	getMainExecutor, getDisplay, service access. No getSystemService (services are exposed directly), no getResources (bundle files under assets/ → generated AssetConstants), no registerReceiver (no BroadcastReceiver).
SharedPreferences / Editor	Full	Backed by LittleFS.
DialogInterface	Full	OnClickListener, OnDismissListener, OnMultiChoiceClickListener, button constants.

android.os

API	Status	Notes / alternative
SystemClock	Full	uptimeMillis/elapsedRealtime.
Handler / Looper / Message	Unsupported	Use Executors.mainExecutor().execute(Runnable) for “post to UI”; for delayed work, a Thread that sleeps then posts, or the animation engine’s withEndAction. There is no postDelayed.
Bundle	Partial	Intent extras only.

android.hardware

API	Status	Notes / alternative
Sensor / SensorManager / SensorEvent / SensorEventListener	Partial	Board-dependent sensors; registration + event callbacks.

Concurrency

API	Status	Notes / alternative
Thread (picodroid.concurrent.Thread)	Full	start() spawns a real FreeRTOS task on device and in the simulator (the sim runs the real kernel). run() override or Runnable target, sleep, join/join(ms), interrupt/isInterrupted/interrupted, isAlive, currentThread, get/setName, getId, yield, UncaughtExceptionHandler (per-thread and default), IllegalThreadStateException on a second start(). synchronized blocks and methods are real kernel mutexes; Object.wait/notify/notifyAll work (timed, interruptible, IllegalMonitorStateException when not owner). Divergences: setPriority and setDaemon are advisory (every Java task runs at one RTOS priority — see the system reference), and a compute-bound thread holds the core until it blocks (no time slicing).
Executor / Executors (mainExecutor / backgroundExecutor)	Full	The recommended concurrency primitive — this is how you “post to the UI thread”.
ExecutorService / Future / Callable / TimeUnit (picodroid.concurrent)	Partial	Executors.newFixedThreadPool(n) and newSingleThreadExecutor(): execute, submit(Runnable/Callable), Future.get/get(timeout, unit)/cancel/isDone/isCancelled, shutdown/shutdownNow/isShutdown/isTerminated/awaitTermination; ExecutionException (with getCause()), CancellationException, TimeoutException, RejectedExecutionException under their java.util.concurrent names. Pure Java over Thread + wait/notify; each worker costs a 16 KiB task stack. Not built into testbench_rp2040 (framework_class_excludes, flash headroom) — nor are the atomics and CountDownLatch below. No invokeAll/invokeAny, no scheduled or cached pools, no CompletableFuture.
AtomicInteger / AtomicLong / AtomicBoolean / AtomicReference (picodroid.concurrent)	Partial	get/set/getAndSet/compareAndSet/incrementAndGet/getAndIncrement/decrementAndGet/addAndGet/getAndAdd. synchronized underneath (one core, one JVM priority). No updateAndGet/lambdas, no AtomicIntegerArray.
CountDownLatch (picodroid.concurrent)	Full	countDown, await, await(timeout, unit), getCount. No Semaphore, CyclicBarrier, ReentrantLock, ConcurrentHashMap, BlockingQueue.

java.* standard library

Enforced at build time: every app’s verifyApiContract Gradle task (part of assemblePapk, so build-apk.sh, sim.sh, build.sh and flash.sh all run it) rejects a java.* class or member pico-jvm does not serve, naming the call site and an alternative. sdk/api-contract.tsv, generated from the runtime’s own tables (scripts/gen-api-contract.sh), is the machine-readable form of this section. With --board <name> (or -Ppicodroid.board=<name>) the same task also rejects classes that board drops from its framework (framework_class_excludes). -Ppicodroid.apiContract=warn downgrades the failure to a report while experimenting.

API	Status	Notes / alternative
Object.clone() / Cloneable	Partial	Shallow copy works, but the Cloneable check is skipped — clone() never throws CloneNotSupportedException.
Interface default methods	Full	Resolved per JVMS §5.4.3.3 (sub-interface overrides win whatever the implements order; I.super.f() works; defaults are found through abstract and builtin superclasses). Exception: a lambda’s own interface defaults — calling a default method on a lambda object runs the lambda body instead, so keep lambda-typed interfaces to their single abstract method.
StringBuilder.append(Object) / String.valueOf(Object) / "" + obj	Full	The argument’s toString() runs first — a Java override, else the builtin one for boxes/enums, else the identity form pkg.Cls@hhhh; null prints null.
Object.equals/hashCode/toString defaults	Partial	Identity semantics as in Java, but hashCode() is the object’s heap slot index (stable for the object’s lifetime, reused after GC) and builtin collections use identity too (new ArrayList<>().hashCode() is not content-based; list.toString() prints java.util.ArrayList@…, not the elements).
instanceof / checkcast	Partial	Strings, arrays, builtin collections under List/Collection/Iterable/Set/Map, boxes under Number/Comparable, lambdas under their interface, and transitive superinterfaces all work; a failed cast throws a catchable ClassCastException (with a null message). A reference array’s element class is not recorded, so (String[]) someObjectArray succeeds where Java would throw.
Boxed wrappers (Integer, Float, …)	Partial	equals/hashCode/compareTo, the compare/hashCode(x) statics and Float.floatToIntBits follow Java 8. The xxxValue() accessors return the box’s own value unconverted (Float.valueOf(2.5f).intValue() yields a float; call the matching accessor, or unbox and convert). Character has isDigit/isLetter/toUpperCase/toLowerCase only, ASCII-only (strings are byte-backed).
Enum.valueOf(Class, String)	Unsupported	The static every enum’s synthetic valueOf(String) delegates to has no builtin (a heap scan cost ~800 B of RP2040 flash). Look the constant up yourself: for (Color c : Color.values()) if (c.name().equals(s)) …. Enum.hashCode() is the ordinal.
Throwable	Partial	addSuppressed/getSuppressed/getCause stored; ExceptionInInitializerError wraps <clinit> throws. A failed <clinit> does not poison the class (no NoClassDefFoundError on re-access).
Comparator + Collections.sort(List, Comparator)	Full	Lambda comparators supported.
Interface-typed collections (List/Set/Collection/Map/Iterable)	Full	Map<String,String> m = new HashMap<>(); and interface-typed fields, parameters, returns, casts, instanceof and enhanced-for all work — the JVM dispatches on the receiver’s runtime class, so the interfaces need no class file. Caveat: your app compiles against the JDK’s full interfaces, so members picodroid does not implement (map.forEach, list.removeIf, Map.putAll, new TreeMap<>()) compile and then fail at run time. The rows in this table are the served surface.
HashMap.entrySet() / Map.Entry	Partial	entrySet(), keySet() and values() views answer iterator() and size(); the key and value views also contains() (k in map.keys). Entries answer getKey()/getValue() (no setValue). Iteration order is the map’s internal order.
HashSet.iterator()	Full	for (x : set) and every iterating idiom on a set; hash order, like the map views. Iterators and map views keep a temporary collection alive for as long as they do (for (String w : text.split(" ")), for (e : makeMap().entrySet())) — the GC pins the iterator’s source.
Map.putAll / List.listIterator / Arrays.equals	Unsupported	No builtin arm: copy with an entrySet() loop, iterate by index, compare arrays element-wise. Kotlin: map += otherMap, list.last { } / indexOfLast { } / findLast { } (they walk a listIterator) and contentEquals hit these.
Float.isNaN(f) / Double.isNaN(d) / isInfinite statics	Unsupported	Use f != f for NaN and a magnitude compare for infinity (Kotlin’s isNaN()/isInfinite()/isFinite() inline to these statics).
String(char[])	Unsupported	Only the byte[] constructors exist; build with StringBuilder.append(char) (Kotlin: chars.concatToString() does this).
Math.round	Partial	Rounds half away from zero (Math.round(-2.5f) is -3; Java gives -2). Kotlin’s roundToInt()/roundToLong() shim spells out Java’s floor(x + 0.5) and is exact.
String.replace(target, replacement)	Partial	An empty target leaves the string unchanged (Java interleaves the replacement between every char).
LinkedHashMap / LinkedHashSet	Partial	Aliases of HashMap / HashSet: insertion order is not preserved. instanceof HashMap/Map/Set hold.
Collection.toArray() / toArray(T[])	Partial	Always returns a fresh Object[] of exactly the collection’s size — the array argument is neither filled nor returned (list.toArray(new String[0]) is the idiom to use; a cast to String[] succeeds because reference arrays carry no element class).
java.util.Locale	Partial	Name-only: Locale.ROOT/US/… read as null, and toUpperCase(Locale)/toLowerCase(Locale) ignore the argument (ASCII only). This is what Kotlin’s uppercase()/lowercase() compile to. No Locale instances.
Class.getName()	Full	Returns dot-form (pkg.Class) per the Java spec.
javax.inject.Inject / Singleton / Scope	Partial	Compile-time only: an annotation processor generates Foo_Factory / Foo_MembersInjector, and Application / Activity / Service are injected automatically before onCreate. SOURCE retention (JSR-330 says RUNTIME) — no runtime annotations, no reflection. javax.inject.Provider<T> / picodroid.di.Lazy<T> (≙ dagger.Lazy) inject anywhere a T can; picodroid.di.Module / picodroid.di.Provides (≙ dagger.Module / dagger.Provides) bind SDK types and interfaces, every module auto-installed. No @Component, @Binds, @Named/qualifiers, custom scopes. Java and Kotlin apps (the Kotlin plugin runs the same processor through kapt; Kotlin shapes: @Inject lateinit var, @Inject constructor, @Module object + @JvmStatic @Provides, @Module class for instance @Provides). See Services & DI.
String.split	Partial	Literal delimiters only — no regex.
BufferedReader / InputStreamReader	Unsupported	Use the byte-oriented picodroid.io streams (FileInputStream/FileOutputStream); there is no char-stream reader layer.

Cross-cutting divergences

• Coordinates and sizes are int px. There is no float MotionEvent coordinate, and no density-independent units — no dp/sp, no getResources().getDisplayMetrics(). Lay out in pixels.
• No resources system. No R class, no res/ directory, no XML layouts, drawables, or strings. Bundle binary assets under assets/ and reference them through the generated AssetConstants (see assets).
• No Handler/Looper. The main loop is an executor-driven dispatcher; use Executors.mainExecutor() and animation timers.
• Custom Interpolators fall back to linear. Standard interpolators (linear/accelerate/decelerate/accelerate-decelerate) map to native easing; an app-defined Interpolator can’t be up-called from the native tick, so it falls back to linear with a Log.w.

Imports

Always import the picodroid.* classes directly — e.g. import picodroid.view.View;, import picodroid.widget.TextView;. There is no android.* import compatibility layer: import android.view.View; will not compile or load. The package names below mirror Android’s only so the API reads the same and intuition transfers; the namespace you import is picodroid.