Architecture

apk.js is layered. Each layer hands a narrower representation to the next.

APK zip
  └── parser        dex/, res/      bytes → classes, resources, layouts
        └── runtime  runtime/       DEX → JavaVM, objects, interpreter
              └── framework          Java API calls → view tree and pixels
                    └── engine       lifecycle, screen, input

Layers

Layer	Directory	Responsibility
Parser	src/dex, src/res	Read binary formats: DEX, AXML, ARSC
Runtime	src/runtime	Class registry, value model, bytecode interpreter
Framework	src/framework	Android API surface backed by Canvas and JavaScript
Entry	apk.js	Public API, device setup, file loading

Runtime

JavaVM owns the class registry, the interpreter, the heap and the method stack. Values are JavaScript objects with a descriptor: JavaObject for instances, JavaArray for arrays, and plain numbers or strings for primitives.

DexInterpreter walks bytecode, maintaining a register file per frame. It dispatches method calls back into the VM, which resolves them against native definitions first and then against DEX classes.

Framework

The framework is a set of native class definitions. Each one implements a slice of an Android class in terms of JavaScript and the Canvas 2D API. A View holds geometry, layout params and a draw method; a ViewGroup additionally knows how to measure and arrange children.

The engine wires the framework to a canvas: it creates the initial activity, drives onCreate, drains the choreographer loop, and routes pointer events into the view tree.

Engine

EmulatorEngine.start(apk) sets up the VM, registers native classes, seeds the virtual filesystem, installs sensor sources, and launches the launcher activity. attachCanvas binds a canvas for rendering and input.

The screen tracks dirty state. When a view calls invalidate, the engine marks the screen dirty and repaints on the next frame.