chore: Add an Android example

adapters/android/Cargo.toml

@@ -8,6 +8,7 @@ categories.workspace = true
 keywords = ["gui", "ui", "accessibility"]
 repository.workspace = true
 readme = "README.md"
+exclude = ["examples"]
 edition.workspace = true
 rust-version.workspace = true
 
@@ -20,3 +21,9 @@ accesskit_consumer = { version = "0.39.0", path = "../../accesskit_consumer" }
 jni = "0.21.1"
 log = "0.4.17"
 
+[dev-dependencies]
+example_common = { path = "../../example_common" }
+
+[[example]]
+name = "hello_world"
+crate-type = ["cdylib"]

adapters/android/README.md

@@ -8,3 +8,18 @@ This adapter is implemented in two layers:
 * The `InjectingAdapter` struct injects accessibility into an arbitrary Android view without requiring the view class to be modified, at the expense of depending on a specific Java class and providing less flexibility in the aspects listed above.
 
 The most convenient way to use `InjectingAdapter` is to embed a precompiled `.dex` file containing the associated Java class and its inner classes into the native code. This approach requires the `embedded-dex` Cargo feature.
+
+## Example
+
+The `examples/` directory contains a runnable example built on the low-level `Adapter`:
+
+### Running the example
+
+Install [cargo-ndk](https://github.com/bbqsrc/cargo-ndk) (version 4 or later) and the Rust target for your device, e.g. `rustup target add aarch64-linux-android`. The Android SDK must be discoverable by Gradle (through `ANDROID_HOME` or a `local.properties` file), and cargo-ndk needs an NDK, which it finds inside the SDK or through `ANDROID_NDK_HOME`. Then, with a device connected or an emulator running:
+
+```sh
+cd examples/hello_world_app
+./gradlew installDebug
+```
+
+By default, the Rust library is only built for `arm64-v8a`. Pass `-PrustAbis=arm64-v8a,x86_64` to build for additional ABIs, such as for an emulator on an x86-64 host. The project can also be opened in Android Studio.