From 5850c514f2931fcaf1091cc8bb92cd8b51646df6 Mon Sep 17 00:00:00 2001
From: Logan McNaughton <848146+loganmc10@users.noreply.github.com>
Date: Tue, 19 May 2026 19:30:09 +0200
Subject: [PATCH] Populate controller list on android (#920)

* list controllers in UI for android

* more

* more
---
 Cargo.lock              |   1 +
 Cargo.toml              |   1 +
 src/ui.rs               |   2 +
 src/ui/android_input.rs | 106 ++++++++++++++++++++++++++++++++++++++++
 src/ui/input.rs         |  14 +++++-
 5 files changed, 122 insertions(+), 2 deletions(-)
 create mode 100644 src/ui/android_input.rs

diff --git a/Cargo.lock b/Cargo.lock
index 055dda8e..69247f2a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2266,6 +2266,7 @@ dependencies = [
  "encoding_rs",
  "fatfs",
  "futures",
+ "jni 0.22.4",
  "mimalloc",
  "postcard",
  "rand 0.10.1",
diff --git a/Cargo.toml b/Cargo.toml
index bceef272..d91ff647 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -46,6 +46,7 @@ dirs = "6.0"
 
 [target.'cfg(target_os = "android")'.dependencies]
 slint = { version = "1.16", default-features = false, features = ["compat-1-2", "std", "backend-android-activity-06", "accessibility"], optional = true }
+jni = "0.22"
 
 [build-dependencies]
 winresource = "0.1"
diff --git a/src/ui.rs b/src/ui.rs
index b191a1bf..b9245424 100644
--- a/src/ui.rs
+++ b/src/ui.rs
@@ -1,3 +1,5 @@
+#[cfg(target_os = "android")]
+pub mod android_input;
 pub mod audio;
 #[cfg(feature = "gui")]
 pub mod cheats;
diff --git a/src/ui/android_input.rs b/src/ui/android_input.rs
new file mode 100644
index 00000000..44abac88
--- /dev/null
+++ b/src/ui/android_input.rs
@@ -0,0 +1,106 @@
+use jni::{Env, JavaVM, bind_java_type};
+
+bind_java_type! {
+    pub AndroidInputDevice => "android.view.InputDevice",
+    fields {
+        #[allow(non_snake_case)]
+        static SOURCE_JOYSTICK: jint,
+        #[allow(non_snake_case)]
+        static SOURCE_GAMEPAD: jint,
+    },
+    methods {
+        static fn get_device_ids() -> jint[],
+        static fn get_device(device_id: jint) -> AndroidInputDevice,
+        fn supports_source(source: jint) -> jboolean,
+        fn is_virtual() -> jboolean,
+        fn is_external() -> jboolean,
+        fn get_vendor_id() -> jint,
+        fn get_product_id() -> jint,
+        fn get_name() -> JString,
+        fn get_descriptor() -> JString,
+    },
+}
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct ControllerInfo {
+    pub name: String,
+    /// Stable ID from [`InputDevice.getDescriptor`](https://developer.android.com/reference/android/view/InputDevice#getDescriptor()).
+    pub descriptor: String,
+}
+
+/// Lists connected gamepads and joysticks using the Android framework.
+pub fn list_controllers() -> Vec<ControllerInfo> {
+    let Some(app) = crate::ui::ANDROID_APP.get() else {
+        eprintln!("Android app not initialized; cannot list controllers");
+        return Vec::new();
+    };
+
+    let vm = unsafe { JavaVM::from_raw(app.vm_as_ptr().cast()) };
+
+    match vm.attach_current_thread(list_controllers_on_jvm) {
+        Ok(controllers) => controllers,
+        Err(err) => {
+            eprintln!("JNI error while listing controllers: {err:?}");
+            Vec::new()
+        }
+    }
+}
+
+fn list_controllers_on_jvm(env: &mut Env<'_>) -> jni::errors::Result<Vec<ControllerInfo>> {
+    let source_gamepad = AndroidInputDevice::SOURCE_GAMEPAD(env)?;
+    let source_joystick = AndroidInputDevice::SOURCE_JOYSTICK(env)?;
+
+    let device_ids = AndroidInputDevice::get_device_ids(env)?;
+    let count = device_ids.len(env)?;
+    let mut ids = vec![0i32; count];
+    if count > 0 {
+        device_ids.get_region(env, 0, &mut ids)?;
+    }
+
+    let mut controllers = Vec::new();
+    for device_id in ids {
+        let device = AndroidInputDevice::get_device(env, device_id)?;
+        if device.is_null() {
+            continue;
+        }
+
+        if device.is_virtual(env)? {
+            continue;
+        }
+
+        if !device.is_external(env)? {
+            continue;
+        }
+
+        if !device.supports_source(env, source_gamepad & source_joystick)? {
+            continue;
+        }
+
+        if device.get_vendor_id(env)? == 0 {
+            continue;
+        }
+
+        if device.get_product_id(env)? == 0 {
+            continue;
+        }
+
+        let name = if let Ok(name) = device.get_name(env)
+            && let Ok(name) = name.try_to_string(env)
+        {
+            name
+        } else {
+            "Unknown controller".to_string()
+        };
+        let descriptor = if let Ok(descriptor) = device.get_descriptor(env)
+            && let Ok(descriptor) = descriptor.try_to_string(env)
+        {
+            descriptor
+        } else {
+            String::new()
+        };
+
+        controllers.push(ControllerInfo { name, descriptor });
+    }
+
+    Ok(controllers)
+}
diff --git a/src/ui/input.rs b/src/ui/input.rs
index 937e73f9..bd890f10 100644
--- a/src/ui/input.rs
+++ b/src/ui/input.rs
@@ -362,7 +362,12 @@ pub fn get_controller_names() -> Vec<String> {
 
 #[cfg(target_os = "android")]
 pub fn get_controller_names() -> Vec<String> {
-    vec!["None".into()]
+    let mut controllers: Vec<String> = ui::android_input::list_controllers()
+        .into_iter()
+        .map(|c| c.name)
+        .collect();
+    controllers.insert(0, "None".into());
+    controllers
 }
 
 #[cfg(not(target_os = "android"))]
@@ -386,7 +391,12 @@ pub fn get_controller_paths() -> Vec<String> {
 #[cfg(target_os = "android")]
 #[cfg(feature = "gui")]
 pub fn get_controller_paths() -> Vec<String> {
-    vec![String::new()]
+    let mut controller_paths: Vec<String> = ui::android_input::list_controllers()
+        .into_iter()
+        .map(|c| c.descriptor)
+        .collect();
+    controller_paths.insert(0, String::new());
+    controller_paths
 }
 
 fn handle_joystick_events(ui: &mut ui::Ui) {