Use egui_demo_lib in android example (#5780)

* [x] I have followed the instructions in the PR template

Cargo.lock

@@ -1973,6 +1973,7 @@ version = "0.1.0"
 dependencies = [
  "android_logger",
  "eframe",
+ "egui_demo_lib",
  "egui_extras",
  "log",
  "winit",

examples/hello_android/Cargo.toml

@@ -12,11 +12,13 @@ publish = false
 # workspace = true
 
 [lib]
-crate-type = ["cdylib"]
+# cdylib is required for Android, lib is required for desktop
+crate-type = ["cdylib", "lib"]
 
 
 [dependencies]
 eframe = { workspace = true, features = ["default", "android-native-activity"] }
+egui_demo_lib = { workspace = true, features = ["chrono"] }
 
 # For image support:
 egui_extras = { workspace = true, features = ["default", "image"] }
@@ -27,3 +29,7 @@ android_logger = "0.14"
 
 [package.metadata.android]
 build_targets = ["armv7-linux-androideabi", "aarch64-linux-android"]
+
+[package.metadata.android.sdk]
+min_sdk_version = 23
+target_sdk_version = 35

examples/hello_android/README.md

@@ -14,7 +14,11 @@ cargo install \
 Build and run:
 
 ```sh
-cargo apk run -p hello_android
+# Run on android
+cargo apk run -p hello_android --lib
+
+# Run on your desktop
+cargo run -p hello_android
 ```
 
 ![](screenshot.png)

examples/hello_android/screenshot.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:7add91d7d6b73f48e98f20d84cba3bd3a950cf97aa31f5e9fa93da9af98e876c
-size 120019
+oid sha256:16bb465d73b7cf8133aee8cdb773a10d213ad23359a21c0bc2af3e4f9893057f
+size 507047

examples/hello_android/src/lib.rs

@@ -1,15 +1,14 @@
-#![cfg(target_os = "android")]
-#![allow(rustdoc::missing_crate_level_docs)] // it's an example
+#![doc = include_str!("../README.md")]
 
-use android_logger::Config;
-use eframe::egui;
-use log::LevelFilter;
-use winit::platform::android::activity::AndroidApp;
+use eframe::{egui, CreationContext};
 
+#[cfg(target_os = "android")]
 #[no_mangle]
-fn android_main(app: AndroidApp) {
+fn android_main(app: winit::platform::android::activity::AndroidApp) {
     // Log to android output
-    android_logger::init_once(Config::default().with_max_level(LevelFilter::Info));
+    android_logger::init_once(
+        android_logger::Config::default().with_max_level(log::LevelFilter::Info),
+    );
 
     let options = eframe::NativeOptions {
         android_app: Some(app),
@@ -18,48 +17,34 @@ fn android_main(app: AndroidApp) {
     eframe::run_native(
         "My egui App",
         options,
-        Box::new(|cc| {
-            // This gives us image support:
-            egui_extras::install_image_loaders(&cc.egui_ctx);
-
-            Ok(Box::<MyApp>::default())
-        }),
+        Box::new(|cc| Ok(Box::new(MyApp::new(cc)))),
     )
     .unwrap()
 }
 
-struct MyApp {
-    name: String,
-    age: u32,
+pub struct MyApp {
+    demo: egui_demo_lib::DemoWindows,
 }
 
-impl Default for MyApp {
-    fn default() -> Self {
+impl MyApp {
+    pub fn new(cc: &CreationContext) -> Self {
+        egui_extras::install_image_loaders(&cc.egui_ctx);
         Self {
-            name: "Arthur".to_owned(),
-            age: 42,
+            demo: egui_demo_lib::DemoWindows::default(),
         }
     }
 }
 
 impl eframe::App for MyApp {
     fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
-        egui::CentralPanel::default().show(ctx, |ui| {
-            ui.heading("My egui Application");
-            ui.horizontal(|ui| {
-                let name_label = ui.label("Your name: ");
-                ui.text_edit_singleline(&mut self.name)
-                    .labelled_by(name_label.id);
+        // Reserve some space at the top so the demo ui isn't hidden behind the android status bar
+        // TODO(lucasmerlin): This is a pretty big hack, should be fixed once safe_area implemented
+        // for android:
+        // https://github.com/rust-windowing/winit/issues/3910
+        egui::TopBottomPanel::top("status_bar_space").show(ctx, |ui| {
+            ui.set_height(32.0);
         });
-            ui.add(egui::Slider::new(&mut self.age, 0..=120).text("age"));
-            if ui.button("Increment").clicked() {
-                self.age += 1;
-            }
-            ui.label(format!("Hello '{}', age {}", self.name, self.age));
 
-            ui.image(egui::include_image!(
-                "../../../crates/egui/assets/ferris.png"
-            ));
-        });
+        self.demo.ui(ctx);
     }
 }

examples/hello_android/src/main.rs

@@ -0,0 +1,9 @@
+use hello_android::MyApp;
+
+fn main() -> eframe::Result {
+    eframe::run_native(
+        "hello_android",
+        Default::default(),
+        Box::new(|cc| Ok(Box::new(MyApp::new(cc)))),
+    )
+}