Logging

You should use the log crate to automatically log to logcat (on-device) or stdout (on-host):

hello_rust_logs/Android.bp:

1. rust_binary {
2. name: "hello_rust_logs",
3. crate_name: "hello_rust_logs",
4. srcs: ["src/main.rs"],
5. rustlibs: [
6. "liblog_rust",
7. "liblogger",
8. ],
9. host_supported: true,
10. }

hello_rust_logs/src/main.rs:

1. //! Rust logging demo.

3. use log::{debug, error, info};

5. /// Logs a greeting.
6. fn main() {
7. logger::init(
8. logger::Config::default()
9. .with_tag_on_device("rust")
10. .with_max_level(log::LevelFilter::Trace),
11. );
12. debug!("Starting program.");
13. info!("Things are going fine.");
14. error!("Something went wrong!");
15. }

Build, push, and run the binary on your device:

1. m hello_rust_logs
2. adb push "$ANDROID_PRODUCT_OUT/system/bin/hello_rust_logs" /data/local/tmp
3. adb shell /data/local/tmp/hello_rust_logs

The logs show up in adb logcat:

1. adb logcat -s rust

1. 09-08 08:38:32.454  2420  2420 D rust: hello_rust_logs: Starting program.
2. 09-08 08:38:32.454  2420  2420 I rust: hello_rust_logs: Things are going fine.
3. 09-08 08:38:32.454  2420  2420 E rust: hello_rust_logs: Something went wrong!

• The logger implementation in liblogger is only needed in the final binary, if you’re logging from a library you only need the log facade crate.