Enable logging in the application user directory

wasmerio/wasmer#1379 is caused when calling a Java method from a wasm file via imports. That prevents the wasm file from calling even android_logger. So I switched to use simplelog to write log on a file

android/app/src/main/java/com/wasmer/android/MainActivity.java

@@ -5,12 +5,13 @@
 
 import android.content.res.AssetManager;
 import android.os.Bundle;
+import android.util.Log;
 
 import java.io.ByteArrayOutputStream;
 import java.io.InputStream;
 
 public class MainActivity extends AppCompatActivity {
-    private static native void JNIExecuteWasm(MainActivity self, byte[] module_bytes) throws Exception;
+    private static native void JNIExecuteWasm(MainActivity self, String logPath, byte[] module_bytes) throws Exception;
 
     @Keep
     public void Test() {
@@ -44,7 +45,8 @@ protected void onCreate(Bundle savedInstanceState) {
 
             // Run the file
             System.out.println("Calling JNIExecuteWasm!");
-            JNIExecuteWasm(this, module_bytes);
+            String logPath = getFilesDir().toString() + "/wasmer_android.log";
+            JNIExecuteWasm(this, logPath, module_bytes);
             System.out.println("Finished calling JNIExecuteWasm!");
         } catch (Exception e) {
             e.printStackTrace();

android/build.gradle

@@ -8,7 +8,7 @@ buildscript {
 
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.6.1'
+        classpath 'com.android.tools.build:gradle:3.6.2'
 
 
         // NOTE: Do not place your application dependencies here; they belong

android_runtime/Cargo.toml

@@ -11,6 +11,7 @@ crate-type = ["dylib"]
 jni = { version = "0.16.0", default-features = false }
 lazy_static = "1.4.0"
 android_logger = "0.8"
+simplelog = "0.7.5"
 wasmer-runtime = { default-features = false, path = "../wasmer/lib/runtime/", features = ["singlepass", "default-backend-singlepass"] }
 wasmer-singlepass-backend = { optional = true, path = "../wasmer/lib/singlepass-backend/" }
 log = "0.4"

android_runtime/src/lib.rs

@@ -4,17 +4,20 @@ extern crate jni;
 #[macro_use]
 extern crate log;
 extern crate android_logger;
+extern crate simplelog;
 
-use android_logger::Config;
 use jni::{
     errors::ErrorKind,
-    objects::{GlobalRef, JClass, JObject},
+    objects::{GlobalRef, JClass, JObject, JString},
     sys::jbyteArray,
     JNIEnv, JavaVM,
 };
 use log::Level;
+use simplelog::*;
+use std::ffi::CStr;
+use std::fs::File;
 use std::sync::Mutex;
-use wasmer_runtime::{compile, func, imports, Ctx, ImportObject, Instance, Module};
+use wasmer_runtime::{compile, func, imports, ImportObject, Instance, Module};
 
 lazy_static! {
     static ref ENV: Mutex<Option<JavaVM>> = { Mutex::new(None) };
@@ -26,9 +29,13 @@ pub unsafe extern "C" fn Java_com_wasmer_android_MainActivity_JNIExecuteWasm(
     env: JNIEnv,
     _: JClass,
     callback: JObject,
+    jlog_path: JString,
     module_bytes: jbyteArray,
 ) {
-    android_logger::init_once(Config::default().with_min_level(Level::Trace));
+    if let Err(err) = init_simplelog(&env, jlog_path) {
+        init_android_logger();
+        warn!("{}", err);
+    }
 
     std::panic::set_hook(Box::new(|panic_info| {
         error!("ERR: {}", panic_info.to_string());
@@ -54,6 +61,28 @@ pub unsafe extern "C" fn Java_com_wasmer_android_MainActivity_JNIExecuteWasm(
     java_test();
 }
 
+fn init_android_logger() {
+    android_logger::init_once(android_logger::Config::default().with_min_level(Level::Trace));
+}
+
+fn init_simplelog(env: &JNIEnv, jlog_path: JString) -> Result<(), String> {
+    let log_path = unsafe {
+        CStr::from_ptr(
+            env.get_string(jlog_path)
+                .map_err(|err| err.to_string())?
+                .as_ptr(),
+        )
+    }
+    .to_str()
+    .map_err(|err| err.to_string())?;
+    WriteLogger::init(
+        LevelFilter::Trace,
+        Config::default(),
+        File::create(log_path).map_err(|err| err.to_string())?,
+    )
+    .map_err(|err| err.to_string())
+}
+
 pub fn load_module(module_bytes: &[u8]) -> Instance {
     // Compile the module.
     let module = compile(&module_bytes).unwrap();
@@ -74,6 +103,7 @@ fn create_import_object(_module: &Module) -> ImportObject {
 }
 
 fn java_test() {
+    info!("BEGIN java_test");
     // Get env.
     let ovm = &*ENV.lock().unwrap();
     let vm = ovm.as_ref().unwrap();