bind/java: reenable asset access.

This is done by moving app.Context to internal/mobileinit,
introducing mobileinit.SetCurrentContext and,
making bind/java depend on it.

TODO: check gomobile bind's proguard rule - context lookup
was implemented through reflection on android.app.AppGlobals class.

Change-Id: Ieb6ad503eeef8c2c1c5836a21c667938c5a701a2
Reviewed-on: https://go-review.googlesource.com/12279
Reviewed-by: David Crawshaw <crawshaw@golang.org>

app/android.c

@@ -45,8 +45,6 @@ jint JNI_OnLoad(JavaVM* vm, void* reserved) {
 	}
 
 	// Load classes here, which uses the correct ClassLoader.
-	current_vm = vm;
-	current_ctx = NULL;
 	current_ctx_clazz = find_class(env, "org/golang/app/GoNativeActivity");
 	current_ctx_clazz = (jclass)(*env)->NewGlobalRef(env, current_ctx_clazz);
 
@@ -61,8 +59,10 @@ void ANativeActivity_onCreate(ANativeActivity *activity, void* savedState, size_
 	JNIEnv* env = activity->env;
 
 	// Note that activity->clazz is mis-named.
-	current_vm = activity->vm;
-	current_ctx = (*env)->NewGlobalRef(env, activity->clazz);
+	JavaVM* current_vm = activity->vm;
+	jobject current_ctx = activity->clazz;
+
+	setCurrentContext(current_vm, (*env)->NewGlobalRef(env, current_ctx));
 
 	// Set TMPDIR.
 	jmethodID gettmpdir = find_method(env, current_ctx_clazz, "getTmpdir", "()Ljava/lang/String;");

app/android.go

@@ -34,17 +34,6 @@ package app
 #include <pthread.h>
 #include <stdlib.h>
 
-// current_vm is stored to initialize other cgo packages.
-//
-// As all the Go packages in a program form a single shared library,
-// there can only be one JNI_OnLoad function for iniitialization. In
-// OpenJDK there is JNI_GetCreatedJavaVMs, but this is not available
-// on android.
-JavaVM* current_vm;
-
-// current_ctx is Android's android.context.Context. May be NULL.
-jobject current_ctx;
-
 jclass current_ctx_clazz;
 
 jclass app_find_class(JNIEnv* env, const char* name);
@@ -58,8 +47,14 @@ import (
 	"unsafe"
 
 	"golang.org/x/mobile/app/internal/callfn"
+	"golang.org/x/mobile/internal/mobileinit"
 )
 
+//export setCurrentContext
+func setCurrentContext(vm *C.JavaVM, ctx C.jobject) {
+	mobileinit.SetCurrentContext(unsafe.Pointer(vm), unsafe.Pointer(ctx))
+}
+
 //export callMain
 func callMain(mainPC uintptr) {
 	for _, name := range []string{"TMPDIR", "PATH", "LD_LIBRARY_PATH"} {
@@ -186,25 +181,6 @@ func onConfigurationChanged(activity *C.ANativeActivity) {
 func onLowMemory(activity *C.ANativeActivity) {
 }
 
-// Context holds global OS-specific context.
-//
-// Its extra methods are deliberately difficult to access because they must be
-// used with care. Their use implies the use of cgo, which probably requires
-// you understand the initialization process in the app package. Also care must
-// be taken to write both Android, iOS, and desktop-testing versions to
-// maintain portability.
-type Context struct{}
-
-// AndroidContext returns a jobject for the app android.context.Context.
-func (Context) AndroidContext() unsafe.Pointer {
-	return unsafe.Pointer(C.current_ctx)
-}
-
-// JavaVM returns a JNI *JavaVM.
-func (Context) JavaVM() unsafe.Pointer {
-	return unsafe.Pointer(C.current_vm)
-}
-
 var (
 	windowDestroyed    = make(chan bool)
 	windowCreated      = make(chan *C.ANativeWindow)

asset/asset_android.go

@@ -61,13 +61,13 @@ import (
 	"sync"
 	"unsafe"
 
-	"golang.org/x/mobile/app"
+	"golang.org/x/mobile/internal/mobileinit"
 )
 
 var assetOnce sync.Once
 
 func assetInit() {
-	ctx := app.Context{}
+	ctx := mobileinit.Context{}
 	C.asset_manager_init(ctx.JavaVM(), ctx.AndroidContext())
 }
 

bind/java/Seq.java

@@ -4,6 +4,8 @@
 
 package go;
 
+import android.app.Application;
+import android.content.Context;
 import android.util.Log;
 import android.util.SparseArray;
 import android.util.SparseIntArray;
@@ -24,6 +26,16 @@ public class Seq {
 			Log.w("GoSeq", "LoadJNI class not found");
 		}
 
+		try {
+			// TODO(hyangah): check proguard rule.
+			Application appl = (Application)Class.forName("android.app.AppGlobals").getMethod("getInitialApplication").invoke(null, (Object[]) null);
+			Context ctx = appl.getApplicationContext();
+			setContext(ctx);
+
+		} catch (Exception e) {
+			Log.w("GoSeq", "Global context not found:" + e);
+		}
+
 		initSeq();
 		new Thread("GoSeq") {
 			public void run() { Seq.receive(); }
@@ -37,6 +49,8 @@ public class Seq {
 		ensure(64);
 	}
 
+	static native void setContext(Context ctx);
+
 	// Ensure that at least size bytes can be written to the Seq.
 	// Any existing data in the buffer is preserved.
 	public native void ensure(int size);

bind/java/SeqTest.java

@@ -17,6 +17,12 @@ public class SeqTest extends AndroidTestCase {
   public SeqTest() {
   }
 
+  public void testAssets() {
+    String want = "Hello, Assets.\n";
+    String got = Testpkg.ReadAsset();
+    assertEquals("Asset read", want, got);
+  }
+
   public void testAdd() {
     long res = Testpkg.Add(3, 4);
     assertEquals("Unexpected arithmetic failure", 7, res);

bind/java/seq_android.c

@@ -435,3 +435,12 @@ Java_go_Seq_recvRes(JNIEnv *env, jclass clazz, jint handle, jobject out_obj) {
 	}
 	RecvRes((int32_t)handle, out->buf, out->len);
 }
+
+JNIEXPORT void JNICALL
+Java_go_Seq_setContext(JNIEnv* env, jclass clazz, jobject ctx) {
+	JavaVM* vm;
+        if ((*env)->GetJavaVM(env, &vm) != 0) {
+		LOG_FATAL("failed to get JavaVM");
+	}
+	setContext(vm, (*env)->NewGlobalRef(env, ctx));
+}

bind/java/seq_android.go

@@ -6,6 +6,7 @@ package java // import "golang.org/x/mobile/bind/java"
 
 //#cgo LDFLAGS: -llog
 //#include <android/log.h>
+//#include <jni.h>
 //#include <stdint.h>
 //#include <string.h>
 //#include "seq_android.h"
@@ -16,6 +17,7 @@ import (
 	"unsafe"
 
 	"golang.org/x/mobile/bind/seq"
+	"golang.org/x/mobile/internal/mobileinit"
 )
 
 const maxSliceLen = 1<<31 - 1
@@ -178,3 +180,8 @@ func init() {
 	seq.EncString = encodeString
 	seq.DecString = decodeString
 }
+
+//export setContext
+func setContext(vm *C.JavaVM, ctx C.jobject) {
+	mobileinit.SetCurrentContext(unsafe.Pointer(vm), unsafe.Pointer(ctx))
+}

bind/java/testpkg/assets/hello.txt

@@ -0,0 +1 @@
+Hello, Assets.

bind/java/testpkg/testpkg.go

@@ -11,8 +11,12 @@ package testpkg
 import (
 	"errors"
 	"fmt"
+	"io/ioutil"
+	"log"
 	"runtime"
 	"time"
+
+	"golang.org/x/mobile/asset"
 )
 
 type I interface {
@@ -156,3 +160,17 @@ func Hello(r Receiver, name string) {
 func GarbageCollect() {
 	runtime.GC()
 }
+
+func ReadAsset() string {
+	rc, err := asset.Open("hello.txt")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer rc.Close()
+
+	b, err := ioutil.ReadAll(rc)
+	if err != nil {
+		log.Fatal(err)
+	}
+	return string(b)
+}

exp/audio/al/al_android.go

@@ -198,7 +198,7 @@ import (
 	"log"
 	"unsafe"
 
-	"golang.org/x/mobile/app"
+	"golang.org/x/mobile/internal/mobileinit"
 )
 
 var (
@@ -247,7 +247,7 @@ var (
 )
 
 func initAL() {
-	ctx := app.Context{}
+	ctx := mobileinit.Context{}
 	switch C.al_init(ctx.JavaVM(), ctx.AndroidContext(), &alHandle) {
 	case C.AL_INIT_RESULT_OK:
 		// No-op.

internal/mobileinit/ctx_android.go

@@ -0,0 +1,61 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package mobileinit
+
+/*
+#include <jni.h>
+#include <stdlib.h>
+
+// current_vm is stored to initialize other cgo packages.
+//
+// As all the Go packages in a program form a single shared library,
+// there can only be one JNI_OnLoad function for initialization. In
+// OpenJDK there is JNI_GetCreatedJavaVMs, but this is not available
+// on android.
+JavaVM* current_vm;
+
+// current_ctx is Android's android.context.Context. May be NULL.
+jobject current_ctx;
+
+// Set current_vm and current_ctx. The ctx passed in must be a global
+// reference instance.
+void set_vm_ctx(JavaVM* vm, jobject ctx) {
+	current_vm = vm;
+	current_ctx = ctx;
+	// TODO: check leak
+}
+*/
+import "C"
+
+import "unsafe"
+
+// SetCurrentContext populates the global Context object with the specified
+// current JavaVM instance (vm) and android.context.Context object (ctx).
+// The android.context.Context object must be a global reference.
+func SetCurrentContext(vm, ctx unsafe.Pointer) {
+	C.set_vm_ctx((*C.JavaVM)(vm), (C.jobject)(ctx))
+}
+
+// TODO(hyangah): should the app package have Context? It may be useful for
+// external packages that need to access android context and vm.
+
+// Context holds global OS-specific context.
+//
+// Its extra methods are deliberately difficult to access because they must be
+// used with care. Their use implies the use of cgo, which probably requires
+// you understand the initialization process in the app package. Also care must
+// be taken to write both Android, iOS, and desktop-testing versions to
+// maintain portability.
+type Context struct{}
+
+// AndroidContext returns a jobject for the app android.context.Context.
+func (Context) AndroidContext() unsafe.Pointer {
+	return unsafe.Pointer(C.current_ctx)
+}
+
+// JavaVM returns a JNI *JavaVM.
+func (Context) JavaVM() unsafe.Pointer {
+	return unsafe.Pointer(C.current_vm)
+}

internal/mobileinit/mobileinit.go

@@ -5,5 +5,5 @@
 // Package mobileinit contains common initialization logic for mobile platforms
 // that is relevant to both all-Go apps and gobind-based apps.
 //
-// Long-term, any code in this package should consider moving into Go stdlib.
+// Long-term, some code in this package should consider moving into Go stdlib.
 package mobileinit