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>

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)
+}