Android: Change headphone detection to call into native.

Making a JNI call from tick tasks is not permitted as the underlying thread
is not attached to the Java VM. This is an error and crashes in the emulator
(which has stricter JNI checks enabled by default).

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@30173 a1c6a512-1295-4272-9138-f99709370657

android/src/org/rockbox/monitors/HeadphoneMonitor.java

@@ -29,7 +29,6 @@ import android.content.IntentFilter;
 public class HeadphoneMonitor extends BroadcastReceiver
 {
     @SuppressWarnings("unused")
-    private int mHpState; /* read by native code */
 
     public HeadphoneMonitor(Context c)
     {
@@ -45,7 +44,7 @@ public class HeadphoneMonitor extends BroadcastReceiver
     public void onReceive(Context arg0, Intent intent)
     {
         int state = intent.getIntExtra("state", -1);
-        mHpState = state;   
+        postHpStateChanged(state);
     }
 
     /* audio becoming noise acts as headphones extracted */
@@ -54,7 +53,9 @@ public class HeadphoneMonitor extends BroadcastReceiver
         @Override
         public void onReceive(Context arg0, Intent arg1)
         {
-            mHpState = 0;   
+            postHpStateChanged(0);   
         }
     }
+    
+    private synchronized native void postHpStateChanged(int state);
 }

firmware/target/hosted/android/button-android.c

@@ -34,8 +34,6 @@ extern JNIEnv *env_ptr;
 extern jclass  RockboxService_class;
 extern jobject RockboxService_instance;
 
-static jobject HeadphoneMonitor_instance;
-static jfieldID headphone_state;
 static int last_y, last_x;
 static int last_btns;
 
@@ -120,13 +118,9 @@ void button_init_device(void)
     jmethodID constructor =     e->GetMethodID(env_ptr, class,
                                                 "<init>",
                                                 "(Landroid/content/Context;)V");
-    HeadphoneMonitor_instance = e->NewObject(env_ptr, class,
+    e->NewObject(env_ptr, class,         
                         constructor,
                         RockboxService_instance);
-    /* cache the battery level field id */
-    headphone_state = (*env_ptr)->GetFieldID(env_ptr,
-                                            class,
-                                            "mHpState", "I");
 }
 
 int button_read_device(int *data)
@@ -145,13 +139,23 @@ int button_read_device(int *data)
     return btn;
 }
 
-
-/* Tell if anything is in the jack. */
+static int hp_state;
+JNIEXPORT void JNICALL
+Java_org_rockbox_monitors_HeadphoneMonitor_postCallHungUp(JNIEnv *env,
+                                                        jobject this,
+                                                        jint state)
+{
+    (void)env; (void)this;
+    hp_state = state;
+}
+/* Tell if anything is in the jack.
+ * 
+ * since this is called from the tick task, which isn't attached to
+ * the dalvik VM, it's not permitted to make JNI calls (therefore
+ * we need the above callback) */
 bool headphones_inserted(void)
 {
-    int state = (*env_ptr)->GetIntField(env_ptr, HeadphoneMonitor_instance,
-                                                            headphone_state);
     /* 0 is disconnected, 1 and 2 are connected */
-    return (state == 0) ? false : true;
+    return (hp_state == 0) ? false : true;
 }
 

firmware/target/hosted/android/kernel-android.c

@@ -60,7 +60,13 @@ void interrupt(void)
 }
 
 /*
- * setup a hrtimer to send a signal to our process every tick */
+ * setup a hrtimer to send a signal to our process every tick
+ *
+ * WARNING: JNI calls are not permitted from tick tasks, as the
+ * underlying thread is not attached to the Java VM
+ *
+ * Can be possibly be attached if it really needs to be. but let's
+ * keep this leightweight */
 void tick_start(unsigned int interval_in_ms)
 {
     int ret = 0;