Android JNI广播到Java

Question

I'm currently working on (an existing) Android app using native c++ code. I want send a broadcast to another Android Java app listening to a BroadcastReceiver. The receiving app is yet working, but I can't figure out how to broadcast data from JNI code either directly or by sending the values to java code and them broadcasting it from Java.

I hope my explanaion is clear. Can someone help me on how to accomplish this?

Thanks!

Answer 1

The easiest way is probably to do it in Java and write a JNI callback to call that Java function. If you do need to do it in C, you'll need to use JNI to create an Intent, then to set the action and extras of the intent, then use JNI to call the sendBroadcast method of your activity to actually send it. Its a lot of boilerplate JNI code, so I'd try to avoid it.

Answer 2

The easiest way is to implement all logic in a Java method:

public class MyClass {
  static {
    System.loadLibrary("mylib_jni");
  }

  public static final String ACTION_TEST = "com.example.action.TEST";
  private final LocalBroadCastManager broadcastManager;

  public MyClass(Context context) {
    broadcastManager = LocalBroadcastManager.getInstance(context);
  }

  @SuppressWarnings("unused")
  private void onSendText(String text) {
    final Intent intent = new Intent(ACTION_TEST).putExtra(Intent.EXTRA_TEXT, text);
    broadcastManager.sendBroadcast(intent);
  }

  private native void sendText();   
}

and just call that method from JNI:

JNIEXPORT void JNICALL Java_com_example_MyClass_1sendText(JNIEnv *env, jobject instance) {
  jclass clazz = (*env)->GetObjectClass(env, instance);
  jmethodID method = (*env)->GetMethodID(env, clazz, "onSendText", "(Ljava/lang/String;)V");
  jstring text = (*env)->NewString(env, "test message");
  (*env)->CallVoidMethod(env, instance, method, text);
}