@Override
public void onDeviceAdded(final MidiDeviceInfo device) {
    // Call all of the locally registered callbacks.
    for(Map.Entry<DeviceCallback, Handler> item : mCallbacks.entrySet()) {
        final DeviceCallback callback = item.getKey();
        Handler handler = item.getValue();
        if(handler == null) {
            callback.onDeviceAdded(device);
        } else {
            handler.post(new Runnable() {
                @Override
                public void run() {
                    callback.onDeviceAdded(device);
                }
            });
        }
    }
}
 

@Override
public void onDeviceRemoved(final MidiDeviceInfo device) {
    for(Map.Entry<DeviceCallback, Handler> item : mCallbacks.entrySet()) {
        final DeviceCallback callback = item.getKey();
        Handler handler = item.getValue();
        if(handler == null) {
            callback.onDeviceRemoved(device);
        } else {
            handler.post(new Runnable() {
                @Override
                public void run() {
                    callback.onDeviceRemoved(device);
                }
            });
        }
    }
}
 

@Override
public void onDeviceStatusChanged(final MidiDeviceStatus status) {
    for(Map.Entry<DeviceCallback, Handler> item : mCallbacks.entrySet()) {
        final DeviceCallback callback = item.getKey();
        Handler handler = item.getValue();
        if(handler == null) {
            callback.onDeviceStatusChanged(status);
        } else {
            handler.post(new Runnable() {
                @Override
                public void run() {
                    callback.onDeviceStatusChanged(status);
                }
            });
        }
    }
}
 

public void registerDeviceCallback(DeviceCallback callback, Handler handler) {
    if (mUseProxy) {
        // Keep our own list of callbacks.
        mCallbacks.put(callback, handler);
    } else {
        mMidiManager.registerDeviceCallback(callback, handler);
    }
}
 

public void unregisterDeviceCallback(DeviceCallback callback) {
    if (mUseProxy) {
        mCallbacks.remove(callback);
    } else {
        // This works on N or later.
        mMidiManager.unregisterDeviceCallback(callback);
    }
}