Android : Dependency injection not working with Dagger

[Kernel freak]

** Copying my own question from Stackoverflow, if users are not there, Link : http://stackoverflow.com/questions/34023673/android-dependency-injection-not-working-with-dagger
Somehow when I last posted the question here, it didn't got posted.

I am working on an Android project in which I am trying to integrate dependency-injection, because that's the last choice I have for integrating some chat services.

The situation is, I am using framework Cometd for PUSH services. Now, in my platform, there are Conversation and there are ChatMessages. In the Conversation class, I am asking the server to give all the friends the user has, so I can subscribe to them, and then send/receive updates.

The unfortunate problem is, whenever a conversation is clicked, it starts new Activity called ChatMessages and shows a list of messages between the users. But now the Conversation class is gone, I don't want to instantiate it, so I thought why not inject its dependency and create 2 methods in each class, which will send/receive messages to each other and update as well. Well, it didn't fan-out.. :-(

Error log :

java.lang.NullPointerException: Attempt to invoke virtual method 'void mycompany.twentynotes.Activity.ChatMessagesActivity.recieveUpdatedMessage(java.lang.String, java.util.Map)' on a null object reference
12-01 15:57:27.871 27424-27860/mycompany.twentynotes W/System.err:     at mycompany.twentynotes.Activity.ConversationActivity.sendMessageToChatActivity(ConversationActivity.java:258)
12-01 15:57:27.871 27424-27860/mycompany.twentynotes W/System.err:     at mycompany.twentynotes.Activity.ConversationActivity$ChatListener.onMessage(ConversationActivity.java:319)
12-01 15:57:27.871 27424-27860/mycompany.twentynotes W/System.err:     at org.cometd.common.AbstractClientSession$AbstractSessionChannel.notifyOnMessage(AbstractClientSession.java:501)
12-01 15:57:27.871 27424-27860/mycompany.twentynotes W/System.err:     at org.cometd.common.AbstractClientSession$AbstractSessionChannel.notifyMessageListeners(AbstractClientSession.java:491)

What I did to get the above error was send a message from browser, which when received by ConversationActivity will be passed to ChatMessages class.

ConversationActivity.java :

public class ConversationActivity extends ApplicationDrawerLoader {


    public final ChatMessagesActivity chatMessagesActivity;

    @Inject
   public ConversationActivity(ChatMessagesActivity chatMessagesActivity){
        this.chatMessagesActivity = chatMessagesActivity;
    }

    public ConversationActivity(){
        chatMessagesActivity = null;
    }


public void sendMessageToChatActivity(String channelName, Map<String,Object> outputData){
        Log.d("We are","in send");
        this.chatMessagesActivity.recieveUpdatedMessage(channelName, outputData);
    }
// And message arrives in class below :

public class ChatListener implements ClientSessionChannel.MessageListener {
        public void onMessage(ClientSessionChannel channel, Message message) {

            sendMessageToChatActivity(channel.toString(),message);
            Log.d("Message is ", message.getJSON());

        }
    }
}

ChatMessagesActivity.java :

public class ChatMessagesActivity extends ApplicationDrawerLoader {

// I require the ConversationActivity class in here, so I can send new messages which are sent by user to PUSH service.
    private final ConversationActivity conversationActivity;

    @Inject
    public ChatMessagesActivity(ConversationActivity conversationActivity){
        this.conversationActivity = conversationActivity;
    }

    public ChatMessagesActivity(){
        conversationActivity = null;
    }

 public void recieveUpdatedMessage(String channelName, Map<String, Object> input){
        Log.d("We recieved the","message in CM");
    }
}

Please note I have added the dagger dependency, but the @Inject is still from javax.inject. I read that Dagger works/implements it, so I hope that's correct then.

build.gradle :

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    compile 'com.android.support:appcompat-v7:22.2.1'
    compile 'com.android.support:appcompat-v7:22.2.1'
    compile 'com.fasterxml.jackson.core:jackson-core:2.6.0'
    compile 'com.fasterxml.jackson.core:jackson-databind:2.6.0'
    compile 'org.springframework.android:spring-android-rest-template:1.0.1.RELEASE'
    compile 'org.springframework.android:spring-android-core:1.0.1.RELEASE'
    compile('org.springframework.android:spring-android-auth:1.0.1.RELEASE') {
        exclude group: 'org.springframework', module: 'commons-logging'
        exclude group: 'org.springframework', module: 'spring-core'
        exclude group: 'org.springframework', module: 'spring-web'
    }
    compile 'com.fasterxml.jackson.core:jackson-annotations:2.6.0'
    compile 'com.google.android.gms:play-services:7.5.0'
    compile 'com.tonicartos:superslim:0.4.13'
    compile 'commons-codec:commons-codec:1.9'
    compile 'com.squareup.picasso:picasso:2.5.2'
    compile 'org.cometd.java:bayeux-api:3.0.6'
    compile 'org.cometd.java:cometd-java-server:3.0.6'
    compile 'org.cometd.java:cometd-java-client:3.0.6'
    compile 'org.cometd.java:cometd-java-annotations:3.0.6'
    compile 'org.slf4j:slf4j-simple:1.7.12'
    compile 'com.google.dagger:dagger:2.0.2'
    compile 'com.google.dagger:dagger-compiler:2.0.2'
}

Now, Is this the correct approach, can you help me with solving the issue, if not a good approach, kindly tell me what should I do..Thanks a lot.. :-)