ConnectivityManager Network is null when specifying to use only wifi

Question

I am trying to store a wifi network (and eventually cellular network) through ConnectivityManager for use later in my program to send data specifically through a local Wifi or cellular network simultaneously. I have followed this post (Make Android simultaneously use WiFi to talk to a device and mobile data to talk to a server? and How to stay connected through mobile network after WIFI is connected on Android?) to try and get it running. However the mWifiNetwork is null. Using debug mode the variable mWifiNetwork shows up as "108" then when the '''onAvailable''' method is complete the variable turns back to null. Not sure why the variable is not storing the network correctly.

I created a class forceWifiNetwork that is called in onResume

forceWifiNetwork.java

public class forceWifiNetwork {

    //setting up a context variable and method to use "getSystemService"
    // this way we do not need to extend MainActivity class to this class
    // But when we initialize this class in main activity we will have to pass in "this" to the class as a parameter

    Context mContext;
    private ConnectivityManager.NetworkCallback mWifiNetworkCallback;
    public Network mWifiNetwork;
    final ConnectivityManager manager;



    public forceWifiNetwork(Context mContext){
        this.mContext = mContext;
        manager = (ConnectivityManager) mContext.getSystemService(Context.CONNECTIVITY_SERVICE);
    }




    public void cellConnect(){

        if (mWifiNetworkCallback == null){

            // Init only once
            mWifiNetworkCallback = new ConnectivityManager.NetworkCallback(){
                @Override
                public void onAvailable(final Network network){
                    try{
                        //Save this network for later use
                        mWifiNetwork = network;
                    }catch(Exception e){
                        Log.i("onAvailable ERROR","Error in onAvailable method");
                    }
                }
            };
        }

        NetworkRequest.Builder wifiBuilder;
        wifiBuilder = new NetworkRequest.Builder();
        //set the transport type to do wifi
        wifiBuilder.addTransportType(NetworkCapabilities.TRANSPORT_WIFI);
        //wifiBuilder.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
        manager.requestNetwork(wifiBuilder.build(),mWifiNetworkCallback);


    }

}

onResume (in MainActivity.java)

    @Override
    public void onResume(){
        super.onResume();

        try {
            forceWifiNetwork myWifiNetwork = new forceWifiNetwork(this);
            myWifiNetwork.cellConnect();
            if (myWifiNetwork.mWifiNetwork == null) {
                Log.i("onResume", "mWifiNetwork is null");
            } else {
                Log.i("onResume", "mWifiNetwork is not null");
            }
        }catch(Exception e){
            Log.i("ERROR IN ONRESUME","error");
            e.printStackTrace();
        }


    }

I also currently have these permissions in AndroidManifest.xml

<uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
    <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />

unmanned15 unmanned15 · Accepted Answer · 2019-10-03T18:15:54

Move the initiation of the forceWifiNetwork in onCreate instead of onResume. The onAvailable method in the ConnectivityManager.Networkcallback I believe may have some underlying Async properties. It would look something like this.

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //creating network variables that store wifi and cell networks
        myWifiNetwork = new forceWifiNetwork(this);


        try {
            myWifiNetwork.cellConnect();
            if (myWifiNetwork.mWifiNetwork == null) {
                Log.i("onCreate", "mWifiNetwork is null");
            } else {
                Log.i("onCreate", "mWifiNetwork is not null");
            }
        }catch(Exception e){
            Log.i("Error in onCreate","error creating network");
            e.printStackTrace();
        }


    }

ConnectivityManager Network is null when specifying to use only wifi

1 Answers