Public class for checking Internet connection to be used before Google sign in and other network activities

Question

I am new to java and android but have set myself a challenge to create an app that my students can use to interact with some of the content in my class (which I hope to have ready for them by the next semester).

I would like the students to be able to sign in to the app with their email address (Google account) and the app also includes a quiz for each section of work (for which their performance is emailed back to me). I would like to ensure that at active connection is available before a network related task is executed. I have looked at a number of SO questions (Detect if android device is connected to the internet ; Detect whether there is an Internet connection available on Android ; How to check internet access on Android? InetAddress never times out ; Checking internet connection on android , How to check internet access on Android? InetAddress never times out ; How to check internet access on Android? InetAddress never times out ; ...) in trying to formulate my own code, but I am not really understanding how to use the AsyncTask to ensure the network request is not being executed by the main thread to prevent getting the NetworkOnMainThreadException. Please could someone guide me to the correct way to use the AsycTask or Threads to perform the Internet Check before performing the sign-in or grades-sending actions in my app.

At the moment I am calling my isNetworkAvailable method from my Activity that handles the sign in activity as follows:

 signInButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (isNetworkAvailable(getApplicationContext())) {
                progressDialog.show();
                Intent intent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);
                startActivityForResult(intent, LOGIN_GOOGLE_NUMBER);
            } else {
                Toast.makeText(getApplicationContext(), "Please ensure that you are connected to the Internet and then try again", Toast.LENGTH_LONG).show();
            }
        }
    });

The method in for checking the Internet connectivity which is part of the Main Signin class looks like this:

// Check if the network is connected (and if Internet is working)
private boolean isNetworkAvailable(Context context) {
    //final ConnectivityManager connectivityManager = ((ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE));
    //return connectivityManager.getActiveNetworkInfo() != null && connectivityManager.getActiveNetworkInfo().isConnected();
    boolean connected = false;
    ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    if (connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.CONNECTED ||
            connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.CONNECTED) {
        //we are connected to a network
        connected = true;
    } else
        connected = false;
    if (connected) {
        checkConnectivity isConnected = new checkConnectivity();
        if (isConnected.hasInternetAccess(getApplicationContext())) {
            return true;
        } else
            return false;
    } else
        return false;
}

and makes reference to the AsyncTask that I wanted to be accessible throughout the app as a separate public class:

public class checkConnectivity extends AsyncTask<Activity, Void, Boolean> {

private static final String TAG = "MyApplication Context";

protected Boolean doInBackground(Activity... activitys) {
    return hasInternetAccess(activitys[0]);
}

// To check for internet before performing sign in activity
public boolean hasInternetAccess(Context context) {
    try {
            HttpURLConnection urlc = (HttpURLConnection)
                    (new URL("http://clients3.google.com/generate_204")
                            .openConnection());
            urlc.setRequestProperty("User-Agent", "Android");
            urlc.setRequestProperty("Connection", "close");
            urlc.setConnectTimeout(1500);
            urlc.connect();
            return (urlc.getResponseCode() == 204 &&
                    urlc.getContentLength() == 0);
    } catch (IOException e) {
            Log.e(TAG, "Error checking internet connection", e);
    }
    return false;
    }
}

I have been coding this incrementally. If I just have the section to test the network connection then it works fine, but when I try and add the http url request then I run into problems.

What is the correct way to define a public class that I can use in different places in the app to ensure that there is an Internet connection, and how do I make the call in that specific activity? Any help will be most appreciated.

Answer 1

When I am stuck some where I usually refer the Plaid app which is good to learn many things. So this is how they are handling network connection in the Plaid app by a Developer at Google.

boolean connected = true;

@Override
protected void onResume() {
    super.onResume();
    checkConnectivity();
}

@Override
protected void onPause() {
    if (monitoringConnectivity) {
        final ConnectivityManager connectivityManager
                = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        connectivityManager.unregisterNetworkCallback(connectivityCallback);
        monitoringConnectivity = false;
    }
    super.onPause();
}

private void checkConnectivity() {
    final ConnectivityManager connectivityManager
                = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    final NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
    connected = activeNetworkInfo != null && activeNetworkInfo.isConnected();

    if(!connected){
        // do some action when not connected
        connectivityManager.registerNetworkCallback(
                    new NetworkRequest.Builder()
                    .addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET).build(),
                    connectivityCallback);
            monitoringConnectivity = true;
    }

}

// Network call back
private ConnectivityManager.NetworkCallback connectivityCallback
        = new ConnectivityManager.NetworkCallback() {
    @Override
    public void onAvailable(Network network) {
        connected = true;
        if (adapter.getDataItemCount() != 0) return;
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                // do stuff when connected
            }
        });
    }

    @Override
    public void onLost(Network network) {
        connected = false;
    }
};

Here you can call the method checkConnectivity()and it will give the result in a field connected.

'AsyncTask' is never executed on the main thread and is safe to do long running task without without causing the UI to freeze. What you should do is create a separate public class (not a inner class) for the 'AsyncTask' and then you will be able to call that class from any activity you want.

Also, never pass Context or Activity to AsyncTask. It might cause memory leak.

EDIT: Based on the OP comment

How AsyncTask works is it takes three generic types <Start,Progress,Result>

• Start indicates what type of parameters are you going to accept. This is delivered onPreExecute() as parameter.
• Progress indicates the type which is responsible for updating Progress of the task e.g.downloading a file. This is delivered as parameter to onProgressUpdate().
• Result indicates what type of result you got after the task finished. This is delivered as parameter to onPostExecute().

All the above three methods are on UI thread and try to do a network operation on them will give you the NetworkOnMainThreadException. However, doInBackground() is the only method executed in the background thread. It also returns a same type as Result(Explained above).

Now since, you want to use the same task at multiple places, what you can do is you can create a listener interface, which will call the activity who had called the task and pass the result as parameter to the activity.

Answer 2

I have made the public class for checking network connection. Try it

ConnectionChecker.java

public class ConnectionChecker {

    private Context mContext;

    public boolean isInternetAvailable() {
        ConnectivityManager cm = (ConnectivityManager) mContext.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = cm.getActiveNetworkInfo();
        return networkInfo!=null && networkInfo.isConnected();
    }
}

And wherever, you need to check internet connection then simply define it's instance by following way,

In my app I have defined in MainActivity.java

public class MainActivity extends BaseActivity {

public ConnectionUtil connectionUtil;

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        connectionUtil = new ConnectionUtil();
}

And I had checked network connection before API calling

Below, one sample method for API

public static void callLikeUnlikeWishApi(final MainActivity mActivity,long wishId, long updateWishId, int type) {

        if (mActivity.connectionUtil.isInternetAvailable()) {

            // Here you define your Api code...
        }  else {
        Toast.makeText(mActivity, "No network connection!!", Toast.LENGTH_SHORT).show();
   }
}