使用类扩展asynctask来检查android活动中的互联网连接

Question

By checking some questions on here I have managed to create the below class in order to check whether the user has an active internet connection. I want to use this in my android activities to check the connection before I load any data from the internet. I would like to ask if this is a suitable way of checking the user's internet connection and I would like someone to provide an example of how this would be called from within an activity (how to pass the context to it and how to obtain the true/false response back in my android activity.

public class ConnectionStatus  {
private Context context;

public ConnectionStatus(Context context){
    this.context=context;
}
public static boolean isNetworkAvailable(Context c) {
    NetworkInfo netInfo = null;
    try {
        ConnectivityManager cm = (ConnectivityManager) c
                .getSystemService(Context.CONNECTIVITY_SERVICE);
        netInfo = cm.getActiveNetworkInfo();
    } catch (SecurityException e) {
        e.printStackTrace();
    }
    return netInfo != null && netInfo.isConnectedOrConnecting();
}
public boolean CheckConnection() {
    if (isNetworkAvailable(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);
        }
    } else {
        Log.d("TAG", "No network available!");
    }
    return false;
}
}

Answer 1

I would get the network info outside the Async Task since it would be easier for you to handle how to react on the given network status.

For the Async Task, you could make it an inner class of your Activity, and check for the network status before calling the execute method of the Async Task.

public class MyActivity extends Activity{

...
...
  private static boolean isNetworkAvailable(Context c) {
    NetworkInfo netInfo = null;
    try {
      ConnectivityManager cm = (ConnectivityManager) c
            .getSystemService(Context.CONNECTIVITY_SERVICE);
      netInfo = cm.getActiveNetworkInfo();
    } catch (SecurityException e) {
      e.printStackTrace();
    // Something bad happen, better return false.
      return false;
    }
    return netInfo != null && netInfo.isConnectedOrConnecting();
  }

//Let's assume you will call your data from the internet like this
  private void getDataFromTheInternet(){
  if (isNetworkAvailable){
     ConnectionStatus cStatus = new ConnectionStatus(getApplicationContext());
    cStatus.execute();
  }else{
  //Prevent the user that there is not a network connection
  }
}

Now, remove the isNetworkAvailable methof from the Asynk Task and there you go.

Additionally you could use a BroadCast receiver to check everytime the connection status changes so your application can react when it's offline or online following this tutorial

Answer 2

Here is an example of an Activity class that includes an AsyncTask, and shows how you could use your ConnectionStatus class in the updated version of your question.

public class MainActivity extends AppCompatActivity {

    TextView textView;

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

        textView = (TextView) findViewById(R.id.text);

        //Create Strings to pass to varargs of AsyncTask
        String s1 = "test1";
        String s2 = "test2";
        new MyAsync().execute(s1, s2);

    }

    class MyAsync extends AsyncTask<String, String, String> {

        ConnectionStatus status;

        @Override
        protected void onPreExecute() {

        }

        @Override
        protected String doInBackground(String... params) {

            String retVal = null;

            //Instantiate your object, use MainActivity.this for Context
            status = new ConnectionStatus(MainActivity.this);

            //capture varargs
            String sOne = params[0];
            String sTwo = params[1];

            boolean something = false;

            //Check network connectivity:
            if (status.CheckConnection()){

                //You have internet, do your network operations here
                //...............

                //Just here for an example:
                if (something == true){
                    retVal = sOne;
                }
                else{
                    retVal = sTwo;
                }

            }

            return retVal;
        }

        @Override
        protected void onPostExecute(String arg) {
            //Update UI here, this runs on the Main UI thread of the Activity
            if (arg != null){
                textView.setText(arg);
            }
        }
    }

}