How to check if internet is available or not in app startup in android?

问题

My app at first loads the datas from internet(I am using webservice) I want to check internet access at app startup.

I will like to check if any forms of internet either 3G or WIFI or GPRS or any other is available or not.
If not available, give message to user like "You need internet access" and exit the app. (Currently i am getting force close error in my app if there is no internet access)
If availabe, start my app normally.
Also, my app is fetches the datas from webservice at different phase, before each phase or operation, i will like to check internet access at first.

How do i do this ?

回答1:

You can use my method:

public static boolean isNetworkAvailable(Context context) 
{
    ConnectivityManager connectivity = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

    if (connectivity != null) 
    {
        NetworkInfo[] info = connectivity.getAllNetworkInfo();

        if (info != null) 
        {
            for (int i = 0; i < info.length; i++) 
            {
                Log.i("Class", info[i].getState().toString());
                if (info[i].getState() == NetworkInfo.State.CONNECTED) 
                {
                    return true;
                }
            }
        }
    }
    return false;
}

回答2:

You can do all this using ConnectivityManager. All the required info is available here

http://developer.android.com/reference/android/net/ConnectivityManager.html

You probably want to stick something like this in the onStart() method of your initial activity (depending on where in your code the connection is fired up and the data is downloaded)

ConnectivityManager cm =  (ConnectivityManager) Context.getSystemService(Context.CONNECTIVITY_SERVICE);

if (cm.getAllNetworkInfo().isConnected()) {
 //proceed with loading 
} else { 
//showErrorDialog 
}

I haven't tested te code so cutting and pasting is probably a bad idea, but this should give you a good starting point. There is plenty of other info if you check the docs.

Also it's might be an idea to handle the lack of connectivity by changing your code so it doesn't just crash if there is no connection, pre haps show a default loading screen? Also your app may fail to get data even if there is a connection available, so you'll want to handle that scenario too.

回答3:

NetworkInfo i = conMgr.getActiveNetworkInfo();
  if (i == null)
    return false;
  if (!i.isConnected())
    return false;
  if (!i.isAvailable())
    return false;
  return true;

来源：https://stackoverflow.com/questions/10194192/how-to-check-if-internet-is-available-or-not-in-app-startup-in-android

标签

android

connectivity