android如何检查wifi已连接但没有互联网连接

Question

android my device connected with wifi but how to if wifi is connected but these is no internet connection

following is my code that i trying to check if no internet connection

public static boolean isConnectedWifi(Context context) {
        NetworkInfo info=null;
        if(context!=null){
            info= IsNetConnectionAvailable.getNetworkInfo(context);
        }
        return (info != null && info.isConnected() && info.getType() == ConnectivityManager.TYPE_WIFI);
    }

it always return true when no internet access

Answer 1

NetworInfo.isAvailable and NetworkInfo.isConnected only indicate whether network connectivity is possible or existed, they can't indicate whether the connected situation has access to the public internet, long story short, they can't tell us the device is online indeed.

To check whether a device is online, try the following methods:

First:

@TargetApi(Build.VERSION_CODES.M)
public static boolean isNetworkOnline1(Context context) {
    boolean isOnline = false;
    try {
        ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkCapabilities capabilities = manager.getNetworkCapabilities(manager.getActiveNetwork());  // need ACCESS_NETWORK_STATE permission
        isOnline = capabilities != null && capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_VALIDATED);
    } catch (Exception e) {
        e.printStackTrace();
    }

    return isOnline;
}

Strength: 1. could run on UI thread; 2. fast and accurate.

Weakness: need API >= 23 and compatibility issues.

Second:

public static boolean isNetworkOnline2() {
    boolean isOnline = false;
    try {
        Runtime runtime = Runtime.getRuntime();
        Process p = runtime.exec("ping -c 1 8.8.8.8");
        int waitFor = p.waitFor();
        isOnline = waitFor == 0;    // only when the waitFor value is zero, the network is online indeed

        // BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));
        // String str;
        // while ((str = br.readLine()) != null) {
        //     System.out.println(str);     // you can get the ping detail info from Process.getInputStream()
        // }
    } catch (IOException e) {
        e.printStackTrace();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }

    return isOnline;
}

Strength: 1. could run on UI thread; 2. you can ping many times and do statistics for min/avg/max delayed time and packet loss rate.

Weakness: compatibility issues .

Third:

public static boolean isNetworkOnline3() {
    boolean isOnline = false;
    try {
        URL url = new URL("http://www.google.com"); // or your server address
        // URL url = new URL("http://www.baidu.com");
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestProperty("Connection", "close");
        conn.setConnectTimeout(3000);
        isOnline = conn.getResponseCode() == 200;
    } catch (IOException e) {
        e.printStackTrace();
    }

    return isOnline;
}

Strength: could use on all devices and APIs.

Weakness: time-consuming operation, can't run on UI thread.

Fourth:

public static boolean isNetworkOnline4() {
    boolean isOnline = false;
    try {
        Socket socket = new Socket();
        socket.connect(new InetSocketAddress("8.8.8.8", 53), 3000);
        // socket.connect(new InetSocketAddress("114.114.114.114", 53), 3000);
        isOnline = true;
    } catch (IOException e) {
        e.printStackTrace();
    }

    return isOnline;
}

Strength: 1. could use on all devices and APIs; 2. relatively fast and accurate.

Weakness: time-consuming operation, can't run on UI thread.

Answer 2

check with the below set of codes.

public boolean isNetworkAvailable(Context context) {
        boolean isOnline = false;
        ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        try {
            if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
                NetworkCapabilities capabilities = manager.getNetworkCapabilities(manager.getActiveNetwork());
                isOnline = capabilities != null && capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_VALIDATED);
            } else {
                NetworkInfo activeNetworkInfo = manager.getActiveNetworkInfo();
                isOnline = activeNetworkInfo != null && activeNetworkInfo.isConnectedOrConnecting();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return isOnline;
    }

Answer 3

The code you are using is just use to check if you are connected to wifi or not. It doesn't check if that wifi is slow or not. (No internet means slow connection).

I tried to use this code. Here, I try to hit google.com and have set a connection timeout value. If here internet speed is good, then result returned is 200. So I check if the result code is 200 or not. If not, I show an alert that there is slow internet connection. Use it in an asyntask, and onPostExecute() check the value of returned result.

HttpURLConnection urlc = null;
    try {
        urlc = (HttpURLConnection) (new URL("http://www.google.com")
                .openConnection());
    } catch (MalformedURLException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    } catch (IOException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }
    urlc.setRequestProperty("User-Agent", "Test");
    urlc.setRequestProperty("Connection", "close");
    urlc.setConnectTimeout(1000); // choose your own timeframe
    urlc.setReadTimeout(2000); // choose your own timeframe
    try {
        urlc.connect();

        // returning connection code.
        return (urlc.getResponseCode());
    } catch (IOException e1) {
        e1.printStackTrace();
    }

Answer 4

After searching for days and after trying various solutions, some are not perfect some are too LONG, below is a solution suggested by LEVIT using SOCKETS which is PERFECT to me. Any one searching on this solution may consult this post. How to check internet access on Android? InetAddress never times out

Below is the portion of the code with example of task in AsyncTask

class InternetCheck extends AsyncTask<Void,Void,Boolean> {

    private Consumer mConsumer;
    public  interface Consumer { void accept(Boolean internet); }

    public  InternetCheck(Consumer consumer) { mConsumer = consumer; execute(); }

    @Override protected Boolean doInBackground(Void... voids) { try {
        Socket sock = new Socket();
        sock.connect(new InetSocketAddress("8.8.8.8", 53), 1500);
        sock.close();
        return true;
    } catch (IOException e) { return false; } }

    @Override protected void onPostExecute(Boolean internet) { mConsumer.accept(internet); }
}
///////////////////////////////////////////////////////////////////////////////////
// Usage

    new InternetCheck(internet -> { /* do something with boolean response */ });

Below is a summary related to the solution Possible Questions Is it really fast enough?

Yes, very fast ;-)

Is there no reliable way to check internet, other than testing something on the internet?

Not as far as I know, but let me know, and I will edit my answer.

What if the DNS is down?

Google DNS (eg 8.8.8.8) is the largest public DNS in the world. As of 2013 it served 130 billion requests a day. Let 's just say, your app would probably not be the talk of the day.

Which permissions are required?

<uses-permission android:name="android.permission.INTERNET" />

Answer 5

To just check if you are connected to the internet by Wi-Fi, have a look at the snippet below:

NetworkInfo getWifi(){
    ConnectivityManager connManager = (ConnectivityManager) getContext().getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo mWifi = connManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
    return mWifi;
}

Check whether it is connected or not by;

if(getWifi().isConnected()) {
//wi-fi connected
}