问题
I need to tell if my device has Internet connection or not. I found many answers like:
private boolean isNetworkAvailable() {
ConnectivityManager connectivityManager
= (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
return activeNetworkInfo != null;
}
(Taken from Detect whether there is an Internet connection available on Android.)
But this is not right, for example if I\'m connected to a wireless network which doesn\'t have Internet access, this method will return true… Is there a way to tell if the device has Internet connection and not if it is only connected to something?
回答1:
You are right. The code you've provided only checks if there is a network connection. The best way to check if there is an active Internet connection is to try and connect to a known server via http.
public static boolean hasActiveInternetConnection(Context context) {
if (isNetworkAvailable(context)) {
try {
HttpURLConnection urlc = (HttpURLConnection) (new URL("http://www.google.com").openConnection());
urlc.setRequestProperty("User-Agent", "Test");
urlc.setRequestProperty("Connection", "close");
urlc.setConnectTimeout(1500);
urlc.connect();
return (urlc.getResponseCode() == 200);
} catch (IOException e) {
Log.e(LOG_TAG, "Error checking internet connection", e);
}
} else {
Log.d(LOG_TAG, "No network available!");
}
return false;
}
Of course you can substitute the http://www.google.com URL for any other server you want to connect to, or a server you know has a good uptime.
As Tony Cho also pointed out in this comment below, make sure you don't run this code on the main thread, otherwise you'll get a NetworkOnMainThread exception (in Android 3.0 or later). Use an AsyncTask or Runnable instead.
If you want to use google.com you should look at Jeshurun's modification. In his answer he modified my code and made it a bit more efficient. If you connect to
HttpURLConnection urlc = (HttpURLConnection)
(new URL("http://clients3.google.com/generate_204")
.openConnection());
and then check the responsecode for 204
return (urlc.getResponseCode() == 204 && urlc.getContentLength() == 0);
then you don't have to fetch the entire google home page first.
回答2:
I have modified THelper's answer slightly, to use a known hack that Android already uses to check if the connected WiFi network has Internet access. This is a lot more efficient over grabbing the entire Google home page. See here and here for more info.
public static boolean hasInternetAccess(Context context) {
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;
}
回答3:
public boolean isInternetWorking() {
boolean success = false;
try {
URL url = new URL("https://google.com");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setConnectTimeout(10000);
connection.connect();
success = connection.getResponseCode() == 200;
} catch (IOException e) {
e.printStackTrace();
}
return success;
}
return true if internet is actually available
Make sure you have these two permission
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
回答4:
If you're targeting Lollipop or higher it's possible to use the new NetworkCapabilities class, i.e:
public static boolean hasInternetConnection(final Context context) {
final ConnectivityManager connectivityManager = (ConnectivityManager)context.
getSystemService(Context.CONNECTIVITY_SERVICE);
final Network network = connectivityManager.getActiveNetwork();
final NetworkCapabilities capabilities = connectivityManager
.getNetworkCapabilities(network);
return capabilities != null
&& capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_VALIDATED);
}
回答5:
You don't necessarily need to make a full HTTP connection. You could try just opening a TCP connection to a known host and if it succeeds you have internet connectivity.
public boolean hostAvailable(String host, int port) {
try (Socket socket = new Socket()) {
socket.connect(new InetSocketAddress(host, port), 2000);
return true;
} catch (IOException e) {
// Either we have a timeout or unreachable host or failed DNS lookup
System.out.println(e);
return false;
}
}
Then just check with:
boolean online = hostAvailable("www.google.com", 80);
回答6:
Based on the accepted answers, I have built this class with a listener so you can use it in the main thread:
First: InterntCheck class which checks for internet connection in the background then call a listener method with the result.
public class InternetCheck extends AsyncTask<Void, Void, Void> {
private Activity activity;
private InternetCheckListener listener;
public InternetCheck(Activity x){
activity= x;
}
@Override
protected Void doInBackground(Void... params) {
boolean b = hasInternetAccess();
listener.onComplete(b);
return null;
}
public void isInternetConnectionAvailable(InternetCheckListener x){
listener=x;
execute();
}
private boolean isNetworkAvailable() {
ConnectivityManager connectivityManager = (ConnectivityManager) activity.getSystemService(CONNECTIVITY_SERVICE);
NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
return activeNetworkInfo != null;
}
private boolean hasInternetAccess() {
if (isNetworkAvailable()) {
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) {
e.printStackTrace();
}
} else {
Log.d("TAG", "No network available!");
}
return false;
}
public interface InternetCheckListener{
void onComplete(boolean connected);
}
}
Second: instantiate an instance of the class in the main thread and wait for the response (if you have worked with Firebase api for android before this should be familiar to you!).
new InternetCheck(activity).isInternetConnectionAvailable(new InternetCheck.InternetCheckListener() {
@Override
public void onComplete(boolean connected) {
//proceed!
}
});
Now inside onComplete method you will get whether the device is connected to the internet or not.
回答7:
try this one
public class ConnectionDetector {
private Context _context;
public ConnectionDetector(Context context) {
this._context = context;
}
public boolean isConnectingToInternet() {
if (networkConnectivity()) {
try {
HttpURLConnection urlc = (HttpURLConnection) (new URL(
"http://www.google.com").openConnection());
urlc.setRequestProperty("User-Agent", "Test");
urlc.setRequestProperty("Connection", "close");
urlc.setConnectTimeout(3000);
urlc.setReadTimeout(4000);
urlc.connect();
// networkcode2 = urlc.getResponseCode();
return (urlc.getResponseCode() == 200);
} catch (IOException e) {
return (false);
}
} else
return false;
}
private boolean networkConnectivity() {
ConnectivityManager cm = (ConnectivityManager) _context
.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = cm.getActiveNetworkInfo();
if (networkInfo != null && networkInfo.isConnected()) {
return true;
}
return false;
}
}
you'll have to add the following permission to your manifest file:
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
Then call like that:
if((new ConnectionDetector(MyService.this)).isConnectingToInternet()){
Log.d("internet status","Internet Access");
}else{
Log.d("internet status","no Internet Access");
}
回答8:
private static NetworkUtil mInstance;
private volatile boolean mIsOnline;
private NetworkUtil() {
ScheduledExecutorService exec = Executors.newSingleThreadScheduledExecutor();
exec.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
boolean reachable = false;
try {
Process process = java.lang.Runtime.getRuntime().exec("ping -c 1 www.google.com");
int returnVal = process.waitFor();
reachable = (returnVal==0);
} catch (Exception e) {
e.printStackTrace();
}
mIsOnline = reachable;
}
}, 0, 5, TimeUnit.SECONDS);
}
public static NetworkUtil getInstance() {
if (mInstance == null) {
synchronized (NetworkUtil.class) {
if (mInstance == null) {
mInstance = new NetworkUtil();
}
}
}
return mInstance;
}
public boolean isOnline() {
return mIsOnline;
}
Hope the above code helps you, also make sure you have internet permission in ur app.
回答9:
The latest way to do that from the documentation is to use the ConnectivityManager to query the active network and determine if it has Internet connectivity.
public boolean hasInternetConnectivity() {
ConnectivityManager cm =
(ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
return (activeNetwork != null &&
activeNetwork.isConnectedOrConnecting());
}
Add these two permissions to your AndroidManifest.xml file:
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
回答10:
Check wifi type in connectivity manager:
//check network connection
ConnectivityManager cm = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
boolean hasNetworkConnection = activeNetwork != null && activeNetwork.isConnectedOrConnecting();
System.out.println("Connection ? : " + hasNetworkConnection);
//check wifi
boolean hasWifiConnection = activeNetwork.getType() == ConnectivityManager.TYPE_WIFI;
System.out.println("Wifi ? : " + hasWifiConnection);
Android Documentation describes 'TYPE_WIFI' as 'A WIFI data connection. Devices may support more than one.'
回答11:
A nice solution to check if the active network have internet connection:
public boolean isNetworkAvailable(Context context) {
ConnectivityManager connectivityManager
= (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
if (connectivityManager != null) {
Network network = connectivityManager.getActiveNetwork();
NetworkCapabilities networkCapabilities = connectivityManager.getNetworkCapabilities(network);
return networkCapabilities != null && networkCapabilities
.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
}
return false;
}
来源：https://stackoverflow.com/questions/6493517/detect-if-android-device-has-internet-connection