有不止一种方法
第一，最短但效率低的方法
只需要网络状态权限
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
然后这个方法，
public boolean activeNetwork () {
ConnectivityManager cm =
(ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
boolean isConnected = activeNetwork != null &&
activeNetwork.isConnected();
return isConnected;
}
正如在回答中所看到的ConnectivityManager是一个解决方案，我只是在一个方法中添加了它，这是一个简化的方法
ConnectivityManager返回true，如果有网络访问而不是互联网访问，这意味着如果你的WiFi连接到路由器，但路由器没有互联网，它返回true，它检查连接可用性
二、高效的方式
需要网络状态和Internet权限
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
然后这门课，
public class CheckInternetAsyncTask extends AsyncTask<Void, Integer, Boolean> {
private Context context;
public CheckInternetAsyncTask(Context context) {
this.context = context;
}
@Override
protected Boolean doInBackground(Void... params) {
ConnectivityManager cm =
(ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
assert cm != null;
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
boolean isConnected = activeNetwork != null &&
activeNetwork.isConnected();
if (isConnected) {
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();
if (urlc.getResponseCode() == 204 &&
urlc.getContentLength() == 0)
return true;
} catch (IOException e) {
Log.e("TAG", "Error checking internet connection", e);
return false;
}
} else {
Log.d("TAG", "No network available!");
return false;
}
return null;
}
@Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
Log.d("TAG", "result" + result);
if(result){
// do ur code
}
}
}
叫CheckInternetAsyncTask
new CheckInternetAsyncTask(getApplicationContext()).execute();
部分解释:-
you have to check Internet on AsyncTask, otherwise it can throw android.os.NetworkOnMainThreadException in some cases
ConnectivityManager used to check the network access if true sends request (Ping)
Request send to http://clients3.google.com/generate_204, This well-known URL is known to return an empty page with an HTTP status 204 this is faster and more efficient than http://www.google.com , read this. if you have website it's preferred to put you website instead of google, only if you use it within the app
Timeout can be changed range (20ms -> 2000ms), 1500ms is commonly used
