在Android上, 我們可能會用ConnectivityManager來檢查連線狀態:
public boolean isOnline() {
ConnectivityManager cm =
(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
return netInfo != null && netInfo.isConnectedOrConnecting();
}
這只能檢查Android device是否有連線到AP, 卻不能知道是否有對外連線的能力.
想要檢查現在裝置是否能對外連線, 目前找到兩種方式:
1. 用ping檢查
public boolean isOnline() {
Runtime runtime = Runtime.getRuntime();
try {
Process ipProcess = runtime.exec("/system/bin/ping -c 1 8.8.8.8");
int exitValue = ipProcess.waitFor();
return (exitValue == 0);
}
catch (IOException e) { e.printStackTrace(); }
catch (InterruptedException e) { e.printStackTrace(); }
return false;
}
2. 連線至DNS檢查
public boolean isOnline() {
try {
int timeoutMs = 1500;
Socket sock = new Socket();
SocketAddress sockaddr = new InetSocketAddress("8.8.8.8", 53);
sock.connect(sockaddr, timeoutMs);
sock.close();
return true;
} catch (IOException e) { return false; }
}
來源參考:
http://stackoverflow.com/questions/1560788/how-to-check-internet-access-on-android-inetaddress-never-times-out
