如何检查Android设备是否连接到网络？

Question

How would i know whether my device is connected the web or not? How can i detect connectivity? Any sample code?

Answer 1

First, you need permission to know whether the device is connected to the web or not. This needs to be in your manifest, in the <manifest> element:

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

Next, you need to get a reference to the ConnectivityManager :

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

From there you need to obtain a NetworkInfo object. For most, this will mean using ConnectivityManager. getActiveNetworkInfo() :

NetworkInfo ni = cm.getActiveNetworkInfo();
if (ni == null) {
    // There are no active networks.
    return false;
}

From there, you just need to use one of NetworkInfo's methods to determine if the device is connected to the internet:

boolean isConnected = ni.isConnected();

Answer 2

First, you need permission to know whether the device is connected to the web or not. This needs to be in your manifest, in the element:

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

then

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

if (connec != null && (
    (connec.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.CONNECTED) || 
    (connec.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.CONNECTED))) { 

        //You are connected, do something online.

} else if (connec != null && (
    (connec.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState() == NetworkInfo.State.DISCONNECTED) ||
    (connec.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState() == NetworkInfo.State.DISCONNECTED ))) {            

        //Not connected.    
        Toast.makeText(getApplicationContext(), "You must be connected to the internet", Toast.LENGTH_LONG).show();

} 

Answer 3

Add this permission in your AppManifest.xml file:

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

The method to check if network is available or not:

boolean isNetworkAvailable() {
  ConnectivityManager cm = (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);

  NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
  boolean isConnected = activeNetwork != null && activeNetwork.isConnectedOrConnecting();
  return isConnected;
}

Source

Answer 4

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