如何在我的android应用程序运行期间检查网络是否具有更改状态？

Question

I'am developing an application for android, which needs network in order to retrieve some information from an xml file. I've got this code, that looking for if the users has enabled the network:

public boolean isOnline() {
    ConnectivityManager cm =
        (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    if (netInfo != null && netInfo.isConnected()) {
        return true;
    }
    return false;
}

I use this function this way:

boolean connected = isOnline(); 

    if(connected) 
        getLocation(); 
    else
        showDialogNetwork();

The function showDialogNetwork() :

    public void showDialogNetwork() {

    new AlertDialog.Builder(this)  
    .setMessage("No network")  
    .setTitle("Error")  
    .setCancelable(false)
    .setPositiveButton(android.R.string.ok, 
        new DialogInterface.OnClickListener() {  
            public void onClick(DialogInterface dialog, int whichButton) {
                // launch settings
                Intent settings = new Intent(android.provider.Settings.ACTION_WIRELESS_SETTINGS);
                startActivity(settings);
            }  
        })
    .setNegativeButton(android.R.string.cancel,
        new DialogInterface.OnClickListener() {  
            public void onClick(DialogInterface dialog, int whichButton) {
                dialog.dismiss();

                // finish activity
                finish();
            }  
        })
    .show();
}

If the network on the device is disabled the showDialogNetwork() will open the network tab in the settings menu. But when the users turn on the WiFi, and the application is running in the background, it doesn't "understand" that the network is turned on. I need the "kill" the app after the network is turned on, to get the information from the internet. How can I constantly check if the network has change state during run time of my application? Thanks in advance, guys :)

Answer 1

Create a BroadcastReceiver with an IntentFilter which 'listens' for...

WifiManager.NETWORK_STATE_CHANGED_ACTION

You can either register for that in code or if you register the BroadcastReceiver in your manifest then use the following for the <intent-filter>

android.net.wifi.STATE_CHANGE

See WifiManager.WIFI_STATE_CHANGED_ACTION

To also monitor mobile Internet connectivity change you would 'listen' for...

ConnectivityManager.CONNECTIVITY_ACTION

In this case use the following in the manifest...

android.net.conn.CONNECTIVITY_CHANGE

Answer 2

You can also listen to changes to your Data Connection using the TelephonyManager -

http://developer.android.com/reference/android/telephony/PhoneStateListener.html#onDataConnectionStateChanged(int )

Even better, register for android.net.conn.CONNECTIVITY_CHANGE broadcast action which includes wifi, data etc -

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

<receiver android:name="com.yourapp.receivers.ConnectionChangeReceiver"
          android:label="Connection">
  <intent-filter>
    <action android:name="android.net.conn.CONNECTIVITY_CHANGE"/>
  </intent-filter>
</receiver>