管理网络用量

private const val DEBUG_TAG = "NetworkStatusExample"
...
val connMgr = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
var isWifiConn: Boolean = false
var isMobileConn: Boolean = false
connMgr.allNetworks.forEach { network ->
    connMgr.getNetworkInfo(network).apply {
        if (type == ConnectivityManager.TYPE_WIFI) {
            isWifiConn = isWifiConn or isConnected
        }
        if (type == ConnectivityManager.TYPE_MOBILE) {
            isMobileConn = isMobileConn or isConnected
        }
    }
}
Log.d(DEBUG_TAG, "Wifi connected: $isWifiConn")
Log.d(DEBUG_TAG, "Mobile connected: $isMobileConn")

private static final String DEBUG_TAG = "NetworkStatusExample";
...
ConnectivityManager connMgr =
        (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
boolean isWifiConn = false;
boolean isMobileConn = false;
for (Network network : connMgr.getAllNetworks()) {
    NetworkInfo networkInfo = connMgr.getNetworkInfo(network);
    if (networkInfo.getType() == ConnectivityManager.TYPE_WIFI) {
        isWifiConn |= networkInfo.isConnected();
    }
    if (networkInfo.getType() == ConnectivityManager.TYPE_MOBILE) {
        isMobileConn |= networkInfo.isConnected();
    }
}
Log.d(DEBUG_TAG, "Wifi connected: " + isWifiConn);
Log.d(DEBUG_TAG, "Mobile connected: " + isMobileConn);

fun isOnline(): Boolean {
    val connMgr = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
    val networkInfo: NetworkInfo? = connMgr.activeNetworkInfo
    return networkInfo?.isConnected == true
}

public boolean isOnline() {
    ConnectivityManager connMgr = (ConnectivityManager)
            getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
    return (networkInfo != null && networkInfo.isConnected());
}

class SettingsActivity : PreferenceActivity(), OnSharedPreferenceChangeListener {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // Loads the XML preferences file
        addPreferencesFromResource(R.xml.preferences)
    }

    override fun onResume() {
        super.onResume()

        // Registers a listener whenever a key changes
        preferenceScreen?.sharedPreferences?.registerOnSharedPreferenceChangeListener(this)
    }

    override fun onPause() {
        super.onPause()

        // Unregisters the listener set in onResume().
        // It's best practice to unregister listeners when your app isn't using them to cut down on
        // unnecessary system overhead. You do this in onPause().
        preferenceScreen?.sharedPreferences?.unregisterOnSharedPreferenceChangeListener(this)
    }

    // When the user changes the preferences selection,
    // onSharedPreferenceChanged() restarts the main activity as a new
    // task. Sets the refreshDisplay flag to "true" to indicate that
    // the main activity should update its display.
    // The main activity queries the PreferenceManager to get the latest settings.

    override fun onSharedPreferenceChanged(sharedPreferences: SharedPreferences, key: String) {
        // Sets refreshDisplay to true so that when the user returns to the main
        // activity, the display refreshes to reflect the new settings.
        NetworkActivity.refreshDisplay = true
    }
}

public class SettingsActivity extends PreferenceActivity implements OnSharedPreferenceChangeListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Loads the XML preferences file
        addPreferencesFromResource(R.xml.preferences);
    }

    @Override
    protected void onResume() {
        super.onResume();

        // Registers a listener whenever a key changes
        getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
    }

    @Override
    protected void onPause() {
        super.onPause();

       // Unregisters the listener set in onResume().
       // It's best practice to unregister listeners when your app isn't using them to cut down on
       // unnecessary system overhead. You do this in onPause().
       getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
    }

    // When the user changes the preferences selection,
    // onSharedPreferenceChanged() restarts the main activity as a new
    // task. Sets the refreshDisplay flag to "true" to indicate that
    // the main activity should update its display.
    // The main activity queries the PreferenceManager to get the latest settings.

    @Override
    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
        // Sets refreshDisplay to true so that when the user returns to the main
        // activity, the display refreshes to reflect the new settings.
        NetworkActivity.refreshDisplay = true;
    }
}

class NetworkActivity : Activity() {

    // The BroadcastReceiver that tracks network connectivity changes.
    private lateinit var receiver: NetworkReceiver

    public override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // Registers BroadcastReceiver to track network connection changes.
        val filter = IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION)
        receiver = NetworkReceiver()
        this.registerReceiver(receiver, filter)
    }

    public override fun onDestroy() {
        super.onDestroy()
        // Unregisters BroadcastReceiver when app is destroyed.
        this.unregisterReceiver(receiver)
    }

    // Refreshes the display if the network connection and the
    // pref settings allow it.

    public override fun onStart() {
        super.onStart()

        // Gets the user's network preference settings
        val sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this)

        // Retrieves a string value for the preferences. The second parameter
        // is the default value to use if a preference value is not found.
        sPref = sharedPrefs.getString("listPref", "Wi-Fi")

        updateConnectedFlags()

        if (refreshDisplay) {
            loadPage()
        }
    }

    // Checks the network connection and sets the wifiConnected and mobileConnected
    // variables accordingly.
    fun updateConnectedFlags() {
        val connMgr = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager

        val activeInfo: NetworkInfo? = connMgr.activeNetworkInfo
        if (activeInfo?.isConnected == true) {
            wifiConnected = activeInfo.type == ConnectivityManager.TYPE_WIFI
            mobileConnected = activeInfo.type == ConnectivityManager.TYPE_MOBILE
        } else {
            wifiConnected = false
            mobileConnected = false
        }
    }

    // Uses AsyncTask subclass to download the XML feed from stackoverflow.com.
    fun loadPage() {
        if (sPref == ANY && (wifiConnected || mobileConnected) || sPref == WIFI && wifiConnected) {
            // AsyncTask subclass
            DownloadXmlTask().execute(URL)
        } else {
            showErrorPage()
        }
    }

    companion object {

        const val WIFI = "Wi-Fi"
        const val ANY = "Any"
        const val SO_URL = "http://stackoverflow.com/feeds/tag?tagnames=android&sort;=newest"

        // Whether there is a Wi-Fi connection.
        private var wifiConnected = false
        // Whether there is a mobile connection.
        private var mobileConnected = false
        // Whether the display should be refreshed.
        var refreshDisplay = true

        // The user's current network preference setting.
        var sPref: String? = null
    }
...

}

public class NetworkActivity extends Activity {
    public static final String WIFI = "Wi-Fi";
    public static final String ANY = "Any";
    private static final String URL = "http://stackoverflow.com/feeds/tag?tagnames=android&sort;=newest";

    // Whether there is a Wi-Fi connection.
    private static boolean wifiConnected = false;
    // Whether there is a mobile connection.
    private static boolean mobileConnected = false;
    // Whether the display should be refreshed.
    public static boolean refreshDisplay = true;

    // The user's current network preference setting.
    public static String sPref = null;

    // The BroadcastReceiver that tracks network connectivity changes.
    private NetworkReceiver receiver = new NetworkReceiver();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Registers BroadcastReceiver to track network connection changes.
        IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
        receiver = new NetworkReceiver();
        this.registerReceiver(receiver, filter);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        // Unregisters BroadcastReceiver when app is destroyed.
        if (receiver != null) {
            this.unregisterReceiver(receiver);
        }
    }

    // Refreshes the display if the network connection and the
    // pref settings allow it.

    @Override
    public void onStart () {
        super.onStart();

        // Gets the user's network preference settings
        SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this);

        // Retrieves a string value for the preferences. The second parameter
        // is the default value to use if a preference value is not found.
        sPref = sharedPrefs.getString("listPref", "Wi-Fi");

        updateConnectedFlags();

        if(refreshDisplay){
            loadPage();
        }
    }

    // Checks the network connection and sets the wifiConnected and mobileConnected
    // variables accordingly.
    public void updateConnectedFlags() {
        ConnectivityManager connMgr = (ConnectivityManager)
                getSystemService(Context.CONNECTIVITY_SERVICE);

        NetworkInfo activeInfo = connMgr.getActiveNetworkInfo();
        if (activeInfo != null && activeInfo.isConnected()) {
            wifiConnected = activeInfo.getType() == ConnectivityManager.TYPE_WIFI;
            mobileConnected = activeInfo.getType() == ConnectivityManager.TYPE_MOBILE;
        } else {
            wifiConnected = false;
            mobileConnected = false;
        }
    }

    // Uses AsyncTask subclass to download the XML feed from stackoverflow.com.
    public void loadPage() {
        if (((sPref.equals(ANY)) && (wifiConnected || mobileConnected))
                || ((sPref.equals(WIFI)) && (wifiConnected))) {
            // AsyncTask subclass
            new DownloadXmlTask().execute(URL);
        } else {
            showErrorPage();
        }
    }
...

}

class NetworkReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        val conn = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
        val networkInfo: NetworkInfo? = conn.activeNetworkInfo

        // Checks the user prefs and the network connection. Based on the result, decides whether
        // to refresh the display or keep the current display.
        // If the userpref is Wi-Fi only, checks to see if the device has a Wi-Fi connection.
        if (WIFI == sPref && networkInfo?.type == ConnectivityManager.TYPE_WIFI) {
            // If device has its Wi-Fi connection, sets refreshDisplay
            // to true. This causes the display to be refreshed when the user
            // returns to the app.
            refreshDisplay = true
            Toast.makeText(context, R.string.wifi_connected, Toast.LENGTH_SHORT).show()

            // If the setting is ANY network and there is a network connection
            // (which by process of elimination would be mobile), sets refreshDisplay to true.
        } else if (ANY == sPref && networkInfo != null) {
            refreshDisplay = true

            // Otherwise, the app can't download content--either because there is no network
            // connection (mobile or Wi-Fi), or because the pref setting is WIFI, and there
            // is no Wi-Fi connection.
            // Sets refreshDisplay to false.
        } else {
            refreshDisplay = false
            Toast.makeText(context, R.string.lost_connection, Toast.LENGTH_SHORT).show()
        }
    }
}

public class NetworkReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        ConnectivityManager conn =  (ConnectivityManager)
            context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = conn.getActiveNetworkInfo();

        // Checks the user prefs and the network connection. Based on the result, decides whether
        // to refresh the display or keep the current display.
        // If the userpref is Wi-Fi only, checks to see if the device has a Wi-Fi connection.
        if (WIFI.equals(sPref) && networkInfo != null
            && networkInfo.getType() == ConnectivityManager.TYPE_WIFI) {
            // If device has its Wi-Fi connection, sets refreshDisplay
            // to true. This causes the display to be refreshed when the user
            // returns to the app.
            refreshDisplay = true;
            Toast.makeText(context, R.string.wifi_connected, Toast.LENGTH_SHORT).show();

        // If the setting is ANY network and there is a network connection
        // (which by process of elimination would be mobile), sets refreshDisplay to true.
        } else if (ANY.equals(sPref) && networkInfo != null) {
            refreshDisplay = true;

        // Otherwise, the app can't download content--either because there is no network
        // connection (mobile or Wi-Fi), or because the pref setting is WIFI, and there
        // is no Wi-Fi connection.
        // Sets refreshDisplay to false.
        } else {
            refreshDisplay = false;
            Toast.makeText(context, R.string.lost_connection, Toast.LENGTH_SHORT).show();
        }
    }
}