NetworkMonitor.java 文件源码

public void listenRoamingState() {
    if (phoneStateListener == null) {
        phoneStateListener = new PhoneStateListener() {
            @Override
            public void onServiceStateChanged(ServiceState serviceState) {
                super.onServiceStateChanged(serviceState);

                final int state = serviceState.getState();
                if (state == ServiceState.STATE_IN_SERVICE
                        || state == ServiceState.STATE_POWER_OFF) {
                    final boolean roamingState = serviceState
                            .getRoaming();
                    if (roamingState != isRoamingOn()) {
                        setRoamingOn(roamingState);
                    }
                }
            }
        };
    }

    TelephonyManager telMgr = (TelephonyManager) context
            .getSystemService(Context.TELEPHONY_SERVICE);
    telMgr.listen(phoneStateListener,
            PhoneStateListener.LISTEN_SERVICE_STATE);
}