frameworks/base/core/java/android/net
ConnectivityManager.java:

裡面有定義各類連線類型: TYPE_WIFI, TYPE_MOBILE_MMS, TYPE_BLUETOOTH, TYPE_DUMMY, TYPE_ETHERNET, TYPE_PROXY,

跟 "目前網路狀態" 有關的，好像是...

    /**
     * Returns details about the currently active default data network. When
     * connected, this network is the default route for outgoing connections.
     * You should always check {@link NetworkInfo#isConnected()} before initiating
     * network traffic. This may return {@code null} when there is no default
     * network.
     * 
This method requires the caller to hold the permission
     * {@link android.Manifest.permission#ACCESS_NETWORK_STATE}.
     *
     * @return a {@link NetworkInfo} object for the current default network
     *        or {@code null} if no default network is currently active
     */
    public NetworkInfo getActiveNetworkInfo() {
        try {
            return mService.getActiveNetworkInfo();
        } catch (RemoteException e) {
            return null;
        }
    }

    /**
     * Returns a {@link Network} object corresponding to the currently active
     * default data network.  In the event that the current active default data
     * network disconnects, the returned {@code Network} object will no longer
     * be usable.  This will return {@code null} when there is no default
     * network.
     * 
This method requires the caller to hold the permission
     * {@link android.Manifest.permission#ACCESS_NETWORK_STATE}.
     *
     * @return a {@link Network} object for the current default network or
     *        {@code null} if no default network is currently active
     */
    public Network getActiveNetwork() {
        try {
            return mService.getActiveNetwork();
        } catch (RemoteException e) {
            return null;
        }
    }

還有一個，好像是要使用網路之前，要call 的...

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另外在 frameworks/opt/net 下也有.. ethernet, ims, voip, wifi 四個 categories..