Question

如何检查设备是否已连接到互联网，或者只是连接到外部wifi网络？因为即使没有网络连接，如果设备连接到外部wifi网络，NetworkInfo也会返回true。

当设备连接到wifi但没有互联网访问时，我的应用程序的网络连接检查类返回true但应用程序崩溃，但它无法访问相应的http网址。

Answer 1

如果您想知道何时有有效的互联网连接，请执行以下操作：

一些静态变量：

/**
 * Set the number of retries when reestablishing Internet connection.
 */
private static int retryConnectionNumber = 0;

/**
 * The maximum number of retries allowed for Internet connection.
 */
private final static int CONNECTION_RETRY_MAX = 5;

/**
 * The timeout of the HTTP request when checking for Internet connection.
 */
private final static int REQUEST_TIMEOUT = 2000;

检查网络是否可用的方法：

private static void isNetworkAvailable(final Handler handler,
            final int timeout) {
        new Thread() {
            private boolean responded = false;

            @Override
            public void run() {
                URL url = null;
                try {
                    url = new URL("http://your_server_addres.com");
                } catch (MalformedURLException e1) {
                    e1.printStackTrace();
                }
                String host = "";
                if (null != url) {
                    host = url.getHost();
                }

                Log.i("NetworkCheck", "[PING] host: " + host);
                Process process = null;
                try {
                    process = new ProcessBuilder()
                            .command("/system/bin/ping", "-c 1",
                                    "-w " + (timeout / 1000), "-n", host)
                            .redirectErrorStream(true).start();
                } catch (IOException e) {
                    e.printStackTrace();
                }

                InputStream in = process.getInputStream();
                StringBuilder s = new StringBuilder();
                int i;

                try {
                    while ((i = in.read()) != -1) {
                        s.append((char) i);

                        if ((char) i == '\n') {
                            Log.i("NetworkCheck",
                                    "[PING] log: " + s.toString());
                            if (s.toString().contains("64 bytes from")) {
                                // If there were a response from the server at
                                // all, we have Internet access
                                responded = true;
                            }
                            s.delete(0, s.length());
                        }
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    // Destroy the PING process
                    process.destroy();

                    try {
                        // Close the input stream - avoid memory leak
                        in.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }

                    // Send the response to the handler, 1 for success, 0
                    // otherwise
                    handler.sendEmptyMessage(!responded ? 0 : 1);
                }
            }
        }.start();
    }

处理程序：

/**
 * Handler used that receives the connection status for the Internet.
 * If no active Internet connection will retry #CONNECTION_RETRY_MAX times
 */
private static Handler listenForNetworkAvailability = new Handler() {
    @Override
    public void handleMessage(Message msg) {
        if (msg.what != 1) { // code if not connected
            Log.i("NetworkCheck", "not connected");

            if (retryConnectionNumber <= CONNECTION_RETRY_MAX) {
                Log.i("NetworkCheck", "checking for connectivity");
                Here you could disable & re-enable your WIFI/3G connection before retry

                // Start the ping process again with delay
                Handler handler = new Handler();
                handler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        isNetworkAvailable(listenForNetworkAvailability, REQUEST_TIMEOUT);
                    }
                }, 5000);
                retryConnectionNumber++;
            } else {
                Log.i("NetworkCheck", "failed to establish an connection");
                // code if not connected
            }
        } else {            
            Log.i("NetworkCheck", "connected");
            retryConnectionNumber = 0;
            // code if connected
        }
    }
}

Answer 2

这样的事情会起作用：

private boolean haveNetworkConnection() {
        boolean haveConnectedWifi = false;
        boolean haveConnectedMobile = false;

        ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo[] netInfo = cm.getAllNetworkInfo();
        for (NetworkInfo ni : netInfo) {
            if (ni.getTypeName().equalsIgnoreCase("WIFI"))
                if (ni.isConnected())
                    haveConnectedWifi = true;
            if (ni.getTypeName().equalsIgnoreCase("MOBILE"))
                if (ni.isConnected())
                    haveConnectedMobile = true;
        }
        return haveConnectedWifi || haveConnectedMobile;
    }

我已经从here复制了这段代码（我理解代码 - 我只是为了方便用户而在这里添加代码+管理员告诉我你应该这样做并记下原帖）。我个人会把它分成两个功能，一个用于移动，一个用于wifi，但这个选择取决于你。

有效的方法来检查慢速互联网连接，并区分网络连接和Android中的实际互联网连接

2 个答案: