Android判断是否可以使用外网

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app在很多时候需要判断是否能够上外网，并将结果反馈给用户。想到这里很多同学估计会想到判断网络通道是不是打开：

public synchronized boolean isNetworkConnected() {
        ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo ni = cm.getActiveNetworkInfo();
        return ni != null && ni.isConnectedOrConnecting();
    }

上面这段代码只能判断出数据通道是否打开，如果3G/4G流量或者WiFi无法使用，那么这个判断将不再适用。
下面，推荐几种判断网络是否真正可用的方案：
方案一、使用Android自带的api去ping IP地址：

public void pingNet() {
        try {
            if (InetAddress.getByName("120.25.236.134").isReachable(3000)) {
                Log.d("morse", "pingNet onSuccess");
            } else {
                Log.d("morse", "pingNet onFailure");
            }
        } catch (Throwable e) {
            Log.d("morse", "pingNet onFailure");
        }
    }

方案二、使用Android自带的api去解析域名：

public void analysisNet() {
        // 这种方式如果ping不通 会阻塞一分钟左右
        // 也是要放在另一个线程里面ping
        try {
            InetAddress addr = InetAddress.getByName("www.baidu.com");
            if (!addr.isLoopbackAddress() && addr instanceof Inet4Address) {
                Log.d("morse", "analysisNet onSuccess ");
            } else {
                Log.d("morse", "analysisNet onFailure 0");
            }
        } catch (Throwable e) {
            Log.d("morse", "analysisNet onFailure 1 " + e);
        }
    }

方案三、使用adt命令去ping IP：

public void ping() {
        String result = null;
        try {
            String ip = "www.baidu.com";// ping 的地址，可以换成任何一种可靠的外网
            Process p = Runtime.getRuntime().exec("ping -c 3 -w 100 " + ip);// ping网址3次
            // 读取ping的内容，可以不加
            InputStream input = p.getInputStream();
            BufferedReader in = new BufferedReader(new InputStreamReader(input));
            StringBuffer stringBuffer = new StringBuffer();
            String content = "";
            while ((content = in.readLine()) != null) {
                stringBuffer.append(content);
            }
            Log.d("------ping-----", "result content : " + stringBuffer.toString());
            // ping的状态
            final int status = p.waitFor();
            if (status == 0) {
                Log.d("morse", "ping onSuccess");
            } else {
                Log.d("morse", "ping onFailure");
            }
        } catch (IOException e) {
            Log.d("morse", "ping onFailure");
        } catch (InterruptedException e) {
            Log.d("morse", "ping onFailure");
        } finally {

        }
    }

方案四、使用socket连接：

private boolean isConnect(String ip) {
        Socket socket = null;
        try {
            socket = new Socket(ip, 80);
            socket.setKeepAlive(true);
            socket.setSoTimeout(10);
            Log.d("morse", socket.isConnected() ? "true" : "false");
            if (socket.isConnected()) {
                socket.sendUrgentData(0xFF);
                Log.d("morse", "连接成功");
                if (0 != count) {
                    count = 0;
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }

注意：使用这种方式一定要发送心跳包，不然检测状态不会改变。