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Android开发中判断当前网络是否可上网，而不是判断是否已连接

问题场景:

最近开发中遇到一个bug,在设置日期和时间时,手动设置时间,开关机时间正常.使用自动获取网络时间,连接可上网的网络,获取时间也是正常.

但在使用静态IP时或者网络不可上网时,获取的时间就是异常的.

问题分析:

代码如下:

private void setAutoTime() { if (isNetworkAvalible(getActivity())) { Log.d("setRTCTime", "===setAutoTime===isNetworkAvalible===="); final Calendar calendar = Calendar.getInstance(); new Thread(new Runnable() { @Override public void run() { URL urlTime = null;//取得资源对象 try { urlTime = new URL("https://www.baidu"); URLConnection uc = urlTime.openConnection();//生成连接对象 uc.setConnectTimeout(3000); ucnnect(); //发出连接 long autoTime = uc.getDate(); //取得网站日期时间 Date date = new Date(autoTime); //转换为标准时间对象 date.getDate(); Log.d("setRTCTime", "===setAutoTime===autoTime====" + autoTime); if (autoTime == 0) { return; } } catch (IOException e) { e.printStackTrace(); } } }).start(); }}public boolean isNetworkAvalible(Context context) {// 获得网络状态管理器 ConnectivityManager connectivityManager = (ConnectivityManager) context .getSystemService(Context.CONNECTIVITY_SERVICE); if (connectivityManager == null) { return false; } else { // 建立网络数组 NetworkInfo[] net_info = connectivityManager.getAllNetworkInfo(); if (net_info != null) { for (int i = 0; i < net_info.length; i++) { // 判断获得的网络状态是否是处于连接状态 if (net_info[i].getState() == NetworkInfo.State.CONNECTED) { return true; } } } } return false;}

以上代码初看并未发现问题,然而仔细分析发现isNetworkAvalible()方法只能判断当前网线是否接入,假如使用的是静态IP,即使网线不接,返回的也是true.问题的根本原因就是这个接口不能判断出静态IP或者网络不能上网的情况.

既然问题原因找到了,那解决办法就是:通过ping网关的方式去检测网络是否能够正常上网.

解决方法:

具体代码如下:

private void setAutoTime() { if (isNetworkAvalible(getActivity())) { Log.d("setRTCTime", "===setAutoTime===isNetworkAvalible===="); final Calendar calendar = Calendar.getInstance(); new Thread(new Runnable() { @Override public void run() { URL urlTime = null;//取得资源对象 try { boolean isNetAval = pingNetWork(getGateway());//ping网关 Log.d("setRTCTime", "===setAutoTime===isNetAval====" + isNetAval); if(!isNetAval){ syncRTCTime();//网络无效使用RTC时间 return; } urlTime = new URL("https://www.baidu"); URLConnection uc = urlTime.openConnection();//生成连接对象 uc.setConnectTimeout(3000); ucnnect(); //发出连接 long autoTime = uc.getDate(); //取得网站日期时间 Date date = new Date(autoTime); //转换为标准时间对象 date.getDate(); Log.d("setRTCTime", "===setAutoTime===autoTime====" + autoTime); if (autoTime == 0) { syncRTCTime();//网络获取不到时间使用RTC时间 return; } syncNetTime(autoTime); //获取到网络时间同步系统时间 } catch (IOException e) { e.printStackTrace(); } } }).start(); }else{ syncRTCTime();//网络未连接使用RTC时间 }}public boolean isNetworkAvalible(Context context) {// 获得网络状态管理器 ConnectivityManager connectivityManager = (ConnectivityManager) context .getSystemService(Context.CONNECTIVITY_SERVICE); if (connectivityManager == null) { return false; } else { // 建立网络数组 NetworkInfo[] net_info = connectivityManager.getAllNetworkInfo(); if (net_info != null) { for (int i = 0; i < net_info.length; i++) { // 判断获得的网络状态是否是处于连接状态 if (net_info[i].getState() == NetworkInfo.State.CONNECTED) { return true; } } } } return false;}/** * 获取网关 * @return*/private String getGateway() {ConnectivityManager connectivity = (ConnectivityManager) getActivity().getSystemService(Context.CONNECTIVITY_SERVICE);LinkProperties properties = connectivity.getLinkProperties(connectivity.getActiveNetwork());String ip = "0.0.0.0";LinkAddress linkAddress = properties.getLinkAddresses().get(1);for (int i = 0; i < properties.getLinkAddresses().size(); i++) {LinkAddress linkAddressTmp = properties.getLinkAddresses().get(i);String tmp = linkAddressTmp.getAddress().getHostAddress();if (!tmpntains(":") && !tmp.equals("0.0.0.0")) {ip = tmp;linkAddress = linkAddressTmp;break;}}String mask = dealWithMask(linkAddress.getPrefixLength());String gateway = "0.0.0.0";for (RouteInfo info : properties.getRoutes()) {String tmp = info.getGateway().getHostAddress();//Log.d(TAG, "initDate: gateway = " + tmp);if (!tmp.equals("0.0.0.0") && !tmpntains("::") && !tmpntains(":")) {gateway = tmp;break;}}return gateway;}private String dealWithMask(int prefixLength) {int mask = 0xffffff << (32 - prefixLength);return ((mask>>24)&0xff) + "." + ((mask>>16)&0xff) + "."+ ((mask>>8)&0xff) + "." + (mask&0xff);}/*** 判断是否是 静态IP 模式* @return*/private static boolean isStaticIp() {boolean state = false;if (mEthernetManager == null) {return false;}IpConfiguration.IpAssignment ipAssignment = mEthernetManager.getConfiguration("eth0").ipAssignment;if (ipAssignment == IpConfiguration.IpAssignment.STATIC) {state = true;} else if (ipAssignment == IpConfiguration.IpAssignment.DHCP) {state = false;}return state;}/*** ping 网关* @param cIP* @return*/private static final boolean pingNetWork(final String cIP) {String result = null;try {Process p = Runtime.getRuntime().exec("ping -c 1 "+cIP);int status = p.waitFor();if (status == 0) {result = "success";return true;} else {// 场景：当静态IP时，不能上网时，p.waitFor() 返回都是false，无法判断。// 通过 p.getInputStream() 获取的信息进行判断// a、不插网线会返还字符串 ping info:From 196.168.1.128: icmp_seq=1 Destination Host Unreachable// b、插网线 为null ping info:// 缺陷：检测时间较长if(isStaticIp()) {InputStream input = p.getInputStream();BufferedReader in = new BufferedReader(new InputStreamReader(input));StringBuffer buffer = new StringBuffer();String line = "";while ((line = in.readLine()) != null) {bufferend(line);if (linentains("Destination Host Unreachable")) {result = "failed";break;}else{result = "success";}//Log.i(TAG, "ping info:" + line);}if(result.equals("success")) {return true;}}else{result = "failed";}}} catch (IOException e) {result = "IOException";} catch (InterruptedException e) {result = "InterruptedException";} finally {//Log.d(TAG, "ping result = " + result);}return false;}private void syncNetTime(long time){final Calendar calendar = Calendar.getInstance();calendar.setTimeInMillis(time);int year = calendar.get(Calendar.YEAR);int month = calendar.get(Calendar.MONTH);int day = calendar.get(Calendar.DAY_OF_MONTH);int hour = calendar.get(Calendar.HOUR_OF_DAY);int minute = calendar.get(Calendar.MINUTE);int sec = calendar.get(Calendar.SECOND);if (time / 1000 < Integer.MAX_VALUE) {((AlarmManager) getActivity().getSystemService(Context.ALARM_SERVICE)).setTime(time);yearAuto = year;monthAuto = month;dayAuto = day;}setRTCTime();}private void syncRTCTime(){final Calendar calendar = Calendar.getInstance();int year = calendar.get(Calendar.YEAR);int month = calendar.get(Calendar.MONTH);int day = calendar.get(Calendar.DAY_OF_MONTH);int hour = calendar.get(Calendar.HOUR_OF_DAY);int minute = calendar.get(Calendar.MINUTE);int sec = calendar.get(Calendar.SECOND);long when = calendar.getTimeInMillis();if (when / 1000 < Integer.MAX_VALUE) {((AlarmManager) getActivity().getSystemService(Context.ALARM_SERVICE)).setTime(when);yearAuto = year;monthAuto = month;dayAuto = day;}setRTCTime();}

目前网络上很多方法都是获取到的网络连接状态,并不能判断网络是否可以正常上网,以上方法可以解决这个问题,不过有时候ping的时候会比较慢一些.

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