Whats wrong with my code for checking if a site is online or not?

Question

I had been working on a app for my college project. It that application i just want to check if a website is available(online) or not. If it is available then open it in webview and if it isn't open a pre specified website.

After some research I landed up till the following code but it does not seem to work. App always opens bing.com (i.e value of flag does not get updated after running pingHost)

public class MainActivity extends Activity {

    WebView web1;
    String Address;
    int flag=0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Timer repeatTask = new Timer();
        repeatTask.scheduleAtFixedRate(new TimerTask() {

            @Override
            public void run() {
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        pingHost("http://www.google.com", 80, 5000);
                        if (flag==1) {
                            web1 = (WebView) findViewById(R.id.webView1);
                            Address = "https://learn2lead.home.blog";
                            WebSettings webSetting = web1.getSettings();
                            webSetting.setBuiltInZoomControls(true);
                            webSetting.setJavaScriptEnabled(true);
                            web1.setWebViewClient(new WebViewClient());
                            web1.loadUrl(Address);
                        } else if (flag==0){
                            web1 = (WebView) findViewById(R.id.webView1);
                            Address = "http://bing.com";
                            WebSettings webSetting = web1.getSettings();
                            webSetting.setBuiltInZoomControls(true);
                            webSetting.setJavaScriptEnabled(true);
                            web1.setWebViewClient(new WebViewClient());
                            web1.loadUrl(Address);
                        }
                    }
                });
            }
        }, 0, 10000);

    public void pingHost(final String host, final int port, final int timeout) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try (Socket socket = new Socket()) {
                    socket.connect(new InetSocketAddress(host, port), timeout);
                    flag = 1;
                } catch (IOException e) {
                    flag = 0;
                }
            }


        }).start();
    }
}

You need to wait for `pingHost` to return before using the `flag` value, why does it need to be a seperate thread? — Scary Wombat, Apr 09 '19 at 05:05
On first glance you seems to be a victim of Asynchronous Call . `pingHost` method running of separate thread . So `flag` is always 0 inside `TimerTask` . You need wait for it to ping competed first . — ADM, Apr 09 '19 at 05:07
Did you wait 10secs to see if it changes to the website you want? Also log the exception in `pingHost` instead of ignoring it. — Kartik, Apr 09 '19 at 05:09
@ScaryWombat App gives runtime error Network on main thread if it is not on sepreate thread — Pranav Gawade, Apr 09 '19 at 05:10
Yes it does not change after 10 seconds. and sadly i dont know how to log because I only started using android studio 2 days back — Pranav Gawade, Apr 09 '19 at 05:12
try `Log.d("tag", e)` or `e.printStacktrace()` before `flag = 0;` — Kartik, Apr 09 '19 at 05:14
I am really beginner in android studio programming. can anyone please do the edits in code and answer here ... sorry for the trouble but i am not able to understand many things that you are saying. @Kartik — Pranav Gawade, Apr 09 '19 at 05:26

UdayaLakmal · Answer 1 · 2019-04-09T07:39:25.720

Try

public class MainActivity extends Activity {

WebView web1;
String Address;
int flag = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Timer repeatTask = new Timer();
    repeatTask.scheduleAtFixedRate(new TimerTask() {

        @Override
        public void run() {
            if (isInternetAvailable()){
                flag = 1;
            }else{
                flag = 0;
            }
            System.out.println("pingHost flag: " + flag );
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    if (flag == 1) {
                        web1 = (WebView) findViewById(R.id.webView1);
                        Address = "https://learn2lead.home.blog";
                        WebSettings webSetting = web1.getSettings();
                        webSetting.setBuiltInZoomControls(true);
                        webSetting.setJavaScriptEnabled(true);
                        web1.setWebViewClient(new WebViewClient());
                        web1.loadUrl(Address);
                    } else if (flag == 0) {
                        web1 = (WebView) findViewById(R.id.webView1);
                        Address = "http://bing.com";
                        WebSettings webSetting = web1.getSettings();
                        webSetting.setBuiltInZoomControls(true);
                        webSetting.setJavaScriptEnabled(true);
                        web1.setWebViewClient(new WebViewClient());
                        web1.loadUrl(Address);
                    }
                }
            });
        }
    }, 0, 10000);
}

public boolean isInternetAvailable() {
    try {
        InetAddress ipAddr = InetAddress.getByName("google.com");
        //You can replace it with your name
        return !ipAddr.equals("");

    } catch (Exception e) {
        return false;
    }
}
}

Modified your posted question to working.

But implementing you should consider about that timer task close and think it really nessary 10sec period.

to check whether internet available this is much reliable and fast

public boolean isInternetAvailable() {
        try {
            int timeoutMs = 1500;
            Socket sock = new Socket();
            SocketAddress sockaddr = new InetSocketAddress("8.8.8.8", 53);

            sock.connect(sockaddr, timeoutMs);
            sock.close();

            return true;
        } catch (IOException e) { return false; }
    }

check : https://stackoverflow.com/a/27312494/1025070

The InetAddress class has a cache to store successful as well as unsuccessful host name resolutions. — Scary Wombat, Apr 09 '19 at 07:00
@ScaryWombat you are right. Please refer https://stackoverflow.com/questions/1560788/how-to-check-internet-access-on-android-inetaddre and check accepted ansewer. — UdayaLakmal, Apr 09 '19 at 07:25
OMG! Worked like charm... I spent two days scraching my head and thinking about it. Thank you so much... @UdayaLakmal — Pranav Gawade, Apr 09 '19 at 13:13

Whats wrong with my code for checking if a site is online or not?

1 Answers1