最简单的解决办法是

在大多数情况下，如果他/她想连接到远程服务器，只会检查互联网连接，所以简单和最好的解决方案是ping你的服务器，如下所示。

public boolean isConnected() {
    final String command = "ping -c 1 yourExmapleDomain.com";
    boolean isConnected = false;
    try {
        isConnected = Runtime.getRuntime().exec(command).waitFor() == 0;
    } catch (InterruptedException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return isConnected;
}

这对我很有用。试试吧。

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    try {
        URL url = new URL("http://stackoverflow.com/posts/11642475/edit" );
        //URL url = new URL("http://www.nofoundwebsite.com/" );
        executeReq(url);
        Toast.makeText(getApplicationContext(), "Webpage is available!", Toast.LENGTH_SHORT).show();
    }
    catch(Exception e) {
        Toast.makeText(getApplicationContext(), "oops! webpage is not available!", Toast.LENGTH_SHORT).show();
    }
}

private void executeReq(URL urlObject) throws IOException
{
    HttpURLConnection conn = null;
    conn = (HttpURLConnection) urlObject.openConnection();
    conn.setReadTimeout(30000);//milliseconds
    conn.setConnectTimeout(3500);//milliseconds
    conn.setRequestMethod("GET");
    conn.setDoInput(true);

    // Start connect
    conn.connect();
    InputStream response =conn.getInputStream();
    Log.d("Response:", response.toString());
}}

这段代码将帮助您找到互联网是否打开。

public final boolean isInternetOn() {
        ConnectivityManager conMgr = (ConnectivityManager) this.con
                .getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo info = conMgr.getActiveNetworkInfo();
        return (info != null && info.isConnected());
}

此外，您应该提供以下权限

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

public boolean isOnline() {
    boolean var = false;
    ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    if ( cm.getActiveNetworkInfo() != null ) {
        var = true;
    }
    return var;
} 

我是这样做的。 我想会更短更有可读性。

干杯!

Saiyan

The other answers that use ConnectivityManager are wrong because having a network connection doesn't mean you have internet access. For example, the user might be connected to a coffee shop's WiFi portal but can't get to the internet. To check that the internet is accessible you have to try to connect to an actual server. Normally when you want to do this you have a specific server in mind that you want to connect to, so go ahead and check if you can connect to that server. Here's a simple method for checking connectivity to a server.

private boolean isOnTheInternet() {
    try {
        URLConnection urlConnection = new URL("http://yourserver").openConnection();
        urlConnection.setConnectTimeout(400);
        urlConnection.connect();
        return true;
    } catch (Exception e) {
        return false;
    }
}

设置ConnectTimeout的原因是，否则它默认为TCP超时，可以有很多秒长。

还要注意的是，Android不允许你在主线程上运行这个程序。

有不止一种编码方式真是太棒了。 下面是我的例子。

ConnectivityManager icheck = getSystemService(Context.CONNECTIVITY_SERVICE);

TextView tv = findViewById(R.id.textView1);

boolean wifi = icheck.getActiveNetworkInfo() != null;
        if(wifi) {
        tv.setText("Internet is on.");  
        } else {
             tv.setText("Internet is off.");    
        }

祝你好运。