在执行 HTTPClient 之前如何检查互联网连接 [重复]

Question

我正在创建 android 应用程序，该应用程序调用我在服务器上创建的 rest 服务，并且服务器正在运行，但由于互联网连接问题，有时我的应用程序运行成功，但有时它崩溃了。我的连接类的代码是

public class CommunicationClass {

@SuppressWarnings("unused")
private static final String TAG = null;
public String Domain;
public HttpClient client;
public HttpPost datapost;
public HttpResponse response;
public BufferedReader reader;
public StringBuilder builder;
public JSONTokener tokener;
public JSONObject finalResult;
List<NameValuePair> namevaluepairs = new ArrayList<NameValuePair>(10);


public void setClient() {
    // TODO Auto-generated method stub
    client = new DefaultHttpClient();
    System.out.println("Created http client");
}
public void setDomain(String st) {
    // TODO Auto-generated method stub
    Domain = st;
    System.out.println("Domain has been set");
}
public void setResponse(){
    response=null;
    System.out.println("Response has been initalized by null");
}
public void setStringBuilder(){
    builder = new StringBuilder();
}
public void setreader(){
    try {
        reader = new BufferedReader(new InputStreamReader(this.response.getEntity().getContent(), "UTF-8"));
        System.out.println("Setting the contents of the Reader");
    } catch (UnsupportedEncodingException e) {
        // TODO Auto-generated catch block
        System.out.println("In the UnsupportedEncodingException catch of the Reader");
        e.printStackTrace();
    } catch (IllegalStateException e) {
        // TODO Auto-generated catch block
        System.out.println("In the IllegalStateException catch of the Reader");
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        System.out.println("In the IOException catch of the Reader");
        e.printStackTrace();
    }

}
public void startpost(String str){
    datapost=new HttpPost(str);
    System.out.println("Created the httppost domain");
}
public void insertdata(String tag,String value){
    namevaluepairs.add(new BasicNameValuePair(tag,value));
    System.out.println("Added the parameter  "+tag);
}
public void trydata(){
    try {
        this.datapost.setEntity(new UrlEncodedFormEntity(this.namevaluepairs));
        System.out.println("Setting the entity");
        try {
            this.response = this.client.execute(this.datapost);
            System.out.println("executing the client");
             if(this.response != null){
                 System.out.println("i am in if of this.response!=null");
             }
             else{
                 System.out.println("i am in else of this.response!=null");
             }
             System.out.println("in response try box");
        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            System.out.println("in ClientProtocolException Catch box");
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            System.out.println("in IOException Catch box");
            e.printStackTrace();
        }
    } catch (UnsupportedEncodingException e) {
        // TODO Auto-generated catch block
        System.out.println("in UnSupported Catch box");
        e.printStackTrace();
    }
}
public void readresponse(){     



    try {
        for (String line = null; (line = reader.readLine()) != null;) {
            builder.append(line).append("\n");

        }
        System.out.println(this.builder);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
     tokener = new JSONTokener(builder.toString());
    try {
         finalResult = new JSONObject(tokener);
        System.out.println("I am in try block of json final result reading");
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        System.out.println("I catch block of jsonException");
        e.printStackTrace();
    } 
}


}

它在 trydata() 行上给了我错误；实际执行 HTTP 客户端，所以我想确保它不应该由于互联网连接而崩溃，但可能会抛出可以捕获或烤面包的异常。伙计们需要这方面的帮助

谢谢！

Answer 1

private boolean isNetworkAvailable() {
    ConnectivityManager connectivityManager 
          = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
    return activeNetworkInfo != null && activeNetworkInfo.isConnected();
}

别忘了：

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

这对我来说很好用。

Answer 2

在调用 Webservice 之前检查 Internet 连接：

 public static boolean isNetworkAvailable(Context context) {
        ConnectivityManager connectivityManager = (ConnectivityManager) context
                .getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetworkInfo = connectivityManager
                .getActiveNetworkInfo();
        return activeNetworkInfo != null && activeNetworkInfo.isConnected();
    }

Answer 3

虽然其他答案是正确的，但它们是部分正确的。如果您想知道您有互联网连接，而不仅仅是连接到 Wi-Fi 热点，您必须 ping 一个站点。 This 是我昨天发现的，如果您已连接但没有通过此热点连接互联网，则可以使用。基本上它 ping 谷歌。对其使用布尔值，并将其放入其他人答案的检查中。

Answer 4

使用这个：

public static Boolean checkForInternetConnection(Context context) {
    final ConnectivityManager conMgr = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    final NetworkInfo activeNetwork = conMgr.getActiveNetworkInfo();
    if (activeNetwork != null && activeNetwork.isConnected()) {
        return true;
    } else {
        return false;
    }

}