当没有互联网连接时，应用程序崩溃

问题描述：

我正在开发一个用户尝试上传文件到AWS S3的Android项目。开发人员身份验证使用AWS Cognito完成。因此，在此过程是在用户尝试将文件上传到S3之前，用户必须使用AWS Cogntio获取凭证。之后用户上传文件。这个过程发生在用户选择文件的背景，然后单击确定。如果互联网可用，一切都会好起来。否则，应用程序崩溃。这是代码的一部分。当没有互联网连接时，应用程序崩溃

这里Auth类扩展了AWSAbstractCognitoDeveloperIdentityProvider。

 Auth developerProvider = new Auth(
        null, 
        "ap-northeast-1:a871fa5f-2-480d-baa6-b4ed31437244", 
        Regions.AP_NORTHEAST_1); 

    CognitoCachingCredentialsProvider credentialsProvider = new CognitoCachingCredentialsProvider(
        this.ctx.getApplicationContext(), 
        developerProvider, 
        Regions.AP_NORTHEAST_1); 

      HashMap<String, String> loginsMap = new HashMap<String, String>(); 
      loginsMap.put("login.cool.app", "7386872"); 
      credentialsProvider.setLogins(loginsMap); 
      credentialsProvider.refresh();

应用在该行

  credentialsProvider.refresh();

错误它显示崩溃：

 I/AmazonHttpClient: Unable to execute HTTP request: Unable to resolve host "cognito-identity.ap-northeast-1.amazonaws.com": No address associated with hostname 
               java.net.UnknownHostException: Unable to resolve host "cognito-identity.ap-northeast-1.amazonaws.com": No address associated with hostname 
                at java.net.InetAddress.lookupHostByName(InetAddress.java:427) 
                at java.net.InetAddress.getAllByNameImpl(InetAddress.java:252) 
                at java.net.InetAddress.getAllByName(InetAddress.java:215) 
                at com.android.okhttp.HostResolver$1.getAllByName(HostResolver.java:29) 
                at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:232) 
                at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:124) 
                at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:272) 
                at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:211) 
                at com.android.okhttp.internal.http.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:382) 
                at com.android.okhttp.internal.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:106) 
                at com.android.okhttp.internal.http.HttpURLConnectionImpl.getOutputStream(HttpURLConnectionImpl.java:217) 
                at com.android.okhttp.internal.http.DelegatingHttpsURLConnection.getOutputStream(DelegatingHttpsURLConnection.java:218) 
                at com.android.okhttp.internal.http.HttpsURLConnectionImpl.getOutputStream(HttpsURLConnectionImpl.java:25) 
                at com.amazonaws.http.UrlHttpClient.writeContentToConnection(UrlHttpClient.java:128) 
                at com.amazonaws.http.UrlHttpClient.execute(UrlHttpClient.java:65) 
                at com.amazonaws.http.AmazonHttpClient.executeHelper(AmazonHttpClient.java:353) 
                at com.amazonaws.http.AmazonHttpClient.execute(AmazonHttpClient.java:196) 
                at com.amazonaws.services.cognitoidentity.AmazonCognitoIdentityClient.invoke(AmazonCognitoIdentityClient.java:533) 
                at com.amazonaws.services.cognitoidentity.AmazonCognitoIdentityClient.getCredentialsForIdentity(AmazonCognitoIdentityClient.java:406) 
                at com.amazonaws.auth.CognitoCredentialsProvider.populateCredentialsWithCognito(CognitoCredentialsProvider.java:627) 
                at com.amazonaws.auth.CognitoCredentialsProvider.startSession(CognitoCredentialsProvider.java:553) 
                at com.amazonaws.auth.CognitoCredentialsProvider.refresh(CognitoCredentialsProvider.java:503) 
                at com.amazonaws.auth.CognitoCachingCredentialsProvider.refresh(CognitoCachingCredentialsProvider.java:462) 
                at com.amazonaws.auth.CognitoCachingCredentialsProvider.getIdentityId(CognitoCachingCredentialsProvider.java:413) 
                at com.amazonaws.auth.CognitoCredentialsProvider.populateCredentialsWithCognito(CognitoCredentialsProvider.java:620) 
                at com.amazonaws.auth.CognitoCredentialsProvider.startSession(CognitoCredentialsProvider.java:553) 
                at com.amazonaws.auth.CognitoCredentialsProvider.refresh(CognitoCredentialsProvider.java:503) 
                at com.amazonaws.auth.CognitoCachingCredentialsProvider.refresh(CognitoCachingCredentialsProvider.java:462) 
                at com.example.sandesh.filer.UpDown.upload.doInBackground(upload.java:89) 
                at com.example.sandesh.filer.UpDown.upload.doInBackground(upload.java:27) 
                at android.os.AsyncTask$2.call(AsyncTask.java:292) 
                at java.util.concurrent.FutureTask.run(FutureTask.java:237) 
                at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 
                at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 
                at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 
                at java.lang.Thread.run(Thread.java:818)

反正有没有尝试抓住它？或任何解决方案，以避免崩溃？

谢谢。

http://developer.android.com/reference/android/net/NetworkInfo.html#isConnected%28%29 – F43nd1r

你为什么不先检查互联网连接？ –

栈跟踪不是来自崩溃，而是INFO级别的日志消息。系统使用ERROR日志级别记录崩溃。 – laalto

答

经过很多的斗争，我想到了它。这个问题是由于互联网连接低而脆弱造成的。虽然应用程序连接到互联网，但这不是一个活跃的互联网连接。无法访问。所以我通过检查应用程序是否连接到互联网来解决问题，并通过ping google.com来查找互联网是否可访问。谢谢。

 public class internetchek extends AsyncTask<Void,Void,Void> { 

public boolean connection; 
Context ctx; 
public internetchek(Context context){ 
    this.ctx = context; 
} 
public internetchek(){ 

} 
@Override 
protected void onPreExecute() { 
    super.onPreExecute(); 
} 

@Override 
protected Void doInBackground(Void... params) { 

    if(isNetworkAvailable(this.ctx)) 
    { 

    Log.d("NetworkAvailable","TRUE"); 
     if(connectGoogle()) 
     { 

      Log.d("GooglePing","TRUE"); 
      connection=true; 
     } 
     else 
     { 

      Log.d("GooglePing","FALSE"); 
      connection=false; 
     } 
    } 
    else { 

     connection=false; 
    } 


    return null; 
} 

@Override 
protected void onPostExecute(Void aVoid) { 
    super.onPostExecute(aVoid); 
} 

public static boolean isNetworkAvailable(Context context) { 
    ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE); 
    NetworkInfo netInfo = cm.getActiveNetworkInfo(); 
    if (netInfo != null && netInfo.isConnected()) { 
     return true; 
    } 
    return false; 
} 

public static boolean connectGoogle() { 
    try { 
     HttpURLConnection urlc = (HttpURLConnection) (new URL("http://www.google.com").openConnection()); 
     urlc.setRequestProperty("User-Agent", "Test"); 
     urlc.setRequestProperty("Connection", "close"); 
     urlc.setConnectTimeout(10000); 
     urlc.connect(); 
     return (urlc.getResponseCode() == 200); 

    } catch (IOException e) { 

     Log.d("GooglePing","IOEXCEPTION"); 
     e.printStackTrace(); 
     return false; 
    } 
}

}

有时你可能会被重定向。更好地使用'return（httpURLConnection.getResponseCode（）> = 200 && httpURLConnection.getResponseCode（） CodeWalker

答

一旦我在我的应用程序中实施了检查，看看是否有任何互联网连接。你可以看看这个，并决定是否要实现这一点。

public class ConnectionDetector { 

private Context context; 

public ConnectionDetector(Context cont){ 
this.context = cont; 
} 

public boolean isConnectingToInternet(){ 
ConnectivityManager connectivity = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE); 
if (connectivity != null) 
{ 
    NetworkInfo[] info = connectivity.getAllNetworkInfo(); 
    if (info != null) { 
     for (int i = 0; i < info.length; i++) { 
      if (info[i].getState() == NetworkInfo.State.CONNECTED) { 
       return true; 
      } 
     } 
    } 

} 
return false; 
} 
}

您可以在OnCreate方法来初始化这个类的一个对象。

最后在你上传文件之前调用这个类的方法。

Boolean isInternetConnected = cd.isConnectingToInternet(); 
if (isInternetConnected) 
{ 
    //upload files here 
}

希望这会有所帮助。

答

你可以用try/catch来包围你的代码。

try { 
    //your code 
} catch(Exception e) { 
Toast.makeText(getApplicationContext(), "Error connecting to network.", Toast.LENGTH_SHORT).show(); 
}

但是可以通过做你运行它的权利之前，网络检查可以防止你的代码的运行不必要的。

当没有互联网连接时，应用程序崩溃

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