Android 无连接时强制关闭

Question

我正在制作一个使用互联网连接的应用程序。当我尝试下载数据，但没有互联网连接时，应用程序强制关闭。如果我希望应用程序不抛出强制关闭消息，而是抛出我自己的消息，例如“没有连接...”，然后关闭 Activity ，我需要做什么。谢谢!

我的 logcat 输出:

09-23 14:56:15.411: E/AndroidRuntime(20770): FATAL EXCEPTION: main
09-23 14:56:15.411: E/AndroidRuntime(20770): java.lang.RuntimeException: Unable to start activity ComponentInfo{lt.prasom/lt.prasom.GoodOffers}: java.lang.NullPointerException
09-23 14:56:15.411: E/AndroidRuntime(20770):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at android.os.Handler.dispatchMessage(Handler.java:99)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at android.os.Looper.loop(Looper.java:130)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at android.app.ActivityThread.main(ActivityThread.java:3683)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at java.lang.reflect.Method.invokeNative(Native Method)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at java.lang.reflect.Method.invoke(Method.java:507)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at dalvik.system.NativeStart.main(Native Method)
09-23 14:56:15.411: E/AndroidRuntime(20770): Caused by: java.lang.NullPointerException
09-23 14:56:15.411: E/AndroidRuntime(20770):    at java.io.StringReader.<init>(StringReader.java:46)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at lt.prasom.functions.XMLParser.getDomElement(XMLParser.java:73)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at lt.prasom.GoodOffers.onCreate(GoodOffers.java:68)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
09-23 14:56:15.411: E/AndroidRuntime(20770):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
09-23 14:56:15.411: E/AndroidRuntime(20770):    ... 11 more

Answer 1

以下函数用于检测设备是否连接到网络。

 public static boolean isNetworkAvailable(Context context) {
     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;
  }

您可以调用该函数，如下所示...

if(!isNetworkAvailable(context))
     // Show Toast here...
else
     //perform action ...

希望有帮助..