讀遙遠的txt文件的Android

Question

我有這樣的代碼來讀取一個遙遠的txt文件的最後一行：

try { 
     URL url = new URL("http://intram.cluny.ensam.fr/meteo/downld02.txt"); 
     BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream())); 
     while(str != null) { 
      ligne=str; 
      str = in.readLine(); 
     } 
     in.close(); 
    } catch (MalformedURLException e) { 
    } catch (IOException e) { 
    } 

此代碼是在工作在我的LG擎天柱L3（安卓2.3.6），但崩潰很細從我的Nexus 7開始（Android 4.2.1）。爲什麼？如何解決它？

編輯： 謝謝您的回答

我不知道什麼是logcat的堆棧跟蹤，但我認爲這是下面的，告訴我，如果我錯了

12-31 18:54:07.469: W/ActivityThread(29021): Application fr.ensam.cluny can be debugged on port 8100... 
12-31 18:54:07.969: D/AndroidRuntime(29021): Shutting down VM 
12-31 18:54:07.969: W/dalvikvm(29021): threadid=1: thread exiting with uncaught exception (group=0x41f6c930) 
12-31 18:54:07.969: E/AndroidRuntime(29021): FATAL EXCEPTION: main 
12-31 18:54:07.969: E/AndroidRuntime(29021): java.lang.RuntimeException: Unable to start activity ComponentInfo{fr.ensam.cluny/fr.ensam.cluny.MainActivity}: android.os.NetworkOnMainThreadException 
12-31 18:54:07.969: E/AndroidRuntime(29021): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at android.app.ActivityThread.access$600(ActivityThread.java:141) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at android.os.Handler.dispatchMessage(Handler.java:99) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at android.os.Looper.loop(Looper.java:137) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at android.app.ActivityThread.main(ActivityThread.java:5039) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at java.lang.reflect.Method.invokeNative(Native Method) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at java.lang.reflect.Method.invoke(Method.java:511) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at dalvik.system.NativeStart.main(Native Method) 
12-31 18:54:07.969: E/AndroidRuntime(29021): Caused by: android.os.NetworkOnMainThreadException 
12-31 18:54:07.969: E/AndroidRuntime(29021): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at java.net.InetAddress.lookupHostByName(InetAddress.java:385) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at java.net.InetAddress.getAllByName(InetAddress.java:214) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:70) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:340) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at libcore.net.http.HttpConnection.connect(HttpConnection.java:128) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:316) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at libcore.net.http.HttpEngine.connect(HttpEngine.java:311) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:290) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:240) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at libcore.net.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:282) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:177) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at java.net.URL.openStream(URL.java:462) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at fr.ensam.cluny.MainActivity.onCreate(MainActivity.java:61) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at android.app.Activity.performCreate(Activity.java:5104) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
12-31 18:54:07.969: E/AndroidRuntime(29021): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
12-31 18:54:07.969: E/AndroidRuntime(29021): ... 11 more 

Answer 1

既然你」我沒有給我們一個堆棧跟蹤，我給這個答案有點猜測。

我的猜測是你得到了NetworkOnMainThreadException。當您嘗試在主UI線程上使用網絡時，此異常會發生在Android 3.0及更高版本上。這也解釋了爲什麼你沒有看到薑餅（Android 2.3）的例外。

要解決此問題，請將所有網絡代碼移動到Thread或AsyncTask。