在使用InputStreamReader进行URL读取时出现异常。

huangapple
go评论117阅读模式
英文:

Exception in using InputStreamReader for URL reading

问题

以下是您提供的内容的翻译部分：

  1. public String GetString() {
  2.     String URL_API = "https://api.openweathermap.org/data/2.5/onecall?lat=52.249137&lon=104.362658&exclude=minutely,daily&appid=8eac3b7a97a56cb537f453eb7a*****";
  3.     String s = "开发异常";
  4.     try {
  5.         URL url = new URL(URL_API);
  6.         URLConnection con = url.openConnection();
  7.         InputStreamReader inputStreamReader = new InputStreamReader(con.getInputStream());
  8.         BufferedReader sc = new BufferedReader(inputStreamReader);
  9.         while ((s = sc.readLine()) != null) {
  10.             s += s + sc.readLine();
  11.         }
  12.     } catch (IOException e) {
  13.         e.printStackTrace();
  14.     }
  15.     return s;
  16. }
  1. 2020-08-23 18:19:29.549 19308-19308/com.example.teststart1 E/AndroidRuntime: FATAL EXCEPTION: main
  2.     Process: com.example.teststart1, PID: 19308
  3.     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.teststart1/com.example.teststart1.MainActivity}: android.os.NetworkOnMainThreadException
  4.         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2723)
  5.         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2784)
  6.         ...
  7.         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823)

请注意，这只是您提供内容的翻译部分，我已经排除了代码以外的所有其他内容。如果您有任何问题或需要进一步的帮助，请随时问我。

英文:

gues! I am doing a program to get weather from json(weathermapApi). I did function for get all text from resource, but Android Studio don't compile my project. Exception on
InputStreamReader inputStreamReader = new InputStreamReader(con.getInputStream());
help me, PLEASE!

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: java -->

  1.  public String GetString() {
  2.         String URL_API= &quot;https://api.openweathermap.org/data/2.5/onecall?lat=52.249137&amp;lon=104.362658&amp;exclude=minutely,daily&amp;appid=8eac3b7a97a56cb537f453eb7a*****&quot;;
  3.         String s = &quot;Exception of develop&quot;;
  4.         try {
  5.             URL url = new URL(URL_API);
  6.             URLConnection con = url.openConnection();
  7.             InputStreamReader inputStreamReader = new InputStreamReader(con.getInputStream());
  8.             BufferedReader sc = new BufferedReader(inputStreamReader);
  9.             while ((s=sc.readLine())!=null) {
  10.               s += s + sc.readLine();
  11.             }
  12.         } catch (IOException e) {
  13.             e.printStackTrace();
  14.         }
  17.         return s;

<!-- end snippet -->

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-html -->

  1. 2020-08-23 18:19:29.549 19308-19308/com.example.teststart1 E/AndroidRuntime: FATAL EXCEPTION: main
  2.     Process: com.example.teststart1, PID: 19308
  3.     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.teststart1/com.example.teststart1.MainActivity}: android.os.NetworkOnMainThreadException
  4.         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2723)
  5.         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2784)
  6.         at android.app.ActivityThread.-wrap12(ActivityThread.java)
  7.         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1523)
  8.         at android.os.Handler.dispatchMessage(Handler.java:102)
  9.         at android.os.Looper.loop(Looper.java:163)
  10.         at android.app.ActivityThread.main(ActivityThread.java:6238)
  11.         at java.lang.reflect.Method.invoke(Native Method)
  12.         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:933)
  13.         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823)
  14.      Caused by: android.os.NetworkOnMainThreadException
  15.         at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1303)
  16.         at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:86)
  17.         at java.net.Inet6AddressImpl.lookupAllHostAddr(Inet6AddressImpl.java:74)
  18.         at java.net.InetAddress.getAllByName(InetAddress.java:752)
  19.         at com.android.okhttp.internal.Network$1.resolveInetAddresses(Network.java:29)
  20.         at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:187)
  21.         at com.android.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:156)
  22.         at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:98)
  23.         at com.android.okhttp.internal.http.HttpEngine.createNextConnection(HttpEngine.java:346)
  24.         at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:329)
  25.         at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:247)
  26.         at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:457)
  27.         at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:405)
  28.         at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:243)
  29.         at com.android.okhttp.internal.huc.DelegatingHttpsURLConnection.getInputStream(DelegatingHttpsURLConnection.java:210)
  30.         at com.android.okhttp.internal.huc.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java)
  31.         at com.example.teststart1.MainActivity.GetString(MainActivity.java:42)
  32.         at com.example.teststart1.MainActivity.onCreate(MainActivity.java:33)
  33.         at android.app.Activity.performCreate(Activity.java:6857)
  34.         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
  35.         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2676)
  36.         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2784)&#160;
  37.         at android.app.ActivityThread.-wrap12(ActivityThread.java)&#160;
  38.         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1523)&#160;
  39.         at android.os.Handler.dispatchMessage(Handler.java:102)&#160;
  40.         at android.os.Looper.loop(Looper.java:163)&#160;
  41.         at android.app.ActivityThread.main(ActivityThread.java:6238)&#160;
  42.         at java.lang.reflect.Method.invoke(Native Method)&#160;
  43.         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:933)&#160;
  44.         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823)&#160;

<!-- end snippet -->

答案1

得分: 0

android.os.NetworkOnMainThreadException

这个异常是在应用程序试图在其主线程上执行网络操作时抛出的。

你应该使用线程，例如：

  1. Thread thread = new Thread(new Runnable() {
  2.     
  3.     @Override
  4.     public void run() {
  5.         try  {
  6.             //在这里添加你的代码
  7.         } catch (Exception e) {
  8.             e.printStackTrace();
  9.         }
  10.     }
  11. });
  13. thread.start();

确保在 Android 的 manifest.xml 文件中添加了这个权限：

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

有几种方法可以避免 android.os.NetworkOnMainThreadException，例如：

  1. 异步任务（Async Task）（已被弃用）
  2. 意图服务和广播接收器（Intent service and broadcast receiver）

你可以使用像以下这样的库：

  1. Volley
  2. Retrofit
  3. OKHTTP

如果你在谷歌上搜索，你可以找到很多在后台调用 API 并在主线程中提供回调的选项或库。

英文:

android.os.NetworkOnMainThreadException

This exception is thrown when an application attempts to perform a networking operation on its main thread.

You should use threads like

  1. Thread thread = new Thread(new Runnable() {
  3.     @Override
  4.     public void run() {
  5.         try  {
  6.             //Your code goes here
  7.         } catch (Exception e) {
  8.             e.printStackTrace();
  9.         }
  10.     }
  11. });
  13. thread.start();

Check that you have added this permission in android manifest.xml file:

  1. &lt;uses-permission android:name=&quot;android.permission.INTERNET&quot;/&gt;

There are several solutions to avoid android.os.NetworkOnMainThreadException like

  1. Async Task (Which is deprecated)
  2. Intent service and broadcast reciever

You can Use libraries like:

  1. Volley
  2. retrofit
  3. OKHTTP

If you google it you can find plenty of option or libraries to call API in background and provide call back in Main thread.

huangapple
  • 本文由 发表于 2020年8月23日 18:32:05
  • 转载请务必保留本文链接：https://go.coder-hub.com/63545921.html
  • android
  • api
  • html
  • java
  • url
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