的Android工作室HttpURLConnection的應用程序崩潰

Question

我是新來的Android和Java的發展，我的工作是Web開發人員和想學習Android的工作室和Java。

像往常一樣學習新語言的時候，我首先要做的就是一些數據庫調用，在此只是JSON調用。

使用HttpURLConnection的，我已經在網上找到例子，它在我的主要功能工作時，我在Android Studio中運行它，但是當我把它裏面按鈕單擊功能和我的手機上運行我的應用程序，我的應用程序崩潰。

我也加了 到清單標籤裏面的AndroidManifest.xml。

這是錯誤我得到

11-22 19:47:46.354 24975-24975/com.example.adis.myapp I/System.out: I am here////////////////////////////////////////// 
11-22 19:47:46.494 24975-24975/com.example.adis.myapp D/AndroidRuntime: Shutting down VM 
11-22 19:47:46.494 24975-24975/com.example.adis.myapp W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x41659e00) 
11-22 19:47:46.514 24975-24975/com.example.adis.myapp E/AndroidRuntime: FATAL EXCEPTION: main 

       Process: com.example.adis.myapp, PID: 24975 
        java.lang.IllegalStateException: Could not execute method for android:onClick 
         at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293) 
       ive Method) 
        Caused by: java.lang.reflect.InvocationTargetException 
         at java.lang.reflect.Method.invokeNative(Native Method) 
         at java.lang.reflect.Method.invoke(Method.java:515) 
         at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
         at android.view.View.performClick(View.java:4457)  
         at android.view.View$PerformClick.run(View.java:18491)  
         at android.os.Handler.handleCallback(Handler.java:733)  
         at android.os.Handler.dispatchMessage(Handler.java:95)  
         at android.os.Looper.loop(Looper.java:136)  
         at android.app.ActivityThread.main(ActivityThread.java:5333)  
         at java.lang.reflect.Method.invokeNative(Native Method)  
         at java.lang.reflect.Method.invoke(Method.java:515)  
         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:895)  
         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:711)  
         at dalvik.system.NativeStart.main(Native Method)  
        Caused by: android.os.NetworkOnMainThreadException 
         at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1148) 
         at java.net.InetAddress.lookupHostByName(InetAddress.java:385) 
         at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236) 
         at java.net.InetAddress.getAllByName(InetAddress.java:214) 
         at com.android.okhttp.internal.Dns$1.getAllByName(Dns.java:28) 
         at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:216) 
         at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:122) 
         at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:292) 
         at com.android.okhttp.internal.http.HttpEngine.sendSocketRequest(HttpEngine.java:255) 
         at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:206) 
         at com.android.okhttp.internal.http.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:345) 
         at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:296) 
         at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponseCode(HttpURLConnectionImpl.java:503) 
         at com.example.adis.myapp.MainActivity.loginFunction(MainActivity.java:85) 
         at java.lang.reflect.Method.invokeNative(Native Method)  
         at java.lang.reflect.Method.invoke(Method.java:515)  
         at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)  
         at android.view.View.performClick(View.java:4457)  
         at android.view.View$PerformClick.run(View.java:18491)  
         at android.os.Handler.handleCallback(Handler.java:733)  
         at android.os.Handler.dispatchMessage(Handler.java:95)  
         at android.os.Looper.loop(Looper.java:136)  
         at android.app.ActivityThread.main(ActivityThread.java:5333)  
         at java.lang.reflect.Method.invokeNative(Native Method)  
         at java.lang.reflect.Method.invoke(Method.java:515)  
         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:895)  
         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:711)  
         at dalvik.system.NativeStart.main(Native Method)  
11-22 19:47:46.524 923-1275/? W/ActivityManager: Force finishing activity com.example.adis.myapp/.MainActivity 

這裏是我的onClick功能

public void loginFunction(View view) throws IOException, JSONException { 


    System.out.println("I am here//////////////////////////////////////////"); 
    try { 

     URL url = new URL("http://echo.jsontest.com/insert-key-here/insert-value-here/key/value"); 
     HttpURLConnection conn = (HttpURLConnection) url.openConnection(); 
     conn.setRequestMethod("GET"); 
     conn.setRequestProperty("Accept", "application/json"); 

     if (conn.getResponseCode() != 200) { 
      throw new RuntimeException("Failed : HTTP error code : " 
        + conn.getResponseCode()); 
     } 

     BufferedReader br = new BufferedReader(new InputStreamReader(
       (conn.getInputStream()))); 

     String output; 
     System.out.println("Output from Server .... \n"); 
     while ((output = br.readLine()) != null) { 
      System.out.println(output); 
     } 

     conn.disconnect(); 

    } catch (MalformedURLException e) { 

     e.printStackTrace(); 

    } catch (IOException e) { 

     e.printStackTrace(); 

    } 



} 

要對我苛刻，如果你看到一些愚蠢的錯誤，甚至初學java應該看到，因爲我不知道。

感謝您:)

Answer 1

停止不允許你讓主線程上的網絡連接，因爲這可以凍結UI線程，使您的應用程序沒有響應。這就是拋出異常的原因。

可以使按鈕關火一個新的線程或的AsyncTask完成動作。

例子： How to fix android.os.NetworkOnMainThreadException?

Answer 2

1. 應用標籤之前給你的AndroidManifest.xml中添加： -

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

2. 即使在平凡的互聯網連接的HTTP請求可能需要大量的時間。因此凍結主UI線程。你可以做的是按下按鈕時啓動一個新的AsyncTask。

   將代碼放在單獨的類，如： -

   public class HTTPRequestTask extends AsyncTask<Void, Void, Void> { 
   
   @Override 
   protected Void doInBackground(Void... params){ 
   System.out.println("I am here//////////////////////////////////////////"); 
   try { 
   URL url = new URL("http://echo.jsontest.com/insert-key-here/insert-value-here/key/value"); 
   HttpURLConnection conn = (HttpURLConnection) url.openConnection(); 
   conn.setRequestMethod("GET"); 
   conn.setRequestProperty("Accept", "application/json"); 
   
   if (conn.getResponseCode() != 200) { 
       throw new RuntimeException("Failed : HTTP error code : " 
         + conn.getResponseCode()); 
   } 
   
   BufferedReader br = new BufferedReader(new InputStreamReader(
        (conn.getInputStream()))); 
   
   String output; 
   System.out.println("Output from Server .... \n"); 
   while ((output = br.readLine()) != null) { 
       System.out.println(output); 
   } 
   
   conn.disconnect(); 
   
   } catch (MalformedURLException e) { 
   
       e.printStackTrace(); 
   
   } catch (IOException e) { 
   
       e.printStackTrace(); 
   
   } 
   

   並修改onClickButton，如： -

   OnButtonclick(...){ ... HTTPRequestTask testTask =new HTTPRequestTask(); testTask.execute(); ...}

   PS - 我已經命名的新類作爲HTTPRequestTask。你可以選擇你自己的名字。