从android市场首次安装android应用程序的问题

Question

我正在访问互联网以获取信息。当我访问互联网时，该应用程序正在关闭。如果该应用程序被删除并重新安装，它不会在我访问互联网时强制关闭。第一次安装该应用程序时会发生这种情况。请帮我弄清楚这一点。

这是堆栈跟踪 -

java.lang.RuntimeException: Unable to start activity ComponentInfo{ListOfDealSites}: java.lang.NullPointerException 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
at android.os.Handler.dispatchMessage(Handler.java:99) 
at android.os.Looper.loop(Looper.java:123) 
at android.app.ActivityThread.main(ActivityThread.java:4627) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:521) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
at dalvik.system.NativeStart.main(Native Method) 
Caused by: java.lang.NullPointerException 
at java.io.DataInputStream.readLine(DataInputStream.java:309) 
at ListOfDealSites.onCreate(ListOfDealSites.java:53) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 
... 11 more 

它还说源方法 - DataInputStream.readLine（）

public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.dealsites); 

    InputStream in = null; 
    try { 
     // Connect to the server to get the list of deal sites 
     in = OpenHttpConnection("Link to deal server"); 
     } 
    catch (IOException e1) { 

     // TODO Auto-generated catch block   
     e1.printStackTrace(); 
    } 

    try { 

       DataInputStream dataIO = new DataInputStream(in); 
     String strLine = null; 
     int i = 0; 

     while((strLine = dataIO.readLine())!= null) // Line 53------ 
     { 
      count = i; 
      NEWDEALSITES[i++] = strLine; 

     } 

     dataIO.close(); 
     in.close(); 
    } 
    catch (IOException e){ 

    // TODO Auto-generated catch block 
    e.printStackTrace(); 
    } 

    count_deals = count/2; 
    newdeals = new String[count_deals+1]; 
    newsites = new String[count_deals+1]; 
    int j, k; 
    for(j = 0, k = 0; k < count; j++) 
    { 
     newdeals[j] = NEWDEALSITES[k++]; 
     newsites[j] = NEWDEALSITES[k++]; 

    } 

    listOfDealSites = (ListView)findViewById(R.id.ListView01); 
    listOfDealSites.setAdapter(new ArrayAdapter<String>(this,R.layout.row,newdeals)); 



} 

//Function to connect to the server. 
private InputStream OpenHttpConnection(String urlString) 
throws IOException 
{ 
    InputStream in = null; 
    int response = -1; 

    URL url = new URL(urlString); 
    URLConnection conn = url.openConnection(); 

    if (!(conn instanceof HttpURLConnection))      
     throw new IOException("Not an HTTP connection"); 

    try{ 
     HttpURLConnection httpConn = (HttpURLConnection) conn; 
     httpConn.setAllowUserInteraction(false); 
     httpConn.setInstanceFollowRedirects(true); 
     httpConn.setRequestMethod("GET"); 
     httpConn.connect(); 

     response = httpConn.getResponseCode();     
     if (response == HttpURLConnection.HTTP_OK) { 
      in = httpConn.getInputStream();         
     }      
    } 
    catch (Exception ex) 
    { 
     throw new IOException("Error connecting");    
    } 
    return in;  
} 

}

Answer 1

问题是由于没有互联网连接造成的。我发现了这个异常，并且发出了一条消息来检查连接。

谢谢大家的帮助。

Answer 2

出于某种原因，OpenHttpConnection被返回null这基本上意味着你在这里没有得到好的回应...

response = httpConn.getResponseCode();     
if (response == HttpURLConnection.HTTP_OK) { 
    in = httpConn.getInputStream();         
} 

这意味着dataIO将是无效的，当你尝试读取线53

从DataInputStream类的构造函数的文档资料...

公共DataInputStream类（InputStream的 中）由于： API等级1

构造上的InputStream新 DataInputStream所英寸

全部读取，然后通过过滤 这个流。请注意，由 读取的数据不是可读的 格式，最有可能是由 创建的DataOutputStream。

警告：通过 空源创建无效的 DataInputStream。 上的所有操作都会失败。

不知道会是什么导致这或如何解决它，但你一定要尝试使用“中”的InputStream创建您的DataInputStream所前检查从OpenHttpConnection返回一个空的结果。