如何解决socket实例化错误？

Question

我尝试通过wifi连接android到打印机，我得到错误NetworkOnMainThreadException。

这里是我的代码：

public void OnClickPrint(View paramView) { 
    File file = new File(DB_PATH); 
    try { 
    Socket client = new Socket("172.230.1.16", 9100); 

     byte[] mybytearray = new byte[(int) file.length()]; 

     fileInputStream = new FileInputStream(file); 
     bufferedInputStream = new BufferedInputStream(fileInputStream); 

     bufferedInputStream.read(mybytearray, 0, mybytearray.length);                 
     outputStream = client.getOutputStream(); 

     outputStream.write(mybytearray, 0, mybytearray.length); // 
     outputStream.flush(); 
     bufferedInputStream.close(); 
     outputStream.close(); 
     client.close(); 

    } catch (UnknownHostException e) { 
     Log.v("a", e.getMessage()); 
     e.printStackTrace(); 
    } catch (IOException e) { 
     Log.v("a", e.getMessage()); 
     e.printStackTrace(); 
    } 
} 

当我按F6跟踪代码，我得到了错误插口实例在Socket client = new Socket("172.230.1.16", 9100); 172.230.1.16是我的打印机的IP。

错误的logcat：

02-28 09:44:40.572: E/AndroidRuntime(1426): FATAL EXCEPTION: main 
    02-28 09:44:40.572: E/AndroidRuntime(1426): java.lang.IllegalStateException: Could not execute method of the activity 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at android.view.View$1.onClick(View.java:3044) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at android.view.View.performClick(View.java:3511) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at android.view.View$PerformClick.run(View.java:14105) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at android.os.Handler.handleCallback(Handler.java:605) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at android.os.Handler.dispatchMessage(Handler.java:92) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at android.os.Looper.loop(Looper.java:137) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at android.app.ActivityThread.main(ActivityThread.java:4424) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at java.lang.reflect.Method.invokeNative(Native Method) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at java.lang.reflect.Method.invoke(Method.java:511) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at dalvik.system.NativeStart.main(Native Method) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): Caused by: java.lang.reflect.InvocationTargetException 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at java.lang.reflect.Method.invokeNative(Native Method) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at java.lang.reflect.Method.invoke(Method.java:511) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at android.view.View$1.onClick(View.java:3039) 
    02-28 09:44:40.572: E/AndroidRuntime(1426):  ... 11 more 
    02-28 09:44:40.572: E/AndroidRuntime(1426): Caused by: android.os.NetworkOnMainThreadException 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1099) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at libcore.io.IoBridge.connectErrno(IoBridge.java:127) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at libcore.io.IoBridge.connect(IoBridge.java:112) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at java.net.Socket.startupSocket(Socket.java:566) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at java.net.Socket.tryAllAddresses(Socket.java:127) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at java.net.Socket.<init>(Socket.java:177) 
    02-28 09:44:40.572: E/AndroidRuntime(1426): at java.net.Socket.<init>(Socket.java:149) 
    02-28 09:44:40.572: E/AndroidRuntime(1426):  at com.example.printertest.MainActivity.OnClickPrint(MainActivity.java:56) 

如何解决呢？

Answer 1

产生的原因：android.os.NetworkOnMainThreadException

您对Android操作系统的主线进行网络操作。我建议你使用AsyncTask。 您应该在AsyncTask中执行长时间运行的网络操作。 AsyncTask支持正确和简单地使用UI线程。该类允许执行后台操作并在UI线程上发布结果，而无需操纵线程和/或处理程序。

public void OnClickPrint(View paramView) 
{ 
    new PrintFile().execute(); 
} 

private class PrintFile extends AsyncTask<Void, Void, Void> 
{ 
    @Override 
    protected Void doInBackground(Void... result) 
    { 
     File file = new File(DB_PATH); 
     try { 
     Socket client = new Socket("172.230.1.16", 9100); 

      byte[] mybytearray = new byte[(int) file.length()]; 

      fileInputStream = new FileInputStream(file); 
      bufferedInputStream = new BufferedInputStream(fileInputStream); 

      bufferedInputStream.read(mybytearray, 0, mybytearray.length);                 
      outputStream = client.getOutputStream(); 

      outputStream.write(mybytearray, 0, mybytearray.length); // 
      outputStream.flush(); 
      bufferedInputStream.close(); 
      outputStream.close(); 
      client.close(); 

     } catch (UnknownHostException e) { 
      e.printStackTrace(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 
     return null; 
    } 
}