httppost 代码编写有关问题.

httppost 代码编写问题...
求各位大神给看看

Java code

Activityprivate Button mButton1,mButton2; private TextView mTextView1; private JoyHttp j;@Override   public void onCreate(Bundle savedInstanceState)   {     super.onCreate(savedInstanceState);     setContentView(R.layout.main);          /*透过findViewById建构子建立TextView与Button对象*/     mButton1 =(Button) findViewById(R.id.myButton1);     mButton2 =(Button) findViewById(R.id.myButton2);    mTextView1 = (TextView) findViewById(R.id.myTextView1);          /*设定OnClickListener来聆听OnClick事件*/    mButton1.setOnClickListener(new Button.OnClickListener()     {       /*重写onClick事件*/      @Override       public void onClick(View v)       {         /*声明网址字符串*/        String uriAPI = "http://localhost:8080";        String message = "123";//        post(uriAPI);        mTextView1.setText(j.post(uriAPI,message));         }     }); Postpublic String post(String uriAPI, String message)  {    String fal = "fal";    HttpPost httpRequest = new HttpPost(uriAPI);    try    {      /* 发出HTTP request */       httpRequest.setEntity(new StringEntity(message));      // httpRequest.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));      /* 取得HTTP response */      HttpResponse httpResponse = new DefaultHttpClient().execute(httpRequest);      /* 若状态码为200 ok */      if (httpResponse.getStatusLine().getStatusCode() == 200)      {        /* 取出响应字符串 */        String strResult = EntityUtils.toString(httpResponse.getEntity());        // mTextView1.setText(strResult);         return strResult;      }      // else       // {       // mTextView1.setText("Error Response: "+httpResponse.getStatusLine().toString());      // }    } catch (ClientProtocolException e)    {      e.printStackTrace();    } catch (IOException e)    {      e.printStackTrace();    } catch (Exception e)    {      e.printStackTrace();    }    return fal;  }

log
09-24 15:39:47.529: E/AndroidRuntime(14810): FATAL EXCEPTION: main
09-24 15:39:47.529: E/AndroidRuntime(14810): java.lang.RuntimeException: Unable to start activity ComponentInfo{irdc.EX08_01/irdc.EX08_01.EX08_01}: java.lang.NullPointerException
09-24 15:39:47.529: E/AndroidRuntime(14810): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1967)
09-24 15:39:47.529: E/AndroidRuntime(14810): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)
09-24 15:39:47.529: E/AndroidRuntime(14810): at android.app.ActivityThread.access$600(ActivityThread.java:127)
09-24 15:39:47.529: E/AndroidRuntime(14810): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)
09-24 15:39:47.529: E/AndroidRuntime(14810): at android.os.Handler.dispatchMessage(Handler.java:99)
09-24 15:39:47.529: E/AndroidRuntime(14810): at android.os.Looper.loop(Looper.java:137)
09-24 15:39:47.529: E/AndroidRuntime(14810): at android.app.ActivityThread.main(ActivityThread.java:4511)
09-24 15:39:47.529: E/AndroidRuntime(14810): at java.lang.reflect.Method.invokeNative(Native Method)
09-24 15:39:47.529: E/AndroidRuntime(14810): at java.lang.reflect.Method.invoke(Method.java:511)
09-24 15:39:47.529: E/AndroidRuntime(14810): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980)
09-24 15:39:47.529: E/AndroidRuntime(14810): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
09-24 15:39:47.529: E/AndroidRuntime(14810): at dalvik.system.NativeStart.main(Native Method)
09-24 15:39:47.529: E/AndroidRuntime(14810): Caused by: java.lang.NullPointerException
09-24 15:39:47.529: E/AndroidRuntime(14810): at irdc.EX08_01.EX08_01.onCreate(EX08_01.java:50)
09-24 15:39:47.529: E/AndroidRuntime(14810): at android.app.Activity.performCreate(Activity.java:4470)
09-24 15:39:47.529: E/AndroidRuntime(14810): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1052)