Question

我有一个应用程序应该发送电话号码到PHP Web服务并获得响应。在我的代码中有一个按钮，它应该执行另一个扩展AsyncTask类的类。

按下按钮时应用程序崩溃的问题。

public class JSONTransmitter extends AsyncTask<JSONObject, JSONObject, JSONObject> 
     {

    String url = "http://192.168.1.6:89/Derdeery/banks.php";


    protected JSONObject doInBackground(JSONObject... data) {
        JSONObject json = data[0];
        HttpClient client = new DefaultHttpClient();
        HttpConnectionParams.setConnectionTimeout(client.getParams(), 100000);
        StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder().permitNetwork().build());
        JSONObject jsonResponse = null;

        HttpPost post = new HttpPost(url);
        try {
            StringEntity se = new StringEntity("json="+json.toString());
            post.addHeader("content-type", "application/x-www-form-urlencoded");
            post.setEntity(se);

            HttpResponse response;
            response = client.execute(post);
            String resFromServer = org.apache.http.util.EntityUtils.toString(response.getEntity());

            jsonResponse=new JSONObject(resFromServer);

            Log.i("Response from server", jsonResponse.getString("msg"));

        } catch (Exception e) { e.printStackTrace();}

        return jsonResponse;
    }

}

主要活动

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
     Button   b = (Button)findViewById(R.id.button1) ;   


        b .setOnClickListener(new OnClickListener() { 
             @Override 
             public void onClick(View view) { 

                 try {
               JSONObject toSend = new JSONObject();
               toSend.put("msg", 1);
              Toast.makeText(getApplicationContext(), mymethod(),Toast.LENGTH_LONG );
                JSONTransmitter transmitter = new JSONTransmitter();
                transmitter.execute(new JSONObject[] {toSend});

            } catch (JSONException e) {
                e.printStackTrace();
            }   

                } 
             });      
    }

logcat的

 12-30 09:02:57.734: W/dalvikvm(792): threadid=1: thread exiting with uncaught exception (group=0x40a70930)
12-30 09:02:57.864: E/AndroidRuntime(792): FATAL EXCEPTION: main
12-30 09:02:57.864: E/AndroidRuntime(792): java.lang.NullPointerException
12-30 09:02:57.864: E/AndroidRuntime(792):  at com.coffeecodes.coffecodesdoodle.MainActivity.mymethod(MainActivity.java:49)
12-30 09:02:57.864: E/AndroidRuntime(792):  at com.coffeecodes.coffecodesdoodle.MainActivity$1.onClick(MainActivity.java:34)
12-30 09:02:57.864: E/AndroidRuntime(792):  at android.view.View.performClick(View.java:4202)
12-30 09:02:57.864: E/AndroidRuntime(792):  at android.view.View$PerformClick.run(View.java:17340)
12-30 09:02:57.864: E/AndroidRuntime(792):  at android.os.Handler.handleCallback(Handler.java:725)
12-30 09:02:57.864: E/AndroidRuntime(792):  at android.os.Handler.dispatchMessage(Handler.java:92)
12-30 09:02:57.864: E/AndroidRuntime(792):  at android.os.Looper.loop(Looper.java:137)
12-30 09:02:57.864: E/AndroidRuntime(792):  at android.app.ActivityThread.main(ActivityThread.java:5039)
12-30 09:02:57.864: E/AndroidRuntime(792):  at java.lang.reflect.Method.invokeNative(Native Method)
12-30 09:02:57.864: E/AndroidRuntime(792):  at java.lang.reflect.Method.invoke(Method.java:511)
12-30 09:02:57.864: E/AndroidRuntime(792):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-30 09:02:57.864: E/AndroidRuntime(792):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-30 09:02:57.864: E/AndroidRuntime(792):  at dalvik.system.NativeStart.main(Native Method)
12-30 09:02:58.146: D/dalvikvm(792): GC_CONCURRENT freed 389K, 16% free 2833K/3340K, paused 74ms+26ms, total 390ms
12-30 09:05:35.477: I/Process(792): Sending signal. PID: 792 SIG: 9

Answer 1

是否可以将此行StringEntity se = new StringEntity("json="+json.toString());替换为StringEntity se = new StringEntity(json.toString());

我的问题是您是否在保存之前将电话号码验证到您的网络服务中，如果是，请发送到JSONObject toSend=new JSONObject(); toSend.put("msg", Phone_Number);

Answer 2

`12-30 09:02:57.864: E/AndroidRuntime(792): java.lang.NullPointerException
12-30 09:02:57.864: E/AndroidRuntime(792):  at com.coffeecodes.coffecodesdoodle.MainActivity.mymethod(MainActivity.java:49)`

问题出在MainActivity.java文件的第49行。也许你应该删除这个Toast。你甚至不会在这个吐司上调用show（）方法。

Toast.makeText(getApplicationContext(), mymethod(),Toast.LENGTH_LONG );

应该是：

 Toast.makeText(getApplicationContext(), mymethod(),Toast.LENGTH_LONG ).show();

在按钮OnClick操作中执行AsyncTask类

2 个答案: