没有错误，但Android应用程序正在重新启动

Question

我是Android开发的新手。我使用volly库连接到localhost。代码构建没有错误，但运行模拟器应用程序正在重述。

这是我的源代码。

signin.php

   <?php
include_once("Dbclass.php");
$obj = new Dbconnection();

$id = $_GET['id'];
$sql = "select * from userdetails where UserId = '".$id."'";
$finalarr = array();
$result = mysqli_query($obj->getdbconnect(),$sql);
while($row = mysqli_fetch_array($result))
{
    $name = $row['UserName'];

    array_push($finalarr,array(
 "name"=>$row['UserId'],
"username"=>$row['UserName']

 )
 );
}

echo json_encode(array("result"=>$finalarr));

?>

这是我的activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:layout_marginEnd="29dp"
        android:layout_marginRight="29dp"
        android:layout_marginTop="61dp"
        android:text="Button" />

    <EditText
        android:id="@+id/editText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignTop="@+id/button"
        android:layout_marginLeft="13dp"
        android:layout_marginStart="13dp"
        android:ems="10"
        android:inputType="textPersonName"
        android:text="Name" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="350dp"
        android:layout_alignParentEnd="true"
        android:layout_alignParentRight="true"
        android:layout_below="@+id/button"
        android:layout_marginTop="111dp"
         />
</RelativeLayout>

这是Config.java

package com.example.namdy.webservice;

/**
 * Created by Namdy on 6/29/2017.
 */

public class Config {


    public static final String DATA_URL = "http://10.0.2.2:8080/Signin.php?id=";
    public static final String KEY_NAME = "username";
   // public static final String KEY_ADDRESS = "address";
   // public static final String KEY_VC = "vc";
    public static final String JSON_ARRAY = "finalarray";
}

最后是MainActivity.java

package com.example.namdy.webservice;

import android.app.ProgressDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

public class MainActivity extends AppCompatActivity {

    private EditText id;
    private Button ok;
    private TextView tx;

    private ProgressDialog loading;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_activity);

        id = (EditText) findViewById(R.id.editText);
        ok = (Button) findViewById(R.id.button);
        tx = (TextView) findViewById(R.id.textView);

        ok.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String id  = ok.getText().toString();
                getdata(id);
            }
        });

    }


    private void getdata(String id)
    {
        loading = ProgressDialog.show(this,"Please wait...","Fetching...",false,false);

        String url = Config.DATA_URL+id;

        StringRequest srt = new StringRequest(url, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                loading.dismiss();
                showJSON(response);
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Toast.makeText(MainActivity.this,error.getMessage().toString(),Toast.LENGTH_LONG).show();

            }
        }

        );


        RequestQueue requestQueue = Volley.newRequestQueue(this);
        requestQueue.add(srt);

    }

    private void showJSON(String response)
    {
             String usname = "";

        try{
            JSONObject obj = new JSONObject(response);
            JSONArray result = obj.getJSONArray(Config.JSON_ARRAY);
            JSONObject collegeData = result.getJSONObject(1);
            usname = collegeData.getString(Config.KEY_NAME);

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

        Toast.makeText(MainActivity.this,usname,Toast.LENGTH_LONG).show();
    }

}

编辑： 这是我的logcat错误。

    --------- beginning of crash
06-30 00:13:09.551 17261-17261/com.example.namdy.webservice E/AndroidRuntime: FATAL EXCEPTION: main
                                                                              Process: com.example.namdy.webservice, PID: 17261
                                                                              java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.toString()' on a null object reference
                                                                                  at com.example.namdy.webservice.MainActivity$3.onErrorResponse(MainActivity.java:65)
                                                                                  at com.android.volley.Request.deliverError(Request.java:524)
                                                                                  at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:101)
                                                                                  at android.os.Handler.handleCallback(Handler.java:751)
                                                                                  at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                  at android.os.Looper.loop(Looper.java:154)
                                                                                  at android.app.ActivityThread.main(ActivityThread.java:6119)
                                                                                  at java.lang.reflect.Method.invoke(Native Method)
                                                                                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
06-30 00:13:21.778 17261-17292/com.example.namdy.webservice E/EGL_emulation: tid 17292: swapBuffers(487): error 0x300d (EGL_BAD_SURFACE)
06-30 00:13:21.778 17261-17292/com.example.namdy.webservice W/OpenGLRenderer: swapBuffers encountered EGL error 12301 on 0xa2256f80, halting rendering...

我的代码有什么问题？

谢谢！