Android没有连接到本地主机？

Question

我收到了这些错误：

07-06 01:04:41.336 1484-1484/quickbook.com.volleyjsonobject W/System.err: com.android.volley.TimeoutError
07-06 01:04:41.336 1484-1484/quickbook.com.volleyjsonobject W/System.err:     at com.android.volley.toolbox.BasicNetwork.performRequest(BasicNetwork.java:147)
07-06 01:04:41.336 1484-1484/quickbook.com.volleyjsonobject W/System.err:     at com.android.volley.NetworkDispatcher.run(NetworkDispatcher.java:114)

我的代码是：

public class MainActivity extends AppCompatActivity {

  Button button;
  TextView Name, Email, Mobile;
  String json_url = "http://10.0.2.2:8080/getinfo.php";

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

    button = (Button) findViewById(R.id.bn);
    Name = (TextView)findViewById(R.id.name);
    Email = (TextView) findViewById(R.id.email);
    Mobile = (TextView) findViewById(R.id.mobile);

    button.setOnClickListener(new View.OnClickListener(){

      @Override
      public void onClick(View v) {
        JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.POST, json_url, (String) null,
             new Listener<JSONObject>() {
               @Override
               public void onResponse(JSONObject response) {
                 try {
                    Name.setText(response.getString("Name"));
                    Email.setText(response.getString("Email"));
                    Mobile.setText(response.getString("Mobile"));
                 } catch (JSONException e) {
                   e.printStackTrace();
                 }
               }
              }, new ErrorListener() {
                   @Override
                   public void onErrorResponse(VolleyError error) {
                     Toast.makeText(MainActivity.this, "something went wrong", Toast.LENGTH_LONG).show();
                     error.printStackTrace();
                   }
               });
         MySingleton.getInstance(MainActivity.this).addToRequestque(jsonObjectRequest);
       }
    });
  }
}

我正试图从本地主机获取一个json对象，但我得到了Volley超时错误。我在graddle.app文件中添加了依赖项。以及清单中的Internet权限。