空指针异常哪里的问题　一天都没找到原因

baozhuwanglei 2017-04-20 12:11:53

java.lang.NullPointerException: Attempt to invoke interface method 'org.xutils.common.task.AbsTask org.xutils.common.TaskController.start(org.xutils.common.task.AbsTask)' on a null object reference

package com.baozhuwanglei.android.a04202017_test;



import android.os.Handler;

import android.os.Message;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.Toast;



import org.xutils.common.Callback;

import org.xutils.common.util.MD5;

import org.xutils.http.RequestParams;

import org.xutils.x;



import java.util.Map;



public class MainActivity extends AppCompatActivity {



    private Button button;



    Handler handler = new Handler() {

        public void handleMessage(Message msg) {



            /*

            switch (msg.what) {

                case 0:

                    Toast.makeText(getApplicationContext(), "a", Toast.LENGTH_SHORT).show();

                    Map<String,String> nmap = (Map<String,String>) msg.obj;

                    for(String key : nmap.keySet()) {

                        Toast.makeText(getApplicationContext(), nmap.get(key), Toast.LENGTH_SHORT).show();

                    }

                    break;

                case 3:

                    Toast.makeText(getApplicationContext(), "bb", Toast.LENGTH_SHORT).show();

                    break;

            }*/

            super.handleMessage(msg);

            Toast.makeText(getApplicationContext(), "handle", Toast.LENGTH_SHORT).show();



        }

    };



    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);



        button = (Button) findViewById(R.id.button_v);

        button.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                Toast.makeText(getApplicationContext(),"test",Toast.LENGTH_SHORT).show();



                new Thread() {

                    public void run() {

                        RequestParams params = new RequestParams("http://10.0.2.2/xiaofanghuiluPhpBzw/public/index/user/login");

                        params.addParameter("username","admin");

                        params.addParameter("password",MD5.md5("admin"));

                        x.http().post(params, new Callback.CommonCallback<String>() {

                            @Override

                            public void onSuccess(String result) {

                                Message msg = new Message();

                                msg.what = 0;

                                msg.obj = result;

                                handler.sendMessage(msg);

                            }

                            @Override

                            public void onError(Throwable ex, boolean isOnCallback) {



                            }



                            @Override

                            public void onCancelled(CancelledException cex) {



                            }



                            @Override

                            public void onFinished() {



                            }

                        });

                        //handler.sendMessage(msg);

                    }

                }.start();

            }

        });

    }

}