android http協議-HttpClientGet 傳輸問題

HttpClientGet 傳輸問題

我一直不明白 就這幾行代碼 單獨在一個工程可以，就這麼復制黏貼就爆空指針異常，我真的，已經陷入無限循環兩天了
求大神指點迷津
上代碼
public class Personlogin1 extends Activity {
private HttpClient client = null;
private Button on_login;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_personlogin1);

    on_login = (Button) findViewById(R.id.onlogin);
    on_login.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            readNet("http://www.weather.com.cn/adat/cityinfo/101010100.html");
        }

        public void readNet(String url) {
            new AsyncTask<String, Void, String>() {

                @Override
                protected String doInBackground(String... arg0) {
                    System.out.println("1");
                    String urlString = arg0[0];
                    System.out.println("2");
                    HttpGet get = new HttpGet(urlString);
                    try {
                        System.out.println("3");
                        HttpResponse response = client.execute(get);

                        System.out.println("4");
                        String value = EntityUtils.toString(response.getEntity());
                         System.out.println("44444444"+value);

                        System.out.println("5");
                        return value;
                    } catch (ClientProtocolException e) {
                        // TODO Auto-generated catch block

                        System.out.println("6");
                        e.printStackTrace();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block

                        System.out.println("7");
                        e.printStackTrace();
                    }
                    return null;
                }

                @Override
                protected void onPostExecute(String result) {
                    System.out.println(result);
                }
            }.execute(url);
        }

    });  
    代碼就這些       ![圖片說明](http://img.ask.csdn.net/upload/201601/25/1453723473_824864.png)

最佳回答：

大哥 你的 client 為null 又沒有實例化，下面就直接執行execute 方法，所以直接報null 出錯了
private HttpClient client = null;

HttpResponse response = client.execute(get);