AsyncTask下载JSON

public class HttpUtils {

// 从网络url上下载字符串
public static String getHttpStr(String url) {
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
try {
HttpResponse response = httpClient.execute(httpGet);// 发起http请求
if (response.getStatusLine().getStatusCode() == 200) {
// 请求成功
HttpEntity entity = response.getEntity();
ByteArrayOutputStream baos = new ByteArrayOutputStream();// 字节数组输出流
InputStream is = entity.getContent(); // 获取输入流
byte[] buffer = new byte[1024];
int ret;
while (true) {
ret = is.read(buffer);
if (ret < 0) {
break;
}
baos.write(buffer, 0, ret); // 读多少、写多少
}
return baos.toString();
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}

public class JSONUtils {

// 读入json字符串并返回List<String>城市列表
// 格式为 {"citys":["北京","上海","山东","河北","广东"]}
public static List<String> parseCityJSONStr(String jsonStr) {
try {
List<String> listCity = new ArrayList<String>();
// JSON字符串中{}表示JSONObject
// 这里创建JSONObject对象
JSONObject jsonObject = new JSONObject(jsonStr);
// 根据json对象中冒号前的内容(key)获取冒号后的内容(value)
// 后面的内容是JSON数组(JSONArray)
JSONArray jsonArr = (JSONArray) jsonObject.get("citys");
// 遍历JSON数组，并把一个一个元素放入List<String>中
for (int i = 0; i < jsonArr.length(); i++) {
// 根据下标获取jsonArr中的元素
String city = (String) jsonArr.get(i);
listCity.add(city);
}
return listCity;
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

return null;
}
}

public class MainActivity extends Activity {

private Spinner spinner;
private String url = "http://10.16.154.26:8080/Web_Product/CityServlet?type=json";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
spinner = (Spinner) findViewById(R.id.spinner);
MyTask task = new MyTask(MainActivity.this,spinner);
task.execute(url);
}
}

public class MyTask extends AsyncTask<String, Void, List<String>> {

private Context context;
private Spinner spinner;

public MyTask(Context context, Spinner spinner) {
super();
this.context = context;
this.spinner = spinner;
}
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
}
@Override
protected List<String> doInBackground(String... params) {
String jsonStr = HttpUtils.getHttpStr(params[0]);
List<String> listCity = JSONUtils.parseCityJSONStr(jsonStr);
return listCity;
}

@Override
protected void onPostExecute(List<String> result) {
ArrayAdapter<String> adapter = new ArrayAdapter<String>(context, android.R.layout.simple_list_item_1,result);
spinner.setAdapter(adapter);
super.onPostExecute(result);
}
}