Android 与远程服务器建立连接时发生logcat错误
在试用了提供的一些解决方案后，我能够从服务器检索响应，但仍然无法显示我正在接收的JSON数组，并且应用程序正在崩溃，请帮助我： Logcat错误Android 与远程服务器建立连接时发生logcat错误,android,Android,在试用了提供的一些解决方案后，我能够从服务器检索响应，但仍然无法显示我正在接收的JSON数组，并且应用程序正在崩溃，请帮助我： Logcat错误 07-07 11:12:09.500: E/AndroidRuntime(1829): FATAL EXCEPTION: main 07-07 11:12:09.500: E/AndroidRuntime(1829): java.lang.RuntimeException: Unable to start activity ComponentInfo{
07-07 11:12:09.500: E/AndroidRuntime(1829): FATAL EXCEPTION: main
07-07 11:12:09.500: E/AndroidRuntime(1829): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.g2k/com.example.g2k.HotelSearch}: java.lang.NullPointerException: println needs a message
07-07 11:12:09.500: E/AndroidRuntime(1829): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
07-07 11:12:09.500: E/AndroidRuntime(1829): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-07 11:12:09.500: E/AndroidRuntime(1829): at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-07 11:12:09.500: E/AndroidRuntime(1829): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-07 11:12:09.500: E/AndroidRuntime(1829): at android.os.Handler.dispatchMessage(Handler.java:99)
07-07 11:12:09.500: E/AndroidRuntime(1829): at android.os.Looper.loop(Looper.java:137)
07-07 11:12:09.500: E/AndroidRuntime(1829): at android.app.ActivityThread.main(ActivityThread.java:5039)
07-07 11:12:09.500: E/AndroidRuntime(1829): at java.lang.reflect.Method.invokeNative(Native Method)
07-07 11:12:09.500: E/AndroidRuntime(1829): at java.lang.reflect.Method.invoke(Method.java:511)
07-07 11:12:09.500: E/AndroidRuntime(1829): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-07 11:12:09.500: E/AndroidRuntime(1829): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-07 11:12:09.500: E/AndroidRuntime(1829): at dalvik.system.NativeStart.main(Native Method)
07-07 11:12:09.500: E/AndroidRuntime(1829): Caused by: java.lang.NullPointerException: println needs a message
07-07 11:12:09.500: E/AndroidRuntime(1829): at android.util.Log.println_native(Native Method)
07-07 11:12:09.500: E/AndroidRuntime(1829): at android.util.Log.v(Log.java:117)
07-07 11:12:09.500: E/AndroidRuntime(1829): at com.example.g2k.HotelSearch.onCreate(HotelSearch.java:22)
07-07 11:12:09.500: E/AndroidRuntime(1829): at android.app.Activity.performCreate(Activity.java:5104)
07-07 11:12:09.500: E/AndroidRuntime(1829): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
07-07 11:12:09.500: E/AndroidRuntime(1829): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
07-07 11:12:09.500: E/AndroidRuntime(1829): ... 11 more
07-07 11:12:14.430: E/Trace(1848): error opening trace file: No such file or directory (2)
public class HotelBook extends Activity {
private String resp;
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> hotelsList;
HashMap<String, String> map;
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_HOTEL = "hotels";
private static final String TAG_PID = "hotel_id";
private static final String TAG_NAME = "hotel_name";
private static final String TAG_AREA = "area";
private static final String TAG_RATING = "star_rating";
private static final String TAG_IMAGE = "image";
private static final String TAG_GOVRATE = "govrating";
private static final String TAG_PRICE = "price";
private String city_id = "feedbacktype2";
// products JSONArray
JSONArray hotels = null;
Button sendPostReqButton;
private static final String url = "http://10.0.2.2/android_connect/search_hotel.php";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_hotelbook);
// Hashmap for ListView
hotelsList = new ArrayList<HashMap<String, String>>();
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
.permitAll().build();
StrictMode.setThreadPolicy(policy);
sendPostReqButton = (Button) findViewById(R.id.button1);
addListenerOnButton();
}
public void addListenerOnButton() {
sendPostReqButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// Get the data
// Loading products in Background Thread
new GetHotel().execute();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_hotelbook, menu);
return true;
}
class GetHotel extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
/*
* pDialog = new ProgressDialog(HotelbookActivity.this);
* pDialog.setMessage("Loading hotels. Please wait...");
* pDialog.setIndeterminate(false); pDialog.setCancelable(false);
* pDialog.show();
*/
}
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("cityid", city_id));
// getting JSON string from URL
JSONObject json = null;
try {
json = jParser.makeHttpRequest(url, "GET", params);
} catch (IOException e1) {
// TODO Auto-generated catch block
// Check your log cat for JSON reponse
Log.e("All hotels: ", e1.toString());
}
// Check your log cat for JSON reponse
Log.d("All hotels: ", json.toString());
try {
// Checking for SUCCESS TAG
int success = 1;
// json.getInt(TAG_SUCCESS);
if (success == 1) {
// products found
// Getting Array of Products
hotels = json.getJSONArray(TAG_HOTEL);
// looping through All Products
for (int i = 0; i < hotels.length(); i++) {
JSONObject c = hotels.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_PID);
String name = c.getString(TAG_NAME);
String area = c.getString(TAG_AREA);
String rating = c.getString(TAG_RATING);
String image = c.getString(TAG_IMAGE);
String price = c.getString(TAG_PRICE);
String govrate = c.getString(TAG_GOVRATE);
// creating new HashMap
map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_PID, id);
map.put(TAG_NAME, name);
map.put(TAG_AREA, area);
map.put(TAG_RATING, rating);
map.put(TAG_IMAGE, image);
map.put(TAG_PRICE, price);
map.put(TAG_GOVRATE, govrate);
// adding HashList to ArrayList
hotelsList.add(map);
}
} else {
}
} catch (JSONException e) {
Log.e("response error", json.toString(), e);
}
return null;
}
protected void onPostExecute(String file_url) {
Intent intent = new Intent(HotelBook.this, HotelSearch.class);
intent.putExtra("map", map);
startActivity(intent);
}
}
}
公共类HotelBook扩展活动{
私有字符串resp；
私人对话；
//创建JSON解析器对象
JSONParser jParser=新的JSONParser（）；
ArrayList酒店列表；
HashMap图；
//JSON节点名称
私有静态最终字符串标记_SUCCESS=“SUCCESS”；
私人静态最终字符串TAG_HOTEL=“hotels”；
私有静态最终字符串TAG_PID=“hotel_id”；
私有静态最终字符串TAG_NAME=“hotel_NAME”；
私有静态最终字符串标记_AREA=“AREA”；
专用静态最终字符串标记\u RATING=“star\u RATING”；
私有静态最终字符串TAG_IMAGE=“IMAGE”；
私有静态最终字符串标记\u GOVRATE=“govrating”；
私有静态最终字符串标记_PRICE=“PRICE”；
私有字符串city_id=“feedbacktype2”；
//产品JSONArray
JSONArray hotels=null；
按钮sendPostReqButton；
私有静态最终字符串url=”http://10.0.2.2/android_connect/search_hotel.php";
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_hotelbook）；
//ListView的Hashmap
hotelsList=newarraylist（）；
StrictMode.ThreadPolicy policy=新建StrictMode.ThreadPolicy.Builder（）
.permitAll（）.build（）；
StrictMode.setThreadPolicy（策略）；
sendPostReqButton=（按钮）findViewById（R.id.button1）；
addListenerOnButton（）；
}
public void addListenerOnButton（）{
sendPostReqButton.setOnClickListener（新的OnClickListener（）{
@凌驾
公共void onClick（视图arg0）{
//获取数据
//在后台线程中加载产品
新建GetHotel（）.execute（）；
}
});
}
@凌驾
公共布尔onCreateOptions菜单（菜单）{
//为菜单充气；这会将项目添加到操作栏（如果存在）。
getMenuInflater（）.充气（R.menu.activity\u hotelbook，menu）；
返回true；
}
类GetHotel任务{
@凌驾
受保护的void onPreExecute（）{
super.onPreExecute（）；
/*
*pDialog=新建进度对话框（HotelbookActivity.this）；
*pDialog.setMessage（“正在加载酒店，请稍候…”）；
*pDialog.setUndeterminate（false）；pDialog.setCancelable（false）；
*pDialog.show（）；
*/
}
受保护的字符串doInBackground（字符串…args）{
//建筑参数
List params=new ArrayList（）；
参数add（新的BasicNameValuePair（“城市id”，城市id））；
//从URL获取JSON字符串
JSONObject json=null；
试一试{
json=jParser.makeHttpRequest（url，“GET”，params）；
}捕获（IOE1异常）{
//TODO自动生成的捕捉块
//检查日志cat中的JSON响应
Log.e（“所有酒店：，e1.toString（））；
}
//检查日志cat中的JSON响应
Log.d（“所有酒店：，json.toString（））；
试一试{
//检查成功标签
int成功=1；
//getInt（TAG_SUCCESS）；
如果（成功==1）{
//发现的产品
//获取一系列产品
hotels=json.getJSONArray（TAG_HOTEL）；
//在所有产品中循环
对于（int i=0；ivalue
地图放置（标签PID，id）；
地图放置（标签名称、名称）；
地图放置（TAG_区域，区域）；
地图放置（标签、等级、等级）；
地图放置（标签图片，图片）；
地图出售（标签价格、价格）；
地图放置（标记为GOVRATE，GOVRATE）；
//将哈希列表添加到ArrayList
添加（地图）；
}
}否则{
}
}捕获（JSONException e）{
Log.e（“响应错误”，json.toString（），e）；
}
返回null；
}
受保护的void onPostExecute（字符串文件\u url）{
意向意向=新意向（HotelBook.this、HotelSearch.class）；
意向。额外（“地图”，地图）；
星触觉（意向）；
}
}
}
public class JSONParser {
InputStream is = null;
JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
// function get json from url
// by making HTTP POST or GET method
public JSONObject makeHttpRequest(String url, String method,
List<NameValuePair> params) throws IOException {
// Making HTTP request
try {
// check for request method
if (method == "POST") {
// request method is POST
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} else if (method == "GET") {
// request method is GET
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
} finally {
is.close();
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
公共类JSONParser{
InputStream=null；
JSONObject jObj=null；
静态字符串json=“”；
//建造师
公共JSONParser（）{
}
//函数从url获取json
//通过使用HTTP POST或GET方法
公共JSONObject makeHttpRequest（字符串url、字符串方法、，
列表参数）引发IOException{
//发出HTTP请求
试一试{
//检查请求方法
如果（方法==“POST”）{
//请求方法为POST
//defaultHttpClient
DefaultHttpClient httpClient=新的DefaultHttpClient（）；
HttpPost HttpPost=新的HttpPost（url）；
setEntity（新的UrlEncodedFormEntity（参数））；
HttpResponse HttpResponse=httpClient.execute（httpPost）；
HttpEntity HttpEntity=httpResponse.getEntity（）；
is=httpEntity.getContent（）；
}else if（方法==“GET”）{
//请求方法是GET
Caused by: java.lang.NullPointerException
07-05 08:36:07.533: E/AndroidRuntime(1073): at
com.example.go2kashmir.HotelbookActivity$GetHotel
.doInBackground(HotelbookActivity.java:154)
Log.d("All hotels: ", json.toString());
All hotels: null
Log.d("MyActivity", "Object of interest is " + objectOfInterest);