更新 4：问题已解决 检查下面的答案
我正在尝试从 PHP Webservice 检索 JSON 结果并将其保存到 ListView 但出现错误
我不确定我的错误是什么，请您帮帮我
我正在关注 Travis (mybringback) 的本教程
他的方法（仅在这一部分）不需要任何参数来获取帖子（它实际上是使用 HIS PHP 方法）但是我的 web 服务方法需要 2 个参数（kioskid（设备 ID），accesstoken），它们保存在 SharedPreferense
更新1：
我修改了Android代码也卸载了旧代码并从beginig（登录等）开始，直到我到达EventListActivity但没有显示列表，我在日志中只有一个错误行（设备中没有错误消息）
Update2：在修改代码并分离UpdateJSON()并尝试在 doInBackground()中获取 JSON 响应之后
更新 3：我添加了 JSONParse 类
我收到一条新的错误消息，提示我在方法updateList()中的setListAdapter(adapter)处收到 NullPointerexception
这是错误日志：
03-26 16:58:38.397: E/AndroidRuntime(16196): FATAL EXCEPTION: main
03-26 16:58:38.397: E/AndroidRuntime(16196): Process: com.test.event, PID: 16196
03-26 16:58:38.397: E/AndroidRuntime(16196): java.lang.NullPointerException
03-26 16:58:38.397: E/AndroidRuntime(16196): at android.widget.SimpleAdapter.getCount(SimpleAdapter.java:93)
03-26 16:58:38.397: E/AndroidRuntime(16196): at android.widget.ListView.setAdapter(ListView.java:480)
03-26 16:58:38.397: E/AndroidRuntime(16196): at android.app.ListActivity.setListAdapter(ListActivity.java:265)
03-26 16:58:38.397: E/AndroidRuntime(16196): at com.decoder.tapway.event1.EventListActivity.updateList(EventListActivity.java:140)
03-26 16:58:38.397: E/AndroidRuntime(16196): at com.decoder.tapway.event1.EventListActivity.access$3(EventListActivity.java:136)
03-26 16:58:38.397: E/AndroidRuntime(16196): at com.decoder.tapway.event1.EventListActivity$LoadEvents.onPostExecute(EventListActivity.java:221)
03-26 16:58:38.397: E/AndroidRuntime(16196): at com.decoder.tapway.event1.EventListActivity$LoadEvents.onPostExecute(EventListActivity.java:1)
03-26 16:58:38.397: E/AndroidRuntime(16196): at android.os.AsyncTask.finish(AsyncTask.java:632)
03-26 16:58:38.397: E/AndroidRuntime(16196): at android.os.AsyncTask.access$600(AsyncTask.java:177)
03-26 16:58:38.397: E/AndroidRuntime(16196): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
03-26 16:58:38.397: E/AndroidRuntime(16196): at android.os.Handler.dispatchMessage(Handler.java:102)
03-26 16:58:38.397: E/AndroidRuntime(16196): at android.os.Looper.loop(Looper.java:136)
03-26 16:58:38.397: E/AndroidRuntime(16196): at android.app.ActivityThread.main(ActivityThread.java:5050)
03-26 16:58:38.397: E/AndroidRuntime(16196): at java.lang.reflect.Method.invokeNative(Native Method)
03-26 16:58:38.397: E/AndroidRuntime(16196): at java.lang.reflect.Method.invoke(Method.java:515)
03-26 16:58:38.397: E/AndroidRuntime(16196): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-26 16:58:38.397: E/AndroidRuntime(16196): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-26 16:58:38.397: E/AndroidRuntime(16196): at dalvik.system.NativeStart.main(Native Method)
这是我试图获取其 JSON 结果的 PHP 函数（Yii 框架）
public function actionEventList(){
if(isset($_POST['kioskid']) && isset($_POST['accesstoken'])){
$response = array();
$kiosk = Kiosk::model()->findByAttributes(array('kioskid'=>$_POST['kioskid'], 'accesstoken'=>$_POST['accesstoken']));
if($kiosk === null){
$response['status'] = '0';
$response['message'] = 'Invalid Kiosk';
} else {
$events = Event::model()->findAllByAttributes(array('createdby'=>$kiosk->userid, 'status'=>'A'));
$list = array();
foreach($events as $row){
$list[] = array('id'=>$row->id, 'name'=>$row->eventname);
}
$response['status'] = '1';
$response['list'] = $list;
}
$this->_sendResponse(200, CJSON::encode($response));
} else {
$this->_sendResponse(400);
}
}
这是我在 android 中的 Java 代码：（更新 2）
最重要的方法是 updateJSONdata()从服务器检索最近的事件
然后我在doInBackground()中调用该方法
public class EventListActivity extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// testing on Server:
private static final String EVENT_LIST_URL = "http://www.XXX.com/XXX/XXX/eventList";
// JSON IDS:
private static final String TAG_STATUS = "status";
private static final String TAG_EVENT_LIST = "list";
private static final String TAG_EVENT_ID = "id";
private static final String TAG_EVENT_NAME = "name";
private static final String TAG_MESSAGE = "message";
// An array of all of our Events
private JSONArray jaEvents = null;
// manages all of our events in a list.
private ArrayList<HashMap<String, String>> arrayEventList;
// prerepare SharedPreferences file name
private static final String PREFS_NAME = "com.MyApp.event";
private SharedPreferences sharedPref ;
String accesstoken, username, kioskid,spKioskid, password ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.event_list_layout);
// setup SharedPreferences file
this.sharedPref = getSharedPreferences(PREFS_NAME,0);
// get data from previous activity
this.accesstoken = sharedPref.getString("accesstoken", null);
this.kioskid = Settings.Secure.getString(getContentResolver(), Settings.Secure.ANDROID_ID);
Toast.makeText(EventListActivity.this, "onCreate\n"+kioskid, Toast.LENGTH_LONG).show();
Toast.makeText(EventListActivity.this, "onCreate\n"+accesstoken, Toast.LENGTH_LONG).show();
}
@Override
protected void onResume() {
super.onResume();
// assign data from SharedPreferences
this.accesstoken = sharedPref.getString("accesstoken", null);
this.kioskid = Settings.Secure.getString(getContentResolver(), Settings.Secure.ANDROID_ID);
Toast.makeText(EventListActivity.this, "onResume\n"+kioskid, Toast.LENGTH_LONG).show();
Toast.makeText(EventListActivity.this, "onResume\n"+accesstoken, Toast.LENGTH_LONG).show();
// loading the comments via AsyncTask
new LoadEvents().execute();
}
/**
* Retrieves recent Events from the server.
*/
public void updateJSONdata() {
arrayEventList = new ArrayList<HashMap<String, String>>();
JSONParser jParser = new JSONParser();
JSONObject jsonObj = jParser.getJSONFromUrl(EVENT_LIST_URL);
try {
jaEvents = jsonObj.getJSONArray(TAG_EVENT_LIST);
// looping through all events according to the json object returned
for (int i = 0; i < jaEvents.length(); i++) {
JSONObject c = jaEvents.getJSONObject(i);
// gets the content of each tag
String eventID = c.getString(TAG_EVENT_ID);
String eventName = c.getString(TAG_EVENT_NAME);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_EVENT_ID, eventID);
map.put(TAG_EVENT_NAME, eventName);
arrayEventList.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
/**
* Inserts the parsed data into the listview.
*/
private void updateList() {
ListAdapter adapter = new SimpleAdapter(this, arrayEventList,
R.layout.single_event_layout, new String[] { TAG_EVENT_ID, TAG_EVENT_NAME}, new int[] { R.id.event_id, R.id.event_name });
setListAdapter(adapter);
ListView lv = getListView();
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// do something
}
});
}
public class LoadEvents extends AsyncTask<String, String, String> {
JSONParser jParser = new JSONParser();
// check for success tag
int status;
String accesstoken ;
String kioskid ;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(EventListActivity.this);
pDialog.setMessage("Loading Events...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected String doInBackground(String... arg0) {
this.accesstoken = sharedPref.getString("accesstoken", null);
this.kioskid = Settings.Secure.getString(getContentResolver(), Settings.Secure.ANDROID_ID);
try {
// building parameters for Logout
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("accesstoken", accesstoken));
params.add(new BasicNameValuePair("kioskid", kioskid));
Log.d("request!", "Starting");
// getting product details by HTTPRequest
JSONObject json = jParser.makeHttpRequest(EVENT_LIST_URL,"POST",params);
// checking your log for JSON response
Log.d("Loding Events Attemp", json.toString());
// assign status to JSON "status" tag
status = json.getInt(TAG_STATUS);
if (status == 1){
// print in console success message + JSON response message
Log.d("Events Loaded Successfully",json.toString());
updateJSONdata();
return json.getString(TAG_MESSAGE);
}else{
// print in console failure message + JSON response message
Log.d("Faild loding Events!", json.getString(TAG_MESSAGE));
return json.getString(TAG_MESSAGE);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
pDialog.dismiss();
updateList();
}
}
}
更新 3
JSONParser 类
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
public JSONObject getJSONFromUrl(String url) {
// making HTTP Request
try {
// Construct the client and the HTTP request.
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
// Execute the POST request and store the response locally.
HttpResponse httpResponse = httpClient.execute(httpPost);
// Extract data from the response.
HttpEntity httpEntity = httpResponse.getEntity();
// Open an inputStream with the data content.
is = httpEntity.getContent();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
// Create a BufferedReader to parse through the inputStream.
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
// Declare a string builder to help with the parsing.
StringBuilder sb = new StringBuilder();
// Declare a string to store the JSON object data in string form.
String line = null;
// Build the string until null.
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
// Close the input stream.
is.close();
// Convert the string builder data to an actual string.
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try to 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;
}
// function get json from url
// by making HTTP POST or GET mehtod
public JSONObject makeHttpRequest(String loginUrl, String method,
List<NameValuePair> params) {
// making HTTP Request
try {
// check for request method
if(method == "POST"){
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(loginUrl);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}else
// check for request method
if(method == "GET"){
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
loginUrl += "?" + paramString;
HttpGet httpGet = new HttpGet(loginUrl);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException 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");
}
is.close();
json = sb.toString();
} catch (IOException e) {
Log.d("Buffer Error","Error Converting Reesult "+e.toString());
}
// try parse the string to JSON Object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error Parsing data" + e.toString());
}
// return JSON String
return jObj;
}
}
single_event_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="@drawable/gradient"
android:orientation="vertical" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="5dp"
android:background="@drawable/post_border_style"
android:orientation="vertical" >
<LinearLayout
android:id="@+id/box"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="2dp"
android:background="@drawable/post_background_style"
android:orientation="horizontal" >
<ImageView
android:id="@+id/imageView1"
android:layout_width="100dp"
android:layout_height="100dp"
android:src="@drawable/tapway_event_logo" />
<LinearLayout
android:id="@+id/box"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="2dp"
android:orientation="vertical"
android:padding="5dp" >
<TextView
android:id="@+id/event_id"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:paddingBottom="2dip"
android:paddingLeft="5dp"
android:paddingTop="6dip"
android:textColor="#333"
android:textSize="16sp"
android:textStyle="bold" />
<TextView
android:id="@+id/event_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingBottom="2dip"
android:paddingLeft="8dp"
android:textColor="#888" >
</TextView>
</LinearLayout>
</LinearLayout>
</LinearLayout>
event_list_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/gradient" >
<LinearLayout
android:id="@+id/top_layover"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:background="@drawable/blue_gradient"
android:orientation="horizontal" >
<TextView
style="@style/BlackText"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center"
android:text="@string/event_list"
android:textAppearance="?android:attr/textAppearanceLarge" />
</LinearLayout>
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/top_layover"
android:background="#fff"
android:divider="@android:color/transparent"
android:scrollbars="none" />
</RelativeLayout>