在这里，我正在分享我的代码如何在列表视图中解析这些数据。首先，我现在使用Json Parser这无法正常工作。现在我正在解析这个，所以我们看不到列表视图。请帮助我谢谢。
import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
public class HomeScreen extends Activity {
ListView listview;
String url;
ArrayList<ParticipantItem> participantArrayList;
ParticipantsAdapter pAdapter;
JSONArray jsonOuterArray;
private ProgressDialog pDialog;
ImageView menu, refresh;
Integer a;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.home_screen);
participantArrayList = new ArrayList<ParticipantItem>();
listview = (ListView) findViewById(R.id.listview);
url = "http://findcourse.net/search_result.php?search=&study_field=17";//"http://findcourse.net/search_result.php?search=" + keywordvalue_get + sf_spinner_get + sl_spinner_get + si_spinner_get + sm_spinner_get;
refresh = (ImageView) findViewById(R.id.refresh);
menu = (ImageView) findViewById(R.id.menu);
new GetData().execute();
System.out.println("The square root of " + url);
listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
}
});
}
//////////////////////
private class GetData extends AsyncTask<String, String, String> {
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(HomeScreen.this);
pDialog.setMessage("Loading...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected void onPostExecute(String result) {
pDialog.dismiss();
if (jsonOuterArray.length() > 0) {
for (int i = 0; i <= jsonOuterArray.length(); i++) {
a = jsonOuterArray.length();
JSONObject jsonObj;
try {
jsonObj = jsonOuterArray.getJSONObject(i);
JSONObject message = jsonObj.getJSONObject("result");
String offered_by_detail = message.getString("offered_by");
String course = message.getString("course");
String logo = message.getString("logo");
String total_views = message.getString("total_views");
String total_course_offered = message.getString("total_course_offered");
String feature_course = message.getString("feature_course");
String total_views_course = message.getString("total_views_course");
String course_info = message.getString("course_info");
String duration = message.getString("duration");
String tution_fee = message.getString("tution_fee");
String other_payable_fee = message.getString("other_payable_fee");
String intake = message.getString("intakesandroid");
String campus = message.getString("campusandroid");
String entry_requirement = message.getString("entry_requirement");
String longitude = message.getString("longitude");
String latitude = message.getString("latitude");
String search_filter = message.getString("search_filter");
String institute_info = message.getString("institute_info");
// Toast.makeText(HomeScreen.this, institute_info, Toast.LENGTH_SHORT).show();
TextView search_filtera = (TextView) findViewById(R.id.search_filter);
// search_filtera.setText("Search for " + String.valueOf(a) + " institutions offering in Agriculture courses");
search_filtera.setText(search_filter);
participantArrayList.add(new ParticipantItem(offered_by_detail, logo, course, total_views, course_info, duration, tution_fee, other_payable_fee, intake, campus, entry_requirement, longitude, latitude, search_filter, institute_info, total_course_offered, feature_course, total_views_course));
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
pDialog.dismiss();
}
}
} else {
}
pAdapter = new ParticipantsAdapter(getApplicationContext(), participantArrayList);
listview.setAdapter(pAdapter);
}
protected String doInBackground(final String... args) {
HttpHandler sh = new HttpHandler();
jsonOuterArray = new JSONArray();
String jsonOuterArray = sh.makeServiceCall(url);
return null;
}
}
}
答案 0 :(得分：0)
错误可能是因为在doInBackground（）中返回null。
使您的Json映射变得简单，将其添加到您的gradle文件
compile 'com.fasterxml.jackson.core:jackson-databind:2.3.2'
然后从Json
中检索对象列表 try {
ObjectMapper objectMapper = new ObjectMapper();
TypeReference<List<ParticipantItem>> mapType = new
TypeReference<List<ParticipantItem>>() {};
participantArrayList= objectMapper.readValue(jsonOuterArray,mapType) ;
} catch (IOException e) {
e.printStackTrace();
}
答案 1 :(得分：0)
您的JsonArray长度为空，您需要从Asyntask中的响应中分配。请参阅下面的代码。
HttpManager：爪哇
public class HttpManager {
public static String getResponse(RequestPackage p) {
BufferedReader reader = null;
String uri = p.getUri();
//Managing GET request using appending parameter to the url
if(p.getMethod().equals("GET")) {
uri += "?" + p.getEncodedParams();
}
try {
URL url = new URL(uri);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setRequestMethod(p.getMethod());
//Managing POST request using OutPutStream
if (p.getMethod().equals("POST")) {
con.setDoOutput(true);
OutputStreamWriter writer = new OutputStreamWriter(con.getOutputStream());
writer.write(p.getEncodedParams());
writer.flush();
}
StringBuilder sb = new StringBuilder();
reader = new BufferedReader(new InputStreamReader(con.getInputStream()));
String line;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
return sb.toString();
}
catch (Exception e) {
e.printStackTrace();
return null;
} finally {
if (reader != null) {
try {
reader.close();
}
catch (IOException ex) {
ex.printStackTrace();
return null;
}
}
}
}
}
RequestPackage.Java
public class RequestPackage {
private String uri;
private String method = "GET";
private Map<String,String> params = new HashMap<>();
public Map<String, Integer> getParamsInt() {
return paramsInt;
}
public void setParamsInt(Map<String, Integer> paramsInt) {
this.paramsInt = paramsInt;
}
private Map<String,Integer> paramsInt = new HashMap<>();
public String getUri() {
return uri;
}
public void setUri(String uri) {
this.uri = uri;
}
public String getMethod() {
return method;
}
public void setMethod(String method) {
this.method = method;
}
public Map<String, String> getParams() {
return params;
}
public void setParams(Map<String, String> params) {
this.params = params;
}
public void setParams(String key, String value) {
params.put(key,value);
}
public String getEncodedParams() {
StringBuilder sb = new StringBuilder();
for(String key : params.keySet()) {
String value = null;
try{
value = URLEncoder.encode(params.get(key),"UTF-8");
}
catch(UnsupportedEncodingException e) {
e.printStackTrace();
}
if(sb.length() > 0)
{
sb.append("&");
}
sb.append(key + "=" + value);
}
return sb.toString();
}
}
MainActivity.Java
public class MainActivity extends AppCompatActivity {
private ProgressDialog pDialog;
ArrayList<Result> participantArrayList;
ParticipantsAdapter pAdapter;
Integer a;
JSONArray jsonOuterArray=null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//For GET request parameter pass through the url.
RequestPackage regPackage = new RequestPackage();
regPackage.setMethod("GET");
regPackage.setUri("http://findcourse.net/search_result.php?search=&study_field=17");
new webTask().execute(regPackage);
}
public class webTask extends AsyncTask<RequestPackage, String, String> {
@Override
protected void onPreExecute() {
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage("Loading...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
//You can also use progress dialog here
Toast.makeText(getApplicationContext(), "Please Wait", Toast.LENGTH_SHORT).show();
}
@Override
protected String doInBackground(RequestPackage... requestPackages) {
String content = HttpManager.getResponse(requestPackages[0]);
return content;
}
@Override
protected void onPostExecute(String result) {
//Webserver will return response in a result variable.
String response = result;
Toast.makeText(getApplicationContext(), response, Toast.LENGTH_LONG).show();
pDialog.dismiss();
try {
JSONArray jsonArray = new JSONArray(response);
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject item = (JSONObject) jsonArray.get(i);
JSONObject message = item.getJSONObject("result");
String offered_by_detail = message.getString("offered_by");
String course = message.getString("course");
String logo = message.getString("logo");
String total_views = message.getString("total_views");
String total_course_offered = message.getString("total_course_offered");
Toast.makeText(MainActivity.this,
logo+ offered_by_detail + course, Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
e.printStackTrace();
pDialog.dismiss();
}
}
}
}