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[英]Simple parse JSON from URL on Android and display in listview or spinner
[英]Simple parse JSON from URL on Android and display in listview
我正在嘗試解析從我的Android應用程序中的URL獲取的JSON結果...
我在互聯網上嘗試了一些例子,但無法讓它發揮作用。 JSON數據如下所示:
[
{
"city_id": "1",
"city_name": "Noida"
},
{
"city_id": "2",
"city_name": "Delhi"
},
{
"city_id": "3",
"city_name": "Gaziyabad"
},
{
"city_id": "4",
"city_name": "Gurgaon"
},
{
"city_id": "5",
"city_name": "Gr. Noida"
}
]
獲取URL並解析JSON數據的最簡單方法是在列表視圖中顯示它
您可以使用AsyncTask
,您必須自定義以滿足您的需求,但類似於以下內容
異步任務有三種主要方法:
onPreExecute()
- 最常用於設置和啟動進度對話框
doInBackground()
- 建立連接並從服務器接收響應(不要嘗試為GUI元素分配響應值,這是一個常見錯誤,無法在后台線程中完成)。
onPostExecute()
- 這里我們不在后台線程中,因此我們可以使用響應數據進行用戶界面操作,或者只是將響應分配給特定的變量類型。 首先,我們將啟動該類,初始化一個String
以將結果保存在方法之外但在類中,然后運行onPreExecute()
方法設置一個簡單的進度對話框。
class MyAsyncTask extends AsyncTask<String, String, Void> {
private ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
InputStream inputStream = null;
String result = "";
protected void onPreExecute() {
progressDialog.setMessage("Downloading your data...");
progressDialog.show();
progressDialog.setOnCancelListener(new OnCancelListener() {
public void onCancel(DialogInterface arg0) {
MyAsyncTask.this.cancel(true);
}
});
}
然后我們需要建立連接以及我們如何處理響應:
@Override
protected Void doInBackground(String... params) {
String url_select = "http://yoururlhere.com";
ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();
try {
// Set up HTTP post
// HttpClient is more then less deprecated. Need to change to URLConnection
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url_select);
httpPost.setEntity(new UrlEncodedFormEntity(param));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
// Read content & Log
inputStream = httpEntity.getContent();
} catch (UnsupportedEncodingException e1) {
Log.e("UnsupportedEncodingException", e1.toString());
e1.printStackTrace();
} catch (ClientProtocolException e2) {
Log.e("ClientProtocolException", e2.toString());
e2.printStackTrace();
} catch (IllegalStateException e3) {
Log.e("IllegalStateException", e3.toString());
e3.printStackTrace();
} catch (IOException e4) {
Log.e("IOException", e4.toString());
e4.printStackTrace();
}
// Convert response to string using String Builder
try {
BufferedReader bReader = new BufferedReader(new InputStreamReader(inputStream, "utf-8"), 8);
StringBuilder sBuilder = new StringBuilder();
String line = null;
while ((line = bReader.readLine()) != null) {
sBuilder.append(line + "\n");
}
inputStream.close();
result = sBuilder.toString();
} catch (Exception e) {
Log.e("StringBuilding & BufferedReader", "Error converting result " + e.toString());
}
} // protected Void doInBackground(String... params)
最后,這里我們將解析返回,在這個例子中它是一個JSON數組然后關閉對話框:
protected void onPostExecute(Void v) {
//parse JSON data
try {
JSONArray jArray = new JSONArray(result);
for(i=0; i < jArray.length(); i++) {
JSONObject jObject = jArray.getJSONObject(i);
String name = jObject.getString("name");
String tab1_text = jObject.getString("tab1_text");
int active = jObject.getInt("active");
} // End Loop
this.progressDialog.dismiss();
} catch (JSONException e) {
Log.e("JSONException", "Error: " + e.toString());
} // catch (JSONException e)
} // protected void onPostExecute(Void v)
} //class MyAsyncTask extends AsyncTask<String, String, Void>
我建議使用JSONParser
類。 它非常易於使用。
public class JSONParser {
static InputStream is = null;
static 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(httpParameters);
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 (Exception ex) {
Log.d("Networking", ex.getLocalizedMessage());
throw new IOException("Error connecting");
}
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 (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// 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;
}
然后在您的應用程序中,創建此類的實例。 如果需要,您可能希望傳遞構造函數“GET”或“POST”。
public JSONParser jsonParser = new JSONParser();
try {
// Building Parameters ( you can pass as many parameters as you want)
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("name", name));
params.add(new BasicNameValuePair("age", 25));
// Getting JSON Object
JSONObject json = jsonParser.makeHttpRequest(YOUR_URL, "POST", params);
} catch (JSONException e) {
e.printStackTrace();
}
JSONObject(html).getString("name");
如何獲取html
字符串: 使用android發出HTTP請求
由於不推薦使用HttpClient
, 這里有一個很好的例子,說明如何使用URLConnection
:
像
HttpHandler.java
一樣創建一個類名。 在下面我已經包含了HttpHandler.java
文件。import android.util.Log; import java.io.BufferedInputStream; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.ProtocolException; import java.net.URL; public class HttpHandler { private static final String TAG = HttpHandler.class.getSimpleName(); public HttpHandler() { } public String makeServiceCall(String reqUrl) { String response = null; try { URL url = new URL(reqUrl); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setRequestMethod("GET"); // read the response InputStream in = new BufferedInputStream(conn.getInputStream()); response = convertStreamToString(in); } catch (MalformedURLException e) { Log.e(TAG, "MalformedURLException: " + e.getMessage()); } catch (ProtocolException e) { Log.e(TAG, "ProtocolException: " + e.getMessage()); } catch (IOException e) { Log.e(TAG, "IOException: " + e.getMessage()); } catch (Exception e) { Log.e(TAG, "Exception: " + e.getMessage()); } return response; } private String convertStreamToString(InputStream is) { BufferedReader reader = new BufferedReader(new InputStreamReader(is)); StringBuilder sb = new StringBuilder(); String line; try { while ((line = reader.readLine()) != null) { sb.append(line).append('\\n'); } } catch (IOException e) { e.printStackTrace(); } finally { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } return sb.toString(); } }
現在,您必須打開
activity.main.xml
以生成JSON解析數據的列表。activity_main.xml
代碼如,<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="in.vetbossel.androidjsonparse.MainActivity"> <ListView android:id="@+id/list" android:layout_width="fill_parent" android:layout_height="wrap_content" /> </RelativeLayout> Hereafter create one xml file, the name is `list_item.xml` used for list the all values from *JSON*. The code is, <?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:orientation="vertical" android:padding="@dimen/activity_horizontal_margin"> <TextView android:id="@+id/name" android:layout_width="fill_parent" android:layout_height="wrap_content" android:paddingBottom="2dip" android:paddingTop="6dip" android:textColor="#3498db" android:textSize="16sp" android:textStyle="bold" /> <TextView android:id="@+id/email" android:layout_width="fill_parent" android:layout_height="wrap_content" android:paddingBottom="2dip" android:textColor="#16a085" android:textStyle="bold" /> <TextView android:id="@+id/mobile" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textColor="#e74c3c" android:textStyle="bold" /> </LinearLayout>
在MainActivity中解析JSON
獲取JSON的值,進行
Http
調用以獲取JSON值。 有許多庫文件將在那里獲取JSON值,如volley庫和改造庫等。通常用於解析JSON值的volley庫和改進庫。 最后,MainActivity.java
代碼如,import android.app.ProgressDialog; import android.os.AsyncTask; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.util.Log; import android.widget.ListAdapter; import android.widget.ListView; import android.widget.SimpleAdapter; import android.widget.Toast; import org.json.JSONArray; import org.json.JSONException; import org.json.JSONObject; import java.util.ArrayList; import java.util.HashMap; public class MainActivity extends AppCompatActivity { private String TAG = MainActivity.class.getSimpleName(); private ProgressDialog pDialog; private ListView lv; // URL to get contacts JSON private static String url = "http://demos.vetbossel.in/ajson/sample"; ArrayList<HashMap<String, String>> contactList; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); contactList = new ArrayList<>(); lv = (ListView) findViewById(R.id.list); new GetContacts().execute(); } /** * Async task class to get json by making HTTP call */ private class GetContacts extends AsyncTask<Void, Void, Void> { @Override protected void onPreExecute() { super.onPreExecute(); // Showing progress dialog pDialog = new ProgressDialog(MainActivity.this); pDialog.setMessage("Please wait..."); pDialog.setCancelable(false); pDialog.show(); } @Override protected Void doInBackground(Void... arg0) { HttpHandler sh = new HttpHandler(); // Making a request to url and getting response String jsonStr = sh.makeServiceCall(url); Log.e(TAG, "Response from url: " + jsonStr); if (jsonStr != null) { try { JSONObject jsonObj = new JSONObject(jsonStr); // Getting JSON Array node JSONArray contacts = jsonObj.getJSONArray("contacts"); // looping through All Contacts for (int i = 0; i < contacts.length(); i++) { JSONObject c = contacts.getJSONObject(i); String id = c.getString("id"); String name = c.getString("name"); String email = c.getString("email"); String address = c.getString("address"); String gender = c.getString("gender"); // Phone node is JSON Object JSONObject phone = c.getJSONObject("phone"); String mobile = phone.getString("mobile"); String home = phone.getString("home"); String office = phone.getString("office"); // tmp hash map for single contact HashMap<String, String> contact = new HashMap<>(); // adding each child node to HashMap key => value contact.put("id", id); contact.put("name", name); contact.put("email", email); contact.put("mobile", mobile); // adding contact to contact list contactList.add(contact); } } catch (final JSONException e) { Log.e(TAG, "Json parsing error: " + e.getMessage()); runOnUiThread(new Runnable() { @Override public void run() { Toast.makeText(getApplicationContext(), "Json parsing error: " + e.getMessage(), Toast.LENGTH_LONG) .show(); } }); } } else { Log.e(TAG, "Couldn't get json from server."); runOnUiThread(new Runnable() { @Override public void run() { Toast.makeText(getApplicationContext(), "Couldn't get json from server. Check LogCat for possible errors!", Toast.LENGTH_LONG) .show(); } }); } return null; } @Override protected void onPostExecute(Void result) { super.onPostExecute(result); // Dismiss the progress dialog if (pDialog.isShowing()) pDialog.dismiss(); /** * Updating parsed JSON data into ListView * */ ListAdapter adapter = new SimpleAdapter( MainActivity.this, contactList, R.layout.list_item, new String[]{"name", "email", "mobile"}, new int[]{R.id.name, R.id.email, R.id.mobile}); lv.setAdapter(adapter); } } }
並且不要忘記為您的清單文件添加Internet權限:
<uses-permission android:name="android.permission.INTERNET" />
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
public class GetJsonFromUrl {
String url = null;
public GetJsonFromUrl(String url) {
this.url = url;
}
public String GetJsonData() {
try {
URL Url = new URL(url);
HttpURLConnection connection = (HttpURLConnection) Url.openConnection();
InputStream is = connection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line;
while ((line = br.readLine()) != null) {
sb.append(line);
}
line = sb.toString();
connection.disconnect();
is.close();
sb.delete(0, sb.length());
return line;
} catch (Exception e) {
return null;
}
}
}
這個類用於發布數據
import android.util.Log;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;
import javax.net.ssl.HttpsURLConnection;
/**
* Created by user on 11/2/16.
*/
public class sendDataToServer {
public String postdata(String requestURL,HashMap<String,String> postDataParams){
try {
String response = "";
URL url = new URL(requestURL);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(15000);
conn.setConnectTimeout(15000);
conn.setRequestMethod("POST");
conn.setDoInput(true);
conn.setDoOutput(true);
OutputStream os = conn.getOutputStream();
BufferedWriter writer = new BufferedWriter(
new OutputStreamWriter(os, "UTF-8"));
writer.write(getPostDataString(postDataParams));
writer.flush();
writer.close();
os.close();
String line;
BufferedReader br=new BufferedReader(new InputStreamReader(conn.getInputStream()));
while ((line=br.readLine()) != null) {
response+=line;
}
Log.d("test", response);
return response;
}catch (Exception e){
return e.toString();
}
}
public String postjson(String url,String json){
try {
URL obj = new URL(url);
HttpURLConnection con= (HttpURLConnection) obj.openConnection();
//add reuqest header
con.setRequestMethod("POST");
con.setRequestProperty("Accept", "application/json");
String urlParameters = ""+json;
// Send post request
con.setDoOutput(true);
con.setDoInput(true);
con.setRequestProperty("Content-Type", "application/json");
OutputStreamWriter wr = new OutputStreamWriter(con.getOutputStream());
wr.write(urlParameters);
wr.flush();
wr.close();
int responseCode = con.getResponseCode();
System.out.println("\nSending 'POST' request to URL : " + url);
System.out.println("Post parameters : " + urlParameters);
System.out.println("Response Code : " + responseCode);
BufferedReader in = new BufferedReader(
new InputStreamReader(con.getInputStream()));
String inputLine;
StringBuffer response = new StringBuffer();
while ((inputLine = in.readLine()) != null) {
response.append(inputLine);
}
in.close();
//print result
System.out.println(response.toString());
return response.toString();
}catch(Exception e){
return e.toString();
}
}
private String getPostDataString(HashMap<String, String> params) throws UnsupportedEncodingException {
StringBuilder result = new StringBuilder();
boolean first = true;
for(Map.Entry<String, String> entry : params.entrySet()){
if (first)
first = false;
else
result.append("&");
result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
result.append("=");
result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
}
return result.toString();
}
/* public String postdata(String url) {
}*/
}
試着:
// your get json request to server..
HttpResponse response = httpClient.execute(httpPost);
HttpEntity entity = response.getEntity();
if(entity != null){
JSONObject respObject = new JSONObject(EntityUtils.toString(entity));
String active = respObject.getString("active");
String name = respObject.getString("name");
String tab1_text = respObject.getString("tab1_text");
//....
}
else{
//Do something here...
}
請參閱此示例以獲取和解析來自服務器的json響應:
http://adblogcat.com/parse-json-data-from-a-web-server-and-display-on-listview/
HttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet();
request.setURI(new URI(url));
HttpResponse response = client.execute(request);
BufferedReader in = new BufferedReader(new InputStreamReader(response
.getEntity().getContent()));
String line = "";
while ((line = in.readLine()) != null) {
JSONObject jObject = new JSONObject(line);
if (jObject.has("name")) {
String temp = jObject.getString("name");
Log.e("name",temp);
}
}
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