ArrayList<HashMap<String, String>> list = new ArrayList<HashMap<String, String>>();
//URL to get JSON Array
private static String url = "http://jsonplaceholder.typicode.com/posts";
//JSON Node Names
// private static final String TAG_OS = "Employee";
private static final String TAG_USER= "userId";
private static final String TAG_NAME = "id";
private static final String TAG_TITLE = "title";
private static final String TAG_BODY = "body";
JSONArray android = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
list = new ArrayList<HashMap<String, String>>();
Btngetdata = (Button)findViewById(R.id.getdata);
Btngetdata.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
new JSONParse().execute();
}
});
}
private class JSONParse extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
ver = (TextView)findViewById(R.id.user);
name = (TextView)findViewById(R.id.id);
api = (TextView)findViewById(R.id.titile);
body =(TextView)findViewById(R.id.body);
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage("Getting Data ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected JSONObject doInBackground(String... args) {
JSONParser jParser = new JSONParser();
// Getting JSON from URL
JSONObject json = jParser.getJSONFromUrl(url);
return json;
}
@Override
protected void onPostExecute(JSONObject json) {
pDialog.dismiss();
try {
// Getting JSON Array from URL
android = json.getJSONArray("");
for(int i = 0; i < android.length(); i++){
JSONObject c = android.getJSONObject(i);
// Storing JSON item in a Variable
String ver = c.getString(TAG_USER);
String name = c.getString(TAG_NAME);
String api = c.getString(TAG_TITLE);
String body =c.getString(TAG_BODY);
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_USER, ver);
map.put(TAG_NAME, name);
map.put(TAG_TITLE, api);
map.put(TAG_BODY, body);
list.add(map);
List=(ListView)findViewById(R.id.list);
ListAdapter adapter = new SimpleAdapter(MainActivity.this, list,
R.layout.list_v,
new String[] { TAG_USER,TAG_NAME, TAG_TITLE,TAG_BODY }, new int[] {
R.id.user,R.id.id, R.id.titile,R.id.body});
List.setAdapter(adapter);
List.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Toast.makeText(MainActivity.this, "You Clicked at "+list.get(+position).get("name"), Toast.LENGTH_SHORT).show();
}
});
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
json parse:-
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 {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
HttpResponse httpResponse = httpClient.execute(httpPost);
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");
}
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;
}
}
Logcat here
java.lang.NullPointerException: Attempt to invoke virtual method 'org.json.JSONArrayorg.json.JSONObject.getJSONArray(java.lang.String)' on a null object reference
at com.example.mind.sqlitedatabase.MainActivity$JSONParse.onPostExecute(MainActivity.java:134)
at com.example.mind.sqlitedatabase.MainActivity$JSONParse.onPostExecute(MainActivity.java:103)
at android.os.AsyncTask.finish(AsyncTask.java:636)
at android.os.AsyncTask.access$500(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:653)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
实际上，当我点击get按钮调用uri进行json解析时，我遇到了问题 但是当在android设备中json = null解析...
答案 0 :(得分：0)
在这里我使用了Volley库，它处理你手动完成的所有事情（Asynctask，json的httprequest）。
我希望它可以帮到你
// JsonObject request
public void getJSONFromUrl(String url) {
RequestQueue queue = Volley.newRequestQueue(getActivity());
JsonObjectRequest jsonObjReq = new JsonObjectRequest(Request.Method.GET,
url, null,
new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
Log.d("Response", "Response" + response);
//handle the json response
handleResponse(response);
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d("Error", "Error: " + error.getMessage());
}
});
queue.add(jsonObjReq);
}
//使用JsonHelper类从 下面的类将帮助将json响应转换为MAP，从map转换为json。 从https://gist.github.com/codebutler/2339666 凌空图书馆使用情况
http://www.androidhive.info/2014/09/android-json-parsing-using-volley/ public void handleResponse(JSONObject response) {
Map<String, Object> map = new HashMap<>();
if(response != null){
try {
// JsonObject to Map
map = JsonHelper.toMap(response);
// boolean isSuccess = map.get("success")
// if(isSuccess){
//}
if (map.size() != 0){
// use the data
}
Log.d("MAp","map" + map);
} catch (JSONException e) {
e.printStackTrace();
}
}
}
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.*;
public class JsonHelper {
public static Object toJSON(Object object) throws JSONException {
if (object instanceof Map) {
JSONObject json = new JSONObject();
Map map = (Map) object;
for (Object key : map.keySet()) {
json.put(key.toString(), toJSON(map.get(key)));
}
return json;
} else if (object instanceof Iterable) {
JSONArray json = new JSONArray();
for (Object value : ((Iterable)object)) {
json.put(value);
}
return json;
} else {
return object;
}
}
public static boolean isEmptyObject(JSONObject object) {
return object.names() == null;
}
public static Map<String, Object> getMap(JSONObject object, String key) throws JSONException {
return toMap(object.getJSONObject(key));
}
public static Map<String, Object> toMap(JSONObject object) throws JSONException {
Map<String, Object> map = new HashMap();
Iterator keys = object.keys();
while (keys.hasNext()) {
String key = (String) keys.next();
map.put(key, fromJson(object.get(key)));
}
return map;
}
public static List toList(JSONArray array) throws JSONException {
List list = new ArrayList();
for (int i = 0; i < array.length(); i++) {
list.add(fromJson(array.get(i)));
}
return list;
}
private static Object fromJson(Object json) throws JSONException {
if (json == JSONObject.NULL) {
return null;
} else if (json instanceof JSONObject) {
return toMap((JSONObject) json);
} else if (json instanceof JSONArray) {
return toList((JSONArray) json);
} else {
return json;
}
}
}