我正在编写一个应用程序，其中我从JSON获取数据，我可以获取类别列表，但每当我点击任何类别时该特定类别下的未获得产品列表始终获取空白活动。
JSON：
[
{
"categoryId": "1",
"categoryTitle": "SmartPhones", "SmartPhones": [
{
"itemId": "1",
"itemTitle": "Galaxy Mega 5.8"
},
{
"itemId": "2",
"itemTitle": "Galaxy Mega 6.3"
}
]
},
{
"categoryId": "2",
"categoryTitle": "Tablets", "Tablets": [
{
"itemId": "1",
"itemTitle": "Galaxy Note 510"
},
{
"itemId": "2",
"itemTitle": "Galaxy Note 800"
}
]
}
]
AlbumsActivity.java [用于类别]：
public class AlbumsActivity extends ListActivity {
// Connection detector
ConnectionDetector cd;
// Alert dialog manager
AlertDialogManager alert = new AlertDialogManager();
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jsonParser = new JSONParser();
ArrayList<HashMap<String, String>> albumsList;
// albums JSONArray
JSONArray albums = null;
// albums JSON url
private static final String URL_ALBUMS = "my.json"; //providing proper URL
// ALL JSON node names
private static final String TAG_ID = "categoryId";
private static final String TAG_NAME = "categoryTitle";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_albums);
cd = new ConnectionDetector(getApplicationContext());
// Check for internet connection
if (!cd.isConnectingToInternet()) {
// Internet Connection is not present
alert.showAlertDialog(AlbumsActivity.this, "Internet Connection Error",
"Please connect to working Internet connection", false);
// stop executing code by return
return;
}
// Hashmap for ListView
albumsList = new ArrayList<HashMap<String, String>>();
// Loading Albums JSON in Background Thread
new LoadAlbums().execute();
// get listview
ListView lv = getListView();
/**
* Listview item click listener
* TrackListActivity will be lauched by passing album id
* */
lv.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View view, int arg2,
long arg3) {
// on selecting a single album
// TrackListActivity will be launched to show tracks inside the album
Intent i = new Intent(getApplicationContext(), TrackListActivity.class);
// send album id to tracklist activity to get list of songs under that album
String album_id = ((TextView) view.findViewById(R.id.album_id)).getText().toString();
i.putExtra("album_id", album_id);
startActivity(i);
}
});
}
/**
* Background Async Task to Load all Albums by making http request
* */
class LoadAlbums extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(AlbumsActivity.this);
pDialog.setMessage("Listing Albums ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting Albums JSON
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
String json = jsonParser.makeHttpRequest(URL_ALBUMS, "GET",
params);
// Check your log cat for JSON reponse
Log.d("Albums JSON: ", "> " + json);
try {
albums = new JSONArray(json);
if (albums != null) {
// looping through All albums
for (int i = 0; i < albums.length(); i++) {
JSONObject c = albums.getJSONObject(i);
// Storing each json item values in variable
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_ID, id);
map.put(TAG_NAME, name);
// adding HashList to ArrayList
albumsList.add(map);
}
}else{
Log.d("Albums: ", "null");
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all albums
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
AlbumsActivity.this, albumsList,
R.layout.list_item_albums, new String[] { TAG_ID,
TAG_NAME }, new int[] {
R.id.album_id, R.id.album_name });
// updating listview
setListAdapter(adapter);
}
});
}
}
}
TrackListActivity.java [用于产品]：
public class TrackListActivity extends ListActivity {
// Connection detector
ConnectionDetector cd;
// Alert dialog manager
AlertDialogManager alert = new AlertDialogManager();
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jsonParser = new JSONParser();
ArrayList<HashMap<String, String>> tracksList;
// tracks JSONArray
JSONArray albums = null;
// Album id
String album_id, album_name;
// tracks JSON url
// id - should be posted as GET params to get track list (ex: id = 5)
private static final String URL_ALBUMS = "my.json"; //providing proper url
// ALL JSON node names
private static final String TAG_ID = "itemId";
private static final String TAG_NAME = "itemTitle";
private static final String TAG_ALBUM = "categoryId";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_tracks);
cd = new ConnectionDetector(getApplicationContext());
// Check if Internet present
if (!cd.isConnectingToInternet()) {
// Internet Connection is not present
alert.showAlertDialog(TrackListActivity.this, "Internet Connection Error",
"Please connect to working Internet connection", false);
// stop executing code by return
return;
}
// Get album id
Intent i = getIntent();
album_id = i.getStringExtra("album_id");
// Hashmap for ListView
tracksList = new ArrayList<HashMap<String, String>>();
// Loading tracks in Background Thread
new LoadTracks().execute();
// get listview
ListView lv = getListView();
/**
* Listview on item click listener
* SingleTrackActivity will be lauched by passing album id, song id
* */
lv.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View view, int arg2,
long arg3) {
// On selecting single track get song information
Intent i = new Intent(getApplicationContext(), SingleTrackActivity.class);
// to get song information
// both album id and song is needed
String album_id = ((TextView) view.findViewById(R.id.album_id)).getText().toString();
String song_id = ((TextView) view.findViewById(R.id.song_id)).getText().toString();
Toast.makeText(getApplicationContext(), "Album Id: " + album_id + ", Song Id: " + song_id, Toast.LENGTH_SHORT).show();
i.putExtra("album_id", album_id);
i.putExtra("song_id", song_id);
startActivity(i);
}
});
}
/**
* Background Async Task to Load all tracks under one album
* */
class LoadTracks extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(TrackListActivity.this);
pDialog.setMessage("Loading songs ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting tracks json and parsing
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// post album id as GET parameter
params.add(new BasicNameValuePair(TAG_ID, album_id));
// getting JSON string from URL
String json = jsonParser.makeHttpRequest(URL_ALBUMS, "GET",
params);
// Check your log cat for JSON reponse
Log.d("Track List JSON: ", json);
try {
JSONObject jObj = new JSONObject(json);
if (jObj != null) {
String album_id = jObj.getString(TAG_ID);
album_name = jObj.getString(TAG_ALBUM);
if (albums != null) {
// looping through All songs
for (int i = 0; i < albums.length(); i++) {
JSONObject c = albums.getJSONObject(i);
// Storing each json item in variable
String song_id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put("album_id", album_id);
map.put(TAG_ID, song_id);
map.put(TAG_NAME, name);
// adding HashList to ArrayList
tracksList.add(map);
}
} else {
Log.d("Albums: ", "null");
}
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all tracks
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
TrackListActivity.this, tracksList,
R.layout.list_item_tracks, new String[] { "album_id", TAG_ID,
TAG_NAME }, new int[] {
R.id.album_id, R.id.song_id, R.id.album_name });
// updating listview
setListAdapter(adapter);
// Change Activity Title with Album name
setTitle(album_name);
}
});
}
}
}
答案 0 :(得分：0)
您将Web服务中的JSON读入JSONObject，但您发布的JSON是JSONArray。尝试这样的东西来解析你的JSON ......
JSONArray jObj = new JSONArray(json);
if (jObj != null) {
for(int i = 0; i < jObj.length(); i++) {
JSONObject cat = jObj.getJSONObject(i);
String id = cat.getString("categoryId");
String title = cat.getString("categoryTitle");
JSONArray devices = cat.optJSONArray(title, null);
for(int j=0; i<devices.length(); j++) {
//get itemId and itemTitle
}
}
}