我正在关注“ http://www.androidhive.info/2012/01/android-json-parsing-tutorial/ ”中关于在 android 中解析 json 的教程。程序崩溃，因为无法在主线程上创建网络连接。所以我添加了异步任务。现在的问题是数据被解析但列表视图没有显示任何内容。
这是我的代码：
AndroidJSONParsingActivity.java
public class AndroidJSONParsingActivity extends ListActivity {
ArrayList<HashMap<String, String>> contactList;
ListAdapter adapter;
// url to make request
private static String url = "http://api.androidhive.info/contacts/";
// JSON Node names
static final String TAG_CONTACTS = "contacts";
static final String TAG_ID = "id";
static final String TAG_NAME = "name";
static final String TAG_EMAIL = "email";
static final String TAG_ADDRESS = "address";
static final String TAG_GENDER = "gender";
static final String TAG_PHONE = "phone";
static final String TAG_PHONE_MOBILE = "mobile";
static final String TAG_PHONE_HOME = "home";
static final String TAG_PHONE_OFFICE = "office";
// contacts JSONArray
JSONArray contacts = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.list_item);
new AsyncTask<String, Void, ArrayList<HashMap<String, String>>>() {
@Override
protected ArrayList<HashMap<String, String>> doInBackground(
String... params) {
// Hashmap for ListView
contactList = new ArrayList<HashMap<String, String>>();
// Creating JSON Parser instance
JSONParser jParser = new JSONParser();
// getting JSON string from URL
final String url1 = params[0];
JSONObject jObj = jParser.getJSONFromUrl(url1);
try {
contacts = jObj.getJSONArray(TAG_CONTACTS);
for (int i = 0; i < contacts.length(); ++i) {
JSONObject contactObj = contacts.getJSONObject(i);
// Storing each json item in variable
String id = contactObj.getString(TAG_ID);
String name = contactObj.getString(TAG_NAME);
String email = contactObj.getString(TAG_EMAIL);
String address = contactObj.getString(TAG_ADDRESS);
String gender = contactObj.getString(TAG_GENDER);
// Phone number is agin JSON Object
JSONObject phone = contactObj.getJSONObject(TAG_PHONE);
String mobile = phone.getString(TAG_PHONE_MOBILE);
String home = phone.getString(TAG_PHONE_HOME);
String office = phone.getString(TAG_PHONE_OFFICE);
// 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);
map.put(TAG_EMAIL, email);
map.put(TAG_PHONE_MOBILE, mobile);
contactList.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
return contactList;
}
@Override
protected void onPostExecute(
ArrayList<HashMap<String, String>> contactList) {
/**
* Updating parsed JSON data into ListView
* */
for(int i=0;i<contactList.size();i++) {
HashMap<String, String> map = contactList.get(i);
Toast.makeText(getApplicationContext(), map.get(TAG_NAME), Toast.LENGTH_LONG).show();
}
Toast.makeText(AndroidJSONParsingActivity.this, "hi", Toast.LENGTH_LONG).show();
adapter = new SimpleAdapter(AndroidJSONParsingActivity.this, contactList,
R.layout.list_item, new String[] { TAG_NAME, TAG_EMAIL,
TAG_PHONE_MOBILE }, new int[] { R.id.name,
R.id.email, R.id.mobile });
}
}.execute(url);
setListAdapter(adapter);
// selecting single ListView item
ListView lv = getListView();
// Launching new screen on Selecting Single ListItem
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String name = ((TextView) view.findViewById(R.id.name))
.getText().toString();
String cost = ((TextView) view.findViewById(R.id.email))
.getText().toString();
String description = ((TextView) view.findViewById(R.id.mobile))
.getText().toString();
// Starting new intent
Intent intent = new Intent(getApplicationContext(),
SingleMenuItemActivity.class);
intent.putExtra(TAG_NAME, name);
intent.putExtra(TAG_EMAIL, cost);
intent.putExtra(TAG_PHONE_MOBILE, description);
startActivity(intent);
}
});
}
}
JSONParser.java
public class JSONParser {
static InputStream inputStream = null;
static JSONObject jObj = null;
static String jsonStr = "";
public JSONParser() {
}
public JSONObject getJSONFromUrl(String url) {
try {
DefaultHttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet(url);
HttpResponse response = client.execute(request);
HttpEntity entity = response.getEntity();
inputStream = entity.getContent();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while((line=reader.readLine()) != null) {
sb.append(line + "\n");
}
inputStream.close();
jsonStr = sb.toString();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
jObj = new JSONObject(jsonStr);
} catch (JSONException e) {
e.printStackTrace();
}
return jObj;
}
}
SingleMenuItemActivity.java
public class SingleMenuItemActivity extends Activity {
TextView tvName, tvEmail, tvMobile;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.list_item);
tvName = (TextView) findViewById(R.id.name);
tvEmail = (TextView) findViewById(R.id.email);
tvMobile = (TextView) findViewById(R.id.mobile);
Bundle bundle = getIntent().getExtras();
tvName.setText(bundle.getString(AndroidJSONParsingActivity.TAG_NAME));
tvEmail.setText(bundle.getString(AndroidJSONParsingActivity.TAG_EMAIL));
tvMobile.setText(bundle.getString(AndroidJSONParsingActivity.TAG_PHONE_MOBILE));
}
}