我正在使用来自http://www.androidhive.info/2012/01/android-json-parsing-tutorial/的示例
当我运行应用程序时，它说我有 java.lang.nullexception 错误！我没有修改应用程序中的任何内容。
这是解析活动：
public class AndroidJSONParsingActivity extends ListActivity {
// url to make request
private static String url = "http://api.androidhive.info/contacts/";
// JSON Node names
private static final String TAG_CONTACT = "contacts";
private static final String TAG_ID = "id";
private static final String TAG_NAME = "name";
private static final String TAG_EMAIL = "email";
private static final String TAG_ADDRESS = "address";
private static final String TAG_GENDER = "gender";
private static final String TAG_PHONE = "phone";
private static final String TAG_PHONE_MOBILE = "mobile";
private static final String TAG_PHONE_HOME = "home";
private static final String TAG_PHONE_OFFICE = "office";
// contacts JSONArray
JSONArray contacts = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Hashmap for ListView
ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>();
// Creating JSON Parser instance
JSONParser jParser = new JSONParser();
// getting JSON string from URL
JSONObject json = jParser.getJSONFromUrl(url);
try {
// Getting Array of Contacts
contacts = json.getJSONArray(TAG_CONTACT);
// looping through All Contacts
for(int i = 0; i < contacts.length(); i++){
JSONObject c = contacts.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
String email = c.getString(TAG_EMAIL);
String address = c.getString(TAG_ADDRESS);
String gender = c.getString(TAG_GENDER);
// Phone number is agin JSON Object
JSONObject phone = c.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);
// adding HashList to ArrayList
contactList.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(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 });
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 in = new Intent(getApplicationContext(), SingleMenuItemActivity.class);
in.putExtra(TAG_NAME, name);
in.putExtra(TAG_EMAIL, cost);
in.putExtra(TAG_PHONE_MOBILE, description);
startActivity(in);
}
});
}
}
这是我的解析器：
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;
}
}
这是我的 logcat 输出：
10-15 04:06:21.879: E/Buffer 错误 (292): 错误转换结果 java.lang.NullPointerException
10-15 04:06:21.879: E/JSON Parser(292): Error parsing data org.json.JSONException: End of input at character 0 of
10-15 04:06:21.889: D/AndroidRuntime(292): Shutting down VM
10-15 04:06:21.889: W/dalvikvm(292): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
10-15 04:06:21.899: E/AndroidRuntime(292): FATAL EXCEPTION: main
10-15 04:06:21.899: E/AndroidRuntime(292): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.androidhive.jsonparsing/com.androidhive.jsonparsing.AndroidJSONParsingActivity}: java.lang.NullPointerException
10-15 04:06:21.899: E/AndroidRuntime(292): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
10-15 04:06:21.899: E/AndroidRuntime(292): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
10-15 04:06:21.899: E/AndroidRuntime(292): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
10-15 04:06:21.899: E/AndroidRuntime(292): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
10-15 04:06:21.899: E/AndroidRuntime(292): at android.os.Handler.dispatchMessage(Handler.java:99)
10-15 04:06:21.899: E/AndroidRuntime(292): at android.os.Looper.loop(Looper.java:123)
10-15 04:06:21.899: E/AndroidRuntime(292): at android.app.ActivityThread.main(ActivityThread.java:4627)
10-15 04:06:21.899: E/AndroidRuntime(292): at java.lang.reflect.Method.invokeNative(Native Method)
10-15 04:06:21.899: E/AndroidRuntime(292): at java.lang.reflect.Method.invoke(Method.java:521)
10-15 04:06:21.899: E/AndroidRuntime(292): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-15 04:06:21.899: E/AndroidRuntime(292): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-15 04:06:21.899: E/AndroidRuntime(292): at dalvik.system.NativeStart.main(Native Method)
10-15 04:06:21.899: E/AndroidRuntime(292): Caused by: java.lang.NullPointerException
10-15 04:06:21.899: E/AndroidRuntime(292): at com.androidhive.jsonparsing.AndroidJSONParsingActivity.onCreate(AndroidJSONParsingActivity.java:58)
10-15 04:06:21.899: E/AndroidRuntime(292): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-15 04:06:21.899: E/AndroidRuntime(292): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
10-15 04:06:21.899: E/AndroidRuntime(292): ... 11 more