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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
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1 回答 1

0 
Error parsing data org.json.JSONException: End of input at character 0

你的json是空的。Web 服务没有返回任何数据。因此它不能被解析。

于 2012-10-15T04:29:59.940 回答