转换结果java.lang.nullpointerexception时出现Android错误

我正在尝试在Android中创建一个简单的登录和注册活动。 我得到了错误

转换结果java.lang.nullpointerexception时出错，分析时出错 data org.json.JSONException

下面是我的代码： JSONPARSER

public class JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }

    // function get json from url
    // by making HTTP POST or GET method
    public JSONObject makeHttpRequest(String url, String method,
                    List<NameValuePair> params) {

            // Making HTTP request
            try {

                    // check for request method
                    if(method == "POST"){
                            // request method is POST
                            // defaultHttpClient
                            DefaultHttpClient httpClient = new DefaultHttpClient();
                            HttpPost httpPost = new HttpPost(url);
                            httpPost.setEntity(new UrlEncodedFormEntity(params));

                            HttpResponse httpResponse = httpClient.execute(httpPost);
                            HttpEntity httpEntity = httpResponse.getEntity();
                            is = httpEntity.getContent();

                    }else if(method == "GET"){
                            // request method is GET
                            DefaultHttpClient httpClient = new DefaultHttpClient();
                            String paramString = URLEncodedUtils.format(params, "utf-8");
                            url += "?" + paramString;
                            HttpGet httpGet = new HttpGet(url);

                            HttpResponse httpResponse = httpClient.execute(httpGet);
                            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;

    }

主要问题在实施Martin建议的解决方案后得到解决。 我现在面临着其他一些错误。LOGCAT附在下面

   10-28 23:17:19.183: D/dalvikvm(449): GC_EXTERNAL_ALLOC freed 78K, 52% free 2599K/5379K, external 897K/1038K, paused 232ms
  10-28 23:17:23.259: W/KeyCharacterMap(449): No keyboard for id 0
  10-28 23:17:23.269: W/KeyCharacterMap(449): Using default keymap: /system/usr/keychars/qwerty.kcm.bin
  10-28 23:17:46.379: E/Buffer Error(449): Error converting result java.lang.NullPointerException
  10-28 23:17:46.389: E/Buffer Error(449): Error converting result java.lang.NullPointerException
  10-28 23:17:46.389: E/JSON Parser(449): Error parsing data org.json.JSONException: End of input at character 0 of 
  10-28 23:17:46.409: E/JSON Parser(449): Error parsing data org.json.JSONException: End of input at character 0 of 

---

这可能是因为密钥甚至不存在，在调用json.getString（“key”）之前执行此操作；方法：

请注意，您首先需要确保键实际存在，否则它可能会抛出JSONException

希望这有助于

---

问候

你能把你的信寄出去吗logcat@Satyen：10-28 22:40:45.879:E/缓冲区错误（373）：转换结果java.lang.NullPointerException 10-28 22:40:45.899:E/缓冲区错误（373）：转换结果java.lang.NullPointerException 10-28 22:40:45.983:E/JSON解析器错误（373）：解析数据org.json.JSONException时出错：输入结束于10-28 22:40:45.989的字符0处：D/AndroidRuntime（373）：关闭VM 10-28 22:40:45.989:W/dalvikvm（373）：threadid=1：线程退出时出现未捕获异常（组=0x40015560）10-28 22:40:46.049:E/AndroidRuntime（373）：致命异常：main 10-28 22:40:46.049:E/AndroidRuntime（373）：如果您需要帮助，请使用坠机事件的完整日志编辑您的问题。很难读入注释（尤其是未格式化的注释），您缺少了一些相关部分。仅供参考，我添加了如下代码：if（json！=null&&！json.isNull（KEY_SUCCESS））{//wahet无论您是否需要json.getString（KEY_SUCCESS）；}if（json.getString（KEY_SUCCESS）！=null）{registerErrorMsg.setText（“”）；String res=json.getString（KEY_SUCCESS）；if（Integer.parseInt（res）==1）{No，如果是这种情况，则在Integer.parseInt（res）上发生NullPonterException，也就是说，您没有在KEY_SUCCESSWell上接收到任何值。唯一的方法是避免我编辑的答案中显示的nullpointerexception，但如果您总是得到null，则意味着您接收的数据有问题…好的，非常感谢您的帮助。将尝试此操作并让您知道。这似乎有效。非常感谢！！！我是fac正在处理缓冲区错误和JSON解析器错误。必须对其进行调试

public class RegisterActivity extends Activity {
Button btnRegister;
Button btnLinkToLogin;
EditText inputFullName;
EditText inputEmail;
EditText inputPassword;
TextView registerErrorMsg;

// JSON Response node names
private static String KEY_SUCCESS = "success";
private static String KEY_ERROR = "error";
private static String KEY_ERROR_MSG = "error_msg";
private static String KEY_UID = "uid";
private static String KEY_NAME = "name";
private static String KEY_EMAIL = "email";
private static String KEY_CREATED_AT = "created_at";


    private class MyAsyncTask extends AsyncTask<String, Void, JSONObject> {

    protected JSONObject doInBackground(String... params) {
        UserFunctions userFunction = new UserFunctions();
        if (params.length != 3)
            return null;
        JSONObject json = userFunction.registerUser(params[0], params[1], params[2]);
        return json;
    }

    protected void onPostExecute(JSONObject json) {
        // check for login response
        try {
            if (json != null && json.getString(KEY_SUCCESS) != null) {
                registerErrorMsg.setText("");
                String res = json.getString(KEY_SUCCESS); 
                if(Integer.parseInt(res) == 1){
                    // user successfully registred
                    // Store user details in SQLite Database
                    DatabaseHandler db = new DatabaseHandler(getApplicationContext());
                    JSONObject json_user = json.getJSONObject("user");

                    // Clear all previous data in database
                    UserFunctions userFunction = new UserFunctions();
                    userFunction.logoutUser(getApplicationContext());
                    db.addUser(json_user.getString(KEY_NAME), json_user.getString(KEY_EMAIL), json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));                        
                    // Launch Dashboard Screen
                    Intent dashboard = new Intent(getApplicationContext(), DashboardActivity.class);
                    // Close all views before launching Dashboard
                    dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                    startActivity(dashboard);
                    // Close Registration Screen
                    finish();
                }else{
                    // Error in registration
                    registerErrorMsg.setText("Error occured in registration");
                }
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}




@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.register);

    // Importing all assets like buttons, text fields
    inputFullName = (EditText) findViewById(R.id.registerName);
    inputEmail = (EditText) findViewById(R.id.registerEmail);
    inputPassword = (EditText) findViewById(R.id.registerPassword);
    btnRegister = (Button) findViewById(R.id.btnRegister);
    btnLinkToLogin = (Button) findViewById(R.id.btnLinkToLoginScreen);
    registerErrorMsg = (TextView) findViewById(R.id.register_error);

    // Register Button Click event
    btnRegister.setOnClickListener(new View.OnClickListener() {         
        public void onClick(View view) {
            String name = inputFullName.getText().toString();
            String email = inputEmail.getText().toString();
            String password = inputPassword.getText().toString();
            new MyAsyncTask().execute(name, email, password);
            UserFunctions userFunction = new UserFunctions();
            JSONObject json = userFunction.registerUser(name, email, password);

            // check for login response
            try {
                if (json.getString(KEY_SUCCESS) != null) {
                    registerErrorMsg.setText("");
                    String res = json.getString(KEY_SUCCESS); 
                    if(Integer.parseInt(res) == 1){
                        // user successfully registred
                        // Store user details in SQLite Database
                        DatabaseHandler db = new DatabaseHandler(getApplicationContext());
                        JSONObject json_user = json.getJSONObject("user");

                        // Clear all previous data in database
                        userFunction.logoutUser(getApplicationContext());
                        db.addUser(json_user.getString(KEY_NAME), json_user.getString(KEY_EMAIL), json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));                        
                        // Launch Dashboard Screen
                        Intent dashboard = new Intent(getApplicationContext(), DashboardActivity.class);
                        // Close all views before launching Dashboard
                        dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                        startActivity(dashboard);
                        // Close Registration Screen
                        finish();
                    }else{
                        // Error in registration
                        registerErrorMsg.setText("Error occured in registration");
                    }
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    });

    // Link to Login Screen
    btnLinkToLogin.setOnClickListener(new View.OnClickListener() {

        public void onClick(View view) {
            Intent i = new Intent(getApplicationContext(),
                    LoginActivity.class);
            startActivity(i);
            // Close Registration View
            finish();
        }
    });
}

10-28 22:40:27.422: D/dalvikvm(373): GC_EXTERNAL_ALLOC freed 78K, 52% free 2599K/5379K,   external 897K/1038K, paused 190ms
10-28 22:40:32.000: W/KeyCharacterMap(373): No keyboard for id 0
10-28 22:40:32.000: W/KeyCharacterMap(373): Using default keymap:     /system/usr/keychars/qwerty.kcm.bin
10-28 22:40:45.879: E/Buffer Error(373): Error converting result    java.lang.NullPointerException
10-28 22:40:45.899: E/Buffer Error(373): Error converting result java.lang.NullPointerException
10-28 22:40:45.983: E/JSON Parser(373): Error parsing data org.json.JSONException: End of input at character 0 of 
10-28 22:40:45.989: D/AndroidRuntime(373): Shutting down VM
10-28 22:40:45.989: W/dalvikvm(373): threadid=1: thread exiting with uncaught exception (group=0x40015560)
10-28 22:40:46.049: E/AndroidRuntime(373): FATAL EXCEPTION: main
10-28 22:40:46.049: E/AndroidRuntime(373): java.lang.NullPointerException
10-28 22:40:46.049: E/AndroidRuntime(373):  at com.example.androidhive.RegisterActivity$1.onClick (RegisterActivity.java:112)
10-28 22:40:46.049: E/AndroidRuntime(373):  at android.view.View.performClick(View.java:2485)
10-28 22:40:46.049: E/AndroidRuntime(373):  at android.view.View$PerformClick.run(View.java:9080)
10-28 22:40:46.049: E/AndroidRuntime(373):  at android.os.Handler.handleCallback(Handler.java:587)
10-28 22:40:46.049: E/AndroidRuntime(373):  at android.os.Handler.dispatchMessage(Handler.java:92)
10-28 22:40:46.049: E/AndroidRuntime(373):  at android.os.Looper.loop(Looper.java:123)
10-28 22:40:46.049: E/AndroidRuntime(373):  at android.app.ActivityThread.main(ActivityThread.java:3683)
10-28 22:40:46.049: E/AndroidRuntime(373):  at java.lang.reflect.Method.invokeNative(Native Method)
10-28 22:40:46.049: E/AndroidRuntime(373):  at java.lang.reflect.Method.invoke(Method.java:507)
10-28 22:40:46.049: E/AndroidRuntime(373):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run (ZygoteInit.java:839)
10-28 22:40:46.049: E/AndroidRuntime(373):  at c om.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
10-28 22:40:46.049: E/AndroidRuntime(373):  at dalvik.system.NativeStart.main(Native Method)
 10-28 22:40:46.309: E/JSON Parser(373): Error parsing data org.json.JSONException: End of input at character 0 of 
10-28 22:40:50.289: I/Process(373): Sending signal. PID: 373 SIG: 9

   10-28 23:17:19.183: D/dalvikvm(449): GC_EXTERNAL_ALLOC freed 78K, 52% free 2599K/5379K, external 897K/1038K, paused 232ms
  10-28 23:17:23.259: W/KeyCharacterMap(449): No keyboard for id 0
  10-28 23:17:23.269: W/KeyCharacterMap(449): Using default keymap: /system/usr/keychars/qwerty.kcm.bin
  10-28 23:17:46.379: E/Buffer Error(449): Error converting result java.lang.NullPointerException
  10-28 23:17:46.389: E/Buffer Error(449): Error converting result java.lang.NullPointerException
  10-28 23:17:46.389: E/JSON Parser(449): Error parsing data org.json.JSONException: End of input at character 0 of 
  10-28 23:17:46.409: E/JSON Parser(449): Error parsing data org.json.JSONException: End of input at character 0 of 

JSONObject json = yourJSON;
if(json != null && !json.isNull(KEY_SUCCESS)){
   //Wahetever you need
   String value = json.getString(KEY_SUCCESS);
   if(value != null && value.length > 0){
       //You will fall here only if there's a value...
   }
}