我正在尝试在Android中创建一个简单的登录和注册活动。 我收到了错误
转换结果java.lang.nullpointerexception时出错，错误解析 data org.json.JSONException。
以下是我的代码： 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;
}
}
USERFUNCTIONS：
public class UserFunctions {
private JSONParser jsonParser;
// Testing in localhost using wamp or xampp
// use http://10.0.2.2/ to connect to your localhost ie http://localhost/
private static String loginURL = "http://49.249.85.221/android_api/";
private static String registerURL = "http://49.249.85.221/android_api/";
private static String login_tag = "login";
private static String register_tag = "register";
// constructor
public UserFunctions(){
jsonParser = new JSONParser();
}
/**
* function make Login Request
* @param email
* @param password
* */
public JSONObject loginUser(String email, String password){
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("tag", login_tag));
params.add(new BasicNameValuePair("email", email));
params.add(new BasicNameValuePair("password", password));
String method=new String();
JSONObject json = jsonParser.makeHttpRequest(loginURL,method, params);
// return json
// Log.e("JSON", json.toString());
return json;
}
/**
* function make Login Request
* @param name
* @param email
* @param password
* */
public JSONObject registerUser(String name, String email, String password){
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("tag", register_tag));
params.add(new BasicNameValuePair("name", name));
params.add(new BasicNameValuePair("email", email));
params.add(new BasicNameValuePair("password", password));
String method=new String();
// getting JSON Object
JSONObject json = jsonParser.makeHttpRequest(registerURL,method, params);
// return json
return json;
}
/**
* Function get Login status
* */
public boolean isUserLoggedIn(Context context){
DatabaseHandler db = new DatabaseHandler(context);
int count = db.getRowCount();
if(count > 0){
// user logged in
return true;
}
return false;
}
/**
* Function to logout user
* Reset Database
* */
public boolean logoutUser(Context context){
DatabaseHandler db = new DatabaseHandler(context);
db.resetTables();
return true;
}
}
REGISTERACTIVITY：
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();
}
});
}
}
当我运行调试器时，它指向行if (json.getString(KEY_SUCCESS) != null)
在RegisterActivity中。我对自己错在哪里毫无头绪。请指导我。
logcat的：
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
在实施Martin建议的解决方案后，主要问题得以解决。 我现在面临一些其他错误。 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
答案 0 :(得分：0)
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：
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...
}
}
请注意，您首先需要确保密钥实际存在，否则它可能会抛出JSONException ...
希望这会有所帮助......
问候！