将json解析为java对象时出错:java.lang.NullPointerException
我正在为我的应用程序创建登录系统。它将登录信息发送到API并返回json 这是LoginActivity.java将json解析为java对象时出错:java.lang.NullPointerException,java,android,json,android-layout,android-asynctask,Java,Android,Json,Android Layout,Android Asynctask,我正在为我的应用程序创建登录系统。它将登录信息发送到API并返回json 这是LoginActivity.java public class LoginActivity extends Activity{ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.log
public class LoginActivity extends Activity{
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
// Login Button Click event
Button btnLogin = (Button) findViewById(R.id.btnLogin);
btnLogin.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
this.retrieveLogin();
}
private void retrieveLogin() {
LoginAsyncTask task = new LoginAsyncTask();
task.execute();
}
});
// Link to Register Screen
Button btnLinkToRegister = (Button) findViewById(R.id.btnLinkToRegister);
btnLinkToRegister.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Intent i = new Intent(getApplicationContext(),RegisterActivity.class);
startActivity(i);
finish();
}
});
}
private class LoginAsyncTask extends AsyncTask<Void, Void, Void> {
Login login2;
private Activity activity;
final EditText inputEmail = (EditText) findViewById(R.id.loginEmail);
final EditText inputPassword = (EditText) findViewById(R.id.loginPassword);
final TextView loginErrorMsg = (TextView) findViewById(R.id.login_error);
String email = inputEmail.getText().toString();
String pwrd = inputPassword.getText().toString();
@Override
protected Void doInBackground(Void... params) {
//System.out.println(loginURL);
try {
//Create an HTTP client
DefaultHttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost(loginURL);
//Perform the request and check the status code
HttpResponse response = client.execute(post);
StatusLine statusLine = response.getStatusLine();
if(statusLine.getStatusCode() == 200) {
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
try {
//Read the server response and attempt to parse it as JSON
Reader reader = new InputStreamReader(content);
Gson gson = new Gson();
this.login2 = gson.fromJson(reader, Login.class);
} catch (Exception ex) {
Log.e(TAG, "Failed to parse JSON due to: " + ex);
failedLoading();
}
} else {
Log.e(TAG, "Server responded with status code: " + statusLine.getStatusCode());
failedLoading();
}
} catch(Exception ex) {
Log.e(TAG, "Failed to send HTTP POST request due to: " + ex);
failedLoading();
}
return null;
}
@Override
protected void onPostExecute(Void result) {
}
}
@Override
protected void onPause() {
super.onPause();
//finish();
}
private void failedLoading() {
runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(LoginActivity.this, "Failed to Register. look at LogCat.", Toast.LENGTH_SHORT).show();
}
});
}
}
消息已成功显示在文本视图上
但当我输入登录的有效数据时,返回的json如下:
{
"result":"KO",
"message":["Make sure you did not misspell your password."]
}
{
"result":"OK",
"message":["Successfull login."],
"values":{"id":"1809","fname":"me","gender":"male"}
}
在这种情况下,我的应用程序强制关闭并获得以下日志:
09-30 12:55:05.445: E/AndroidRuntime(14593): FATAL EXCEPTION: main
09-30 12:55:05.445: E/AndroidRuntime(14593): java.lang.NullPointerException
09-30 12:55:05.445: E/AndroidRuntime(14593): at com.kabelash.sk.LoginActivity$LoginAsyncTask.onPostExecute(LoginActivity.java:128)
09-30 12:55:05.445: E/AndroidRuntime(14593): at com.kabelash.sk.LoginActivity$LoginAsyncTask.onPostExecute(LoginActivity.java:1)
09-30 12:55:05.445: E/AndroidRuntime(14593): at android.os.AsyncTask.finish(AsyncTask.java:631)
09-30 12:55:05.445: E/AndroidRuntime(14593): at android.os.AsyncTask.access$600(AsyncTask.java:177)
09-30 12:55:05.445: E/AndroidRuntime(14593): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
09-30 12:55:05.445: E/AndroidRuntime(14593): at android.os.Handler.dispatchMessage(Handler.java:99)
09-30 12:55:05.445: E/AndroidRuntime(14593): at android.os.Looper.loop(Looper.java:137)
09-30 12:55:05.445: E/AndroidRuntime(14593): at android.app.ActivityThread.main(ActivityThread.java:4898)
09-30 12:55:05.445: E/AndroidRuntime(14593): at java.lang.reflect.Method.invokeNative(Native Method)
09-30 12:55:05.445: E/AndroidRuntime(14593): at java.lang.reflect.Method.invoke(Method.java:511)
09-30 12:55:05.445: E/AndroidRuntime(14593): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
09-30 12:55:05.445: E/AndroidRuntime(14593): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
09-30 12:55:05.445: E/AndroidRuntime(14593): at dalvik.system.NativeStart.main(Native Method)
但我找不到任何解决办法。有人请帮忙。我需要你的价值观课程。因为你的变量在课堂上可能会出现整数偏差。在Json数据中,idisstring我以前从未尝试过gson,但我总是使用parser类来解决Json问题
public class JSONParser {
static InputStream is;
static JSONObject jObj;
static String json = "";
public JSONParser()
{
}
public JSONObject makeHttpRequest(String Url, String Method, List<NameValuePair> params)
{
try {
if (Method == "POST")
{
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) {
// TODO: handle exception
e.printStackTrace();
} catch (ClientProtocolException e) {
// TODO: handle exception
e.printStackTrace();
} catch (IOException e) {
// TODO: handle exception
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) {
// TODO: handle exception
Log.e("Buffer Error", "Error converting result " + e.toString());
}
try{
jObj = new JSONObject(json);
} catch (JSONException e) {
// TODO: handle exception
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
return jObj;
} }
什么是
LoginActivity.java
中的第118行?这是第118行:if(login2.getResult().equals(“OK”)){@Nirmal:你想干什么say@Raghunandan:我如何解决它?&登录无效。是的。Gson解析器没有找到字符串id变量。@nurisezgin:我已经创建了Values类,您能回答我的问题吗请参阅有关Values的帖子。java类您将id变量类型更改为string。它必须是string。(在json数据id值字符串中)尝试私有字符串id.Try“startActivity(new Intent(LoginActivity.this,Splash.class)),可能您的对象空用户直接StartActivityTanks获取您的答案。我从未尝试过此方法,但如果您让我知道如何更改LoginActivity,那么我可以尝试一下,看看它是否解决了我的问题
protected String doInBackground(String... p) {
try {
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("email", email));
params.add(new BasicNameValuePair("password", password));
JSONObject json = new JSONParser.makeHttpRequest(loginURL, "POST/GET", params);
success = json.getString("success");
if (success.equals("ok")
// do something
}// try } // background
// try this way
public void setId(String id){
this.id = Integer.parseInt(id);
}