编辑：我改变了
User user;
UserLocalStore userLocalStore;
为：
User user = new User("","");
UserLocalStore userLocalStore = new UserLocalStore(ctx);
但现在我
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference
at com.serk.comparateurL3F1.UserLocalStore.<init>(UserLocalStore.java:18)
at com.serk.comparateurL3F1.BackgroundTask.<init>(BackgroundTask.java:43)
at com.serk.comparateurL3F1.LoginActivity$2.onClick(LoginActivity.java:59)
at android.view.View.performClick(View.java:5565)
at android.view.View$PerformClick.run(View.java:22047)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5849)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:763)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:653)
我正在使用登录/注册功能来管理应用程序并希望保存用户信息，以便在共享首选项的帮助下在导航器中显示它们但我无法添加它 这是我得到的错误
FATAL EXCEPTION: AsyncTask #1
Process: com.serk.comparateurL3F1, PID: 6471
java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:318)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:803)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.serk.comparateurL3F1.User.setMail(java.lang.String)' on a null object reference
at com.serk.comparateurL3F1.BackgroundTask.doInBackground(BackgroundTask.java:117)
at com.serk.comparateurL3F1.BackgroundTask.doInBackground(BackgroundTask.java:34)
at android.os.AsyncTask$2.call(AsyncTask.java:304)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:803)
登录/注册发生的后台任务以及我尝试保存用户数据的位置：
public class BackgroundTask extends AsyncTask<String, Void, String> {
String register = "http://comparateur.16mb.com/register.php";
String login = "http://comparateur.16mb.com/login.php";
Context ctx;
Activity activity;
AlertDialog.Builder builder;
ProgressDialog progressDialog;
User user;
UserLocalStore userLocalStore;
public BackgroundTask(Context ctx){
this.ctx = ctx;
activity = (Activity)ctx;
}
@Override
protected void onPreExecute() {
builder = new AlertDialog.Builder(activity);
progressDialog = new ProgressDialog(ctx);
progressDialog.setTitle("Wait...");
progressDialog.setMessage("Connection to server");
progressDialog.setIndeterminate(true);
progressDialog.setCancelable(false);
progressDialog.show();
}
@Override
protected String doInBackground(String... params) {
String method = params[0];
if (method.equals("register")){
try {
URL url = new URL(register);
HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
httpURLConnection.setRequestMethod("POST");
httpURLConnection.setDoOutput(true);
httpURLConnection.setDoInput(true);
OutputStream outputStream = httpURLConnection.getOutputStream();
BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
String mail = params[1];
String name = params[2];
String password = params[3];
String data = URLEncoder.encode("mail", "UTF-8")+"="+URLEncoder.encode(mail, "UTF-8")+"&"+
URLEncoder.encode("name", "UTF-8")+"="+URLEncoder.encode(name, "UTF-8")+"&"+
URLEncoder.encode("password", "UTF-8")+"="+URLEncoder.encode(password, "UTF-8");
bufferedWriter.write(data);
bufferedWriter.flush();
bufferedWriter.close();
outputStream.close();
InputStream inputStream = httpURLConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
StringBuilder stringBuilder = new StringBuilder();
String line = "";
while ( (line=bufferedReader.readLine())!=null ){
stringBuilder.append(line+"\n");
}
httpURLConnection.disconnect();;
Thread.sleep(5000);
return stringBuilder.toString().trim();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (ProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
else if(method.equals("login")){
try {
URL url = new URL(login);
HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
httpURLConnection.setRequestMethod("POST");
httpURLConnection.setDoOutput(true);
httpURLConnection.setDoInput(true);
OutputStream outputStream = httpURLConnection.getOutputStream();
BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
String mail, password;
mail = params[1];
user.setMail(mail);
password = params[2];
String data = URLEncoder.encode("mail", "UTF-8")+"="+URLEncoder.encode(mail, "UTF-8")+"&"+
URLEncoder.encode("password", "UTF-8")+"="+URLEncoder.encode(password, "UTF-8");
bufferedWriter.write(data);
bufferedWriter.flush();
bufferedWriter.close();
outputStream.close();
InputStream inputStream = httpURLConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
StringBuilder stringBuilder = new StringBuilder();
String line = "";
while ( (line=bufferedReader.readLine())!=null ){
stringBuilder.append(line+"\n");
}
httpURLConnection.disconnect();;
Thread.sleep(5000);
return stringBuilder.toString().trim();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (ProtocolException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
return null;
}
@Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}
@Override
protected void onPostExecute(String json) {
try {
progressDialog.dismiss();
JSONObject jsonObject = new JSONObject(json);
JSONArray jsonArray = jsonObject.getJSONArray("server_response");
JSONObject jo = jsonArray.getJSONObject(0);
String code = jo.getString("code");
String message = jo.getString("message");
if (code.equals("reg_true")){
showDialog("Register succes", message, code);
}
else if (code.equals("reg_false")){
showDialog("Register fail", message, code);
}
else if (code.equals("login_true")){
user.setName(message);
userLocalStore.storeUserData(user);
Intent intent = new Intent(activity, MainActivity.class);
intent.putExtra("message", message);
activity.startActivity(intent);
}
else if (code.equals("login_false")){
showDialog("Login fail", message, code);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
public void showDialog(String title, String message, String code){
builder.setTitle(title);
if (code.equals("reg_true") || code.equals("reg_false")){
builder.setMessage(message);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
activity.finish();
}
});
}
else if (code.equals("login_false")){
builder.setMessage(message);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
EditText mail, password;
mail = (EditText) activity.findViewById(R.id.lMail);
password = (EditText) activity.findViewById(R.id.lPassword);
mail.setText("");
password.setText("");
dialog.dismiss();
}
});
}
AlertDialog alertDialog = builder.create();
alertDialog.show();
}
}
如果有任何事情发生，所有文件都在这个github中：https://github.com/serkserk/ComparateurL3F1
答案 0 :(得分：0)
您需要初始化user对象。
你在这一行获得NullPointerException
user.setMail(mail);
因为用户是null。