如果选中了checkbock，我想保存登录数据。
但是当我拨打session.saveSession(user, password);时，应用程序崩溃了......
我不知道我的错误在哪里:(
Start.java
package de.hoell.jobcontrol;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;
import org.json.JSONException;
import org.json.JSONObject;
import de.hoell.jobcontrol.query.Functions;
import de.hoell.jobcontrol.session.SessionManager;
public class Start extends Activity {
Button btnLogin;
EditText InputName;
EditText InputPass;
CheckBox InputCheck;
public static String user;
private String password;
SessionManager session;
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_ERROR = "error";
private static final String TAG_MESSAGE = "message";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start);
//Importing all assets like buttons, text fields
InputName = (EditText) findViewById(R.id.login_name);
InputPass = (EditText) findViewById(R.id.login_pass);
btnLogin = (Button) findViewById(R.id.button);
InputCheck = (CheckBox) findViewById(R.id.checkBox);
btnLogin.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View view)
{
new JSONLogin().execute();
}
});
}
private class JSONLogin extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(Start.this);
pDialog.setMessage("Sending Data ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected JSONObject doInBackground(String... args) {
user = InputName.getText().toString();
password = InputPass.getText().toString();
Functions Function = new Functions();
JSONObject json = Function.loginUser(user, password);
// check for login response
// check log cat fro response
Log.d("Create Response", json.toString());
return json;
}
@Override
protected void onPostExecute(JSONObject json) {
pDialog.dismiss();
try {
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// successfully logged in
if (InputCheck.isChecked()){
System.out.println("Checkbox is gesetz daten werden gespeichert ");
session.saveSession(user, password);
}
else{
System.out.println("Checkbox is leer daten werden NICHT gespeichert");
}
Intent i = new Intent(getApplicationContext(), MainActivity.class);
startActivity(i);
// closing this screen
finish();
} else {
Toast.makeText(getApplicationContext(), "Falscher Login-Name / Falsches Passwort!!!", Toast.LENGTH_SHORT).show();
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.start, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_info) {
Toast.makeText(getApplicationContext(), "Version 0.0.6", Toast.LENGTH_SHORT).show();
return true;
}
return super.onOptionsItemSelected(item);
}
}
SessionManager.java
package de.hoell.jobcontrol.session;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import java.util.HashMap;
import de.hoell.jobcontrol.MainActivity;
import de.hoell.jobcontrol.Start;
/**
* Created by Hoell on 21.11.2014.
*/
public class SessionManager {
// Shared Preferences reference
SharedPreferences pref;
// Editor reference for Shared preferences
SharedPreferences.Editor editor;
// Context
Context _context;
// Shared pref mode
int PRIVATE_MODE = 0;
// Sharedpref file name
private static final String PREFER_NAME = "AndroidExamplePref";
// All Shared Preferences Keys
private static final String IS_USER_LOGIN = "IsUserLoggedIn";
// User name (make variable public to access from outside)
public static final String KEY_USER = "user";
// Email address (make variable public to access from outside)
public static final String KEY_PWD = "pwd";
// Constructor
public SessionManager(Context context){
this._context = context;
pref = _context.getSharedPreferences(PREFER_NAME, PRIVATE_MODE);
editor = pref.edit();
}
//Create login session
public void saveSession(String user, String pwd){
// Storing login value as TRUE
editor.putBoolean(IS_USER_LOGIN, true);
// Storing user in pref
editor.putString(KEY_USER, user);
// Storing pwd in pref
editor.putString(KEY_PWD, pwd);
// commit changes
editor.commit();
System.out.println("Daten gespeichert:"+user + pwd);
}
/**
* Check login method will check user login status
* If false it will redirect user to login page
* Else do anything
* */
public boolean checkLogin(){
// Check login status
if(!this.isUserLoggedIn()){
// user is not logged in redirect him to Login Activity
Intent i = new Intent(_context, Start.class);
// Closing all the Activities from stack
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
// Add new Flag to start new Activity
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
// Staring Login Activity
_context.startActivity(i);
return true;
}
return false;
}
/**
* Get stored session data
* */
public HashMap<String, String> getUser(){
//Use hashmap to store user credentials
HashMap<String, String> user = new HashMap<String, String>();
// user name
user.put(KEY_USER, pref.getString(KEY_USER, null));
// user email id
user.put(KEY_PWD, pref.getString(KEY_PWD, null));
// return user
return user;
}
/**
* Clear session details
* */
public void logoutUser(){
// Clearing all user data from Shared Preferences
editor.clear();
editor.commit();
// After logout redirect user to Login Activity
Intent i = new Intent(_context,Start.class);
// Closing all the Activities
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
// Add new Flag to start new Activity
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
// Staring Login Activity
_context.startActivity(i);
}
// Check for login
public boolean isUserLoggedIn(){
return pref.getBoolean(IS_USER_LOGIN, false);
}
}
logcat的
11-24 09:56:31.222 417-1662/de.hoell.myfirstapp E/JSON﹕ {"tag":"login","success":1,"error":0,"message":"erfolgreich eingelogt!"}
11-24 09:56:31.232 417-1662/de.hoell.myfirstapp D/Create Response﹕ {"message":"erfolgreich eingelogt!","error":0,"success":1,"tag":"login"}
11-24 09:56:31.262 417-417/de.hoell.myfirstapp I/System.out﹕ Checkbox is gesetz daten werden gespeichert
11-24 09:56:31.262 417-417/de.hoell.myfirstapp D/AndroidRuntime﹕ Shutting down VM
11-24 09:56:31.262 417-417/de.hoell.myfirstapp W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x4180cda0)
11-24 09:56:31.262 417-417/de.hoell.myfirstapp E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: de.hoell.myfirstapp, PID: 417
java.lang.NullPointerException
at de.hoell.jobcontrol.Start$JSONLogin.onPostExecute(Start.java:104)
at de.hoell.jobcontrol.Start$JSONLogin.onPostExecute(Start.java:65)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:157)
at android.app.ActivityThread.main(ActivityThread.java:5356)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：3)
你永远不会初始化SessionManager。在onCreate中添加
session = new SessionManager(this);
在开始AsyncTask
答案 1 :(得分：0)
这是NullPointerException
session.saveSession(user, password);
在您的代码中，您已声明会话，但已初始化。所以它抛出空指针异常
在使用之前，您需要初始化变量会话。
session = new SessionManager(getApplicationContext());
这将解决问题。
答案 2 :(得分：0)
在使用SessionManager类的任何方法之前，您必须初始化SessionManager对象：
示例：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start);
//Importing all assets like buttons, text fields
InputName = (EditText) findViewById(R.id.login_name);
InputPass = (EditText) findViewById(R.id.login_pass);
btnLogin = (Button) findViewById(R.id.button);
InputCheck = (CheckBox) findViewById(R.id.checkBox);
session = new SessionManager(this);
btnLogin.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View view)
{
new JSONLogin().execute();
}
});
}