到目前为止，我已经完成了登录，创建共享偏好和使用导航抽屉的应用程序。
现在我正试图在没有运气的情况下实现用户注销。
我在这里发布代码，希望你能帮助我。从昨晚开始，它让我疯狂：
public class MainActivity extends Activity {
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
//private CharSequence mDrawerTitle;
// private CharSequence mTitle; private String [] mPlanetTitles;
public static String usuarioID;
public static String dispositivo;
public static SessionManager session;
ConnectionDetector cd;
static Httppostaux post;
static String URL_connect="http://www.myserver.net/api/logout.php";
TextView dispo;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
// mTitle = mDrawerTitle = getTitle();
mPlanetTitles = getResources().getStringArray(R.array.planets_array);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.left_drawer);
cd = new ConnectionDetector(getApplicationContext());
session = new SessionManager(getApplicationContext());
session.checkLogin();
dispo=(TextView)findViewById(R.id.dispositivo);
HashMap<String, String> usuario = session.getUserDetails();
usuarioID = usuario.get(SessionManager.KEY_USER_ID);
// set a custom shadow that overlays the main content when the drawer opens
mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
// set up the drawer's list view with items and click listener
mDrawerList.setAdapter(new ArrayAdapter<String>(this,
R.layout.drawer_list_item, mPlanetTitles));
mDrawerList.setOnItemClickListener(new DrawerItemClickListener());
// enable ActionBar app icon to behave as action to toggle nav drawer
// getActionBar().setDisplayHomeAsUpEnabled(true);
// getActionBar().setHomeButtonEnabled(true);
// ActionBarDrawerToggle ties together the the proper interactions
// between the sliding drawer and the action bar app icon
mDrawerToggle = new ActionBarDrawerToggle(
this, /* host Activity */
mDrawerLayout, /* DrawerLayout object */
R.drawable.ic_drawer, /* nav drawer image to replace 'Up' caret */
R.string.drawer_open, /* "open drawer" description for accessibility */
R.string.drawer_close /* "close drawer" description for accessibility */
) {
public void onDrawerClosed(View view) {
//getActionBar().setTitle(mTitle);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
public void onDrawerOpened(View drawerView) {
//getActionBar().setTitle(mDrawerTitle);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
selectItem(0);
}
}
@Override
public void onBackPressed() {
Intent intent = new Intent(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_HOME);
startActivity(intent);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
/* Called whenever we call invalidateOptionsMenu() */
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// The action bar home/up action should open or close the drawer.
// ActionBarDrawerToggle will take care of this.
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
// Handle action buttons
switch(item.getItemId()) {
default:
return super.onOptionsItemSelected(item);
}
}
/* The click listner for ListView in the navigation drawer */
private class DrawerItemClickListener implements ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectItem(position);
}
}
private void selectItem(int position) {
// update the main content by replacing fragments
Fragment fragment = new PlanetFragment();
Bundle args = new Bundle();
args.putInt(PlanetFragment.ARG_PLANET_NUMBER, position);
fragment.setArguments(args);
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.content_frame, fragment).commit();
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
setTitle(mPlanetTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
}
@Override
public void setTitle(CharSequence title) {
//mTitle = title;
//getActionBar().setTitle(mTitle);
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
mDrawerToggle.syncState();
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
mDrawerToggle.onConfigurationChanged(newConfig);
}
public static class PlanetFragment extends Fragment {
public static final String ARG_PLANET_NUMBER = "planet_number";
public PlanetFragment() {
// Empty constructor required for fragment subclasses
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_planet, container, false);
int i = getArguments().getInt(ARG_PLANET_NUMBER);
String secciones = getResources().getStringArray(R.array.planets_array)[i];
if (i == 6){
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setMessage("Esta acción cerrará su sesión y lo desconectará de nuestro sistema.")
.setCancelable(false)
.setPositiveButton("Si", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
new asynclogout().execute(usuarioID);
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
}
return rootView;
}
public boolean loginstatus(String usuarioID ) {
String logstatus="0";
ArrayList<NameValuePair> postparameters2send= new ArrayList<NameValuePair>();
postparameters2send.add(new BasicNameValuePair("usuario",usuarioID));
//realizamos una peticion y como respuesta obtenes un array JSON
JSONArray jdata=post.getserverdata(postparameters2send, URL_connect);
if (jdata!=null && jdata.length() > 0){
JSONObject json_data; //creamos un objeto JSON
try {
json_data = jdata.getJSONObject(0); //leemos el primer segmento en nuestro caso el unico
logstatus=json_data.getString("logstatus");
Log.e("loginstatus","logstatus= "+logstatus);//muestro por log que obtuvimos
} catch (JSONException e) {
e.printStackTrace();
}
//validamos el valor obtenido
if (logstatus=="0"){// [{"logstatus":"0"}]
Log.e("loginstatus ", "invalido");
return false;
}else
{
Log.e("loginstatus", "valido");
return true;
}
}else{
Log.e("JSON ", "ERROR");
return false;
}
}
//validamos si no hay ningun campo en blanco
public boolean checklogindata(String username ,String password ){
if (username.equals("") || password.equals("")){
Log.e("Login ui", "checklogindata user or pass error");
return false;
}else{
return true;
}
}
class asynclogout extends AsyncTask< String, String, String > {
String usuarioID;
protected String doInBackground(String... params) {
//obtnemos usr y pass
usuarioID=params[0];
//enviamos y recibimos y analizamos los datos en segundo plano.
if (loginstatus(usuarioID)==true){
return "ok"; //login valido
}else{
return "err"; //login invalido
}
}
protected void onPostExecute(String result) {
Log.e("onPostExecute=",""+result);
if (result.equals("ok")){
session.logoutUser();
}
}
}
}
}
问题是当我尝试注销用户时，logcat给了我这个错误：
10-05 13:09:36.060: E/AndroidRuntime(756): FATAL EXCEPTION: AsyncTask #1
10-05 13:09:36.060: E/AndroidRuntime(756): java.lang.RuntimeException: An error occured while executing doInBackground()
10-05 13:09:36.060: E/AndroidRuntime(756): at android.os.AsyncTask$3.done(AsyncTask.java:299)
10-05 13:09:36.060: E/AndroidRuntime(756): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
10-05 13:09:36.060: E/AndroidRuntime(756): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
10-05 13:09:36.060: E/AndroidRuntime(756): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
10-05 13:09:36.060: E/AndroidRuntime(756): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
10-05 13:09:36.060: E/AndroidRuntime(756): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
10-05 13:09:36.060: E/AndroidRuntime(756): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
10-05 13:09:36.060: E/AndroidRuntime(756): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
10-05 13:09:36.060: E/AndroidRuntime(756): at java.lang.Thread.run(Thread.java:856)
10-05 13:09:36.060: E/AndroidRuntime(756): Caused by: java.lang.NullPointerException
10-05 13:09:36.060: E/AndroidRuntime(756): at com.gettford.community.MainActivity$PlanetFragment.loginstatus(MainActivity.java:252)
10-05 13:09:36.060: E/AndroidRuntime(756): at com.gettford.community.MainActivity$PlanetFragment$asynclogout.doInBackground(MainActivity.java:322)
10-05 13:09:36.060: E/AndroidRuntime(756): at com.gettford.community.MainActivity$PlanetFragment$asynclogout.doInBackground(MainActivity.java:1)
10-05 13:09:36.060: E/AndroidRuntime(756): at android.os.AsyncTask$2.call(AsyncTask.java:287)
10-05 13:09:36.060: E/AndroidRuntime(756): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
10-05 13:09:36.060: E/AndroidRuntime(756): ... 5 more
然后应用程序崩溃。
答案 0 :(得分：0)
您尚未初始化post。因此，你得到NullPointerException。初始化post。
试
post= new Httppostaux();