I have some problem. sometimes when I just try to run my application, it is going to be force close. I don't know why it is going to be happened. here are my source code. AlertDialog.Builder alert = new AlertDialog.Builder(this); alert.setCancelable(false); //AlertDialog.Builder alert = new AlertDialog.Builder(this); ..... alert.setPositiveButton("Ok", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int whichButton) { no_pasien = no_pas.getText().toString(); new LoginProses().execute(); ..... alert.show(); class LoginProses extends AsyncTask<String, String, String> { protected void onPreExecute() { super.onPreExecute(); ...... } protected String doInBackground(String... args) { List<NameValuePair> params = new ArrayList<NameValuePair>(); params.add(new BasicNameValuePair("no_pasien", no)); JSONObject json = jsonParser.makeHttpRequest(url_login, "POST", params); try { int success = json.getInt(TAG_SUCCESS); if (success == 1) { // successfully created product pasien = json.getJSONArray("pasien"); JSONObject c = pasien.getJSONObject(0); int id = c.getInt("id"); new Temporary().setIdPasien(id); Intent goMainAct = new Intent(); // goMainAct.putExtra("id", id); goMainAct.setClass(Login.this, MainActivity.class); finish(); startActivity(goMainAct); } else { // failed to create product Intent getReload = getIntent(); getReload.putExtra("status", 1); finish(); startActivity(getReload); } } catch (JSONException e) { if(pDialog.isShowing()){ pDialog.dismiss(); } } return null; } protected void onPostExecute(String file_url) { // dismiss the dialog once done pDialog.dismiss(); } } here is the log error for my problem: //HERE IS THE LOG: 06-25 22:57:23.836: E/WindowManager(7630): Activity com.iteadstudio.Login has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@41939850 that was originally added here 06-25 22:57:23.836: E/WindowManager(7630): android.view.WindowLeaked: Activity com.iteadstudio.Login has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@41939850 that was originally added here 06-25 22:57:23.836: E/WindowManager(7630): at android.view.ViewRootImpl.<init>(ViewRootImpl.java:344) 06-25 22:57:23.836: E/WindowManager(7630): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:267) 06-25 22:57:23.836: E/WindowManager(7630): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:215) 06-25 22:57:23.836: E/WindowManager(7630): at android.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:140) 06-25 22:57:23.836: E/WindowManager(7630): at android.view.Window$LocalWindowManager.addView(Window.java:537) 06-25 22:57:23.836: E/WindowManager(7630): at android.app.Dialog.show(Dialog.java:278) 06-25 22:57:23.836: E/WindowManager(7630): at com.iteadstudio.Login$LoginProses.onPreExecute(Login.java:122) 06-25 22:57:23.836: E/WindowManager(7630): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:561) 06-25 22:57:23.836: E/WindowManager(7630): at android.os.AsyncTask.execute(AsyncTask.java:511) 06-25 22:57:23.836: E/WindowManager(7630): at com.iteadstudio.Login$3.onClick(Login.java:95) 06-25 22:57:23.836: E/WindowManager(7630): at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166) 06-25 22:57:23.836: E/WindowManager(7630): at android.os.Handler.dispatchMessage(Handler.java:99) 06-25 22:57:23.836: E/WindowManager(7630): at android.os.Looper.loop(Looper.java:137) 06-25 22:57:23.836: E/WindowManager(7630): at android.app.ActivityThread.main(ActivityThread.java:4441) 06-25 22:57:23.836: E/WindowManager(7630): at java.lang.reflect.Method.invokeNative(Native Method) 06-25 22:57:23.836: E/WindowManager(7630): at java.lang.reflect.Method.invoke(Method.java:511) 06-25 22:57:23.836: E/WindowManager(7630): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:823) 06-25 22:57:23.836: E/WindowManager(7630): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:590) 06-25 22:57:23.836: E/WindowManager(7630): at dalvik.system.NativeStart.main(Native Method) 06-25 22:57:23.946: D/dalvikvm(7630): GC_CONCURRENT freed 782K, 6% free 14319K/15203K, paused 4ms+3ms 06-25 22:57:23.976: D/AndroidRuntime(7630): Shutting down VM 06-25 22:57:23.976: W/dalvikvm(7630): threadid=1: thread exiting with uncaught exception (group=0x40ab4210) 06-25 22:57:23.986: E/AndroidRuntime(7630): FATAL EXCEPTION: main 06-25 22:57:23.986: E/AndroidRuntime(7630): java.lang.IllegalArgumentException: View not attached to window manager 06-25 22:57:23.986: E/AndroidRuntime(7630): at android.view.WindowManagerImpl.findViewLocked(WindowManagerImpl.java:587) 06-25 22:57:23.986: E/AndroidRuntime(7630): at android.view.WindowManagerImpl.removeView(WindowManagerImpl.java:324) 06-25 22:57:23.986: E/AndroidRuntime(7630): at android.view.WindowManagerImpl$CompatModeWrapper.removeView(WindowManagerImpl.java:151) 06-25 22:57:23.986: E/AndroidRuntime(7630): at android.app.Dialog.dismissDialog(Dialog.java:321) 06-25 22:57:23.986: E/AndroidRuntime(7630): at android.app.Dialog$1.run(Dialog.java:119) 06-25 22:57:23.986: E/AndroidRuntime(7630): at android.app.Dialog.dismiss(Dialog.java:306) 06-25 22:57:23.986: E/AndroidRuntime(7630): at com.iteadstudio.Login$LoginProses.onPostExecute(Login.java:177) 06-25 22:57:23.986: E/AndroidRuntime(7630): at com.iteadstudio.Login$LoginProses.onPostExecute(Login.java:1) 06-25 22:57:23.986: E/AndroidRuntime(7630): at android.os.AsyncTask.finish(AsyncTask.java:602) 06-25 22:57:23.986: E/AndroidRuntime(7630): at android.os.AsyncTask.access$600(AsyncTask.java:156) 06-25 22:57:23.986: E/AndroidRuntime(7630): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615) 06-25 22:57:23.986: E/AndroidRuntime(7630): at android.os.Handler.dispatchMessage(Handler.java:99) 06-25 22:57:23.986: E/AndroidRuntime(7630): at android.os.Looper.loop(Looper.java:137) 06-25 22:57:23.986: E/AndroidRuntime(7630): at android.app.ActivityThread.main(ActivityThread.java:4441) 06-25 22:57:23.986: E/AndroidRuntime(7630): at java.lang.reflect.Method.invokeNative(Native Method) 06-25 22:57:23.986: E/AndroidRuntime(7630): at java.lang.reflect.Method.invoke(Method.java:511) 06-25 22:57:23.986: E/AndroidRuntime(7630): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:823) 06-25 22:57:23.986: E/AndroidRuntime(7630): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:590) 06-25 22:57:23.986: E/AndroidRuntime(7630): at dalvik.system.NativeStart.main(Native Method)