시작한지 얼마 안된 초보라그런지 . . 
androidhive.info 여기서 소스 얻어서 연습하고있습니다. ^^ 다른 초보분들도 참고하시면 좋을듯요.

class BackgroundTask extends AsyncTask<String, String, String>{

@Override
protected String doInBackground(String... args) {
//StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
//StrictMode.setThreadPolicy(policy);
String email = inputEmail.getText().toString();
String password = inputPassword.getText().toString();
UserFunctions userFunction = new UserFunctions();
Log.d("Button", "Login");
JSONObject json = userFunction.loginUser(email, password);

// check for login response
try {
if (json.getString(KEY_SUCCESS) != null) {
loginErrorMsg.setText("");
String res = json.getString(KEY_SUCCESS); 
if(Integer.parseInt(res) == 1){
// user successfully logged in
// Store user details in SQLite Database
DatabaseHandler db = new DatabaseHandler(getApplicationContext());
JSONObject json_user = json.getJSONObject("user");
// Clear all previous data in database
userFunction.logoutUser(getApplicationContext());
db.addUser(json_user.getString(KEY_NAME), json_user.getString(KEY_EMAIL), json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));
}else{
// Error in login
loginErrorMsg.setText("Incorrect username/password");
}
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}

어디서 소스 구해다가 연습해보고 있는데,, 안드로이드가 네트워크 연결 등은 UI스레드에 직접 접근하지 못하게 한다고 해서

Asynctask를 이용하세요 ~ 라는 것을 보고 만들어 보고 있었습니다. 일단

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);

위에 코드 적용시켜서 UI스레드에서 바로 실행시켰을땐 문제없이 잘 됐는데,

asyncTask를 사용하니 자꾸 오류가 나네요 ㅠ 

로그고양이도 첨부하겠습니다. ㅠㅠ

05-04 07:30:40.336: E/AndroidRuntime(719): FATAL EXCEPTION: AsyncTask #1
05-04 07:30:40.336: E/AndroidRuntime(719): java.lang.RuntimeException: An error occured while executing doInBackground()
05-04 07:30:40.336: E/AndroidRuntime(719): at android.os.AsyncTask$3.done(AsyncTask.java:278)
05-04 07:30:40.336: E/AndroidRuntime(719): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
05-04 07:30:40.336: E/AndroidRuntime(719): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
05-04 07:30:40.336: E/AndroidRuntime(719): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
05-04 07:30:40.336: E/AndroidRuntime(719): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
05-04 07:30:40.336: E/AndroidRuntime(719): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
05-04 07:30:40.336: E/AndroidRuntime(719): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
05-04 07:30:40.336: E/AndroidRuntime(719): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
05-04 07:30:40.336: E/AndroidRuntime(719): at java.lang.Thread.run(Thread.java:856)
05-04 07:30:40.336: E/AndroidRuntime(719): Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
05-04 07:30:40.336: E/AndroidRuntime(719): at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:4039)
05-04 07:30:40.336: E/AndroidRuntime(719): at android.view.ViewRootImpl.invalidateChild(ViewRootImpl.java:722)
05-04 07:30:40.336: E/AndroidRuntime(719): at android.view.ViewRootImpl.invalidateChildInParent(ViewRootImpl.java:771)
05-04 07:30:40.336: E/AndroidRuntime(719): at android.view.ViewGroup.invalidateChild(ViewGroup.java:4005)
05-04 07:30:40.336: E/AndroidRuntime(719): at android.view.View.invalidate(View.java:8576)
05-04 07:30:40.336: E/AndroidRuntime(719): at android.view.View.invalidate(View.java:8527)
05-04 07:30:40.336: E/AndroidRuntime(719): at android.widget.TextView.checkForRelayout(TextView.java:6760)
05-04 07:30:40.336: E/AndroidRuntime(719): at android.widget.TextView.setText(TextView.java:3306)
05-04 07:30:40.336: E/AndroidRuntime(719): at android.widget.TextView.setText(TextView.java:3162)
05-04 07:30:40.336: E/AndroidRuntime(719): at android.widget.TextView.setText(TextView.java:3137)
05-04 07:30:40.336: E/AndroidRuntime(719): at com.success.Success.SuccessActivity$BackgroundTask.doInBackground(SuccessActivity.java:142)
05-04 07:30:40.336: E/AndroidRuntime(719): at com.success.Success.SuccessActivity$BackgroundTask.doInBackground(SuccessActivity.java:1)
05-04 07:30:40.336: E/AndroidRuntime(719): at android.os.AsyncTask$2.call(AsyncTask.java:264)
05-04 07:30:40.336: E/AndroidRuntime(719): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
05-04 07:30:40.336: E/AndroidRuntime(719): ... 5 more
05-04 07:30:41.236: W/IInputConnectionWrapper(719): showStatusIcon on inactive InputConnection
05-04 07:30:42.846: E/WindowManager(719): Activity com. success . Success . SuccessActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@41b01048 that was originally added here
05-04 07:30:42.846: E/WindowManager(719): android.view.WindowLeaked: Activity com. success . Success . SuccessActivityhas leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@41b01048 that was originally added here
05-04 07:30:42.846: E/WindowManager(719): at android.view.ViewRootImpl.<init>(ViewRootImpl.java:344)
05-04 07:30:42.846: E/WindowManager(719): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:267)
05-04 07:30:42.846: E/WindowManager(719): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:215)
05-04 07:30:42.846: E/WindowManager(719): at android.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:140)
05-04 07:30:42.846: E/WindowManager(719): at android.view.Window$LocalWindowManager.addView(Window.java:537)
05-04 07:30:42.846: E/WindowManager(719): at android.app.Dialog.show(Dialog.java:278)
05-04 07:30:42.846: E/WindowManager(719): at com. success. Success. SuccessActivity$BackgroundTask.onPreExecute(SuccessActivity .java:194)
05-04 07:30:42.846: E/WindowManager(719): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:561)
05-04 07:30:42.846: E/WindowManager(719): at android.os.AsyncTask.execute(AsyncTask.java:511)
05-04 07:30:42.846: E/WindowManager(719): at com. success . Success . SuccessActivity $1.onClick( SuccessActivity.java:107)
05-04 07:30:42.846: E/WindowManager(719): at android.view.View.performClick(View.java:3511)
05-04 07:30:42.846: E/WindowManager(719): at android.view.View$PerformClick.run(View.java:14105)
05-04 07:30:42.846: E/WindowManager(719): at android.os.Handler.handleCallback(Handler.java:605)
05-04 07:30:42.846: E/WindowManager(719): at android.os.Handler.dispatchMessage(Handler.java:92)
05-04 07:30:42.846: E/WindowManager(719): at android.os.Looper.loop(Looper.java:137)
05-04 07:30:42.846: E/WindowManager(719): at android.app.ActivityThread.main(ActivityThread.java:4424)
05-04 07:30:42.846: E/WindowManager(719): at java.lang.reflect.Method.invokeNative(Native Method)
05-04 07:30:42.846: E/WindowManager(719): at java.lang.reflect.Method.invoke(Method.java:511)
05-04 07:30:42.846: E/WindowManager(719): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
05-04 07:30:42.846: E/WindowManager(719): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
05-04 07:30:42.846: E/WindowManager(719): at dalvik.system.NativeStart.main(Native Method)



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