android.os.NetworkOnMainThreadException at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1145)

Question

I am developing my first Android app and had built in mostly based on research. When I try to login my user I get the android.os.NetworkOnMainThreadException error. I have read online that Async should be used to make sure that this error doesn't occur but I have no idea how to do that.

Below is all my code.

My User Login Form Activity:

    import java.util.HashMap;     import org.json.JSONException;     import org.json.JSONObject;     import android.app.Activity;     import android.content.Intent;     import android.os.Bundle;     import android.util.Log;     import android.view.View;     import android.widget.Button;     import android.widget.EditText;     import android.widget.TextView;     import com.finecalc.library.DatabaseHandler;     import com.finecalc.library.UserFunctions;       public class UserLogin extends Activity {     Button userlogin;     Button back;     Button login;     EditText inputEmail;     EditText inputPassword;     TextView loginErrorMsg;  // JSON Response node names private static String KEY_SUCCESS = "success"; private static String KEY_ERROR = "error"; private static String KEY_ERROR_MSG = "error_msg"; private static String KEY_UID = "uid"; private static String KEY_NAME = "name"; private static String KEY_EMAIL = "email"; private static String KEY_CREATED_AT = "created_at";  @Override public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.user_login);      // Importing all assets like buttons, text fields     inputEmail = (EditText) findViewById(R.id.inputemail);     inputPassword = (EditText) findViewById(R.id.inputpassword);     login = (Button) findViewById(R.id.login);     //Button register = (Button) findViewById(R.id.register);     back =(Button)findViewById(R.id.back);      loginErrorMsg = (TextView) findViewById(R.id.login_error);      // Login button Click Event     login.setOnClickListener(new View.OnClickListener() {          public void onClick(View view) {             String email = inputEmail.getText().toString();             String password = inputPassword.getText().toString();             UserFunctions userFunction = new UserFunctions();             JSONObject json = userFunction.loginUser(email, password);              // check for login response             try {                 //if (json.getString(KEY_SUCCESS) != null) {                 if(json != null && !(json).isNull(KEY_SUCCESS)){                     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));                                                 // Launch Dashboard Screen                         Intent dashboard = new Intent(getApplicationContext(), DashboardActivity.class);                          // Close all views before launching Dashboard                         dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);                         startActivity(dashboard);                          // Close Login Screen                         finish();                      }else{                         // Error in login                         loginErrorMsg.setText("Incorrect username/password");                     }                 }             } catch (JSONException e) {                 e.printStackTrace();             }         }     });    }    } 

DatabaseHandler

     import java.util.HashMap;      import android.content.ContentValues;      import android.content.Context;      import android.database.Cursor;      import android.database.sqlite.SQLiteDatabase;      import android.database.sqlite.SQLiteOpenHelper;      public class DatabaseHandler extends SQLiteOpenHelper {  // All Static variables // Database Version private static final int DATABASE_VERSION = 1;  // Database Name private static final String DATABASE_NAME = "androidlta_api";  // Login table name private static final String TABLE_LOGIN = "login";  // Login Table Columns names private static final String KEY_ID = "id"; private static final String KEY_NAME = "name"; private static final String KEY_EMAIL = "email"; private static final String KEY_UID = "uid"; private static final String KEY_CREATED_AT = "created_at";  public DatabaseHandler(Context context) {     super(context, DATABASE_NAME, null, DATABASE_VERSION); }  // Creating Tables @Override public void onCreate(SQLiteDatabase db) {     String CREATE_LOGIN_TABLE = "CREATE TABLE " + TABLE_LOGIN + "("             + KEY_ID + " INTEGER PRIMARY KEY,"             + KEY_NAME + " TEXT,"             + KEY_EMAIL + " TEXT UNIQUE,"             + KEY_UID + " TEXT,"             + KEY_CREATED_AT + " TEXT" + ")";     db.execSQL(CREATE_LOGIN_TABLE); }  // Upgrading database @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {     // Drop older table if existed     db.execSQL("DROP TABLE IF EXISTS " + TABLE_LOGIN);      // Create tables again     onCreate(db); }  /**  * Storing user details in database  * */ public void addUser(String name, String email, String uid, String created_at) {     SQLiteDatabase db = this.getWritableDatabase();      ContentValues values = new ContentValues();     values.put(KEY_NAME, name); // Name     values.put(KEY_EMAIL, email); // Email     values.put(KEY_UID, uid); // Email     values.put(KEY_CREATED_AT, created_at); // Created At      // Inserting Row     db.insert(TABLE_LOGIN, null, values);     db.close(); // Closing database connection }  /**  * Getting user data from database  * */ public HashMap<String, String> getUserDetails(){     HashMap<String,String> user = new HashMap<String,String>();     String selectQuery = "SELECT  * FROM " + TABLE_LOGIN;      SQLiteDatabase db = this.getReadableDatabase();     Cursor cursor = db.rawQuery(selectQuery, null);     // Move to first row     cursor.moveToFirst();     if(cursor.getCount() > 0){         user.put("name", cursor.getString(1));         user.put("email", cursor.getString(2));         user.put("uid", cursor.getString(3));         user.put("created_at", cursor.getString(4));     }     cursor.close();     db.close();     // return user     return user; }  /**  * Getting user login status  * return true if rows are there in table  * */ public int getRowCount() {     String countQuery = "SELECT  * FROM " + TABLE_LOGIN;     SQLiteDatabase db = this.getReadableDatabase();     Cursor cursor = db.rawQuery(countQuery, null);     int rowCount = cursor.getCount();     db.close();     cursor.close();      // return row count     return rowCount; }  /**  * Re crate database  * Delete all tables and create them again  * */ public void resetTables(){     SQLiteDatabase db = this.getWritableDatabase();     // Delete All Rows     db.delete(TABLE_LOGIN, null, null);     db.close(); }     } 

UserFunctions

      import java.util.ArrayList;       import java.util.List;        import org.apache.http.NameValuePair;       import org.apache.http.message.BasicNameValuePair;       import org.json.JSONObject;          import android.content.Context;        import android.util.Log;        public class UserFunctions {  private JSONParser jsonParser;  // Testing in localhost using LAMP  private static String loginURL = "http://127.0.0.1/android_api/index.php"; private static String registerURL = "http://127.0.0.1/android_api/index.php";  private static String login_tag = "login"; private static String register_tag = "register";  // constructor public UserFunctions(){     jsonParser = new JSONParser(); }  /**  * function make Login Request  * @param email  * @param password  * */ public JSONObject loginUser(String email, String password){     // Building Parameters     List<NameValuePair> params = new ArrayList<NameValuePair>();     params.add(new BasicNameValuePair("tag", login_tag));     params.add(new BasicNameValuePair("email", email));     params.add(new BasicNameValuePair("password", password));     JSONObject json = jsonParser.getJSONFromUrl(loginURL, params);     // return json     // Log.e("JSON", json.toString());     return json; }  /**  * function make Login Request  * @param name  * @param email  * @param password  * */ public JSONObject registerUser(String name, String licencenumber, String email, String password){     // Building Parameters     List<NameValuePair> params = new ArrayList<NameValuePair>();     params.add(new BasicNameValuePair("tag", register_tag));     params.add(new BasicNameValuePair("name", name));     params.add(new BasicNameValuePair("licencenumber",licencenumber));     params.add(new BasicNameValuePair("email", email));     params.add(new BasicNameValuePair("password", password));      // getting JSON Object     JSONObject json = jsonParser.getJSONFromUrl(registerURL, params);     // return json     return json; }  /**  * Function get Login status  * */ public boolean isUserLoggedIn(Context context){     DatabaseHandler db = new DatabaseHandler(context);     int count = db.getRowCount();     if(count > 0){         // user logged in         return true;     }     return false; }  /**  * Function to logout user  * Reset Database  * */ public boolean logoutUser(Context context){     DatabaseHandler db = new DatabaseHandler(context);     db.resetTables();     return true; }        } 

JSONParser

      import java.io.BufferedReader;       import java.io.IOException;       import java.io.InputStream;       import java.io.InputStreamReader;       import java.io.UnsupportedEncodingException;       import java.util.List;       import org.apache.http.HttpEntity;       import org.apache.http.HttpResponse;       import org.apache.http.NameValuePair;       import org.apache.http.client.ClientProtocolException;       import org.apache.http.client.entity.UrlEncodedFormEntity;       import org.apache.http.client.methods.HttpPost;       import org.apache.http.impl.client.DefaultHttpClient;       import org.json.JSONException;       import org.json.JSONObject;        import android.util.Log;        public class JSONParser {  static InputStream is = null; static JSONObject jObj = null; static String json = "";  // constructor public JSONParser() {  }  public JSONObject getJSONFromUrl(String url, List<NameValuePair> params) {      // Making HTTP request     try {         // defaultHttpClient         DefaultHttpClient httpClient = new DefaultHttpClient();         HttpPost httpPost = new HttpPost(url);         httpPost.setEntity(new UrlEncodedFormEntity(params));          HttpResponse httpResponse = httpClient.execute(httpPost);         HttpEntity httpEntity = httpResponse.getEntity();         is = httpEntity.getContent();      } catch (UnsupportedEncodingException e) {         e.printStackTrace();     } catch (ClientProtocolException e) {         e.printStackTrace();     } catch (IOException e) {         e.printStackTrace();     }      try {         BufferedReader reader = new BufferedReader(new InputStreamReader(                 is, "iso-8859-1"), 8);         StringBuilder sb = new StringBuilder();         String line = null;         while ((line = reader.readLine()) != null) {             sb.append(line + "n");         }         is.close();         json = sb.toString();        // Log.e("JSON", json);     } catch (Exception e) {         Log.e("Buffer Error", "Error converting result " + e.toString());     }      // try parse the string to a JSON object     try {         jObj = new JSONObject(json);                } catch (JSONException e) {         Log.e("JSON Parser", "Error parsing data " + e.toString());     }      // return JSON String     return jObj;  } 

}

My AndroidManifest also includes:
<uses-permission android:name="android.permission.INTERNET" />.

Below is my error:

08-02 04:39:23.410: D/(2642): HostConnection::get() New Host Connection established 0xb97a3b90, tid 2642 08-02 04:39:23.480: W/EGL_emulation(2642): eglSurfaceAttrib not implemented 08-02 04:39:23.480: D/OpenGLRenderer(2642): Enabling debug mode 0 08-02 04:39:29.150: W/EGL_emulation(2642): eglSurfaceAttrib not implemented 08-02 04:39:33.650: D/InputEventConsistencyVerifier(2642): KeyEvent: ACTION_UP but key was not down. 08-02 04:39:33.650: D/InputEventConsistencyVerifier(2642):   in android.widget.EditText{b1fa92d8 VFED..CL .F...... 0,82-240,118 #7f07001c app:id/inputpassword} 08-02 04:39:33.650: D/InputEventConsistencyVerifier(2642):   0: sent at 7133734000000, KeyEvent { action=ACTION_UP, keyCode=KEYCODE_TAB, scanCode=15, metaState=0, flags=0x8, repeatCount=0, eventTime=7133734, downTime=7133655, deviceId=0, source=0x101 } 08-02 04:39:38.231: D/dalvikvm(2642): GC_FOR_ALLOC freed 177K, 8% free 2964K/3192K, paused 21ms, total 24ms 08-02 04:39:38.321: D/AndroidRuntime(2642): Shutting down VM 08-02 04:39:38.321: W/dalvikvm(2642): threadid=1: thread exiting with uncaught exception (group=0xb1cd3b20) 08-02 04:39:38.331: E/AndroidRuntime(2642): FATAL EXCEPTION: main 08-02 04:39:38.331: E/AndroidRuntime(2642): Process: com.finecalc.ltafinecalculator, PID: 2642 08-02 04:39:38.331: E/AndroidRuntime(2642): android.os.NetworkOnMainThreadException 08-02 04:39:38.331: E/AndroidRuntime(2642):     at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1145) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at libcore.io.IoBridge.connectErrno(IoBridge.java:127) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at libcore.io.IoBridge.connect(IoBridge.java:112) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at java.net.Socket.connect(Socket.java:843) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:119) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:144) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at com.finecalc.library.JSONParser.getJSONFromUrl(JSONParser.java:41) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at com.finecalc.library.UserFunctions.loginUser(UserFunctions.java:42) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at com.finecalc.ltafinecalculator.UserLogin$1.onClick(UserLogin.java:57) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at android.view.View.performClick(View.java:4438) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at android.view.View$PerformClick.run(View.java:18422) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at android.os.Handler.handleCallback(Handler.java:733) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at android.os.Handler.dispatchMessage(Handler.java:95) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at android.os.Looper.loop(Looper.java:136) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at android.app.ActivityThread.main(ActivityThread.java:5017) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at java.lang.reflect.Method.invokeNative(Native Method) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at java.lang.reflect.Method.invoke(Method.java:515) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 08-02 04:39:38.331: E/AndroidRuntime(2642):     at dalvik.system.NativeStart.main(Native Method) 08-02 04:39:41.111: D/(2670): HostConnection::get() New Host Connection established 0xb97a3cc0, tid 2670 08-02 04:39:41.181: W/EGL_emulation(2670): eglSurfaceAttrib not implemented 08-02 04:39:41.181: D/OpenGLRenderer(2670): Enabling debug mode 0 08-02 04:39:45.771: W/EGL_emulation(2670): eglSurfaceAttrib not implemented 08-02 04:39:48.371: W/EGL_emulation(2670): eglSurfaceAttrib not implemented 08-02 04:39:50.971: D/dalvikvm(2670): GC_FOR_ALLOC freed 123K, 6% free 3018K/3192K, paused 28ms, total 32ms 08-02 04:39:51.581: W/EGL_emulation(2670): eglSurfaceAttrib not implemented 08-02 04:39:51.811: D/dalvikvm(2670): GC_FOR_ALLOC freed 152K, 6% free 3380K/3584K, paused 22ms, total 31ms 08-02 04:40:18.351: W/EGL_emulation(2670): eglSurfaceAttrib not implemented 08-02 04:40:21.741: W/EGL_emulation(2670): eglSurfaceAttrib not implemented 08-02 04:40:23.021: D/AndroidRuntime(2670): Shutting down VM 08-02 04:40:23.021: W/dalvikvm(2670): threadid=1: thread exiting with uncaught exception (group=0xb1cd3b20) 08-02 04:40:23.031: E/AndroidRuntime(2670): FATAL EXCEPTION: main 08-02 04:40:23.031: E/AndroidRuntime(2670): Process: com.finecalc.ltafinecalculator, PID: 2670 08-02 04:40:23.031: E/AndroidRuntime(2670): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.finecalc.ltafinecalculator/com.finecalc.ltafinecalculator.UserRegister}: java.lang.NullPointerException 08-02 04:40:23.031: E/AndroidRuntime(2670):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at android.app.ActivityThread.access$800(ActivityThread.java:135) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at android.os.Handler.dispatchMessage(Handler.java:102) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at android.os.Looper.loop(Looper.java:136) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at android.app.ActivityThread.main(ActivityThread.java:5017) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at java.lang.reflect.Method.invokeNative(Native Method) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at java.lang.reflect.Method.invoke(Method.java:515) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at dalvik.system.NativeStart.main(Native Method) 08-02 04:40:23.031: E/AndroidRuntime(2670): Caused by: java.lang.NullPointerException 08-02 04:40:23.031: E/AndroidRuntime(2670):     at com.finecalc.ltafinecalculator.UserRegister.onCreate(UserRegister.java:26) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at android.app.Activity.performCreate(Activity.java:5231) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 08-02 04:40:23.031: E/AndroidRuntime(2670):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159) 08-02 04:40:23.031: E/AndroidRuntime(2670):     ... 11 more 

Answer 1

This exception is thrown when application attempts to perform a networking operation in the main thread. Use below code in your onViewCreated to avoid this error else Call your networking operations (getting data from web server) request in thread or Asynch class.

public void onViewCreated(View view, Bundle savedInstanceState)  {     int SDK_INT = android.os.Build.VERSION.SDK_INT;     if (SDK_INT > 8)      {         StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()                 .permitAll().build();         StrictMode.setThreadPolicy(policy);         //your codes here      } } 

Answer 2

Try to add this code:

Add this code below the line in you user login activity

         setContentView(R.layout.user_login);         if (android.os.Build.VERSION.SDK_INT > 9)         {             StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();             StrictMode.setThreadPolicy(policy);         } 

Hope this may help you!