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

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!

Answer 3

Below code used in Kotlin,
minSdkVersion 14
If your minSdkVersion less than 21 from app-level build.gradle then used below one
if (Build.VERSION.SDK_INT > 9) {
val policy = ThreadPolicy.Builder().permitAll().build()
StrictMode.setThreadPolicy(policy)
}
minSdkVersion 21
If your minSdkVersion 21 or above from app-level build.gradle then used below one
val policy = ThreadPolicy.Builder().permitAll().build()
StrictMode.setThreadPolicy(policy)

Answer 4

use AsyncTask to run long running api call to different thread.
Example Code
import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
public class AsyncExample extends Activity{
private String url="http://www.google.co.in";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
apiCall();
}
private void apiCall() {
new AsyncCaller().execute();
}
private class AsyncCaller extends AsyncTask<Void, Void, Void>
{
ProgressDialog pdLoading = new ProgressDialog(AsyncExample.this);
#Override
protected void onPreExecute() {
super.onPreExecute();
//this method will be running on UI thread
pdLoading.setMessage("\tLoading...");
pdLoading.show();
}
#Override
protected Void doInBackground(Void... params) {
//this method will be running on background thread so don't update UI frome here
//do your long running http tasks here,you dont want to pass argument and u can access the parent class' variable url over here
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
//this method will be running on UI thread
pdLoading.dismiss();
}
}
}