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Android- Null pointer exception from getStringExtra using intent send a value to another activity by button click

I am facing the problem when I use Intent to send a value to another activity by click a button. I have tried to solve it in many ways but it always show NullPointerException although I declared it clearly.
Here is my code.
Manufacturer.java
package com.example.student.macheckcar;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
public class Manufacturer extends AppCompatActivity {
public String message;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_manufacturer);
Button toyota = (Button) findViewById(R.id.Toyota);
Button subaru = (Button) findViewById(R.id.Subaru);
Button audi = (Button) findViewById(R.id.Audi);
toyota.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
message = "Toyota";
goAnother(message.toString());
}
});
subaru.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
message = "Subaru";
goAnother(message);
}
});
audi.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
message = "Audi";
goAnother(message);
}
});
}
protected void goAnother(String brand){
Intent i = new Intent(Manufacturer.this, ShowCarPrice.class);
i.putExtra("brand", brand);
startActivity(i);
}
}
Showcarprice.java
package com.example.student.macheckcar;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.view.Window;
import java.util.ArrayList;
public class ShowCarPrice extends AppCompatActivity {
private Cursor cursor;
private ArrayList<String> price;
private ArrayAdapter<String> aa;
private DBprice dbPrice;
private Manufacturer maFact;
SQLiteDatabase db;
ListView list;
Intent intent = getIntent();
String brand = intent.getStringExtra("brand");
#Override
protected void onCreate(Bundle savedInstanceState) {
requestWindowFeature(Window.FEATURE_NO_TITLE);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_show_car_price);
list = (ListView) findViewById(R.id.listView);
dbPrice = new DBprice(this);
db = dbPrice.getWritableDatabase();
cursor = db.rawQuery("SELECT " + dbPrice.KEY_TASK + " FROM " + dbPrice.TABLE_NAME + " WHERE Manufacturer = ?", new String[] {brand});
price = new ArrayList<String>();
cursor.moveToFirst();
while ( !cursor.isAfterLast() ){
price.add(cursor.getString(cursor.getColumnIndex(dbPrice.KEY_TASK)));
cursor.moveToNext();
}
aa = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, price);
list.setAdapter(aa);
}
public void onPause() {
super.onPause();
dbPrice.close();
db.close();
}
}
And the error:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.student.macheckcar, PID: 934
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.student.macheckcar/com.example.student.macheckcar.ShowCarPrice}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.example.student.macheckcar.ShowCarPrice.<init>(ShowCarPrice.java:22)
at java.lang.Class.newInstanceImpl(Native Method)
at java.lang.Class.newInstance(Class.java:1208)
at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2101)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233) 
at android.app.ActivityThread.access$800(ActivityThread.java:135) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:136) 
at android.app.ActivityThread.main(ActivityThread.java:5001) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:515) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 
at dalvik.system.NativeStart.main(Native Method) 
Please help.

UPDATE
public class ShowCarPrice extends AppCompatActivity {
// OK, Create the objects, variables here if needed
Intent intent;
String brand;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.your_activity_layout);
// You should assign the intent here (in onCreate method)
intent = getIntent();
// Then, the string variable
brand = intent.getStringExtra("brand");
// You can also check whether or not received a valid value
if (brand != null && !brand.isEmpty())
// do something with brand value
else
// brand value is null or empty
}
}

Well, you call getIntent() at the wrong position. You should call getIntent() in method onCreate() , and I don't know why you keep intent as a member of your activity. If I were you I just do
String brand = getIntent().getStringExtra("brand");
in onCreate() method.

get your intent and extras of intent in onCreate() method of activity just check below link for this
https://stackoverflow.com/a/5265952/5316836

Runtime error with passing data between activities. Android

I really can't figure out what's the problem here, I did almost the same example i got from somewhere on net and it's working, but this one reports a runtime error when I click on the button to switch to secondActivity. But before I set up onActivityResult in first and sending result in second activity, it switched fine.
It's a little bit longer code, but it's nothing complicated. In first activity you click button to go to second activity, and there you pick two numbers, which are stored in object and sent by intent back to the first activity, and in first activity in textview you get the total of those numbers.
MainActivity
package com.example.parcelablevezba4;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
TextView tv1;
Button btn;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv1 = (TextView)findViewById(R.id.tv1);
btn = (Button)findViewById(R.id.btn);
btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Intent i = new Intent(MainActivity.this, SecondActivity.class);
startActivityForResult(i, 42);
}
});
}
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if(requestCode == 42){
if(resultCode == RESULT_OK){
Object obj2 = data.getParcelableExtra("obje");
int total = obj2.getFirstSummand() + obj2.getSecondSummand();
tv1.setText(obj2.getFirstSummand()+"+"+obj2.getSecondSummand()+"is "+total);
}else if(resultCode == RESULT_CANCELED){
Toast.makeText(getApplicationContext(), "CANCELED", Toast.LENGTH_SHORT).show();
}
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
SecondActivity
package com.example.parcelablevezba4;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.content.Intent;
public class SecondActivity extends Activity {
EditText et1;
EditText et2;
Button btnOk;
int firstSummand;
int secondSummand;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
et1 = (EditText)findViewById(R.id.etFirst);
et2 = (EditText)findViewById(R.id.etSecond);
btnOk = (Button)findViewById(R.id.btnOk);
firstSummand = Integer.parseInt(et1.getText().toString());
secondSummand = Integer.parseInt(et2.getText().toString());
btnOk.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent resultIntent = new Intent();
Object obj = new Object();
obj.setFirstSummand(firstSummand);
obj.setSecondSummand(secondSummand);
resultIntent.putExtra("obje", obj);
setResult(RESULT_OK,resultIntent);
finish();
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.second, menu);
return true;
}
}
Object class
package com.example.parcelablevezba4;
import android.os.Parcel;
import android.os.Parcelable;
public class Object implements Parcelable {
private int firstSummand;
private int secondSummand;
public Object(){}
public Object(Parcel p){
this.firstSummand; = p.readInt();
this.secondSummand; = p.readInt();
}
public int getFirstSummand(){
return this.firstSummand;
}
public int getSecondSummand(){
return this.secondSummand;;
}
public void setFirstSummand(int f){
this.firstSummand = f;
}
public void setSecondSummand(int s){
this.secondSummand; = s;
}
#Override
public int describeContents() {
// TODO Auto-generated method stub
return 0;
}
#Override
public void writeToParcel(Parcel p, int flag) {
p.writeInt(firstSummand);
p.writeInt(secondSummand);
}
public static Parcelable.Creator<Object> CREATOR = new Parcelable.Creator<Object>() {
#Override
public Object createFromParcel(Parcel source) {
// TODO Auto-generated method stub
return new Object(source);
}
#Override
public Object[] newArray(int size) {
// TODO Auto-generated method stub
return new Object[size];
}
};
}
I translated this from my language, so if I mistyped somewhere sorry about that.
Error
08-17 13:20:22.933: E/AndroidRuntime(743): FATAL EXCEPTION: main
08-17 13:20:22.933: E/AndroidRuntime(743): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.parcelablevezba4/com.example.parcelablevezba4.SecondActivity}: java.lang.NumberFormatException: unable to parse '' as integer
08-17 13:20:22.933: E/AndroidRuntime(743): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
08-17 13:20:22.933: E/AndroidRuntime(743): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
08-17 13:20:22.933: E/AndroidRuntime(743): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
08-17 13:20:22.933: E/AndroidRuntime(743): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
08-17 13:20:22.933: E/AndroidRuntime(743): at android.os.Handler.dispatchMessage(Handler.java:99)
08-17 13:20:22.933: E/AndroidRuntime(743): at android.os.Looper.loop(Looper.java:123)
08-17 13:20:22.933: E/AndroidRuntime(743): at android.app.ActivityThread.main(ActivityThread.java:3683)
08-17 13:20:22.933: E/AndroidRuntime(743): at java.lang.reflect.Method.invokeNative(Native Method)
08-17 13:20:22.933: E/AndroidRuntime(743): at java.lang.reflect.Method.invoke(Method.java:507)
08-17 13:20:22.933: E/AndroidRuntime(743): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-17 13:20:22.933: E/AndroidRuntime(743): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-17 13:20:22.933: E/AndroidRuntime(743): at dalvik.system.NativeStart.main(Native Method)
08-17 13:20:22.933: E/AndroidRuntime(743): Caused by: java.lang.NumberFormatException: unable to parse '' as integer
08-17 13:20:22.933: E/AndroidRuntime(743): at java.lang.Integer.parseInt(Integer.java:362)
08-17 13:20:22.933: E/AndroidRuntime(743): at java.lang.Integer.parseInt(Integer.java:332)
08-17 13:20:22.933: E/AndroidRuntime(743): at com.example.parcelablevezba4.SecondActivity.onCreate(SecondActivity.java:30)
08-17 13:20:22.933: E/AndroidRuntime(743): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-17 13:20:22.933: E/AndroidRuntime(743): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
08-17 13:20:22.933: E/AndroidRuntime(743): ... 11 more

It looks like one of your EditTexts are returning an empty string:
firstSummand = Integer.parseInt(et1.getText().toString());
secondSummand = Integer.parseInt(et2.getText().toString());
And then you try to parse that empty string.
Add a log before or even better a check:
String edit1 = et1.getText().toString();
String edit2 = et2.getText().toString();
Log.e("TAG", "First: "+edit1+" Second: "+edit2);
firstSummand = (edit1.isEmpty()) ? 0 : Integer.parseInt(edit1);
secondSummand = (edit2.isEmpty()) ? 0 : Integer.parseInt(edit2);

"(1) near ";": syntax error" and "Caused by: java.lang.NullPointerException" android java

As the title suggests, have had a few errors based on source code. Attempted to find a combination of ;: within the file however was not found.
01-14 18:49:12.384: E/SQLiteLog(17346): (1) near ";": syntax error
01-14 18:49:12.384: E/CurrentItems(17346): Could not create or open the database
01-14 18:49:12.474: W/dalvikvm(17346): threadid=1: thread exiting with uncaught exception (group=0x40c83498)
01-14 18:49:12.474: E/test(17346): Exception
01-14 18:49:12.484: E/AndroidRuntime(17346): FATAL EXCEPTION: main
01-14 18:49:12.484: E/AndroidRuntime(17346): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.foodcalculator/com.example.foodcalculator.CurrentItems}: java.lang.NullPointerException
01-14 18:49:12.484: E/AndroidRuntime(17346): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2062)
01-14 18:49:12.484: E/AndroidRuntime(17346): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2087)
01-14 18:49:12.484: E/AndroidRuntime(17346): at android.app.ActivityThread.access$600(ActivityThread.java:133)
01-14 18:49:12.484: E/AndroidRuntime(17346): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1198)
01-14 18:49:12.484: E/AndroidRuntime(17346): at android.os.Handler.dispatchMessage(Handler.java:99)
01-14 18:49:12.484: E/AndroidRuntime(17346): at android.os.Looper.loop(Looper.java:137)
01-14 18:49:12.484: E/AndroidRuntime(17346): at android.app.ActivityThread.main(ActivityThread.java:4792)
01-14 18:49:12.484: E/AndroidRuntime(17346): at java.lang.reflect.Method.invokeNative(Native Method)
01-14 18:49:12.484: E/AndroidRuntime(17346): at java.lang.reflect.Method.invoke(Method.java:511)
01-14 18:49:12.484: E/AndroidRuntime(17346): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:808)
01-14 18:49:12.484: E/AndroidRuntime(17346): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:575)
01-14 18:49:12.484: E/AndroidRuntime(17346): at dalvik.system.NativeStart.main(Native Method)
**01-14 18:49:12.484: E/AndroidRuntime(17346): Caused by: java.lang.NullPointerException**
01-14 18:49:12.484: E/AndroidRuntime(17346): at com.example.foodcalculator.CurrentItems.onCreate(CurrentItems.java:73)
01-14 18:49:12.484: E/AndroidRuntime(17346): at android.app.Activity.performCreate(Activity.java:5008)
01-14 18:49:12.484: E/AndroidRuntime(17346): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
01-14 18:49:12.484: E/AndroidRuntime(17346): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2026)
01-14 18:49:12.484: E/AndroidRuntime(17346): ... 11 more
Main class
package com.example.foodcalculator;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class Homepage extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
super.onCreate(savedInstanceState);
setContentView(R.layout.homepage);
final Button addButton = (Button) findViewById(R.id.scanner);
final Button editInventoryButton = (Button) findViewById(R.id.editItem);
final Button currentInventoryButton = (Button) findViewById(R.id.currentItems);
final Button settingsButton = (Button) findViewById(R.id.settings);
addButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(view.getContext(), AddItem.class);
startActivity(intent);
}
});
currentInventoryButton.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View view) {
Intent intent = new Intent(view.getContext(), CurrentItems.class);
startActivity(intent);
}
});
editInventoryButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
// TODO Auto-generated method stub
Intent intent = new Intent(view.getContext(), EditItems.class);
startActivity(intent);
}
});
settingsButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
// TODO Auto-generated method stub
Intent intent = new Intent(view.getContext(), Settings.class);
startActivity(intent);
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
static final class ProductData {
String barcode;
String title;
Double quantity;
}
}
Current Items class
package com.example.foodcalculator;
import java.util.ArrayList;
import java.util.Scanner;
import android.app.ListActivity;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
public class CurrentItems extends ListActivity {
private final String DATABASE_NAME = "foodcalculator.db";
private final String PRODUCT_TABLE = "products";
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
ArrayList<String> results = new ArrayList<String>();
SQLiteDatabase foodDB = null;
try {
foodDB = this.openOrCreateDatabase(DATABASE_NAME, MODE_PRIVATE,
null);
foodDB.execSQL("CREATE TABLE IF NOT EXISTS " + PRODUCT_TABLE
+ " (barcode String, format String,"
+ " title String, price Double;");
foodDB.execSQL("INSERT INTO " + PRODUCT_TABLE
+ " Values ('564565645665','Beans',1.5);");
Cursor c = foodDB.rawQuery("SELECT FROM " + PRODUCT_TABLE, null);
if (c != null) {
if (c.moveToFirst()) {
do {
String title = c.getString(c.getColumnIndex("title"));
Double quantity = c.getDouble(c
.getColumnIndex("Quantity"));
results.add("" + title + ",Quantity: " + quantity);
} while (c.moveToNext());
}
}
this.setListAdapter(new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, results));
} catch (SQLiteException se) {
Log.e(getClass().getSimpleName(),
"Could not create or open the database");
} finally {
if (foodDB != null)
foodDB.execSQL("DELETE FROM " + PRODUCT_TABLE);
foodDB.close();
}
super.onCreate(savedInstanceState);
setContentView(R.layout.current_inventory);
final Button scanButton = (Button) findViewById(R.id.addButton);
final Button editInventoryButton = (Button) findViewById(R.id.editItemCurrent);
scanButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
// TODO Auto-generated method stub
Intent intent = new Intent(view.getContext(), Scanner.class);
startActivity(intent);
}
});
editInventoryButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
// TODO Auto-generated method stub
Intent intent = new Intent(view.getContext(), EditItems.class);
startActivity(intent);
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
}
All help will be greatly appreciated!

The issue in your SQL code is in CurrentItems, here:
+ " title String, price Double;");
You're missing an end parenthesis after Double. It should read as follows:
+ " title String, price Double);");

The problem is that scanButton is null at that point. Since you initialize it with
final Button scanButton = (Button) findViewById(R.id.addButton);
the problem is most likely that your layout (current_inventory.xml) does not have a button with id of addButton. (If no view with that id is found, then findViewById will return null.)
If you run the Android lint tool, it will catch errors like this.

line 73, scanButton.setOnClickListener(new View.OnClickListener()
scanButton is null.
findViewById looks for a view with the id addButton in current_inventory.xml which is the current inflated layout. If it does not find the view then you end up with NullPointerException.
I think the syntax error is bcoz of price Double;

fatal error. launching activity in android

I want to access Confirmation activity from login activity. i was able to launch confirmation activity when i didn't have login and registration activity. login and registration works perfect without confirmation activity. and dashboard activity and confirmation activity works perfect without login and registration activity.
Registration Activity.
package com.example.androidhive;
import org.json.JSONException;
import org.json.JSONObject;
import com.example.androidhive.library.DatabaseHandler;
import com.example.androidhive.library.UserFunctions;
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;
public class RegisterActivity extends Activity {
Button btnRegister;
Button btnLinkToLogin;
EditText inputFullName;
EditText inputEmail;
EditText inputPassword;
TextView registerErrorMsg;
// 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.register);
// Importing all assets like buttons, text fields
inputFullName = (EditText) findViewById(R.id.registerName);
inputEmail = (EditText) findViewById(R.id.registerEmail);
inputPassword = (EditText) findViewById(R.id.registerPassword);
btnRegister = (Button) findViewById(R.id.btnRegister);
btnLinkToLogin = (Button) findViewById(R.id.btnLinkToLoginScreen);
registerErrorMsg = (TextView) findViewById(R.id.register_error);
// Register Button Click event
btnRegister.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
String name = inputFullName.getText().toString();
String email = inputEmail.getText().toString();
String password = inputPassword.getText().toString();
UserFunctions userFunction = new UserFunctions();
JSONObject json = userFunction.registerUser(name, email, password);
// check for login response
try {
if (json.getString(KEY_SUCCESS) != null) {
registerErrorMsg.setText("");
String res = json.getString(KEY_SUCCESS);
if(Integer.parseInt(res) == 1){
// user successfully registred
// 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 Registration Screen
finish();
}else{
// Error in registration
registerErrorMsg.setText("Error occured in registration");
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
});
// Link to Login Screen
btnLinkToLogin.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Intent i = new Intent(getApplicationContext(),
LoginActivity.class);
startActivity(i);
// Close Registration View
finish();
}
});
}
}
Login 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.example.androidhive.library.DatabaseHandler;
import com.example.androidhive.library.UserFunctions;
public class LoginActivity extends Activity {
Button btnLogin;
Button btnLinkToRegister;
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.login);
// Importing all assets like buttons, text fields
inputEmail = (EditText) findViewById(R.id.loginEmail);
inputPassword = (EditText) findViewById(R.id.loginPassword);
btnLogin = (Button) findViewById(R.id.btnLogin);
btnLinkToRegister = (Button) findViewById(R.id.btnLinkToRegisterScreen);
loginErrorMsg = (TextView) findViewById(R.id.login_error);
// Login button Click Event
btnLogin.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
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));
// 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();
}
}
});
// Link to Register Screen
btnLinkToRegister.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Intent i = new Intent(getApplicationContext(),
RegisterActivity.class);
startActivity(i);
finish();
}
});
}
}
Dashboard Activity:-
package com.example.androidhive;
import android.app.Activity;
import com.example.androidhive.ConfirmationActivity;
import com.example.androidhive.R;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.webkit.JavascriptInterface;
import android.webkit.JsResult;
import android.webkit.WebChromeClient;
import android.webkit.WebView;
import android.widget.Toast;
import android.widget.Button;
import com.example.androidhive.library.UserFunctions;
public class DashboardActivity extends Activity {
UserFunctions userFunctions;
Button btnLogout;
private String resultString="";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/**
* Dashboard Screen for the application
* */
// Check login status in database
userFunctions = new UserFunctions();
if(userFunctions.isUserLoggedIn(getApplicationContext())){
setContentView(R.layout.dashboard);
btnLogout = (Button) findViewById(R.id.btnLogout);
btnLogout.setOnClickListener(new View.OnClickListener() {
public void onClick(View arg0) {
// TODO Auto-generated method stub
userFunctions.logoutUser(getApplicationContext());
Intent login = new Intent(getApplicationContext(), LoginActivity.class);
login.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(login);
// Closing dashboard screen
finish();
}
});
}else{
// user is not logged in show login screen
Intent login = new Intent(getApplicationContext(), LoginActivity.class);
login.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(login);
// Closing dashboard screen
finish();
}
}
public class WebAppInterface {
Context mContext;
/** Instantiate the interface and set the context */
WebAppInterface(Context c) {
mContext = c;
}
/** Show a toast from the web page */
#JavascriptInterface
public void showToast(String toast) {
Toast.makeText(mContext, toast, Toast.LENGTH_SHORT).show();
}
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if(requestCode==0)
if (resultCode == RESULT_OK) {
//Use Data to get string
resultString = data.getStringExtra("RESULT_STRING");
LaunchWebView(resultString);
}
super.onActivityResult(requestCode, resultCode, data);
}
private void LaunchWebView(String resultString)
{
WebView engine=(WebView)findViewById(com.example.androidhive.R.id.web_engine);
//engine.getSettings().setJavaScriptEnabled(true);
String[] array=resultString.split(":");
engine.getSettings().setLoadsImagesAutomatically(true);
//engine.getSettings().setBuiltInZoomControls(true);
engine.getSettings().setUseWideViewPort(true);
engine.setWebChromeClient(new MyJavaScriptChromeClient());
engine.loadUrl("http://74.101.168.139/snapshot.cgi?user="+array[0]+"&pwd="+array[1]+"&count=0" + "&resolution=32"+ "&rate=6");
}
public void btnRefresh_ClicHandler(View view)
{
if(resultString!="")
LaunchWebView(resultString);
}
public void btnHome(View arg)
{
Intent intent=new Intent(this,ConfirmationActivity.class);
int result=0;
startActivityForResult(intent, result);
}
private class MyJavaScriptChromeClient extends WebChromeClient {
#Override
public boolean onJsAlert(WebView view, String url, String message,
JsResult result) {
// TODO Auto-generated method stub
return super.onJsAlert(view, null, message, result);
}
}
}
Confirmation Activity : -
package com.example.androidhive;
import com.example.androidhive.R;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
public class ConfirmationActivity extends Activity {
EditText txtPassword=null;
EditText txtUsername=null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_confirmation);
}
public static final class menu2 {
public static final int confirmation=0x7f080000;
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(menu2.confirmation, menu);
return true;
}
public void btnCancel_ClickHandler(View arg)
{
finish();
}
public void btnOk_ClickHandler(View arg)
{
txtUsername=(EditText)findViewById(com.example.androidhive.R.id.txtUserName);
txtPassword=(EditText)findViewById(com.example.androidhive.R.id.txtPassword);
if(txtUsername.getText().length()==0)
{
Toast.makeText(getApplicationContext(),
"User name can not be empty.", Toast.LENGTH_LONG).show();
return;
}
if(txtPassword.getText().length()==0)
{
Toast.makeText(getApplicationContext(),
"Password can not be empty.", Toast.LENGTH_LONG).show();
return;
}
Intent intent=new Intent();
intent.putExtra("RESULT_STRING",txtUsername.getText()+ ":"+txtPassword.getText());
setResult(RESULT_OK, intent);
finish();
}
}
Android Manifest.
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.androidhive"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk android:minSdkVersion="8"
android:targetSdkVersion="18"/>
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<application
android:icon="#drawable/ic_launcher"
android:label="#string/app_name" >
<activity
android:label="#string/app_name"
android:name=".DashboardActivity" >
</activity>
<!-- Confirmation Activity -->
<activity
android:label="Confiramtion Activity"
android:name=".ConfiramtionActivity"></activity>
<!-- Login Activity -->
<activity
android:label="Login Account"
android:name=".LoginActivity"></activity>
<!-- Register Activity -->
<activity
android:label="Register New Account"
android:name=".RegisterActivity">
<intent-filter >
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
Android Fatal Error PLeaseeee Help:-
11-15 16:55:40.948: E/AndroidRuntime(858): FATAL EXCEPTION: main
11-15 16:55:40.948: E/AndroidRuntime(858): android.os.NetworkOnMainThreadException
11-15 16:55:40.948: E/AndroidRuntime(858): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1133)
11-15 16:55:40.948: E/AndroidRuntime(858): at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84)
11-15 16:55:40.948: E/AndroidRuntime(858): at libcore.io.IoBridge.connectErrno(IoBridge.java:127)
11-15 16:55:40.948: E/AndroidRuntime(858): at libcore.io.IoBridge.connect(IoBridge.java:112)
11-15 16:55:40.948: E/AndroidRuntime(858): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
11-15 16:55:40.948: E/AndroidRuntime(858): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
11-15 16:55:40.948: E/AndroidRuntime(858): at java.net.Socket.connect(Socket.java:842)
11-15 16:55:40.948: E/AndroidRuntime(858): at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:119)
11-15 16:55:40.948: E/AndroidRuntime(858): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:144)
11-15 16:55:40.948: E/AndroidRuntime(858): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
11-15 16:55:40.948: E/AndroidRuntime(858): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
11-15 16:55:40.948: E/AndroidRuntime(858): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
11-15 16:55:40.948: E/AndroidRuntime(858): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
11-15 16:55:40.948: E/AndroidRuntime(858): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
11-15 16:55:40.948: E/AndroidRuntime(858): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
11-15 16:55:40.948: E/AndroidRuntime(858): at com.example.androidhive.library.JSONParser.getJSONFromUrl(JSONParser.java:47)
11-15 16:55:40.948: E/AndroidRuntime(858): at com.example.androidhive.library.UserFunctions.loginUser(UserFunctions.java:32)
11-15 16:55:40.948: E/AndroidRuntime(858): at com.example.androidhive.LoginActivity$1.onClick(LoginActivity.java:61)
11-15 16:55:40.948: E/AndroidRuntime(858): at android.view.View.performClick(View.java:4240)
11-15 16:55:40.948: E/AndroidRuntime(858): at android.view.View$PerformClick.run(View.java:17721)
11-15 16:55:40.948: E/AndroidRuntime(858): at android.os.Handler.handleCallback(Handler.java:730)
11-15 16:55:40.948: E/AndroidRuntime(858): at android.os.Handler.dispatchMessage(Handler.java:92)
11-15 16:55:40.948: E/AndroidRuntime(858): at android.os.Looper.loop(Looper.java:137)
11-15 16:55:40.948: E/AndroidRuntime(858): at android.app.ActivityThread.main(ActivityThread.java:5103)
11-15 16:55:40.948: E/AndroidRuntime(858): at java.lang.reflect.Method.invokeNative(Native Method)
11-15 16:55:40.948: E/AndroidRuntime(858): at java.lang.reflect.Method.invoke(Method.java:525)
11-15 16:55:40.948: E/AndroidRuntime(858): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-15 16:55:40.948: E/AndroidRuntime(858): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-15 16:55:40.948: E/AndroidRuntime(858): at dalvik.system.NativeStart.main(Native Method)

This exception is thrown when application tries to access network in main thread. This is forbidden as accessing resources over network may take indefinite amount of time and your main thread will be blocked untill network operation finishes, thus making your app frozen to the user.
Instead in your onClick() method you should start a new AsyncTask which will do the networking. After the task finishes proceed with updating the ui (changing activity etc.).

Cannot Resolve NullPointerException On Service Class

I have been tasked to resolve an issue for a group project at my university however I cannot seem to resolve an issue with a NullPointerException in my service class. Our goal is to create a script which continually monitors the android history until it finds a match - then executes a warning class if the service class finds a match in the browser history. The issue occurs on line 71 (of service class) however I do not know how to resolve the issue.
Service Class:
public class Service_class extends Service {
String Dirty1 = "www.pornhub.com";
String Dirty2 = "www.playboy.com";
String Dirty3 = "www.playboy.com";
String Dirty4 = "www.playboy.com";
String Dirty5 = "www.playboy.com";
String Dirty6 = "www.playboy.com";
String Dirty7 = "www.playboy.com";
String Dirty8 = "www.playboy.com";
String Dirty9 = "www.playboy.com";
String Dirty10 = "www.playboy.com";
#Override
public IBinder onBind(Intent arg0) {
return null;
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
Toast.makeText(this, "Service Started", Toast.LENGTH_LONG).show();
return START_STICKY;
}
#Override
public void onDestroy() {
super.onDestroy();
Toast.makeText(this, "Service Stopped", Toast.LENGTH_LONG).show();
}
#Override
public void onCreate() {
super.onCreate();
TextView tv = (TextView) findViewById(R.id.hello);
String[] projection = new String[] { Browser.BookmarkColumns.TITLE,
Browser.BookmarkColumns.URL };
Cursor cursor = managedQuery(android.provider.Browser.BOOKMARKS_URI,
projection, null, null, null);
String urls = "";
if (cursor.moveToFirst()) {
String url1 = null;
String url2 = null;
do {
String url = cursor.getString(cursor.getColumnIndex(Browser.BookmarkColumns.URL));
if (url.toLowerCase().contains(Dirty1)) {
} else if (url.toLowerCase().contains(Dirty2)) {
} else if (url.toLowerCase().contains(Dirty3)) {
} else if (url.toLowerCase().contains(Dirty4)) {
} else if (url.toLowerCase().contains(Dirty5)) {
} else if (url.toLowerCase().contains(Dirty6)) {
} else if (url.toLowerCase().contains(Dirty7)) {
} else if (url.toLowerCase().contains(Dirty8)) {
} else if (url.toLowerCase().contains(Dirty9)) {
} else if (url.toLowerCase().contains(Dirty10)) {
//if (url.toLowerCase().contains(Filthy)) {
urls = urls
+ cursor.getString(cursor.getColumnIndex(Browser.BookmarkColumns.TITLE)) + " : "
+ url + "\n";
Intent intent = new Intent(Service_class.this, Warning.class);
Service_class.this.startActivity(intent);
}
} while (cursor.moveToNext());
// tv.setText(urls);
}
}
private void setContentView(int main3) {
// TODO Auto-generated method stub
}
private TextView findViewById(int hello) {
// TODO Auto-generated method stub
return null;
}
private Cursor managedQuery(Uri bookmarksUri, String[] projection,
Object object, Object object2, Object object3) {
// TODO Auto-generated method stub
return null;
}}
Main.java
import java.util.Calendar;
import com.parse.ParseAnalytics;
import com.parse.ParseObject;
import android.app.Activity;
import android.app.AlarmManager;
import android.app.AlertDialog;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.TrafficStats;
import android.net.wifi.WifiInfo;
import android.net.wifi.WifiManager;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Chronometer;
import android.widget.TextView;
public class Main extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main3);
// Start service using AlarmManager
Calendar cal = Calendar.getInstance();
cal.add(Calendar.SECOND, 10);
Intent intent = new Intent(Main.this, Service_class.class);
PendingIntent pintent = PendingIntent.getService(Main.this, 0, intent,
0);
AlarmManager alarm = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
alarm.setRepeating(AlarmManager.RTC_WAKEUP, cal.getTimeInMillis(),
36000 * 1000, pintent);
// click listener for the button to start service
Button btnStart = (Button) findViewById(R.id.button1);
btnStart.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startService(new Intent(getBaseContext(), Service_class.class));
}
});
// click listener for the button to stop service
Button btnStop = (Button) findViewById(R.id.button2);
btnStop.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
stopService(new Intent(getBaseContext(), Service_class.class));
}
});
}}
LOGCAT:
04-15 13:58:49.980: D/AndroidRuntime(1994): Shutting down VM
04-15 13:58:50.000: W/dalvikvm(1994): threadid=1: thread exiting with uncaught exception (group=0x40cc7930)
04-15 13:58:50.000: E/AndroidRuntime(1994): FATAL EXCEPTION: main
04-15 13:58:50.000: E/AndroidRuntime(1994): java.lang.RuntimeException: Unable to create service com.nfc.linked.Service_class: java.lang.NullPointerException
04-15 13:58:50.000: E/AndroidRuntime(1994): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2539)
04-15 13:58:50.000: E/AndroidRuntime(1994): at android.app.ActivityThread.access$1600(ActivityThread.java:141)
04-15 13:58:50.000: E/AndroidRuntime(1994): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
04-15 13:58:50.000: E/AndroidRuntime(1994): at android.os.Handler.dispatchMessage(Handler.java:99)
04-15 13:58:50.000: E/AndroidRuntime(1994): at android.os.Looper.loop(Looper.java:137)
04-15 13:58:50.000: E/AndroidRuntime(1994): at android.app.ActivityThread.main(ActivityThread.java:5041)
04-15 13:58:50.000: E/AndroidRuntime(1994): at java.lang.reflect.Method.invokeNative(Native Method)
04-15 13:58:50.000: E/AndroidRuntime(1994): at java.lang.reflect.Method.invoke(Method.java:511)
04-15 13:58:50.000: E/AndroidRuntime(1994): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-15 13:58:50.000: E/AndroidRuntime(1994): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-15 13:58:50.000: E/AndroidRuntime(1994): at dalvik.system.NativeStart.main(Native Method)
04-15 13:58:50.000: E/AndroidRuntime(1994): Caused by: java.lang.NullPointerException
04-15 13:58:50.000: E/AndroidRuntime(1994): at com.nfc.linked.Service_class.onCreate(Service_class.java:71)
04-15 13:58:50.000: E/AndroidRuntime(1994): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2529)
04-15 13:58:50.000: E/AndroidRuntime(1994): ... 10 more
04-15 14:00:23.770: D/AndroidRuntime(2047): Shutting down VM
04-15 14:00:23.770: W/dalvikvm(2047): threadid=1: thread exiting with uncaught exception (group=0x40cc7930)

Your method managedQuery() returns null
private Cursor managedQuery(Uri bookmarksUri, String[] projection,
Object object, Object object2, Object object3) {
// TODO Auto-generated method stub
return null;
}}
So when you try to execute a method on null you will get a NullPointerException.
Cursor cursor = managedQuery(android.provider.Browser.BOOKMARKS_URI,
projection, null, null, null); // cursor will be null
String urls = "";
if (cursor.moveToFirst()) { // this will be NPE
Make your managedQuery() method return an instantiated Cursor object.