Adrian Lee Adrian Lee - 2 months ago 22
Android Question

Android Studio :: E/AndroidRuntime﹕ FATAL EXCEPTION:

My app crashed the moment i run it. I need help. Thank you very much in advance.

I'm kinda new on android studio, not sure what i did wrong.

Error:

09-14 02:55:11.013 4502-4502/com.example.adrian.loginregister E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.adrian.loginregister, PID: 4502
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.adrian.loginregister/com.example.adrian.loginregister.LoginActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.adrian.loginregister.LoginActivity.onCreate(LoginActivity.java:23)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
at android.app.ActivityThread.-wrap11(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5417) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)


Below are the LoginActivity.java

package com.example.adrian.loginregister;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class LoginActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);

final EditText etUsername = (EditText) findViewById(R.id.etUsername);
final EditText etPassword = (EditText) findViewById(R.id.etPassword);
final Button bLogin = (Button) findViewById(R.id.bLogin);
final TextView bRegister = (TextView) findViewById(R.id.bRegister);

bRegister.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
Intent registerIntent = new Intent(LoginActivity.this, RegisterActivity.class);
LoginActivity.this.startActivity(registerIntent);
}
});
}
}


This is the activty_login.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.adrian.loginregister.LoginActivity">

<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/etUsername"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:hint="Username" />

<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/etPassword"
android:layout_below="@+id/etUsername"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignRight="@+id/etUsername"
android:layout_alignEnd="@+id/etUsername"
android:hint="Password" />

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Login"
android:id="@+id/bLogin"
android:layout_below="@+id/etPassword"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceMedium"
android:text="Register here"
android:id="@+id/tvRegister"
android:layout_below="@+id/bLogin"
android:layout_centerHorizontal="true" />
</RelativeLayout>


 
I've been trying to figure out for hours. Can't seem to get it to work. Crashes every time i try to run it.

Answer

try to change

final TextView bRegister = (TextView) findViewById(R.id.bRegister); 

line to

final TextView bRegister = (TextView) findViewById(R.id.tvRegister);

becuase in your xml file you are giving Register TextView Id to tvRegister. your are giving wrong Id in initliazation.