I am new to development of android and i don't have a fair idea how to read logcat. I am trying to develop android webview application but ran into these errors.  E/AndroidRuntime:  FATAL EXCEPTION: main E/AndroidRuntime:  Process: com.tech.neucial, PID: 25698 E/AndroidRuntime:  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tech.neucial/com.tech.neucial.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setHomeButtonEnabled(boolean)' on a null object reference E/AndroidRuntime:   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2329) E/AndroidRuntime:   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2391) E/AndroidRuntime:   at android.app.ActivityThread.access$900(ActivityThread.java:147) E/AndroidRuntime:   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1296) E/AndroidRuntime:   at android.os.Handler.dispatchMessage(Handler.java:102) E/AndroidRuntime:   at android.os.Looper.loop(Looper.java:135) E/AndroidRuntime:   at android.app.ActivityThread.main(ActivityThread.java:5256) E/AndroidRuntime:   at java.lang.reflect.Method.invoke(Native Method) E/AndroidRuntime:   at java.lang.reflect.Method.invoke(Method.java:372) E/AndroidRuntime:   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:898) E/AndroidRuntime:   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693) E/AndroidRuntime:  Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setHomeButtonEnabled(boolean)' on a null object reference E/AndroidRuntime:   at com.tech.neucial.MainActivity.onCreate(MainActivity.java:39) E/AndroidRuntime:   at android.app.Activity.performCreate(Activity.java:5933) E/AndroidRuntime:   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105) E/AndroidRuntime:   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2282) E/AndroidRuntime:   ... 10 more   I have tried every possible way to understand but no resolve. Here is the source code.   PS: i am uploading whole source because i don't know which file has cause the issue and there have been 5 or 6 files which i can't paste here.  Thanks.
What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?
What’s the correct URL for placing a call on an iPhone? Set limit to one author when using "et al." in biblatex In the header of my document I set the maximal author names to 2:  \usepackage[style=authoryear-icomp, maxbibnames=9, maxcitenames=2, backend=biber]{biblatex}   Now, when I cite texts with two authors, LaTeX gives me the following:     (Author_A/ Author_B 2012: 232)   When I have three authors or more, LaTeX makes it:     (Author_A/ Author_B et al. 2012: 232)   But I want LaTeX to just name the first author if there are more than two authors ... like this:     (Author_A et al. 2012: 232)   Any tips on how to achieve this ? Schwarz's Lemma, fixed points question This is from an old qualifying examination question.  If f is holomorphic in the unit disk $D$ and $|f(z)|&lt;1$ for all $z\in D$. Suppose also that $f$ has two distinct fixed points in $D$ then $f(z)=z$ for every $z\in D$  I know that I have to use the Schwarz's lemma and may be make use of Möbius transformations. I tried setting $g(z)=\phi_a\circ f\circ \phi_{-a}$. But that does not seem to work because I don't see why $|g(z)|=|z|$ for some non zero $z$.   Any helpful hints are greatly appreciated.  Edit: Of course the $a$ above is one of the fixed points. Singular or Plural setting to a variable. PHP Need Help Fixing Grub after Installing Ubuntu 13.04 x64 Alongside Windows 8 on a Lenovo IdeaPad Y400 with UEFI I have a Lenovo IdeaPad Y400 that came pre-installed with Windows 8. I would like to run Ubuntu alongside it in a dual-boot configuration. I've spent the past week fiddling around, re-installing both Windows and Linux in various configurations, and I've come awfully close to success, but seem to have hit a snag with Grub.  For my most recent attempt, I took the following steps:   Disabled Secure Boot Re-imaged Windows 8 from a hidden recovery partition, effectively restoring the machine to factory state Activated an option called Legacy Support in the BIOS (or is it UEFI now?) Booted Ubuntu 13.04 x64 from a USB stick, chose "install alongside Windows" and accepted all default options After a restart, found that I could boot Ubuntu, but could not boot Windows Once into Ubuntu, I ran Boot Repair with recommended settings and accepted all defaults. When Boot Repair finished, I was presented with the following message:      The boot files of [The OS now in use - Ubuntu 13.04] are far from the   start of the disk. Your BIOS may not detect them. You may want to   retry after creating a /boot partition (EXT4, >200MB, start of the   disk). This can be performed via tools such as gParted. Then select   this partition via the [Separate /boot partition:] option of [Boot   Repair]. ()    I followed the instructions at the url in the message, creating a 1GB EXT 4 partition near the start of the drive  when I tried to run Boot Repair again, the "Separate /boot partition" option on the "Grub Location" tab was disabled.  The new partition is /dev/sda11 and has the label GRUB. On restart, I get the following error message:      error: file '/boot/grub/i386-pc/normal.mod' not found.    grub rescue>    However, if I manually choose the boot partition by hitting F12, I can boot into Windows no problems. Selecting Ubuntu from the boot device menu gives me a Grub menu with the following options:      Ubuntu      Advanced options for Ubuntu       Windows UEFI recovery bootmgfw.efi      Windows Boot UEFI recovery       Windows UEFI recovery LrsBootmgr.efi      Windows Boot UEFI recovery bkpbootx64.efi       Windows Recovery Environment (loader) (on /dev/sda3)       Windows 8 (loader) (on /dev/sda5) System setup    Selecting Ubuntu from this menu allows me to get to my Ubuntu desktop. I haven't tried the other options yet for fear of losing the progress that I've made.   So it looks like I have successfully dual-booted the machine, but that Grub is broken for some reason or another.   My current partition scheme can be seen at:   Thanks in advance - Jonathan Prove: If $a$ and $b$ are odd integers, then $8\mid (a^2-b^2)$  So far I have: $$8\mid \left((2n+1)^2-(2m+1)^2\right)\Longleftrightarrow 8\mid \left(4n^2+4n+1-4m^2-4m-1\right) $$ Is this right so far? Where do I go from here? Step by step explanation please! How to include PDF pages without a newpage before the first page? Shadow Incorrect at Bottom of Edge In the images below, I have a cube that is sticking up about two thirds through a plane. But, despite the fact that the cube is not hovering over the plane, the shadow seems to indicate otherwise. How can I fix this shadow? Add a duplicate:0|1 search operator I already derived a QM expectation value for ordinary momentum which is: $$ \langle p \rangle=  \int\limits_{-\infty}^{\infty} \overline{\Psi}  \left(- i\hbar\frac{d}{dx}\right) \Psi \, d x $$ And I can read clearly that operator for momentum equals $\widehat{p}=- i\hbar\frac{d}{dx}$. Is there an easy way to derive an expectation value for $\langle p^2 \rangle$ and its QM operator $\widehat{p^2}$? What are the badges I can earn on each site, and what are the exact criteria for earning each badge? Why is there an "electric" potential drop across the resistor? An electric potential difference is created when two charges are separated. In a capacitor, there is a clear accumulation of opposite charges on the two separated plates, therefore work has to be done in moving an unit charge from one plate to another, against the electric field.   But, , a potential difference is created in a resistor due to the heat produced by the collision and increased lattice vibrations. So there is an energy loss across the resistor, yes, but how does this energy loss due to heat create an electric potential difference. In other words, do electrons accumulate on one or both sides of the resistor? If not, why should we do electric work in moving from one end of the resistor to another. If the difference in energy is not due to electric work, then that's not electric potential, is it? Force alt + tab to switch only on current workspace in GNOME shell I am looking for a clean and fast method to force GNOME in Ubuntu 14.04 to switch between active apps only on the current workspace when pressing the shortcut alt + tab. Object of class mysqli_result could not be converted to string Real definition of "countable set" How to manually mount a partition? There are many questions on automatically mounting or problems encountered during mounting that I've read here. But none on how to manually mount a partition. How to remove duplicate values from a multi-dimensional array in PHP How can I remove duplicate values from a multi-dimensional array in PHP?  Example array:  Array (     [0] =&gt; Array     (         [0] =&gt; abc         [1] =&gt; def     )      [1] =&gt; Array     (         [0] =&gt; ghi         [1] =&gt; jkl     )      [2] =&gt; Array     (         [0] =&gt; mno         [1] =&gt; pql     )      [3] =&gt; Array     (         [0] =&gt; abc         [1] =&gt; def     )      [4] =&gt; Array     (         [0] =&gt; ghi         [1] =&gt; jkl     )      [5] =&gt; Array     (         [0] =&gt; mno         [1] =&gt; pql     )  ) Partial instead of full markers are shown in PGFplots When using  \documentclass{article} \usepackage{pgfplots} \begin{document} \begin{tikzpicture}         \begin{axis}                     \addplot             [                 red,                 solid,                 mark=x,                 domain=-3e-3:3e-3,                 samples=50             ]              {exp(-x^2/(2e-3^2))/(1e-3*sqrt(2*pi))};         \end{axis}     \end{tikzpicture}    \end{document}   the markers look fine, see    , but when I replace solid with, for instance, loosely dashed, so  \documentclass{article} \usepackage{pgfplots} \begin{document} \begin{tikzpicture}         \begin{axis}                     \addplot             [                 red,                 loosely dashed,                 mark=x,                 domain=-3e-3:3e-3,                 samples=50             ]              {exp(-x^2/(2e-3^2))/(1e-3*sqrt(2*pi))};         \end{axis}     \end{tikzpicture}    \end{document}   the markers only show partially instead of fully, see    . How can I use loosely dashed with full markers showing? Are there perfect elastic collisions in Nature? Programmatically create a user and assign a role