Android AsyncTask: "An error occured while executing doInBackground()"
What is a NullPointerException, and how do I fix it?
I have got codes like the following (generated by Kile). How can I add a caption. I guess I should have used the table environment. Is there any solution now?  \newcommand{\mc}[3]{\multicolumn{#1}{#2}{#3}} \begin{center} \begin{tabular}{rccll}      &amp;   &amp; \mc{3}{c}{Colin}\\      &amp;   &amp; a &amp; \mc{1}{c}{b} &amp; \mc{1}{c}{c}\\\cline{3-5} Rose &amp; \mc{1}{c|}{A} &amp; \mc{1}{c|}{(1,2)} &amp; \mc{1}{c|}{(2,5)} &amp; \mc{1}{c|}{(4,4)}\\\cline{3-5}      &amp; \mc{1}{c|}{B} &amp; \mc{1}{c|}{(7,4)} &amp; \mc{1}{c|}{(3,5)} &amp; \mc{1}{c|}{(0,6)}\\\cline{3-5} \end{tabular} \end{center} I accidentally opened Orca Screen Reader from the Dash when I was trying to open Screenshot. Now everything I type or click on is spoken out loud.  How do I make it stop?  For reference, here is a screenshot of Orca Screen Reader running: I tried to choose a answer for a question on SA and someone immediately answered with the correct response. I try to click the check box and it says wait 2 min. I keep clicking until it changes from 2 min to 1 min. I wait 60 seconds on my watch and click again and it says please wait 59 seconds.  The 2 minute mark should have said 3 and the 1 minute mark was really 2.  It seems that this has , which is a lot more inconvenient than 59 seconds. Why is voltage same for the two resistors connected parallel in circuit? We know that the electric field inside resistor produced by battery is the actual thing that pushes the electrons in it to move and thus producing some current. We also know that strength of electric field can be described by the electric flux which is the total amount of fields passing through an area. That flux when combined(multiplied) with charge of electron gives the amount of force on it. Now comes our two resistors R1 and R2. Assuming a number of field lines coming out of a terminal going towards another terminal through these resistors, the field lines should get divided into the resistances R1 and R2. Therefore giving a reduced flux through each resistor than in a series. Which will then give a lower voltage for both resistors. Wasn't the electric fields strength divided across resistors in parallel? What is the main cause of voltage? How electrons get a force to produce current even when the wire is very long in? I think it is better to understand with reality than analogy. Please don't give misleading pictures Do the following negations mean the same thing? I don't think you understood me. / I think you misunderstood me.    Do these senteces mean the same thing? If not, what's the difference?  Edit: I just realized that I asked something different from what I originally wanted. So I am also interested in the following comparison:     I don't think you understand me. / I think you don't understand me. Say $\mathbf{x} \in \mathbb{R}^n$, what is the common notation to extract the first component as an operation?  Something like $\mathcal{P}_j = \mathbf{x}_j$? $\mathbf{x}_j$ is the j-th component.   I need this because I have a function $f(\mathbf{x}) \approx \mathbf{x}$, so I need something like $\mathcal{P}f(\mathbf{x}) \approx \mathbf{x}_j$ since my metric is defined for a single component of $\mathbf{x}_j$. How to create old looking/ cracked glass I am looking for old looking cracked glass for a window in a shack scene. I have looked everywhere but can find a tutorial or material or model on this please can someone help me on this thanks What is the agreed upon definition of a "positive definite matrix"? How could Thranduil have met a dragon? I stumbled upon an example, which needed to be compiled with the additional option --shell-escape. Using this option it worked just fine, but I'm curious:     Why or when is this option needed and what does it actually do? When something gets wet, it usually appears darker. This can be observed with soil, sand, cloth, paper, concrete, bricks...  What is the reason for this? How does water soaking into the material change its optical properties? Is "The empty set is a subset of any set" a convention? Recently I learned that for any set A, we have $\varnothing\subset A$.  I found some explanation of why it holds.     $\varnothing\subset A$ means "for every object $x$, if $x$ belongs to the empty set, then $x$ also belongs to the set A". This is a vacuous truth, because the antecedent ($x$ belongs to the empty set) could never be true, so the conclusion always holds ($x$ also belongs to the set A). So $\varnothing\subset A$ holds.   What confused me was that, the following expression was also a vacuous truth.     For every object  $x$, if $x$ belongs to the empty set, then $x$ doesn't belong to the set A.   According to the definition of the vacuous truth, the conclusion ($x$ doesn't belong to the set A) holds, so $\varnothing\not\subset A$ would be true, too.  Which one is correct? Or is it just a convention to let $\varnothing\subset A$? It seems like I'm doing something wrong when using foreach variables to indicate node numbers. The two foreach loops are anchoring the paths to the east of each node. Why does this happen?    \documentclass{article}  \usepackage{tikz} \usetikzlibrary{backgrounds,fit,patterns,decorations.pathreplacing,calc}  \makeatletter \tikzset{   labelnode/.style={draw=none, fill=none, black},   latentnode/.style={draw, minimum width=5mm, shape=circle, ultra thick, black},   dagconn/.style={arrows=-&gt;, black, thick}, } \makeatother  \begin{document} \begin{tikzpicture}[scale=1]  \pgfmathsetmacro{\colgap}{1.6}  \pgfmathsetmacro{\rowgap}{1.3}   \node[labelnode] (x1) at (\colgap*0,\rowgap*1) {$X_1$};  \node[labelnode] (x2) at (\colgap*1,\rowgap*1) {$X_2$};  \node[labelnode] (x3) at (\colgap*2,\rowgap*1) {$X_3$};   \node[latentnode,blue] (x4) at (\colgap*0,\rowgap*0) {$X_4$};  \node[latentnode,red] (x5) at (\colgap*1,\rowgap*0) {$X_5$};  \node[labelnode] (x6) at (\colgap*2,\rowgap*0) {$X_6$};   \foreach \c in {1,...,2} {    \foreach \r in {1,...,2} {      \pgfmathsetmacro{\st}{(((\r-1)*3)+\c)}      \pgfmathsetmacro{\en}{\st+1}      \draw[dagconn] ([xshift=0.2cm]x\st) to ([xshift=-0.9cm]x\en);    }  }   \foreach \c in {1,...,3} {    \foreach \r in {1,...,1} {      \pgfmathsetmacro{\st}{((\r-1)*3)+\c}      \pgfmathsetmacro{\en}{\st+3}      \draw[dagconn] (x\st) to (x\en);    }  } \end{tikzpicture} \end{document} Prove the following inequality:   $$\dfrac{e^x + e^{-x}}2 \le e^{\frac{x^2}{2}}$$   This should be solved using Taylor series.  I tried expanding the left to the 5th degree and the right site to the 3rd degree, but it didn't help.  Any tips? Workflow for developing add-on/script I'm trying to figure out a good workflow for developing scripts and add-ons in Blender. Here's what I'm currently doing as I try my luck with a PyNode add-on:   Open blender Create a text editor panel Open my script (external text file) Edit my script in a nice external editor Reload the script Save the .blend file Run the script   Now that I can see what my code does, this Blender instance has been modified, so I can't (make changes to my script and) run my script again. So I do this:   Close blender Open blender with the .blend from step 6 and repeat steps 4-7, over and over and over..   Is there a better workflow for this sort of thing? How to create fixed width table columns with text raggedright/centered/raggedleft? I would like to create a table with some columns' width specified, while the text in those columns should be centered both horizontally and vertically. I found out that  \usepackage{array} \begin{tabular}{| c | c | m{5cm} |}   vertically centers the text in the last column, but justifies it horizontally (like text in normal paragraphs).  Update: With Jake's method, it seems both \\ and \hline cause an error. How to fix it? Will be glad for a little hint: let x and n be positive integer such that $1+x+x^2+\dots+x^{n-1}$ is a prime number then show that n is prime LaTeX Editors/IDEs Keeping track of where everyone is is hard.  I could be out in the wasteland while Dogmeat will let me know he found something. That's great, but then it's a chore trying to find him a lot of times. Sometimes, he'll even run ahead and attack enemies and I'll lose sight of him. Only if I leave an area sufficiently far enough, he'll come back and meet with me which isn't always possible. I know I can listen out for him but visual indicators would be better. But none of this works if I sent him to a settlement but needed to find him and he hasn't returned yet.  Is there anything we can do to make locating companions in the world easier? How do I avoid rendering glitches from overlapping faces? For instance, here I have two cubes that are offset only on the x-axis. When I render them (using Blender's internal renderer), the overlapping faces interfere with each other and the result looks awful. A quick and easy solution would be to offset them by just a smidget, but is there another solution that allows faces to overlap and not exhibit this graphical glitch?