How to save an activity's state? As stated in the question, I want to know how to save an activity's state. My application has a list of products and allows the user to click on a product, starting the second activity that displays all the information about that product. On that second activity, the user can "Add the product to the shopping cart" by pressing a button.  When you press the button, the 3rd activity starts. It's a listview displaying the added product's name and price - as shown in the below code.  How do I save the data added so that if I go back and add another product, it adds it to the listview below the one already there?   I hope the question is clear, if not, please ask and i'll add whatever is needed.   Thanks in advance :)  package activity_app;  import java.util.ArrayList; import java.util.HashMap;  import android.app.ListActivity; import android.content.Intent; import android.os.Bundle; import android.widget.ListAdapter; import android.widget.ListView; import android.widget.SimpleAdapter;  public class shopping_cart extends ListActivity {   private ListView lv;  private Intent intent;  private String name;  private String price;  ArrayList&lt;HashMap&lt;String, String&gt;&gt; oslist;  private static final String PROD_PRICE ="price";  private static final String PROD_NAME = "name";  ListAdapter adapter;   @Override  protected void onCreate(Bundle savedInstanceState) {   super.onCreate(savedInstanceState);   setContentView(R.layout.shopping_cart_activity);   getActionBar().setTitle("Ordered Products");    intent = getIntent();   name = intent.getStringExtra("PROD_NAME");   price = intent.getStringExtra("PROD_PRICE");   oslist = new ArrayList&lt;HashMap&lt;String, String&gt;&gt;();    HashMap&lt;String, String&gt; map = new HashMap&lt;String, String&gt;();   map.put(PROD_NAME, name);   map.put(PROD_PRICE, price);   oslist.add(map);     adapter = new SimpleAdapter(shopping_cart.this, oslist,             R.layout.shoppingcart,             new String[] {PROD_NAME, PROD_PRICE}, new int[] {R.id.name, R.id.Price});     setListAdapter(adapter);
How to save an activity state using save instance state? I've been working on the Android SDK platform, and it is a little unclear how to save an application's state. So given this minor re-tooling of the 'Hello, Android' example:  package com.android.hello;  import android.app.Activity; import android.os.Bundle; import android.widget.TextView;  public class HelloAndroid extends Activity {    private TextView mTextView = null;    /** Called when the activity is first created. */   @Override   public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);      mTextView = new TextView(this);      if (savedInstanceState == null) {        mTextView.setText("Welcome to HelloAndroid!");     } else {        mTextView.setText("Welcome back.");     }      setContentView(mTextView);   } }   I thought it would be enough for the simplest case, but it always responds with the first message, no matter how I navigate away from the app.  I'm sure the solution is as simple as overriding onPause or something like that, but I've been poking away in the documentation for 30 minutes or so and haven't found anything obvious.
This question is from a set of optional, much harder problems from my first year analysis course, but the subject material is norms on $\mathbb R^K$.  (c) Show that there exists a constant $C &gt; 0$ such that for all $\mathbf x ∈ \mathbb R^k$, $||\mathbf x||\le C||\mathbf x||_\infty$  Hint: Use the standard unit vectors to write $\mathbf x = x_1\mathbf e_1 +. . .+x_n \mathbf e_n$, and use the triangle inequality.  (d) Show that there also exists a constant $c &gt; 0$ such that for all $x ∈ \mathbb R^k$, $||\mathbf x||_\infty \le c||\mathbf x||$  Hint: If it isn’t true, then you can find a sequence $⟨\mathbf x_n⟩$ such that $||\mathbf x_n||$ is bounded but $c_n := ||x_n||_∞ → ∞$. (Why?) Think about the sequence $⟨\mathbf x_n/c_n⟩$. The Bolzano-Weierstrass theorem may be of assistance.  Note that the unspecified norm represents any norm for $\mathbb R^k$. I've done part c), but am stuck on part d). I've had a look for proofs on other questions on MSE, but none of them seem relevant to the hint given, and frequently the terminology is too advanced for me.  I tried considering the case if it isn't true, as suggested, but I can't see how to bound any sequence using that. Any help would be much appreciated. What is potential energy truly? I have a problematic question for which I have been unable to attain a satisfactory answer. What is  truly?   -  I have read about how potential energy can be seen as the "highering" of an object within a field, be it gravitational, electromagnetic, etc.   In a way, an object is lifted to a higher position, and when it eventually falls down again energy is released back.  The object does not even have to be "lifted" beforehand, as with the case of asteroids.   However, since energy cannot be destroyed, it must somehow be stored, yet how does energy truly store itself within a field? It seems hard for me to grasp that energy can physically be stored within the positioning of an object?  I can't really get my head around how a field conserves energy within it. Kinetic energy on the other hand, can be, for me, intuitively understood, as the object really is "moving" and energy manifests itself through motion.  Can anyone elaborate on this, perhaps give reasoning as to why a field can in fact "store" energy? Please point out any fallacious or naive views I seem to hold. Proving a vector space is infinite-dimensional Let $S$ be a vector space. Suppose that for any positive integer $n$, there exists a linearly independent subset $S_n ⊆ V$ of size $n$.   How do you show that $S$ is not finite dimensional but infinite-dimensional.  I understand that to be finite dimensional then it must have a finite then  there exists a finite set that such at $\operatorname{Span}(T)=S$. So would it be right to prove by contradiction that there is not a finite spanning set that satisfies $\operatorname{Span}(T)=S$, and hence I could argue that the vector space $S$ is infinite dimensional.  How would I show that $S$ does not have a spanning set $T$, such that $\operatorname{Span}(T)=S$? How do I use variables in a sed command? Does anyone know how to find the radius of convergence of the series $\sum\ z^{n!}$, where $z$ is a complex number?  I tried to use the definition: $$\frac{1}{R}=\limsup\left|\frac{a_{n+1}}{a_{n}}\right|$$ but I wasn't successful. Column line overshooting the horizontal line in table \begin{tabular}{|m{3.5cm}|m{5.5cm}|m{4.5cm}|} \hline \emph{Category of Benefits} &amp; \emph{General Benefit} &amp; \emph{Operational Advantages} \\ \hline \multirow{3}{*}{\pbox{3.5cm}{Robust operational performance}} &amp; \multirow{3}{*}{\pbox{5.5cm}{One sensor can contribute information while other are unavailable, denied(jammed), or lack coverage of a target or event}} &amp; -Allows continued operation despite jamming \\ &amp;  &amp; -Graceful degradation \\ &amp;  &amp; -Increased probability of detection \\ \hline  \multirow{2}{*}{\pbox{3.5cm}{Extended spatial coverage}} &amp; \multirow{2}{*}{\pbox{5.5cm}{One sensor can look where another cannot}} &amp; -Increased survivability \\ &amp;  &amp; -Probability of detection increased  \\ \hline \label{tab1.1} \end{tabular}   For the LateX code mentioned above the table which comes looks like this ![enter image description here][1]   In the resulting table, column 1 vertical line overshoots the last horizontal line.  What is the problem? How do I share a folder on SAMBA? How can I simulate a slow machine in a VM? How to enable root login? How do we know that $F = ma$, not $F = k \cdot ma$ It seems intuitive that $a\; \propto \frac{F}{m}$, as the greater the force that is applied on an object, the greater its acceleration will be. Inversely, the greater the mass of the object, the slower the acceleration will be.  However, when rewriting proportions as equations, you must introduce a constant of proportionality, and in this case of a direct proportion, if $a \propto \frac{F}{m}$ then when rewriting as an equation you will have $$a = k\cdot\frac{F}{m}$$  In order to get the standard formula $F = ma$ this constant must be $1$. However, how do we know that this is the case? How do we know that the constant isn't $2$ and the formula $F = \frac{1}{2}ma$, for instance? How to change Function (Fn) Key behavior on wireless Logitech keyboard I do have a wireless Logitech K750 keyboard (silver Mac version) connected to a Lenovo ThinkPad (via the unifying USB receiver, together with a wireless Logitech mouse M705) and currently running Ubuntu 12.04.  By default the F-keys are mapped as multimedia/function keys, e.g. Play  /Pause. As I don't use them very often, I want the F-keys to behave like the "real" F-keys (F1-F12). How can I do that?  I know there is an option in the BIOS settings, but this only toggles the built-in keyboard of the notebook, not on my wireless keyboard.  I know there is a way to change this for the Apple wireless keyboard (), but there is no "parameters" directory in /sys/module/hid_logitech_dj/.  Any ideas? Or is there maybe a way to do this in a later Ubuntu version (13.04)?  UPDATE:  lsusb -d 046d: shows Bus 002 Device 005: ID 046d:c52b Logitech, Inc. Unifying Receiver  UPDATE 2: Thanks a lot for your help Lekensteyn. Finally  works just fine. In the "Known Issues" of Solaar it says that it does not work with the Nano Receiver. But I have one and it works just fine. Just don't forget to read the installation instructions and run the rules.d/install.sh script. It also recognized my M705 Mouse. How do I restore the default repositories? There are now errors when updating and I cannot install most software due to a corrupted  /etc/apt/sources.list   file. Is there a copy I can download to replace it?  The file would be for Ubuntu 12.04 (Final Beta) in the United States. Event binding on dynamically created elements? Paperback novel about a man who kills a birdlike alien on his balcony with a watering can Finding an expression for $\tan (a+ b + y)$ which involves only $\tan a, \tan b,$ and $\tan y$. How to find this ?   I'm stuck at $1$ and how to $1$ to change the tangent associated with a,b or c.  I meant this ,everybody.  $\frac{tan(a)+tan(b)+tan(y)−tan(a)tan(b)tan(y)}{1−tan(a)tan(b)−tan(a)tan(y)−tan(b)tan(y)}$ Natural Sort Order in C# Difference between a gerund acting as subject and an infinitive acting as a subject? I am wondering whether there is any difference between a gerund acting as subject and an infinitive acting as a subject. How to safely change OS name in grub boot menu? I have a system where I am dual-booting Ubuntu GNOME 15.10 and Ubuntu GNOME 16.04, however after installing Ubuntu GNOME 16.04, I have found that in the GRUB boot entry list it is called "Ubuntu", whereas the other one is called something like "Ubuntu GNOME 15.10", is there any way I can change the text of the "Ubuntu" one to "Ubuntu GNOME 16.04"? And also change the names of the other options so that instead of "Advanced options for Ubuntu" it says "Advanced options for Ubuntu GNOME 16.04" etc?  I rather do it manually if it is safe to do so, or a piece of software could be recommended, however nothing from a PPA or other untrusted not official source (I will only install software from the Ubuntu official repositories). When conducting a t-test why would one prefer to assume (or test for) equal variances rather than always use a Welch approximation of the df? It seems like when the assumption of homogeneity of variance is met that the results from a Welch adjusted t-test and a standard t-test are approximately the same.  Why not simply always use the Welch adjusted t? What will happen when Winter Bash is over? Tomorrow (January 2nd 2019) is the day that Winter Bash will be gone.  So I am thinking: Will there be some sort of a final ranking page anywhere?  It would be nice so I don't need to keep going to  every day to see my rank.  If there isn't going to be anything like that, what should I do to see my final rank on Winter Bash?