new plotter

android-app-core/res/values/text_strings.xml

@@ -282,5 +282,6 @@
     <string name="cpp_onscreen_remove_icon_message">You can remove second icon in applications\' list from application settings or by pressing next button</string>
     <string name="cpp_onscreen_remove_icon_button_text">Remove icon</string>
     <string name="cpp_this_change_may_require_reboot">This change may require reboot</string>
+    <string name="cpp_plot_3d">3D</string>
 
 </resources>

android-app-core/src/main/java/org/solovyev/android/calculator/CalculatorDisplayMenuItem.java

@@ -85,7 +85,13 @@ public enum CalculatorDisplayMenuItem implements LabeledMenuItem<CalculatorDispl
             assert generic != null;
 
             final List<Constant> variables = new ArrayList<Constant>(CalculatorUtils.getNotSystemConstants(generic));
-            final Constant xVariable = variables.get(0);
+
+            final Constant xVariable;
+            if ( variables.size() > 0 ) {
+                xVariable = variables.get(0);
+            } else {
+                xVariable = null;
+            }
 
             final Constant yVariable;
             if ( variables.size() > 1 ) {

android-app-core/src/main/java/org/solovyev/android/calculator/plot/PlotInput.java

@@ -15,7 +15,7 @@ public class PlotInput {
     @NotNull
     private Generic function;
 
-    @NotNull
+    @Nullable
     private Constant xVariable;
 
     @Nullable
@@ -26,7 +26,7 @@ public class PlotInput {
 
     @NotNull
     public static PlotInput newInstance(@NotNull Generic function,
-                                        @NotNull Constant xVariable,
+                                        @Nullable  Constant xVariable,
                                         @Nullable Constant yVariable) {
         PlotInput result = new PlotInput();
 
@@ -42,7 +42,7 @@ public class PlotInput {
         return function;
     }
 
-    @NotNull
+    @Nullable
     public Constant getXVariable() {
         return xVariable;
     }